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.

Early August Insect Update

It has been a number of days since we last reported on Alabama insects. So what has been happening? First of all, August has been dominated early-on with little insect activity other than the bug complex in cotton. Second has been the weather, we had sun yesterday, August 19, for the first time in about 10 days. During this period, rainfall has been measured in inches varying from low single figures to double digits, depending on the location. Up to 4 inches in a 24 hour period has been common. This has resulted in bridges and roadways being washed out and public schools closing during the beginning of the fall term. Agriculturally wise, sprayers have been unable to get into fields and aerial applicators are over booked. Fortunately, insects have overall been low with just a few exceptions. The bug complex has been over threshold in many but not all cotton fields. In the past few days the caterpillar complex has built to damaging levels in soybeans. Some fields have been sprayed by plane for the lep complex, primarily loopers and velvetbean caterpillars. The heaviest infested fields are those where growers just preventatively added a pyrethroid when they were applying a fungicide.

It has been my experience in research plots that an application of a pyrethroid just prior to an infestation of foliage feeding caterpillars is like throwing gasoline on a fire. We usually see much higher numbers of soybean loopers where a pyrethroid application has been made within the previous 10-14 days. My advice to growers is that if they feel they must add something to their fungicide, just add 2 or 3 ounces of a product like Dimilin which does not disrupt the beneficial insects.

Once we have a damaging level of foliage feeders the first thing we need to do is to quantify the species present and the numbers. Five to seven caterpillars per foot of row will usually result in 30% or more foliage loss and therefore require controls. Treatment thresholds for sweep nets on drill beans are not quite as well defined. However, 2 to 5 per sweep would likely require controls. As to species, velvetbean, green cloverworms, corn earworms (podworms) and stink bugs can all be controlled with a pyrethroid. However, if many soybean loopers are in the mix, then one of the newer lep materials will be required. These are, in chemical alphabetical order: Belt, at 2-3 oz.; Steward at 7 oz.; Intrepid at 4-6 oz.; Prevathon at 18-20 oz.; tracer or Blackhawk at 1.5-2 oz. per acre.

One additional thing should be added about soybean looper control, especially if application is by air. Looper eggs are deposited on the lower leaves of the plant, therefore they infest the plant deep within the canopy. As the larvae mature they feed upward through the canopy. In order for any of the newer chemistry to be effective, the leaf containing the droplet has to be eaten. Therefore, it may take several days to fully suppress a looper population. It has been my experience that the surviving  larvae behind application will be early instar larvae found lower in the canopy. Most of these looper insecticides are very rainfast and have long residual on the leaves, so don’t panic if you see a few small loopers behind an application.

I will be on research farms for the next several days and will get back soon if we see or hear of damaging levels of insects developing.

Soybean Loopers Threaten Alabama's Soybean Yields

Soybean loopers became an economic threat to soybean growers in Baldwin County (on the Gulf  Coast) this year during the first week of August. Soybean loopers were treated in many Blackbelt (west central Alabama) soybean fields this week as looper numbers increased and defoliation levels rose. Now farmers on both sides of the Tennessee River are preparing to spray numerous soybean fields for this pest for the first time since 1988. Densities of soybean loopers at the Fairhope Research station across the bay from Mobile were an average of 8 per sweep (all sizes) in test plots that were averaging an estimated 10 to 15% defoliation when an insecticide was applied on August 7. Eight days later defoliation in untreated plots ranged from 25 to 40%. Farmers in the Tennessee Valley have found as many as 3 loopers per sweep this week and defoliation levels are steadily heading toward the 20% threshold level in many fields.  Farmers in north Alabama west of I-65 are watching the weather hoping that they can find  an opportune time to spray the loopers during  a projected 5 day period of scattered showers. Most of the soybeans in the Tennessee Valley were planted behind wheat and yield potential is good presently. These later planted soybeans are mostly in the R4 to R5 stage of development and need another good rain to produce a strong yield.  One such field that is being monitored in Franklin county was running one looper per sweep on August 25 and had 5% defoliation. This field had 2 loopers per sweep (all sizes) on August 30 and 10% defoliation.  A few loopers had pupated in the field and had attached themselves with silk to the undersides of leaves. No diseased worms were observed while sampling. Stink bugs are also present in these fields but numbers are mostly below the threshold of 2 per 15 sweeps from bloom to mid-pod fill and 3 per 15 sweeps after mid-pod. Three-cornered alfalfa hopper (3-CAH) numbers are usually running from less than one to two per sweep .  Pod worm numbers are very low in most fields. Chemicals currently listed in the Extension Soybean IPM guide for soybean looper control are Belt 4SC, Intrepid 2F, Steward 1.25 SC and Tracer 4 SC. None of these products will control stink bugs or 3CAH’s. Belt, Steward and Tracer are labeled for control of pod worms in soybean. Hopefully, one application will be sufficient this year to manage soybean loopers but growers should continue to monitor fields following looper sprays to insure that populations do not rebound.

By: Tim Reed- Extension Entomologist and Ron Smith- Entomologist and Professor Emeritus

Update for the Week of August 19

Our April-planted cotton is beginning to open, and has varying levels of boll rot due to the weather the past 7-14 days. This same weather pattern of frequent thunderstorms and overcast conditions has been ideal for the spread of leaf spot diseases in out late planted cotton.

Insects have been light-to-nonexistent in recent days. There are a few plant bugs present and stink bug numbers have increased in some fields. I am not sure if either are at damaging levels, especially the plant bugs.

I believe we could safely say that leaf spot diseases are potentially more important than insects for the remainder of the season.

