Critical Period for Bollworm Escapes on 2 Gene Cotton in AL

Ron Smith

Extension Entomologist, Auburn University

We are entering the most critical period of bollworm presence during the next 20 days (July 15-Aug 1). This increase in bollworm activity began last week (July 9-13) along the Gulf Coast and the Mobile/Santa Rosa County (Jay) FL area. By July 20^th, we should see an increased bollworm egg lay in Central AL (Montgomery, Prattville, Selma areas). By the 25^th this increase may reach Cherokee County in the northeast, and by August 1^st the Tennessee Valley area of northern AL.

Increased bollworm moth presence was noted last week as far north as Pike and Barber County (Troy) area. This increased moth activity will be influenced by the planting date and acreage of corn planted in a given region of the state. Most all bollworm were corn earworms in corn previous generation. This life cycle is about 30 days and the eggs in corn were deposited during the white or pink silk stge. About 30 days later these moths that emerged from corn are looking for their next host. Cotton is the best host they will find in AL (not soybeans or peanuts).

Many (but not all) fields in all areas of the state had more worm damaged bolls in 2017 than we had seen since 1995. If we want to prevent this from happening again, the next 2 weeks are critical.

I assume that most realize now that our 2 gene cotton has lost some level of effectiveness against the bollworm species. When resistance is a factor, the problem usually gets worse over time—it seldom gets better.

Now, what should fieldmen be looking for?

1.     Eggs in terminals or on the fruiting structures: square bracts, white or red blooms (threshold on 2 gene cotton is 20 eggs/100 plants)

2.     Damaged squares in the upper canopy – may find more damage to small squares near the terminal in Phytogen varieties (5% damage is threshold).

3.     Newly hatched larvae

May find in small squares in Phytogen varieties

May find more in open white blooms or underneath red or dried blooms in Delta Pine and other varieties

(5% of plants with small larvae is threshold)

These small larvae are white when they have just hatched and will turn pale green within a day or so.

One thing that makes them stand out in a white bloom is they will have a black or dark brown head. Often the head is the best thing to look for since being dark stands out from the white bloom petals. (See Picture)

Once a significant increase in eggs or small larvae are detected—do not waste more time in the field. Get the word to the grower and get the sprayer loaded. Every 24 hour period that passes from detection to treating means less effectiveness with your insecticide. Also note that these bollworm moths will likely seek out our oldest and most promising cotton to deposit eggs in.

Now what treatment options do we have? Basically two. We can try the older chemistry, pyrethroids, or we can go to the newer chemistry, Besiege and Prevathon.

Things to consider here: bollworms have shown levels of resistance to pyrethroids in many areas of the cotton belt. However, the pyrethroid chemistry is much less expensive. Pyrethroids have about a 4-5 day residual on bollworms, where they are still active.

The newer chemistry Beseige and Prevathon have about 10+ days of residual on bollworms, depending on the rate applied.

If using pyrethroids, I suggest the highest labeled rate. If using Beseige, I suggest 8-9 oz/ac. If using Prevathon, I suggest 16-18 oz/ac. Besiege contains a low rate of Karate pyrethroid in the mixture. If you need tarnished plant bug or stink bug control, you will need to add about 1 oz of additional Karate, or equivalent pyrethroid, to the tank mixture. Prevathon has no activity on plant bugs or stink bugs.

In summary, this is the time to be ready to react to bollworms in 2 gene cotton. I will be tweeting as I hear of increased pressure in a region, county, or area.

I will be conducting tests on thresholds, timing, and chemical choices at our research farm at Prattville in Central AL, so will be in the field a lot within the next 2 weeks or so.

Stay in touch with the Syngenta Pest Patrol reports for up to date observations on bollworms. To sign up for the Syngenta Pest Patrol Updates for Alabama, register online at syngentaus.com/pestpatrol or register via text by texting pestpat11 to 97063.

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Blog: http://alabama-insects.blogspot.com/

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Silverleaf Whitefly Control in Cotton

The silverleaf whitefly (SLWF) is a devastating economic pest of cotton. A multi-county area surrounding Tifton, GA was heavily infested in 2016. In 2017, this infested area has spread over much of the 1.3 million acres of cotton planted in Georgia. In early to mid August of 2017, these SLWF infestations have spread throughout the Wiregrass area of southeastern Alabama.

The SLWF was first observed on cotton in Alabama in Mobile county in 1997. This pest has historically been associated with the more arid regions of cotton production such as California, Arizona, and the Rio Grande Valley of southern Texas. Major outbreaks occurred in those areas in 1992 and 1993.

SLWF has sucking mouthparts and their feeding is similar to aphids. This feeding will stunt plants and reduce their vigor. However, a more serious problem is their secretion of honeydew, which falls in lower parts of the plant. This would be lower leaves during the growing season but open bolls as the plants mature. A sooty mold grows in this honeydew, which will reduce the quality of the lint once cotton begins to open.

Heavy infestations of SLWF can cause premature defoliation. SLWF are not known to die off from a naturally occuring fungus like aphids. SLWF populations continue to increase until cotton is defoliated or until the leaves drop from SLWF feeding.

The first sign of a SLWF infestation will be the presence of whiteflies clustering around the plant terminal or underneath the terminal leaves. The adults will fly when disturbed, Population increases will be observed about two plus weeks after the first presence of adults. SLWF adults deposit eggs underneath the leaves. These eggs hatch into a crawler stage which finds a place under the leaf to begin feeding. This immature stage is then immobile until it develops into an adult. The total life cycle of the SLWF is 15-18 days, depending on the temperature.

