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.

Insect and Weather Update for the week of July 9th 2012

The past 10 days have been characterized by heat, drought, scattered thunderstorms, aphids, and in some cases spider mite decisions. Some areas have received one or more rainfall events of 1 to 3 inches or more while others are still suffering extreme drought. Some of these storms have brought high winds, downed trees, demolished buildings and hail.

Insects have been rather quiet overall. Many field men have made aphid treatment decisions with significant acres treated. In at least one incidence, both aphids and mites were at treatment levels. Other more sporadic fields have needed adult tarnished plant bug controls. In the majority of cases the plant bug population has now shifted to immatures. In these cases field men need to switch from sweep nets to drop cloths to quantify these immature plant bugs. Two or three immatures per drop could be considered a threshold level requiring treatments, especially if “dirty” blooms are present. Pinhead square retention is no longer the best way to look for plant bug damage since they spend more time down in the canopy feeding on larger squares (which later become dirty blooms).

I have not had any calls yet, but field men in the southern areas of the state need to pay attention to stink bugs since our oldest fields are now at week three, four or more of bloom. Weeks three through six of bloom is when stink bugs are most damaging. A good threshold for treatment during this period is 10-15% internal damage to quarter diameter (still soft) 10-12 day old bolls. Look for brown areas near the seed  and warts on the inside boll wall where stink bugs have penetrated in search of a protection source in the form of developing seed. If the population of stink bugs is primarily the southern green species then we have choices of both pyrethroid and phosphates. However, as most likely the case, the population may be predominately brown stink bugs. Here we would need a phosphate such as Bidrin or either a high rate of bifenthrin and get decent suppression.

Reports were just received of an increase of small larvae on peanuts in south-central Alabama. My guess would be that they are tobacco budworms. By July 15, newly hatched larvae will more likely be corn earworms.

Current Insects in Cotton at Economic Levels

Today I would like to discuss three insects that are occurring in cotton at economic levels in certain fields. Two of these insects are actually impacting other crops, particularly soybeans and peanuts, as well.

Adult tarnished plant bugs (TPB’s) are being reported at moderate to high levels in some fields statewide. More findings are reported each day and there are likely many fields where they are present but have not been observed yet. At this point, no one has reported high pinhead square loss. This square loss is what we like to base our treatment decisions on. However, based on past experiences, once the adult TPB’s are present it is just a matter of time until some level of square loss is detected. These are all migratory adults that have moved into cotton from wild hosts. They will feed on pinhead squares, which cause abortion, and also deposit eggs in the plant stems. These eggs will hatch in two plus weeks into an immature field generation. The longer the period that adults are allowed to roam in fields, the longer the period of hatching immatures will be in coming weeks. Knowing this, growers can make their own decision as to when controls should be applied.

The second insect I will mention is the tobacco budworm (TBW). An extended flight of budworms has been ongoing in various areas for about two weeks already. This is of no significance to 98% of the states acreage that is planted to Bollgard II or WideStrike varieties. However, this makes a tricky situation in conventional cotton that may need plant bug sprays during this TBW period. This TBW flight is also impacting later planted peanuts that have a limited amount of vegetative growth. Budworm moths seem to be attracted to peanuts with a vegetative width of 3-4 inches. Earlier peanuts that have six of more inch vegetative width do not appear to have as many budworms present. We collected about 250 quarter inch budworms yesterday at Headland, Alabama on about 600 row feet. This was not what I would consider an economic or treatable level. However, up to four budworms per row foot have been reported in some fields and controls, with the newer chemistry, have been applied.

The third insect that is causing widespread concern in cotton at present is the three-cornered alfalfa hopper (3CAH). Numerous fields in the Tennessee Valley area of northern Alabama have had damaging levels of 3CAH reported. This problem has extended as far south as Talladega County. Treatments have been applied. Soybeans are also experiencing a problem with this insect, even more so than cotton, and over a much larger geographical area. 3CAH damage is caused by the girdling of the main stem of both cotton and soybeans by both the adult and immature 3CAH. No good thresholds exist from Alabama research. Usually this problem and damage is greater on field borders but consultants have reported damage field wide in both cotton and soybeans. Treatment thresholds are difficult to develop for 3CAH, just as they are for grasshoppers. Treatments sometimes have to be made based on the risk that certain species present, and not the level of damage observed. Sweep nets are very effective in documenting the number of 3CAH per row foot.

