Heavy Plant Bug Season May be Becoming a Reality

Last week, aphids began to build in spots in fields statewide. Ordinarily, I would recommend to let the natural fungus take out the aphids. However, each field and season presents a different picture. The fungus always works, however sometimes it is a week to 10 days later than we would like. Since we have a lot of late maturing cotton this season, I don’t feel we need to let aphids set our cotton back any further. Even if aphids do not cause yield losses, when an entire field is drooped down from aphid stress, we are likely seeing some maturity delay. For this reason, in 2018, I am suggesting that if a grower is going over a field for weed control or PGR application, then I would add an aphid control insecticide in the spray. We have some very economical choices for aphid control when they can be piggy backed with a trip over the field for another purpose.

Now on to plant bugs – I say plant bugs because we could easily have both the tarnished and the clouded species in some fields. In fact, I picked up some clouded species in sweeps in cotton last week in central AL. Historically, we have had more clouded in wet springs. Maybe because we get a better growth on button bush, a wild host for clouded in wet seasons. Button bush is a plant that likes low, swampy habitat, and excessive rainfall gives us that. No matter whether it is TPB or CPB, our scouting thresholds and controls are the same.

Now let’s talk about the TPB. The rainfall in the past month has kept their primary wild host, daisy fleabane, fresh and it appears that 2 generations have developed on fleabane. In mid May, we had mostly adults here in Central and South AL. Now, in both South and North AL (including the TN Valley), we have another generation that was just mid aged immatures the second week of June. This means that we will likely have a migration from fleabane into cotton that will last for 3-4 weeks. Therefore, feeding and egg laying in cotton by these migrating adults will last 3-4 weeks. This will result in a long emergence of immatures in cotton beginning about first bloom.

We may need multiple applications pre bloom in some fields to control migrating adults. Then we may also need multiple applications post bloom for the immatures as they hatch. I hope I am over estimating what could be a bad plant bug year. This is not what we needed on 2 gene cotton. Multiple plant bug sprays just before the CEW flight comes from corn will result in more escape bollworms in mid-late July.

One thing we can do if this scenario happens is to use a plant bug application for adults about first bloom and add the IGR Diamond to the tank mix. Diamond will add residual control on hatching immature plant bugs for 10-20 days, depending on the rate used.

I will be focusing and making observations on plant bugs for about the next 3-4 weeks, and I will keep everyone updated on what we are seeing. The first report of high numbers of adult TPBs in cotton came from west central AL on June 19.

An Extension publication overviewing plant bugs was prepared by Barry Freeman, our resident plant bug expert in 1999 and can be found online at http://www.aces.edu/pubs/docs/A/ANR-0180/ANR-0180.pdf. Life cycles, damage, scouting, and management have not changed over the years. Every season and field are different, which requires close monitoring in order to make the proper management decisions.

2018 Treatment thresholds and control recommendations can be found in ACES publication # ANR-0415, “Cotton IPM Guide” available online at http://www.aces.edu/pubs/docs/I/IPM-0415/IPM-0415.pdf

If fieldmen, growers, or consultants have plant bug observations, please call or text and share with me at 334-332-9501. You may email me at smithrh@auburn.edu.

Insect and Crop Update for the Week of June 23

After going weeks with light to moderate thrips pressure, damage was heavy on 4-7 leaf cotton in early June, especially in SW Alabama.

Cotton was growing rapidly but thrips damage on true leaves was showing heavy damage from about the 4^th to 7^th true leaf. (Peanuts also were taking heavy damage during this same period.)

The thrips window is over now and we need to shift our focus to spider mites, aphids and the plant bug complex which includes tarnished plant bugs, fleahoppers and an occasional clouded plant bug.

Mites are primarily found in the TN Valley region of North Alabama and some treatments were being applied last week.

I noticed the first aphids on April planted cotton in central Alabama last Friday (June 21).

Plant bug numbers (adults) were down last week but nymphs are beginning to appear in our earliest planted cotton (mid-April). I would suggest using a sweep net to sample adults for the next 2-3 weeks, depending on the age of the cotton. As we approach first bloom I would switch to a drop cloth and concentrate on the presence of immature plant bugs.

Also, field men should now be looking at pinhead square set. Fields surveyed on June 21 were setting about 90% of the fruit. However, some plants had up to 30% square loss at that point. I believe you will find that migrating adult tarnished plant bugs will seek out the earliest planted and most lush cotton fields. My thought is that this cotton provides the best shade from the 95 degree temperatures, and is the best host for plant bugs.

While looking for pinhead square set I noticed a number of white eggs, likely tobacco budworms. They would not be a concern now, but in the old days it would have created a real predicament. Spraying for plant bugs during a budworm moth flight would have been expensive and also put the grower on a treatment treadmill for the remainder of the season. Sometimes we forget how well we have it compared to the pre-Bollgard years.

On another insect – a few stink bugs are already present in cotton. Normally we do not worry about stink bugs until about the third week of bloom, when we have bolls that are 10-12 days old. However, when stink bugs are present at bloom they will attack thumb sized bolls as soon as the bloom tag sheds. Any feeding to bolls this size will cause the boll to abort. Therefore, fieldmen need to be alert for adult stink bugs in early bloom cotton as they monitor for plant bugs with a sweepnet. Stink bugs will not damage squares or blooms but will seek out these first small bolls.

Since some of our corn was planted later than desired, stink bugs will likely remain with that host until the post roasting ear stage when the kernels become hard. At that time we may have a large movement into other crops such as cotton, soybeans and peanuts.

One word about Kudzu bugs on soybeans. Numbers of adults are out of site on many of our April planted beans. In fact, adult numbers are beginning to decrease in some fields now but numerous immatures are present, which is the trigger we use to treat the field. Fieldmen who have not experienced this insect may overlook these immatures when they are small. They will be a clear to greenish color and very small after hatching.

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.

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.

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.

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”?

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.