Treatment decisions for SLWF can be made by examining for the presence or absence of immatures on the 5th main stem leaf below the terminal. Controls are recommended when 50% of the plants have immatures on the lower surface of this leaf. Immatures will appear oval, flattened, and yellowish in color. They can be separated from aphids by their flattened shape and the absence of appendages and movement.

Points to remember about SLWF as expressed by Dr. Phillip Roberts, Extension entomologist, UGA: Do not overreact but be careful to not underreact to this pest. You cannot get behind with controls and ever catch up. Try not to do anything to make the situation worse. Do not treat for other pests unless necessary. When controlling other pests, use the most selective insecticides on beneficial insects. Cotton is not safe from SLWD damage until the day it is defoliated for harvest. Growers should try to get to defoliation time with green leaves in the plant terminal with no honeydew present.

Rainfall may reduce the number of adults but will have no effect on the immature stage underneath leaves. The damage potential from the SLWF is greatest on late planted cotton (late May-June). This pest prefers hairy leaf or semi-hairy leaf varieties over smooth leaf ones. Hot and dry conditions are favorable for more rapid SLWF reproduction.

Controlling SLWF in 2017 will be very expensive and challenging due to the unavailability or short supply of most recommended controls. The most effective control can be achieved with the insect growth regulator (IGR) type insecticides Knack or Courier. Both work on the immature stage. Their activity is slow but they have long residual. It is advisable to wait 10-14 days after treatment before making opinions about benefits.

Other products that have activity on the SLWF are acetamiprid (Assail/Intruder), Venom, and Sivanto. Centric at high label rates will suppress the adult stage.

Rambling Thoughts About the 2017 Weather and Tarnished Plant Bugs in Cotton

I will say up front that no two seasons are exactly alike when considering the weather, crop conditions, and potential insect damage. 2017 has already been uniquely different than any season I remember. Delayed planting, excessive rainfall, mild winter, and warm spring are just a few of the factors that could affect the movement, numbers, and level of damage from plant bugs to this year's cotton crop. Only by close monitoring of plant bug numbers and their damage over the next 4-6 weeks will we know how to deal with this pest.

We need to begin sampling the oldest and largest cotton immediately with sweep nets for adult tarnished plant bugs. In addition, we should keep check on our square set by making pinhead square retention counts. 80% retention is considered our treatment threshold. In other words, we do not want to lose more than 20% of our small squares to plant bug damage.

If past history is any help, abundant to excessive rainfall in June tends to keep wild host plants like fleabane fresh a little longer. This slows or prolongs the movement of plant bugs into cotton. After fleabane dries down, no other wild host is attractive to adult plant bugs, therefore cotton is the best host they have. The movement of plant bugs into cotton has already begun. This migration could continue for several weeks. This slow extended migration may not reach what we would call a threshold or treatable level, making treatment decisions difficult. In hot, dry springs, these adult plant bugs leave fleabane in high numbers over a relatively short period of time, say 7-14 days. This sort of rapid movement into cotton is easier to detect and to make treatment decisions for.

There are a number of other factors that could influence the severity of the plant bug issue in cotton this season. Overall, I would estimate that the maturity of our cotton is a little behind where it normally is this time of year. Will plant bugs move past these fields in search of the oldest most mature cotton? April cotton may serve as a trap crop for plant bugs in 2017. That would be to our advantage. Since early June, we have had a lot of cloudy days with temperatures in the 70s or 80s. Plant bug survival on cotton has likely been higher under these conditions. This could spell higher damage levels in coming weeks. Plant bug adults, and especially their immature offspring, do not fare well under drought conditions and high temperatures (over 95°F), leaving cotton plants under a stressed and wilted condition.

Water logged spoils, which many fields have had during the month of June, can result in some pinhead square abortion. This effect would be very difficult to separate from plant bug injury. How can we distinguish this square loss from plant bug injury? The easiest way would be to use a sweep net to document that some level of plant bugs are actually in the field. One additional little trick that could help us answer this question was developed by our Arkansas entomology friends several years ago. This technique takes a little time, precision, and magnification. The tool needed would be a "pinhead square slicer." Take a damaged pinhead square from the plant (square will be brown or black in color), use a sharp razor, and slice the square in half. If it aborted due to weather, the inside content will still be present but deteriorating, whereas if it has been damaged by a plant bug, the interior will be hollow. Plant bugs tend to dissolve the contents and suck the interior of the square as food.

Plant bugs will likely be the primary cotton insect focus of entomologists, consultants, scouts, farmers, and other interested parties until well into July this season. We need to recognize this and not allow plant bugs to further limit our maturity and potential yield in 2017.

Update for the Week of August 4, 2014

The most significant insect event in the past week was the reports of plant bug tolerance to all labeled or recommended insecticides in the Tennessee Valley of North Alabama. Several of our most experienced consultants are reporting that all classes of chemistry are suppressing plant bugs but their presence and damage behind applications are still above threshold levels. This has required repeated sprays and now tank mixtures with two recommended insecticides. Under these conditions, input costs for cotton insects, particularly plant bugs, make cotton an unattractive crop option going into the 2015 season. Some areas of the mid-south have been dealing with this problem for several years. At this point, the Alabama situation appears to be confined to the Tennessee Valley area.

It has been my experience that once plant bugs get embedded in rank cotton in July, they have always been difficult to control, requiring multiple applications. So now, we have insecticide tolerance in addition to a coverage issue. Looking ahead I see a larger role for the IGR Diamond during the early bloom period in future years.

Now to a quick oversight of other insect problems on cotton and other crops; stink bugs, primarily brown, are requiring controls in some cotton fields. However, overall they are not as heavy and widespread as expected. Aphids are showing back up in some fields requiring controls. Spider mites are present in many fields. It seems like we get more calls about mite control following weeks of high temperature and dry conditions.

