Monday, August 30, 2010

Soybean Loopers Occurring over the Southeast

Soybean loopers are the dominant caterpillar species occurring over a multi state area of the southeastern United States. Several states, including Arkansas, Georgia and the Carolinas are all experiencing looper outbreaks. I observed my first soybean field with treatable levels of loopers in Baldwin county on 8/26. Based on what is happening over a large area, Alabama growers need to be very alert for looper outbreaks.

Soybean loopers may occur at damaging levels in soybeans, peanuts, or late maturing cotton fields. Looper eggs are deposited on the underside of leaves in the lower part of the crop canopy. The tiny, hair like, early instar larvae can go undetected for several days. As they mature they move up the plant canopy with their defoliation. Therefore, the foliage loss is often unnoticeable for a week or more. A high percent of the total foliage consumed is during the last 3-4 days of the larval cycle. I have always considered somewhere between 5 and 8 larvae per row foot as an economic level. The amount of canopy available in a crop like soybeans would have some bearing on the economic threshold. I will have to depend on my entomology friends to set a sweep net threshold for drill soybeans. I’ll be checking around for that threshold since late planted drill beans behind wheat may be at the greatest risk.

Insecticides that work well on soybean looper are: Steward, Intrepid, Tracer, and recently labeled Belt. Both Diamond and Dimilin (Insect Growth Regulators) also give adequate to good suppression. Products like pyrethroids, Lannate, Larvin, Sevin, Lorsban and methyl parathion do not give measurable control of soybean loopers in Alabama.

Wednesday, August 25, 2010


Many fields are beginning to open and the plants have few developing bolls near the terminal. Therefore, insects are of little concern. The extreme heat coupled with drought a few weeks back took care of our top crop. Late maturing fields that caught a scattered thunderstorm should be watched for stink bugs until the last bolls we expect to harvest are 20-25 days old. Several growers have expressed concern about the number of hard locked lower bolls due to boll rot. What began as a promising cotton crop has turned into a below average yield potential for the state as a whole. The southwestern region of the state had the best rainfall pattern and will likely have the best yields.


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.


Many of the same caterpillar species found in soybeans are also at sub-economic levels in peanuts. The one exception is fall armyworm. Another “flush”, about 20-30 small larvae per row foot, was found in peanuts near Shorter, AL (Macon county) yesterday (August 24). These armyworms do not always occur in all fields on a given farm. The same products – pyrethroids, Intrepid and Dimilin also provide good control of fall armyworms in peanuts. The quickest kill will come from pyrethroids while the longest residual will come from Intrepid and Dimilin.

Recent Field Tours

More than 100 growers, ag suppliers and related agencies were in attendance at a recent Field Day. The 34th annual East Central Tour was held on August 13th. This tour began 34 years ago primarily to view the “magic” cotton insect control obtained with Ambush, Pounce and Pydrin pyrethroids. They provided better control than anything that generation of growers had ever observed.
The annual Wiregrass Research Farm field day was held on August 20th. The latest research results on peanuts, cotton, corn and soybeans were presented.

Twin Link Field Day

I had the opportunity to participate in the Bayer Twin Link dual-Bt technology field tour near Blackville, SC, on August 23rd. Research on this technology was observed on the Clemson Edisto Research and Education Center and on the Carolina Ag Research farm (Dr. Mike McCarty). Both locations have had some of the highest bollworm pressure I have ever observed. Untreated conventional cotton had 100% boll damage and some foliage loss to bollworms. The Bayer Twin Link Bt technology did not give perfect control under this level of pressure but showed impressive results.

Monday, August 16, 2010

Insect Blog 8-16-10

Weather- Temperatures remain high 90-95 degrees Fahrenheit and rainfall extremely scattered statewide, as of today (8/16). Hay, pastures, peanuts and soybeans in many areas would profit greatly from rainfall. Most cotton fields are beyond benefit from water.
Fall Armyworms- Populations continue in hay, pastures and peanuts. However, in many south Alabama locations the previous generation has cycled out. Another generation may be possible 2-3 weeks ahead.
Tobacco Budworms- An extremely heavy moth flight and egg lay was observed on cotton in Seminole County, GA on 8/11. Only late planted conventional cotton will be at risk from this pest. However, it might be noted that budworms are now infesting soybeans in sizable numbers in some southern locations.
Podworms/Soybeans- Soybean growers should be very alert for corn earworm infestations on beans that are anywhere from R1-R7 (blooming to filled pods that are still green).
Bean Leaf Beetles/Soybeans- Several Tennessee Valley fields have subeconomic levels of bean leaf beetles in soybeans.
Lesser Corn Stalk Borer/Peanuts- Dr. Ayanava Majumdar, Extension peanut entomologist, has issued a high alert for LCSB in peanuts based on a sharp increase in moth numbers captured in traps. Counties in extreme southeastern Alabama are also very hot and dry, which is ideal weather for LCSB outbreaks.
New Registration (Belt)- Belt insecticide, marketed by Bayer, received registration on soybeans on 8/12. The label rate is 2-3 oz per acre. Belt has activity on most all caterpillar pests and is at its best on foliage feeders.

Monday, August 9, 2010

Fall Armyworms

The most significant agricultural insect event of the past week has been the explosion of fall armyworms (grass strain) across Southern Alabama. They were reported from the Mobile county area of the west and personally observed in the Elba-Kinston area (Coffee County) on Friday (8/7) and the Eufaula area (Barbour County) in the east on Saturday (8/8). This outbreak can be found on pastures, hay fields, lawns, athletic fields and peanuts. Numbers observed range from 5 to more than 20 per square foot in grasses or per row foot in peanuts. Some of the most commonly used controls include Intrepid, Dimilin, pyrethroids, Traces and Steward.

