Update for the week of July 29th

The dominant question last week was concerning spider mite control. Several calls were received from consultants or agri fieldmen in the southern part of the state. Their question was not so much what to spray with (chemical choice) but instead when to spray. Most were scheduling stink bug sprays within a few days and wanted to know whether to add a miticide or not. Without seeing the fields, that is a difficult decision to make over the phone. My thoughts were that it could depend somewhat on how widespread the mites were in the field, the level of mite infestation and maybe most importantly – what is the weather outlook for the next 7-10 days.

Mite populations seem to hold steady in good rainfall patterns but explode during hot-dry weather. Even though we have had scattered thunderstorms for the past several weeks, there are many places where no rainfall has occurred. Last week was hot, mid 90’s or higher all week, so mites likely increased in number.

My suggestion would be to go ahead and treat mites if the weather outlook is for hot dry weather for the next 5-7 days. Most of our mites controls this season have been with abamectin (Agri Mek) at 8 oz/ac and results have been good.

Stink bug populations are still hanging around, in low numbers in many fields. However, from personal experience in a plant bug trial area in central Alabama that is located adjacent to corn, stink bug numbers have exploded in the past two weeks. Both brown and southern green species are well above the threshold level on the corn-cotton borders. Where cotton yields are promising and quarter diameter 10 day old bolls are still developing, stink bugs should be watched closely and controlled when above threshold. Cotton is at various stages now so our “dynamic threshold” would depend on where we are in the blooming-boll development cycle. Remember that 10% is our suggested threshold from weeks 3 through about 6 of bloom.

One other call was received last week concerning one or more fields in Baldwin County (Gulf Coast) infested with damaging levels of the garden fleahopper. We had several fields in recent seasons with this pest in the Mobile county area. The GFH seems to be primarily a foliage feeder but can damage every leaf in a field.

As of this date the bollworm/budworm complex is almost non-detectable, even in cotton with no caterpillar technology.

Fleahoppers and Silver Leaf Whiteflies Reported in Southwest Alabama

After two uneventful weeks with little cotton insect news, several points have been learned this week. Consultants from the Mobile area of SW Alabama voiced that the cotton fleahopper has been their most persistent insect this season. This area also has another fleahopper species in the mix, that being the garden fleahopper. Fleahoppers are not difficult to control but populations can rebound very quickly within 5-7 days. Also in this same area, silver leaf whiteflies (SLWF) are infesting a few cotton fields that are planted adjacent to melon fields. Controls were needed for this insect.

Stink bugs, tarnished plant bugs and "worms" in cotton

My cotton insect observations this week were as follows: many fields have a number of immature (late instar, soon to be adult) tarnished plant bugs. This stage of immature, along with the adult stage, is what will be giving us our “dirty” blooms in the days ahead. Mixed in with these immature TPBs are a few fleahoppers (both immature and adults) and a few immature clouded plant bugs. Many fields would profit from a plant bug complex “clean-up” spray if it has not already been done during the past two weeks.

Aphids have built rapidly during the past week in a number of fields. Where cotton is currently under drought stress, the presence of aphids and honeydew on all plants might influence the choice of chemistry for this bug clean-up spray.

Several fields of April planted cotton in southeast Alabama had treatable levels of “worms” this week. These worms were likely already about a week old on July 15, which means the eggs were deposited around July 5. This was during the period when most moths observed were tobacco budworms. Appropriate chemistry would be needed if targeting these worms. By next week (July 19-26) the eggs deposited will likely be bollworms and pyrethroids would be the most economical chemistry.

Even though the percent internal boll damage may not have increased in recent days, the brown stink bug problem has not gone away. My thought as to why the percent damage hasn’t gone up is due the fact that peak boll production is close in cotton planted in late April. Let me explain. A week or two ago we had about one boll per row foot about 10-12 days old (the size stink bugs prefer). Some of our stink bug damage levels at that time were running 20% or more. At one per foot this would be about 14000 bolls per acre x 20% or 2800 per acre with internal damage. At present these same fields have up to 3 or more 10-12 day old bolls per row foot. This would mean that 42000 bolls per acre are at risk, but the stink bug population hasn’t increased greatly at this point. The percent internal stink bug damaged bolls has gone down in many fields but that doesn’t mean we are not taking economic damage. Ten percent damage to 42000 bolls per acre is 4200 bolls. Percentages can be misleading. The damage we are incurring is a function of two things – the number of bugs present and the number of bolls at risk. In the old days this situation existed with the number of squares and the number of boll weevils. The damage percent would go down prior to increasing rapidly.

Not only will we wake up one day a couple of weeks down the road with more internal stink bug damage than we thought, but also with a sharp increase in the percent damage. This will be a function of more stink bugs present by then, but also a reduction in the number of bolls per acre that are in the desired feeding size. Borrowing a line from one of our recent politicians “this makes sense to me – does it to you”?

Aphids and bug complex building, fall armyworms in second generation in pastures, fleahoppers appear

We’re getting more reports of aphids building in cotton. They’ve been slow to increase but still have reached treatable levels in some fields. While we were doing our beat sheets last week, I noticed in some of the older cotton that immature brown stink bugs were turning up where we had adult brown stink bugs earlier. So, they’ve been in there long enough now to turn over a generation. Most of the plant bug population right now are in immature forms coming off of the June adults. Fields that were sprayed for bugs appear to be pretty clean, but others have populations now that are at or will shortly be at damaging levels, so we’re really close to making applications to clean up the bug complex on everything.

We’re still not seeing signs of the huge tobacco budworm flight that was underway in southwest Georgia 2 weeks ago. It’s amazing how fast budworm activity drops off as you travel 2 counties west into Alabama. We have a long history of similar patterns – heavy pressure in south Georgia but hardly anything in southeast Alabama. We’re into the second generation of fall armyworms, the grass strain, in coastal Bermuda and other hay fields in southeast Alabama.

The garden fleahopper has been causing damage in a 25-acre cotton field in Mobile County. This is the first time I’ve seen the pest in cotton in the 39 years I’ve been working the crop and didn’t know for sure what the insect was when a consultant emailed me samples of the pest and damage. But Mississippi State University recently released an excellent color insect guide for cotton, and the garden fleahopper was included in it, which allowed me to ID the insect. Evidently, it’s been enough of a pest at some point in Mississippi cotton that it made the book.

I have a feeling we’ll see a lot of brown stink bugs in soybeans when they start setting pods. They’re certainly nearby, although probably not in soybeans to any degree yet. Stink bugs are smart enough that they won’t hang around too long in a crop that doesn’t provide a food source. Typically, they’ll leave corn within a week of when it starts drying down and, as if on cue, they’ll shift into soybeans when they start setting pods. We’re following a population of them right now at our Gulf Coast research station.