Tobacco Budworms in Early Season

A tobacco budworm moth flight this week resulted in eggs being deposited in cotton terminals as far north as Prattville, Alabama. On June 5^th, about 40 budworms were collected from 100 tobacco plants at Prattville. All plants had feeding signs but parasites and predators were working on the population. Budworm feeding was also noted on tobacco planted as a sentinel crop at Headland, Alabama yesterday (June 7^th).

A call was received a few minutes ago about what is believed to be budworm larvae on peanuts from the Covington County Alabama-Florida panhandle area. These peanuts were young and had a limited amount of foliage with up to four budworm larvae (3-7 days old) per row foot. This same situation occurred about 3-4 years ago where budworms defoliated some fields of peanuts in June. At this early stage of the season, controls may be necessary due to the limited amount of vegetative growth of the peanuts.

Tarnished Plant Bugs Found

A significant level of adult tarnished plant bugs was found this morning (June 4^th) in nine true leaf cotton in Autauga County Alabama. Levels of up to five adults per 100 plants were reported. No pin head square loss was observed but it is likely just a matter of time until damage is observed. Controls are planned.

In addition to these tarnished plant bugs, eggs, most likely tobacco budworms, were also reported.

Overview of 2011 Cotton Insect Season

Early Season Pests
Thrips were extremely heavy from about April 15 to May 20. A major contributor to this heavy migration of thrips from wild hosts and wheat into cotton was the extreme drought conditions and absence of rainfall events during this period.

Plant Bugs
One peak movement of adult TPB into cotton occurred between June 20 and July 1. The majority of this infestation only happened in the earlier planted fields (most mature cotton). One insecticide application was targeted to these adult TPB’s when they were detected. Few immatures were detected in these fields in the coming weeks, so no in-field generation occurred. This may have been influenced by the extreme temperatures that occurred during this period (98-102⁰F).

Bollworm
Subeconomic numbers of bollworms occurred over an extended period from about July 15 to August 10. Few fields ever reached treatment threshold. 2011 was like the lowest bollworm pressure year on record. End-of-season damage boll counts on untreated genetic cotton were less than one boll per 10 feet.

Tobacco Budworm
Budworm numbers were non-detectable to extremely light all season long. Budworm larvae were too low to detect on conventional cotton and even on attractive crops such as tobacco when used as a sentinel crop.

Aphids
Aphid numbers were very slow to build in 2011 but also slow to crash due to naturally occurring diseases. The fungal disease was slow to develop which left aphids in the system much later than normal. Aphids normally peak and crash prior to, or at, the early boll set stage but this did not happen in 2011. Also, observations indicated a resurgence of aphids in the mid canopy area of the plants in late season as opposed to the terminal area.

Stink Bugs
Stink bugs in 2011 were fewest in number and damage of any year since the boll weevil was eradicated. This was likely due to the colder than normal winter temperature effect on the southern green species and the extreme spring heat and drought effect on the brown species. The majority of the few stink bugs observed in 2011 was the brown species.

Fall Armyworms
The “rice or grass” strain of the fall armyworm was abundant over much of the season in pastures, hay, and grasses. This strain will feed on peanuts but not on corn or cotton. They are easy to control on pastures with pyrethroids and numerous other labeled agricultural insecticides.

Aphid numbers continue to build, while most insects numbers remain at moderate levels

Insect conditions have not changed greatly in the past week or so. Aphids have continued to build in more fields. All other insects are low to moderate levels (mostly sub-threshold). These include plant bugs (including a few clouded plant bugs coming into the mix), bollworms, tobacco budworms and stink bugs. Most growers do not have enough of a single species to apply controls for. The two biggest surprises at this point in the season are the low number of bollworms and the low number of stink bugs in most fields. Numerous fields of conventional cotton still have less than 2 bollworms per 100 plants. Boll damage to stink bugs is less than 10% in most fields.

Most of the state has had abundant thunderstorms for several consecutive weeks. Cotton yield prospects have improved greatly and, if conditions continue, numerous fields have two bale plus potential. The two biggest limitations we now have are fields with “skippy” stands and too much late maturing cotton.