In soybeans we are beginning to see loopers as far north as Montgomery in older beans. So far they are only at about a third of a threshold level. Scouts are reporting an occasional corn earworm and velvetbean caterpillar in the soybean mix. The same holds true for peanuts.

Fall armyworms (grass strain) are on about every crop except cotton now. Hay, grasses, peanuts, soybeans are all experiencing the need for repeated applications for FAW. We could safely say that FAW’s have about worn out their welcome, even though they are easy to control. It seems like their preferred row crop is soybeans planted in wheat stubble. Some fields are now on their third infestation and replanting has been required due to near 100% defoliation.

In many ways, 2014 has been like “old times” to Extension entomologists with numerous phone calls about when to treat and what chemical to choose. We don’t feel like step-children to the weed resistance and disease issues this season.

Scouting crops is the first step in all insect management and control programs.

Insect Update for the Week of July 7

A combination of adult tarnished plant bugs and clumping aphids are being reported from more fields and areas around the state each day. Overall, little rainfall has fallen in about two weeks. Therefore, crops, especially corn and cotton, are under some level of stress. Therefore, most growers are choosing to target both plant bugs and aphids with this application.

I have not had any calls on mites in the past few days but that does not mean that populations are not building in select fields. So far, abamectin at 10 oz. per acre has given good control on mites in treated fields.

Immature plant bugs are present now in the oldest cotton. I have observed several fields where a threshold of three immatures per 5 feet has been recorded on a black drop cloth. When plant bugs become imbedded in cotton in July (all stages present – eggs, immatures and adults) quite often multiple applications are needed to bring the population under control. For those that want to use the IGR Diamond, now is the time to do so. An adulticide plus Diamond, at 6-9 oz. per acre, should give control of the population for 14 plus days. It is my opinion that most of the adult plant bugs have now left wild host plants and are now in cotton. We just don’t seem to get that many moving from corn here in Alabama.

Moth traps in central Alabama captured an abundant number of both bollworm and budworm moths last week. 2014 may be the year that fieldmen, consultants, and scouts really prove their worth. There is just no way to time the appropriate chemistry at the proper time without someone monitoring insects. This looks like an above average insect year for cotton and we haven’t even reached the primary stink bug window yet. In sweeping for adult plant bugs last week, I was capturing brown stink bugs in about every set of sweeps.

How to Control Spider Mite and Plant Bug Infestations

Additional reports of economic spider mite infestations continue to come in, particularly from central and south Alabama. The heaviest infestations are already causing significant leaf shed in early square cotton. Fieldmen have reported that the lower leaves that show the greatest damage do not always have high mite numbers. Mites will continue to move up the plant to fresher leaves as the older leaves get ready to drop. Fieldmen should look a couple of nodes above the most damaged leaves in order to get a good handle on the number of mites present.

Several materials are recommended for mite control. However, some of these materials only seem to work in some locations. Examples are: bifenthrin, chlorpyriphos, dimethoate and propargite. One product in our 2014 recommendations is no longer on the market – dicofol. That leaves the newer mite chemistry as our best choice for control. These are abamectin (Agri-Mek), extoxazole (Zeal), fenpyroximate (Portal), and spiromesifen (Oberon). Abamectin is the most economical and has been the most widely selected for mite control. Ag suppliers are encouraged to have some on inventory since spider mites appear to be a growing problem.

Plant bugs continue to be reported in cotton that is squaring or approaching bloom. Plant bug immatures are now present in some of our oldest cotton. This indicates that adults deposited eggs a couple of weeks ago. Plant bug eggs are deposited into the stems of the plant in the more rapid growing areas. Therefore TPB eggs are not visible to fieldmen.

Adult plant bugs feed on tiny pin head squares in pre bloom cotton. Therefore pin head square retention is a good survey technique. Adult TPB’s can best be quantified with a sweep net. Once cotton begins to bloom, plant bugs seem to prefer feeding down in the canopy on the older squares. This results in “dirty blooms”. At this point (blooming cotton) a pin head square retention count is not the most reliable survey technique. It is also at this time that we begin to focus on the immature plant bugs instead of just the adults. The best tool for measuring immatures is the drop cloth. Therefore, in normal maturity cotton, we switch from a sweep net to a drop cloth about July 1-10 each season. Early instar nymphs are very small with long antennae and pale green in color. They move about more rapidly on a drop cloth than other insect species that may appear on the drop cloth in July.

The next few weeks should be focused on adult and immature plant bug numbers by fieldmen. While doing plant bug counts, aphids and spider mites can be observed. After July, or about the 3^rd or 4^th week of bloom, our primary focus should be on stink bugs. This would be true for the lower southeastern area of the cotton belt.

Cotton Insect and Pest Contols

We were cruising along last week with cotton insects kinda quiet. Thrips control was winding down on our latest planted cotton. The most prevalent observation was the white margined borrower bug, which could be found in most all fields. They were on cotton with 3 or 4 true leaves up to cotton knee high and squaring.

This week things have changed dramatically. Not to say every field has insect problems. However, in some fields, consultants are finding some level of plant bugs, spider mites, aphids and a few stink bugs. Generally, the older the cotton, the greater the chance some combination of these pests are present.

Let’s take these pests one at a time. Some have observed adult plant bugs feeding in terminals of pre-square cotton. Others report that plant bugs have dropped square retention to below 80% in cotton that will bloom within 7-10 days. A few stink bugs can already be found in these older fields. As we know from previous experience, stink bugs will attack bolls just after the dried bloom drops off if there are no larger bolls to feed on.

