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.

Rambling Thoughts About the 2017 Weather and Tarnished Plant Bugs in Cotton

I will say up front that no two seasons are exactly alike when considering the weather, crop conditions, and potential insect damage. 2017 has already been uniquely different than any season I remember. Delayed planting, excessive rainfall, mild winter, and warm spring are just a few of the factors that could affect the movement, numbers, and level of damage from plant bugs to this year's cotton crop. Only by close monitoring of plant bug numbers and their damage over the next 4-6 weeks will we know how to deal with this pest.

We need to begin sampling the oldest and largest cotton immediately with sweep nets for adult tarnished plant bugs. In addition, we should keep check on our square set by making pinhead square retention counts. 80% retention is considered our treatment threshold. In other words, we do not want to lose more than 20% of our small squares to plant bug damage.

If past history is any help, abundant to excessive rainfall in June tends to keep wild host plants like fleabane fresh a little longer. This slows or prolongs the movement of plant bugs into cotton. After fleabane dries down, no other wild host is attractive to adult plant bugs, therefore cotton is the best host they have. The movement of plant bugs into cotton has already begun. This migration could continue for several weeks. This slow extended migration may not reach what we would call a threshold or treatable level, making treatment decisions difficult. In hot, dry springs, these adult plant bugs leave fleabane in high numbers over a relatively short period of time, say 7-14 days. This sort of rapid movement into cotton is easier to detect and to make treatment decisions for.

There are a number of other factors that could influence the severity of the plant bug issue in cotton this season. Overall, I would estimate that the maturity of our cotton is a little behind where it normally is this time of year. Will plant bugs move past these fields in search of the oldest most mature cotton? April cotton may serve as a trap crop for plant bugs in 2017. That would be to our advantage. Since early June, we have had a lot of cloudy days with temperatures in the 70s or 80s. Plant bug survival on cotton has likely been higher under these conditions. This could spell higher damage levels in coming weeks. Plant bug adults, and especially their immature offspring, do not fare well under drought conditions and high temperatures (over 95°F), leaving cotton plants under a stressed and wilted condition.

Water logged spoils, which many fields have had during the month of June, can result in some pinhead square abortion. This effect would be very difficult to separate from plant bug injury. How can we distinguish this square loss from plant bug injury? The easiest way would be to use a sweep net to document that some level of plant bugs are actually in the field. One additional little trick that could help us answer this question was developed by our Arkansas entomology friends several years ago. This technique takes a little time, precision, and magnification. The tool needed would be a "pinhead square slicer." Take a damaged pinhead square from the plant (square will be brown or black in color), use a sharp razor, and slice the square in half. If it aborted due to weather, the inside content will still be present but deteriorating, whereas if it has been damaged by a plant bug, the interior will be hollow. Plant bugs tend to dissolve the contents and suck the interior of the square as food.

Plant bugs will likely be the primary cotton insect focus of entomologists, consultants, scouts, farmers, and other interested parties until well into July this season. We need to recognize this and not allow plant bugs to further limit our maturity and potential yield in 2017.

Insect Update for the Week of July 7

A combination of adult tarnished plant bugs and clumping aphids are being reported from more fields and areas around the state each day. Overall, little rainfall has fallen in about two weeks. Therefore, crops, especially corn and cotton, are under some level of stress. Therefore, most growers are choosing to target both plant bugs and aphids with this application.

I have not had any calls on mites in the past few days but that does not mean that populations are not building in select fields. So far, abamectin at 10 oz. per acre has given good control on mites in treated fields.

Immature plant bugs are present now in the oldest cotton. I have observed several fields where a threshold of three immatures per 5 feet has been recorded on a black drop cloth. When plant bugs become imbedded in cotton in July (all stages present – eggs, immatures and adults) quite often multiple applications are needed to bring the population under control. For those that want to use the IGR Diamond, now is the time to do so. An adulticide plus Diamond, at 6-9 oz. per acre, should give control of the population for 14 plus days. It is my opinion that most of the adult plant bugs have now left wild host plants and are now in cotton. We just don’t seem to get that many moving from corn here in Alabama.

Moth traps in central Alabama captured an abundant number of both bollworm and budworm moths last week. 2014 may be the year that fieldmen, consultants, and scouts really prove their worth. There is just no way to time the appropriate chemistry at the proper time without someone monitoring insects. This looks like an above average insect year for cotton and we haven’t even reached the primary stink bug window yet. In sweeping for adult plant bugs last week, I was capturing brown stink bugs in about every set of sweeps.

Update for the First Week of July

The Alabama cotton crop is growing rapidly resulting from abundant rainfall from multiple thunderstorms that have occurred during the last 10-14 days.

Insect wise things have been rather quiet on cotton but not the case with soybeans which I will discuss later.

Tarnished plant bug numbers have not increased as rapidly as expected in fields that I have observed. An occasional adult and or nymph can be found, depending on the age of the cotton. Migrating adults went to the earlier planted cotton first and have had time to now produce offspring. Cotton planted on April 10 is now blooming in Autauga County, Alabama.

To my surprise, I’m finding as many adult southern green stink bugs as I am adult plant bugs. We need to begin watching stink bugs in early bloom cotton. As I have stated before, these stink bugs will feed on thumb size bolls as soon as the dried bloom sheds. A huge stink bug population is waiting in corn. These adults will migrate to cotton, soybeans and peanuts as corn begins to dry down. This may be the largest population in corn that I have ever observed. There seems to be mating pairs in every corn plant at our research farms in Shorter and Prattville, Alabama this week. Most are the southern green species with an occasional brown in the mix. That will be to our advantage in a few weeks since the pyrethroid chemistry does a nice job controlling the green species.

The other insect that is building on cotton is aphids. They are clumped in terminals on occasional plants in numerous fields at present. These clumps will spread field wide before natural diseases wipe out the population. I would project that aphid population decline will not occur until around July 20.

The most intense insect pressure at present is Kudzu bug populations on soybeans in select fields throughout the state. Ten to 50 adults and over 200 immatures per plant can be found in many April planted beans. More adult Kudzu bugs are moving into beans from Kudzu daily. Beans will have to be scouted weekly for the remainder of this and future seasons. One to three sprays may be needed to protect beans this season. This will open the door to pod and foliage feeding caterpillars for the remainder of the season.

Information on the management and control of the Kudzu bug in soybeans has been posted in blog entries previous to this one and also on the Alabama Crops website (alabamacrops.com).