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.

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.

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

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

Weather and Insects Affect Late Season Cotton, Soybean and Peanuts

The greatest impact on cotton during the past two weeks has been the lack of rainfall. Drought and intense heat has resulted in the shed of all fruit less than 10 day old bolls from the terminals of plants. This will tend to shorten additional boll production by 2 to 3 weeks and will likely reduce the “top crop” by 200 or so pounds of lint in many fields. Rainfall in the next 7 days would still help fill top bolls that are not mature.

As the result of the above conditions, the insect control season, especially stink bugs, is about over. A few southern green stink bugs can be found in late maturing fields or “swag” areas that remain green in more mature cotton fields. Thresholds for these would be 30-50% internal boll damage on 10-12 day old bolls. A few fields would still profit from stink bug controls.

Tobacco budworms have been extremely low all season but field observations and pheromone traps indicate an increase in the past week or two. Also, bollworm moths are abundant this week in the southern counties of the state.

Soybean Insects- Soybean loopers are at economic levels of 5 or more per row foot in some Gulf Coast area soybeans. Chemical choices (in no particular order) are: Intrepid, Steward, Belt, Tracer and Besiege (Coragen and Karate). Dimilin will give good suppression and long residual. On cotton, the same can be said for Diamond.

Peanut Insects- Scouts reported a mixture of foliage feeding worms in peanuts in Monroe County (S.W. Alabama) about 10 days ago. Many of these were controlled or either they have cycled out by now. This mixture was dominated by bollworm and fall armyworm (grass strain) species. Also in the mix were a few green cloverworms, loopers, and granulate cutworms. Pyrethroids gave nice control of this mix.

Soybean Loopers in Southwest Georgia

Soybean loopers were discovered in cotton in Seminole county, southwest Georgia, last week. There were only about 2-4 per foot of row which is below treatment levels. However, since this is a little early for loopers to appear, they will have to be watched for in coming weeks.

Soybeans

- Looper populations seemed to have peaked out. In most instances defoliation was between 5 and 20% where no controls were applied. Therefore, populations were below threshold level in most fields.

- Velvetbean caterpillars were found at damaging levels in one field of late maturing beans (R-4/5) in Baldwin county on September 12th. Velvetbean caterpillars are much more economic to control than loopers since pyrethroids do a nice job on VBC.

Soybeans

Loopers are the dominant soybean insect, up to 30% defoliation and damaging levels in some fields. A few velvetbean caterpillar and green cloverworms are in the mix. The “grass” strain of the fall armyworm does not appear to feed to a significant degree on soybeans. And, stink bug populations are not as high as anticipated.

Red banded stink bugs were discovered on the Wiregrass Research Farm, Headland, AL (Henry Co.) this week. Since they were found about 180 miles west of Headland last month, they likely may be present in other locations across south Alabama.

Cotton

- A few late maturing fields are still being scouted for insects, primarily brown stink bugs and soybean loopers.
- Defoliation is proceeding on more fields each day and week.
- Harvesting has begun in a few locations. I observed a picker running about 8:00pm yesterday (9/2) in southeast Dallas county.
- Yield potential is all over the board (250 lbs- 1600 lbs/ac.)

Soybeans

Economic levels of soybean loopers, fall armyworms (FAW) and velvetbean caterpillars (VBC) are as far north as Marion Junction in Dallas county and FAWs are occurring near Prattville in Autauga county. Soybean loopers, usually a southern latitude insect are occurring at all points within the state. Both VBC and FAW can be controlled with less expensive chemistry than can the loopers.

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.

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.