Added to these bug problems are the presence of aphids and spider mites. Aphids can be found clustering in the terminals of some plants in fields of older cotton. This is typically the way an economic aphid infestation usually begins. Spider mites have been treated in some fields already. Good results were obtained with Abamectin at 10 oz. per acre. Mites are still on borders of other fields and do not appear to be spreading yet.

With the combinations of pests present, it is difficult to control multiple species without a tank mix combination. My advice to growers, agrifieldmen and consultants would be to narrow your pest spectrum to the two species that offer the most near term damage potential and select a chemical or combination that will control those. It is just too early for me to consider three way tank mix combinations. At this time I believe it would be wise to target plant bugs (and stink bugs) first and I would place aphids second. These species can be controlled with a tank mix of two materials that would be rather inexpensive. A product that will give good control of plant bugs and stink bugs would be my first choice in the tank. If this product does not control aphids, I would add one that did.

This would leave the mite issue unaddressed. I just feel that we need to protect fruit first and deal with stress from spider mites in the weeks ahead.

There are a number of ways to tackle this tank mix issue for bugs and sucking pests. One would be a mix of pyrethroid and imidacloprid. There are too many to mention all at this time. I will be happy to discuss the various options by phone at 334-332-9501 if you are having problems deciding what approach to take.

Good luck and I’ll be back as we observe or hear of other information to pass along.

Updates from June 20, 2014

• Several more reports from diverse areas of the state about adult plant bugs at damaging levels in pin head square and older cotton.
• Plant bugs continue to increase on wild host plants on roadsides and field borders. Both dark (old) adults and immatures present in SE AL.
• Tobacco Budworms foliage feeding on peanuts near Enterprise, AL. Newer chemistry (Belt, Blackhawk, Steward) will be necessary for control.
• Fall armyworm (likely grass strain) feeding on peanuts in southwest AL. Pyrethroids will give excellent control.
• Snails in abundant numbers observed on cotton from Walnut Hill, FL to Columbus, MS. No controls suggested but net sampling for plant bugs difficult.

Final Insect Update of the Season

The Alabama row crop insect control season is rapidly winding down. The few areas that still need attention for a few more weeks are as follows. We need to protect bolls on June planted cotton from stink bug injury until the bolls are approximately 25 days old. We still have plenty of time left in the season to mature small bolls that are present from blooms the last week of August. On soybeans, stink bugs continue to reproduce and feed on pods. Late planted, June to early July, soybeans will be susceptible to stink bug feeding for several more weeks. Stink bug adults will leave other crops when they mature and seek out late planted soybeans as their last host before heading for overwintering sites. I expect to see high numbers of stink bugs in many of these late maturing soybean fields. The good thing is that one application to economic levels of stink bugs in both cotton and soybeans made now should hold populations below damaging levels for the remainder of the season. Stink bug populations currently contain both the brown and southern green species. A high rate of most pyrethroids on soybeans should give adequate suppression. Kudzu bug adults are still present in many soybean fields but they are not as numerous in most fields as they were back a month or so ago. Their numbers seemed to have peaked in April and May planted beans back in the late June to early August window.

Overall 2013 has been a light insect year in Alabama for most species. A summary of what I have observed is the following. For cotton, thrips were moderate to heavy. However, their movement from wild hosts to cotton occurred in May instead of April. Therefore, their damage period coincided with our mid-planting period cotton instead of the earliest planted as happens most seasons. Plant bugs, aphids and spider mites were very light overall. Bollworms and tobacco budworms were low to nonexistent, even in fields of conventional cotton. I have conventional cotton on three research stations spread across the central and southern areas of Alabama. One had to search very hard all season to find a single larva or damaged fruit. Stink bugs were the only cotton insect that occurred at damaging levels in most fields in-season.

In soybeans, Kudzu bugs were extremely heavy in many early planted soybean fields. This was the first year that many soybean growers have had to deal with the Kudzu bug. Others will likely have their first experience in 2014. When all is said and done, I believe we will be able to handle this insect with one, or at most two, well timed sprays. Late maturing beans will likely still see a big buildup of stink bugs in coming weeks as other crops mature and dry down. The foliage feeding complex of green cloverworms, velvetbean caterpillars and soybean loopers have been very light in 2013. This follows the most widespread infestations of the past 40 years last season. Podworms have been very light in soybeans for the past two seasons.

This has been a very unusual year rainfall wise. This may be the only season during my 41 years here as our Extension Entomologist where we had too much rain.

With these comments we will end our in season blogs unless something unusual shows up. I hope my comments have been helpful to those of you that are receiving them. Hopefully we can continue this blog, the Syngenta Insect Hotline, and our tweets during the 2014 season.

Stink Bugs Showing Up in Fields

Based on calls from consultants during the past seven days, most insect attention on cotton in Alabama has now shifted to the stink bug complex. This appears to be the appropriate thing to do since no other widespread destructive insect is being reported and a high number of stink bugs are being reported from all the major row crops. This began with wheat during the spring months. Stink bug numbers later shifted to corn. High numbers have been reported in recent weeks in peanuts, with increasing numbers being reported in both cotton and soybeans.

If we back up and review the situation since the end of the 2012 season, this is as expected. Stink bugs built high numbers on soybeans late last season resulting in a high level entering overwintering sites. This past winter was mild and we did not have the excessive high temperatures or extended drought this spring to limit a 2013 population build up.

This complex included both the brown and the southern green species. In the more southern counties within Alabama, the leaf footed bug is also in the mix. Leaf footed bug damage is identical to stink bug damage to cotton bolls. The important thing here is that, control wise, they are more like the brown stink bug. Phosphide insecticides do a much better job in controlling brown stink bugs and leaf footed bugs than do pyrethroids. Growers will need to keep this in mind as they select their chemical for treatment decisions. In Alabama, escape bollworms on Bollgard and Widestrike cotton varieties have not presented a big enough problem to select a pyrethroid over a phosphate for stink bug control. Field monitoring between July 20 and August 10 will determine if that trend holds true for the 2013 season.