Insect Complex Developing

Several fields were surveyed yesterday (7/6/2010) in central Alabama. My findings were as follows: aphids continue to be low to non-detectable in many fields; drop cloth samples yielded early instar immature plant bugs, and an occasional fleahopper, frequent adult clouded plant bugs, and adult brown stink bugs. All of these were at non-treatable levels at the present. However, as each day and each week passes the bug complex will become more abundant and damaging to the point that the entire complex will require controls. I would key on damage to the thumb sized bolls (until quarter diameter bolls are present) for stink bug decision and to a combination of dirty blooms and the number of immature plant bugs per row foot for that species.

I would advise field surveyors to begin switching from a sweep net to the drop cloth as cotton begins to bloom. The majority of the plant bug population for the next couple of weeks will be immatures that have hatched from eggs deposited by migrating adults during the month of June.

The large tobacco budworm flight has not reached southeast Alabama yet. I will be in southeastern Alabama tomorrow and will observe for moths, eggs, and small larvae at that time.

Calls received this week have centered on what to use for a complex of aphids, plant bugs and brown stink bugs. No one chemical would be the top choice for this complex. A pre-mix or a tank mix of two chemical classes would likely give the most effective control of this complex.

Tobacco Budworm Moth Flight

Another significant insect event is now occurring in extreme southwestern Georgia. Consultants yesterday were reporting a very heavy tobacco budworm moth flight with eggs on most every plant. This event means nothing to growers who have planted Bollgard or WideStrike varieties. However, to those with fields planted to conventional varieties, it is a different predicament. On the one hand they have adult stink bugs and hatching immature plant bugs, while on the other they need beneficials to be present during this upcoming budworm flight. This budworm moth activity will likely extend across southern counties of Alabama during the next 10 days, and may even reach the central Alabama area. Tobacco plants, grown as a sentinel crop in Prattville, AL had budworms from the previous generation of budworms. The budworm egg lay on tobacco at Headland, (southeast Alabama) continued from Memorial Day in May until about June 20. It will be difficult to advise growers with conventional cotton during the first weeks of July. They just need to realize that most worms will be budworm species and pyrethroids will not give worm control during this window of the season.

Spider mites, tarnished plant bugs, tobacco budworms, stink bugs, and yellow striped armyworms observed

Cotton 6/21/2010 - Spider mites were reported infesting select fields in Talladega county today. This is the second call I have had concerning mites on cotton in the past week. This problem could spread in coming weeks with the hot weather. Thunderstorms rumbled through parts of the state on Saturday. But, some areas remain dry with intense heat.

I have received no new reports of tarnished plant bug (TPB) activity. Hopefully, this heavy migration from wild hosts will be of short duration. Fields that were treated for TPBs in southwest Alabama are clean this week with high square retention. Unsprayed fields have some level of plant bugs left but they do not appear to be causing greater than 20% square loss.

Today, I collected early instar tobacco budworm larvae from tobacco at the Gulf Coast Research Center. Tobacco is being used as a sentinel crop at three sites to monitor budworm activity (Prattville, Fairhope, and Headland, AL). Based on observations, it appears that some level of budworm egg lay has been going on for two or more weeks. Growers with conventional cotton should be very selective in spraying for any other insect during this budworm flight. Keep beneficials in conventional cotton as long as possible. Hopefully, up to July 15 in central Alabama and July 20 in central Alabama.

One insect that may make it difficult to leave uncontrolled after the first week of bloom is the stink bug. Numerous brown stink bugs (BSB) can be found in many fields at present. They will not damage pre-bloom cotton but as soon as the bloom drops they will attack the thumb sized boll causing abortion from the plant. I am seeing a level of BSBs that will require controls in many fields by the second week of bloom. It does not appear that these BSB are moving to corn or other hosts, but instead are just waiting for the first small bolls. In fact, when those in corn begin looking for a new home, we likely will have many move into cotton.

Yellow striped armyworms, in low numbers, were observed in numerous BGII fields in Monroe county today.

On other crops - tobacco budworms, fall armyworms and yellow striped armyworms were reported feeding as foliage feeders on peanuts in Monroe county (southwest AL) today. Numbers were low (one per 4-5 row feet) in many fields but a few fields had numbers approaching concern and will be watched closely during the next 7-10 days. The average peanut field has about six inches of foliage at this time.