Other then stink bugs, no significant insect numbers were observed or reported in cotton last week. Soybeans continue to be infested with grasshoppers and three cornered alfalfa hoppers as reported by Dr. Tim Reed. Low levels of stink bugs, loopers, green cloverworms and bean leaf beetles are being observed. No widespread outbreak of podworms (corn ear worms) have been reported

Friday, August 6, 2010

Soybean Insect Update-Tim Reed


Tim Reed, Extension Entomologist

August 5, 2010

During the first week of August I inspected soybean fields in Tuscaloosa county that had significant numbers of both grasshoppers and three-cornered alfalfa hoppers (3CAH). Grasshoppers feed primarily on the foliage but they can also feed on pods. No noticeable pod feeding was found on the plants the farmer and I inspected. 3CAH feed around the stem of young plants, girdling the stem near the soil surface. Young seedling plants may lodge from the girdling. When bean pods are set, maturing plants may break over from early seedling damage. Both adult and nymph 3CAH’s will also feed on the petioles of leaves, blooms, and pods. Pod petiole feeding will cause pods to drop to the ground, reducing yield. Soybean plants are most susceptible to main stem girdling when plants are 10 inches or less in height. Once the plant is taller than 10 inches, the main stem is not the preferred feeding site, but the leaf, bloom, and pod petioles may be fed upon. It should be noted that often plants that have been girdled and do not lodge will produce normal yields. The literature reports that 3CAH feeding on leaf petioles and pod stems interferes with photosynthesis and the flow of nutrients to developing seed. Sweep net sampling indicated populations of both insect pests were as high as 3 per sweep. The treatment threshold for grasshoppers once soybeans are in the bloom to pod –fill stage is when plants have 20% defoliation . The pod feeding threshold for grasshoppers in Mississippi is to treat when 50% of plants have one or more pods fed on by grasshoppers. The treatment threshold for 3CAH is one per sweep when plants are more than 10 inches tall.
Treatment decisions for the Tuscaloosa county fields were complicated by the fact that high temperatures had resulted in a significantly reduced pod set to date, even in an irrigated field. (More information about the effects of high temperatures on soybean pod set can be found in the Mississippi Crop Situation Newsletter for July 16, 2010 at After consulting with Dr. Ron Smith the farmer decided to treat the soybeans with the maximum labeled rate of a pyrethroid since many of the grasshoppers were immature and will be much easier to kill now than when they become adults. I had one soybean farmer tell me that one year he could not kill the grasshoppers in one of his northeast Alabama soybean fields and they ruined the crop. The goal of this treatment decision was to hopefully reduce the grasshopper numbers sufficiently to avoid a potential yield loss later and to significantly reduce the numbers of 3CAH’s. Inspection of more soybean fields in Marengo county revealed that a high level of plants (in a field with a 40% stand of soybeans) had sustained a high percentage of girdling when the plants were small. Sweep net sampling broke over many of these girdled plants. The 3CAH population in this field was less than one per sweep and I recommended that the grower wait another week and check the field again before making an insecticide application. The farmers in both Tuscaloosa and Marengo county were reminded that once they treated their soybeans and eliminated the beneficial insect/spider species they faced a greater risk of incurring damaging populations of “worms”.

Mississippi State Extension Entomologist Angus Catchot recently reported that over the last several weeks Mississippi Extension workers have had numerous reports of tobacco budworm moths being flushed in soybeans in the delta region of the state. Ryan Jackson and Clint Allen with USDA-ARS in Stoneville have been collecting populations of bollworms missed with pyrethroids in soybeans. Three populations collected the week of July 25th in the delta behind a pyrethroid application turned out to be 7%, 28%, and 60% tobacco budworms. Tobacco budworms are resistant to pyrethroid insecticides in MS (and in Alabama). Angus stated that although, in some areas of the state budworm numbers may be high in soybeans, most populations are low compared to the bollworm numbers. If high numbers of larvae are left behind a pyrethroid application it is recommended to get a positive ID on the larvae before retreating the field. Two characteristics that can be used to distinguish tobacco budworm larvae from cotton bollworm larvae are depicted in the July 30 Mississippi Crop Situation newsletter which can be viewed at ( Some Mississippi farmers have chosen to let remaining worms cycle given the cost of treatment for tobacco budworm. Cotton bollworm (i.e. pod worm) populations have thus far been much lower than normal in Alabama soybeans.

Monday, August 2, 2010

Effect of Heat and Drought on Cotton Crops

Last week's heat and drought was devastating to a high percent of our cotton crop in Alabama. Fields that had good moisture up until July 23 were shedding everything from stress by July 30. In my opinion this stress has cut about 4 weeks off of our cotton production season. Within a few more days the only fruit remaining on the plants will be bolls that are more than 20 days old. Plant bugs, bollworms, and budworms are likely a thing of the past for the 2010 cotton season. Even stink bugs will shortly find that the remaining fruit is too hard to penetrate internally. Growers may wish to watch the swag or greener areas of their fields. Insects may congregate in the lush areas for a while longer. We have plenty of time to recover and set more fruit but scattered thunderstorms will not provide the moisture to turn the cotton around.