In a few weeks, as we begin to make more stink bug control decisions in soybeans, we will have to work more with the pyrethroid chemistry to suppress the brown stink bugs in the complex. Research trials across the south point to bifenthrin as their superior pyrethroid for brown stink bugs in soybeans. We can improve the percent control by using the higher labeled rates.

Back to cotton, here is how we suggest making treatment decisions. First, select a minimum of 25 ten to twelve day old bolls that are still soft to the touch and can be crushed by hand. Select more bolls from at least two locations from larger fields. Crush these bolls and observe for internal injury. Note, it may make this process faster by first separating the bolls with external feeding signs from those that have none. First, crush the bolls with external feeding only and determine the percent that have internal injury. If a threshold is reached, then the remainder of the bolls with no external feeding signs will not need to be crushed. Internal damage may consist of one or more warts on the inside of the boll wall, damaged seed or stained lint. Second, the decision maker needs to know how long that particular field has been in the blooming stage. Most stink bug injury and loss is coming during weeks three though five or six of bloom. This is the period when most harvestable bolls are being set.

In Alabama, I suggest using a 10% internal damage threshold during weeks three though six of bloom. An insecticide application will usually suppress stink bug numbers for seven to ten days unless a field borders another untreated crop with high numbers of stink bugs. If has been my experience that stink bugs do not move rapidly across fields like plant bugs as they reinfest. The first four to ten rows adjacent to corn or peanuts seem to get most of the migration initially.

In our heaviest stink bugs years, cotton in the coastal plains of the southeast have required up to four applications. Under most conditions however, only two or three sprays may be warranted.

One last thing I will mention today is that, in the past, stink bugs seem to cause more internal boll damage in wet seasons than in dry seasons. That being the case, and unless the weather changes, we need to be extra cautious of stink bug damage to cotton in 2013.

Update for the First Week of July

The Alabama cotton crop is growing rapidly resulting from abundant rainfall from multiple thunderstorms that have occurred during the last 10-14 days.

Insect wise things have been rather quiet on cotton but not the case with soybeans which I will discuss later.

Tarnished plant bug numbers have not increased as rapidly as expected in fields that I have observed. An occasional adult and or nymph can be found, depending on the age of the cotton. Migrating adults went to the earlier planted cotton first and have had time to now produce offspring. Cotton planted on April 10 is now blooming in Autauga County, Alabama.

To my surprise, I’m finding as many adult southern green stink bugs as I am adult plant bugs. We need to begin watching stink bugs in early bloom cotton. As I have stated before, these stink bugs will feed on thumb size bolls as soon as the dried bloom sheds. A huge stink bug population is waiting in corn. These adults will migrate to cotton, soybeans and peanuts as corn begins to dry down. This may be the largest population in corn that I have ever observed. There seems to be mating pairs in every corn plant at our research farms in Shorter and Prattville, Alabama this week. Most are the southern green species with an occasional brown in the mix. That will be to our advantage in a few weeks since the pyrethroid chemistry does a nice job controlling the green species.

The other insect that is building on cotton is aphids. They are clumped in terminals on occasional plants in numerous fields at present. These clumps will spread field wide before natural diseases wipe out the population. I would project that aphid population decline will not occur until around July 20.

The most intense insect pressure at present is Kudzu bug populations on soybeans in select fields throughout the state. Ten to 50 adults and over 200 immatures per plant can be found in many April planted beans. More adult Kudzu bugs are moving into beans from Kudzu daily. Beans will have to be scouted weekly for the remainder of this and future seasons. One to three sprays may be needed to protect beans this season. This will open the door to pod and foliage feeding caterpillars for the remainder of the season.

Information on the management and control of the Kudzu bug in soybeans has been posted in blog entries previous to this one and also on the Alabama Crops website (alabamacrops.com).

Insect and Crop Update for the Week of June 23

After going weeks with light to moderate thrips pressure, damage was heavy on 4-7 leaf cotton in early June, especially in SW Alabama.

Cotton was growing rapidly but thrips damage on true leaves was showing heavy damage from about the 4^th to 7^th true leaf. (Peanuts also were taking heavy damage during this same period.)

The thrips window is over now and we need to shift our focus to spider mites, aphids and the plant bug complex which includes tarnished plant bugs, fleahoppers and an occasional clouded plant bug.

Mites are primarily found in the TN Valley region of North Alabama and some treatments were being applied last week.

I noticed the first aphids on April planted cotton in central Alabama last Friday (June 21).

Plant bug numbers (adults) were down last week but nymphs are beginning to appear in our earliest planted cotton (mid-April). I would suggest using a sweep net to sample adults for the next 2-3 weeks, depending on the age of the cotton. As we approach first bloom I would switch to a drop cloth and concentrate on the presence of immature plant bugs.

Also, field men should now be looking at pinhead square set. Fields surveyed on June 21 were setting about 90% of the fruit. However, some plants had up to 30% square loss at that point. I believe you will find that migrating adult tarnished plant bugs will seek out the earliest planted and most lush cotton fields. My thought is that this cotton provides the best shade from the 95 degree temperatures, and is the best host for plant bugs.

While looking for pinhead square set I noticed a number of white eggs, likely tobacco budworms. They would not be a concern now, but in the old days it would have created a real predicament. Spraying for plant bugs during a budworm moth flight would have been expensive and also put the grower on a treatment treadmill for the remainder of the season. Sometimes we forget how well we have it compared to the pre-Bollgard years.

