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23
Jul
2012
Update on the insect situation in Arkansas
Author: Gus Lorenz, Extension Entomologist

Cotton

Plant Bugs

Plant bug populations have exploded in most cotton growing areas. In our untreated check plots this week at Marianna, we averaged over 3 plant bugs per row foot with some plots averaging 5 per row foot. At 7 days post treatment, few of the treatments kept plant bugs below threshold.  If you are experiencing these types of numbers you have to do a couple of things: 1) shorten the time interval between applications. Instead of 7-10 days between applications, you may need to go to 5 days between applications, at least until you get numbers to acceptable levels; and, 2) you need to use tank mixes. Single product applications just aren’t as effective as tank mixes for control of plant bug numbers in heavy infestations.

Bollworm

Bollworm trap counts dropped this past week but remain high. We have fairly high levels of establishment in dual gene cotton in the southern one-half of the state in blooms and under stuck dried blooms, and several fields have been treated.  Scout down in the plant to find developing populations. It appears this population is moving into cotton in central and northeast Arkansas late this week and should continue through the upcoming week.

Soybean

Bollworm

Bollworms have definitely moved into soybean fields this past week. Treatment level has been observed in several fields throughout the southeast and up through central Arkansas. We received several reports and saw several fields running above treatment level (9 bollworms/ 25 sweeps). Numbers aren’t nearly as high as last year but are sufficient to warrant treatment. As we have mentioned, the fields most often seen at treatment level are fields that are blooming and setting small pods (R2-R3). However, since we are also getting reports of bollworms in lapped beans at R4-R5, we encourage you to check all fields at this time for developing infestations.

Particularly in the higher infestations, we strongly recommend using something other than a pyrethroid. If you choose to use a pyrethroid, we suggest adding acephate (0.5 lb/ A) to get acceptable control. For fields with bollworm and stink bug this combination may be the best option. Otherwise, products of choice would include Belt, Steward and Tracer.

Threecornered Alfalfa Hoppers

We are seeing large numbers of threecornered alfalfa hoppers (TCAH) moving into fields in the last week or two, and I have received several calls about what to do with them.  We are seeing them in the fields we are sweeping, and it’s not uncommon to see one per sweep or even higher. In my opinion, based on the work we have done in the Midsouth, I can’t recommend treating for TCAH. An application of acephate or pyrethroid will open the door for really damaging soybean pests like bollworms, loopers and other pests.

Stink Bugs

Stink bug numbers are reaching treatment level in many of the earliest planted fields of soybean, particularly this past week. Many of these fields are late R5 (full-size pods) to R6 (full-size bean in the pod). This is the stage of development when soybean becomes very attractive to stink bugs. Fields that were running 3-4 stinkbugs per 25 sweeps jumped to 15-25 stink bugs per 25 sweeps in a week. In some fields, the number of brown stink bugs is as high as 40% of the population or higher. Remember brown stink bugs are a little tougher to control than green stink bugs. Bifenthrin and/or acephate are recommended for brown stink bugs. We recommend you check early planted soybeans now for developing populations.

Spider Mites

We have received several calls and seen a few fields with spider mites developing usually in small spots in the field and along field edges. There are three products currently labeled that have spider mite activity: bifenthrin (Brigade, Discipline, Fanfare, Tundra, Sniper), Dimethoate, and Lorsban. If you are seeing severe symptomology  (yellowing) and high infestations, you may want to consider spot treatments.


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