Growers who have peanuts or soybeans should monitor these crops carefully for the remainder of the season. Peanuts are attractive to a number of foliage feeding insects – including loopers, fall armyworms, bollworms, budworms, green cloverworms, velvet bean caterpillars and cutworms. Two peanut fields in Monroe County were identified last week with a high infestation of the garden fleahopper. To my knowledge this is the first time for this insect on peanuts. I am not sure what kind of damage potential they present. However, in cotton this pest can cause extensive foliage damage by leaving all leaves with stippling type feeling.

This same type of damage in peanuts would seem to be just as economic as a foliar disease.

Soybeans would be susceptible to damage from all the leps mentioned under peanuts plus the pod feeders – podworms and stink bugs. Many of our beans are late, planted behind wheat, and were just in full bloom the past 10 days. These beans will be susceptible to insect injury for weeks ahead. Only by scouting will growers know when economic insect losses are occurring and when controls are needed. We already have some fields in Baldwin County with damaging levels of soybean loopers. Foliage loss was as high as 35% last week when I made surveys in that area. Soybeans will be the last crop that stink bugs are attracted to this season. Even though it has been a light stink bug season, if they all accumulate in soybeans late season, controls will likely be needed.

I have heard little from the Kudzu bug on soybeans after finding them in the northeast counties of Cherokee and Cleburne back in July. Follow up surveys are needed in that area whenever time permits.

As the season winds down we will get back with further updates as new information becomes available and the situation changes.

Soybean Insect Pest Update

Fall armyworms have been reported infesting pastures across Alabama and last week this pest was found feeding on soybeans in Lawrence County in the Town Creek area. These fall armyworms appeared to have moved from a bermudagrass pasture and crossed a wooded area to reach the soybeans. The caterpillars were feeding on the soybean foliage in the portion of the soybean field adjacent to the woods. Since this report from last week, fall armyworms and yellow striped armyworms have been found in many soybean fields in North Alabama at densities as high as 3 to 4 per 15 sweeps. Since theses armyworms have been found across the R2 to R6 soybeans, it is likely that these worms were derived from eggs deposited in the fields by moths. Only a very limited number of soybean fields have been treated strictly for foliage feeders in Alabama thus far---but numbers of green clover worms are increasing in north Alabama and velvetbean caterpillar numbers are increasing in south Alabama as far north as Monroe county. The economic threshold for foliage feeding caterpillars from pod set to maturity is as follows: Prevent greater than 20-percent leaf  loss. Treat prior to 20-percent leaf loss when five to eight foliage feeding caterpillars (soybean loopers, armyworms, green clover worms, velvetbean caterpillars)  0.25 inch long or longer, are present per foot of row.

Treat when you catch an average of 1.5 foliage feeding worms per sweep. Soybean loopers are harder to dislodge with a sweep net and each looper should be counted twice. Each larva eats a high percentage of the total amount of foliage it consumes during the last 4 to 5 days of the larval cycle. If disease is present in the population growers may wish to delay application  for 2 to 3 days, especially if larvae are less than a half inch long and populations are not much above the minimal threshold. Both fungal and viral disease can wipe out a caterpillar infestation within a week under the right conditions. Podworm and stink bug numbers have been below threshold levels thus far in the vast majority of soybean fields.  However soybeans planted behind wheat could see increasing populations of these two pests as we enter the pod-fill stage.  Three-cornered alfalfa hopper (3CAH) numbers are variable (usually less than 2 per sweep) but numbers in most untreated fields are increasing.  Some growers who applied a fungicide to their soybeans have also included an insecticide to reduce 3CAH numbers.  As soybeans mature we will see more fields with multiple insect pest species present.  At times there will be 2 or more species at densities which are just below treatment threshold levels. It can be difficult to make a treatment decision in this situation.  If you need assistance in making a soybean treatment decision you can call me at 256-627-3450.

By: Tim Reed

Pest Update

The dominant factor in cotton the past one to three weeks has been the drought and heat. The weather has impacted both the crop directly and management decisions for insects. Some localized areas received rainfall on July 1 or 2. However, most cotton remains under stress from lack of moisture.

Aphids are the insect of primary concern since populations have built in many fields, putting additional stress on plants. Most growers delayed treatment decisions for aphids until this week – waiting for either rainfall or natural diseases. However, many are wisely spraying for aphids this week.

In some fields plant bugs are also present. Adults have diminished statewide but immatures have begun to emerge in many fields. I have also noted the presence of fleahoppers (both adults and nymphs) and clouded plant bugs in the mix. Field men have reported a large increase of bollworm moths in southwest Alabama fields this week.

Another significant even in row crop insects occurred during the past week. Kudzu bugs were observed feeding on soybeans in numerous fields in Cherokee County and in other fields in north Cleburne County and near Collinsville in Dekalb County. This pest has the potential to dramatically impact soybean production in Alabama as it already has in Georgia, South Carolina and North Carolina. First of all, soybeans will need to now be “scouted” as cotton has been since the late 1950’s. Mid-season (July) sprays will likely be required which will open the door for greater problems with podworms. Additional later sprays for the Kudzu bug will also be necessary. We will talk later about scouting techniques, thresholds and the selection on appropriate chemistry.

Soybeans

A sub-threshold level of several caterpillar species can be found in most fields statewide. These include green cloverworms, soybean loopers, podworms, fall armyworms, and in the southern areas of the state, velvetbean caterpillars.

If the fall armyworms should occur at treatable levels, growers need to know that they are likely the “grass” strain which can be controlled rather economically with pyrethroids, Intrepid or Dimilin.

Stink bugs, especially the brown species, are at treatable levels in some bean fields. Growers should remember that stink bugs affect the quality of beans more so than the yield. Where brown stink bugs are the primary target, I would suggest a high rate of one of the labeled pyrethroids. These include: Baythroid XL, Brigade (Discipline), Prolex, Karate Z, or Mustang Max. Several of these have multiple generic brand names.