On another insect – a few stink bugs are already present in cotton. Normally we do not worry about stink bugs until about the third week of bloom, when we have bolls that are 10-12 days old. However, when stink bugs are present at bloom they will attack thumb sized bolls as soon as the bloom tag sheds. Any feeding to bolls this size will cause the boll to abort. Therefore, fieldmen need to be alert for adult stink bugs in early bloom cotton as they monitor for plant bugs with a sweepnet. Stink bugs will not damage squares or blooms but will seek out these first small bolls.

Since some of our corn was planted later than desired, stink bugs will likely remain with that host until the post roasting ear stage when the kernels become hard. At that time we may have a large movement into other crops such as cotton, soybeans and peanuts.

One word about Kudzu bugs on soybeans. Numbers of adults are out of site on many of our April planted beans. In fact, adult numbers are beginning to decrease in some fields now but numerous immatures are present, which is the trigger we use to treat the field. Fieldmen who have not experienced this insect may overlook these immatures when they are small. They will be a clear to greenish color and very small after hatching.

June 2013 Scouting Schools

2013 Alabama Scouting Shortcourses Announced

 

The following cotton scouting shortcourses will be conducted by Auburn Extension staff:

 

June 11: Autaugaville, Alabama, County Ag Center, Highway 14, for central and west Alabama

 

June 12: Headland, Alabama, Wiregrass Research and Extension Center, for southeast Alabama

 

June 18: Belle Mina, Alabama, Tennessee Valley Research and Extension Center, for northern Alabama

 

Cotton and soybean insects (description, recognition, life history and damage), seasonal occurrence, management recommendations and threshold levels will be discussed. Identification and scouting for cotton diseases will also be covered.

 

At the Headland and Belle Mina locations a special section will also focus on managing glyphosphate resistant weeds.

 

Commercial pesticide applicator recertification points will be awarded. Each program begins at 8:30 AM and will conclude after lunch with in-field visits.

 



Plant Bug Surveys in Wild Hosts

Historically, years of abundant spring rainfall resulting in delayed cotton planting have been some of our highest plant bug damage years.

Plant bug damage can be more pronounced when the migration of adults from wild host plants occurs prior to or about the time cotton is setting the first pinhead squares (6^th to 8^th true leaf). One reason for this is that when adult plant bugs feed on pre square cotton they feed in the terminal or growing tip. This feeding can disrupt the physiology of the plant causing abnormal growth (crazy cotton). This abnormal growth can delay fruiting for several weeks.

On May 20, I surveyed one of the primary spring host plants (daisy fleabane) for tarnished plant bugs in Alabama. On that date in Henry County (southeast Alabama) I found that about one-half of the plant bug population was dark (older) adults about ready to migrate to a new host. In past years, cotton is about the only host that is attractive at this time of the spring. Most wild spring hosts are now drying down. The remaining one-half of the population on May 20 were immatures of all stages. This means that the migration to cotton could be extended for a several week period which is common in wet springs.

On May 30, I made a second survey in the same area and found fewer immatures but more light colored younger adults. This may indicate that the older adults have moved to a new host already and some of the immatures are now young adults. I made a second survey on daisy fleabane on May 30 about 80-90 miles farther north than the first one. In this survey I found that they majority of the population was still immature. The fleabane was still greener and fresher at this location which means the plant bug population was in perfect sync with the host plants.

Only time will tell what this means in 2013. However, scouts, consultants and field men should be alert for the presence of adult plant bugs in cotton, and specifically late planted cotton, in the next 10-30 days.

Cotton Growing and Thrip and Grasshopper Treatments

Some of the April planted cotton is finally beginning to grow since the nights have become warmer. April 17 planted cotton at Prattville, AL now has 4-6 true leaves and is about 5 inches high. Thrips pressure is still heavy enough to cause a moderate level of visible injury to true leaves when no foliar insecticide was applied. Most cotton planted in April 2013 definitely needed a foliar spray at the 1-2 true leaf stage. Plants that emerged after May 15 likely will not need this foliar application.

I have had several calls this week about making a combination spray to target thrips and grasshoppers as an over the top herbicide is applied. My comment was positive to do this but realizing that some of the grasshopper population is now adults and will be difficult to control without going to the highest labeled rates of whatever insecticides are applied. I suggest staying with a lower rate and just targeting the thrips and immature grasshoppers.

I will come back in a few days to look ahead at out next potential cotton insect – tarnished plant bug. It has been my experience that wet springs, with delayed planting, have the potential to be bad plant bug years.

Thrips and Cotton Update

A lot of cotton has been planted this week (May 13-17). This is the first time many areas have been dry enough since early April. However, believe it or not, much of central Alabama missed rains in the last weather front and it is already too dry for seed to germinate.

Cotton that has emerged has not made much growth to this point. Cloudy weather, cool nights and a moderate number of thrips has severely hampered seedling growth. Based on my observations from monitoring four thrips research trials, I would suggest that the cooler than normal temperatures, especially at night, has done more to prevent seedling plant growth than has thrips injury.

Thrips numbers have not been abnormally high. In fact, it does not appear that the mass movement of thrips from grains and other wild host plants have occurred yet. Thrips damage is moderate to heavy primarily due to the fact that plants are not growing due to cool nights.

Cotton planted this week (May 13-17) should have better growing conditions and grow off rapidly. If that is the case, thrips injury will be minimal in spite of thrips numbers.

I would suggest that cotton emerging after May 20 will not need a foliar spray to supplement seed treatments. My thrips trials planted on April 10 did not emerge and put on a true leaf until more than 21 days after planting. In this situation, much of the thrips control provided by the seed treatments had dropped considerably before a true leaf even emerged.

The bottom line is that growing conditions, moisture and temperature are more important than thrips numbers or the type of thrips control a grower chooses.



No seed treatment and no foliar spray. Plant date 4/10/13.



Seed treatment and foliar spray. Plant date 4/10/13.



 

Update for the Week of September 9

As we observed and stated last week, soybeans in Alabama are experiencing the most widespread outbreak of foliage feeding insects of the past 41 seasons. This outbreak has been going on for about three weeks or more. However, some growers are just now discovering the situation. This has led to the most calls and questions that Dr. Tim Reed and I have ever received during one week. I will attempt to summarize the questions and what our responses have been.

Most calls begin with – “I have worms in my soybeans, when do I need to treat and what insecticide do I need to use?”

First of all, in most all fields we are dealing with a mix of soybean loopers (SL), velvetbean caterpillars (VBC), and green cloverworms (GCW). Loopers are statewide, VBC are a significant part of the mix in south and central Alabama while GCW are a large part of the mix in northern areas of the state. Loopers are resistant to pyrethroids, Lannate and all of the older chemistry. Since they are part of the mix statewide, we must go to the newer chemistry (in alphabetical order): Belt 3 oz.; Blackhawk (Tracer) 2 oz.; Intrepid 4-8 oz.; or Steward 7 oz. Prices for Belt, Blackhawk and Steward will be somewhere between $15 and $20 per acre. Intrepid will range from about $7 to $14, depending on the rate used. The 4 oz. rate has been what most growers have chosen due to economics. However, where significant foliage loss has already occurred and worm numbers are high, this 4 oz. rate is not adequate. At least 5 or 6 oz. of Intrepid will be needed.

In addition to worms, most all soybean fields have some level of stink bugs present. None of the worm materials will control stink bugs. Therefore, a pyrethroid or acephate (Orthene or generic) at 0.75 lb./ai must be added. This rate of acephate makes pyrethroids the most economic choice. The majority of our stink bugs are the green or southern green species, which pyrethroids control very well.

Now back to what a threshold is on foliage loss. Depending on the stage of beans, our threshold is 20-30% foliage loss. That does not mean that we wait for that level before treating. We treat in advance when we find worm numbers that will give that level of loss. Also, we must allow 4-5 days for products like Intrepid to control the worms. However, foliage consumption will normally end much sooner. Big factors, which are seldom mentioned in discussing foliage loss thresholds in soybeans, are the amount of moisture available to the crop and the reproductive stage of the beans. Soybeans can compensate at a much higher level when soil moisture is available and we have that statewide at present. Also, soybeans will replace lost foliage when they are still in the blooming stage.

How many worms does it take to cause 20-30% foliage loss? In traditional row beans, where a drop cloth can be used, somewhere between 4 and 8 larvae per row foot will give 20-30% foliage loss. The size of the beans is also a variable here. Due to the good moisture in August, many of our beans are waist high and have lots of foliage. Many of our beans in 2012 are drilled. Therefore, a sweep net is needed to get a measure of worm numbers. I suggest taking 10 sweep samples. Some states recommend treatment when about one larva per sweep is found. I have found in 2012 that it takes about 3 or 4 worms per sweep to cause 20-30% foliage loss. Another factor to consider is how long the worm infestation has been ongoing. In fields I have monitored, the answer is three or more weeks. New worms just keep hatching, so where a subthreshold has been present for 15-20 days, much of the lower canopy has already been consumed by the worms. In this situation a 10% foliage loss can turn into a 30-40% loss in 7 days.

In summary, I feel that our Extension educational program on soybean insects has been very inadequate and we promise to do better beginning with winter meetings. However, growers must also do their part in managing insects in soybeans, especially when they are worth $17-18 per bushel. We do not know what level of insect pressure 2013 will present, but if we plan to stay on top of the insect situation, soybeans will need to be monitored by a trained or experienced person at least weekly during the season, just like we have done in cotton for the last 60 years.

Update for Week of August 26

The cotton insect control season is basically over. I say that realizing that there are a few late maturing fields within the state that may still need a stink bug spray. There are even fewer fields that have high numbers of tarnished and clouded plant bugs present. Where growers are attempting to make a top crop, in fields that have exceptional yield potential, plant bug controls may still be applied. Our greatest concern now in cotton is boll rot and disease. The past few days of overcast skies and rain showers have increased boll rot. The next weeks forecast is much the same. Other than a few southwestern counties, the state was spared from the excessive rainfall from Isaac.

At present, the insect action is primarily happening in soybeans and to a limited degree in peanuts. The lep feeders are occurring on soybeans state wide. We have more soybean loopers on beans in the Tennessee Valley area of North Alabama than I can ever remember. This complex also includes the green cloverworm statewide and the velvetbean caterpillar as far north as Selma and Montgomery in central Alabama.

Loopers, (all are the soybean looper, more difficult to control) are occurring at 1 to 8 or more per sweep. Most of our beans are drill so we cannot use a drop cloth. Our threshold experience with loopers using drop cloths is well established at 5-8 per row foot. We are wrestling with a sweep net threshold. Two loopers per sweep are not causing more than 5% foliage loss while 8 per sweep is causing 30-35% foliage loss. Our threshold is 20% foliage loss with beans at the stage they are now. So somewhere between 2 and 8 loopers per sweep is a treatable level. Based on my field observations I would treat in the neighborhood of four loopers per sweep.

Stink bugs are increasing in beans and will likely continue to do so in the days ahead. Therefore, in many fields a stink bug material (pyrethroid) or acephate (Orthene) may need to be added as we treat for loopers with the recommended insecticides of Tracer (Blackhawk), Intrepid, Steward or Belt.

One or more soybean fields in Southwest Alabama are infested with the garden fleahopper at damaging levels. This is a first for this insect on soybeans. They occurred on peanuts in that area a couple of weeks ago.

Some peanut fields are also infested with this mix of caterpillar pests. In this mix we are also finding fall armyworms, southern armyworms, corn earworms, cutworms, yellow striped armyworms and immature burrowing bugs.

Both soybeans and peanuts need to be scouted weekly for the remainder of this season and future seasons. The old method of spraying an insecticide on soybeans or peanuts when fungicides are applied is really just a stab in the dark. The odds of this being good timing for insect control is somewhere between slim and none. With the price of beans we have to do a better job with insect control than automatic sprays based on the stage of the beans.

Most of our comments in the next week or so will be directed towards soybeans and peanuts.

Update for the Week of August 12

Last week was rather quiet insect wise on cotton. Many areas received thunderstorms throughout the past 7 days. The comments that I will make today are based on observations made in the field from several different areas of the state last week.

The first point is when to back off of stink bug controls. Our early April cotton is beyond the eighth or ninth week of bloom with few to no 10-12 day old bolls remaining. In fact, my test plots of PHY 375 planted April 9 had several open bolls per plant early last week. Even with cotton that still has a few 10-12 day old bolls remaining, stink bug numbers are so low in most fields that a stink bug threshold could never be reached. I would not be concerned at all with 10-20% internal damage as cotton is maturing out and beginning to open. For those who would be spraying with ground equipment, and that would consist of the majority of growers in Alabama, a ground rig going through mature cotton would destroy far more good bolls than the few smaller bolls near the top of the plant that stink bugs might injure.

Spider mites populations held steady last week but did not seem to increase, likely due to the frequent thunderstorm occurrence. I would just keep an eye on them and delay treatment decision as long as the current weather pattern holds.

One of the heaviest tobacco budworm flights seen in several years has been ongoing in the southern counties. Moths, eggs, and small larvae have occurred in high numbers from Dothan in the southeast to Fairhope in the southwest. This will have no impact on cotton with Bollgard or WideStrike technology. However, conventional varieties are a different story. I was in research plots of conventional cotton with no insect technology at Fairhope, AL on August 7 and found 32% worm square damage with 9% of the squares containing live larvae. Who says the technology has less value than it once did? In the old days, what would we do under this level of pressure, with thunderstorms occurring every afternoon?

Growers that may be impacted by this budworm pressure are soybean and peanut producers. If these crops are infested with budworms then the newer chemistry will be required because pyrethroids would not perform at all.

Chemical choices would be, in alphabetical order: Belt, Steward, or Tracer and possibly Lannate. Some might include Intrepid with this group but I do not know how effective it would be on budworms. Peanut growers should monitor their fields closely for the next 7 to 10 days for budworm numbers. New growers applying a fungicide to soybeans should not automatically add a pyrethroid for insurance purposes. If an insecticide is added in a preventative mode, I would suggest Dimilin at 2 oz. for future foliage feeders.

One other soybean pest that I will mention in closing is soybean loopers. Most soybean fields have a few green cloverworms or an occasional looper. However, one field in Baldwin County was observed last week with about 10 loopers per foot with about 10-15% foliage loss already. Therefore, all fields are not alike and must be scouted to stay on top of the soybean insects.

Corynespora Leaf Spot

In those areas that have gotten good rain or are irrigated, Corynespora leaf spot has become an issue in cotton.  Much of the cotton acreage in Baldwin Co, an area that has gotten good rain, has been treated at least once with either Twinline or Headline fungicides.  While Phytogen varieties, which previously were shown to be susceptible to Corynespora leaf spot, have been damage, this disease is also a threat to defoliate other cotton varieties as well.

While it’s getting late, producers and consultants should be advised to check cotton for symptoms of Corynespora leaf spot as they scout weekly for insect pests.  Labels for both Twinline and Headline specify that the first fungicide application may be made when first symptoms appear in the lower leaf canopy.  Dryland or irrigated cotton with a 2+ bale/A yield potential that’s getting good rain should be targeted for treatment with a fungicide.

In research trials at outlying units, noticeable disease development has been seen in fungicide trials in dryland cotton at the Gulf Coast Research and Extension Center and irrigated cotton at the Plant Breeding Unit.  At GCREC, heavier leaf spotting was noted in Phytogen 499 as compared with DPL 1050, which suffered only light disease development.   In the PBU study, noticeable leaf spotting with some (10%) defoliation was noted in Phytogen 499, while some spotting on the lowest leaves was found in DPL 1050.  Hard to tell in both trials whether or not the single application of Headline has had much impact on disease spread.  My intention is to evaluate disease development in cotton variety trials at both of those locations as well as Wiregrass Research and Extension Center sometime in the next week.   In the good looking dryland fungicide and variety trials at the Field Crops unit at EV Smith, disease development is minimal.  So, frequent showers or irrigation appears to be a critical trigger for disease development and spread.  If you want to look at trials at the outlying units, get an outline from the station superintendent.

I have also seen minor leaf spotting caused by Stemphylium and Alternaria fungi in cotton.  Leaf spotting attributed to these fungi are associated with a potash deficiency.   Individual leaf spot lesions are much smaller when compared with Corynespora leaf spot.  On Phytogen 499, the target or zonate pattern leaf spots associated with Cercospora leaf spot have a diameter of up to ¾ inches and are circular compared with the unevenly shaped, and much smaller Stemphylium or Alternaria leaf spots.

If you have any questions with the diagnosis of this disease, send a sample overnight fedex or UPS to the Plant Diagnostic Laboratory, S Donahue Dr., Auburn University, AL 36849.

By: Austin Hagan