This week I picked up two adult lygus bugs, one near the fairgrounds and one near La Salle. These insects can feed on cotton terminals, squares, flowers, and small bolls. They prefer to feed on clovers, dock, mustard, pigweed, vetches, and wild sunflowers. Both fields I found them in had a few larger pigweeds present.
The adults are 1/4 an inch long, and have a dark triangle in the middle of the back. They have wings, and vary in color from a pale green, to a yellow brown with black markings.
The nymphs are uniformly pale green with red tipped antennae. The reddish tipped antennae paired with the black spots on the backs of the nymphs makes them easier to distinguish from fleahopper nymphs.
Lygus bug feeding can cause deformed bolls, damaged anthers in blooms, damaged petals, shedding of squares and small bolls, and stunted plant growth. Lygus bugs do not often reach threshold level numbers in this area.
I prefer using a drop cloth to look for lygus bugs, but you can also sample with a sweep net. The current threshold with most of our fields would be 2-3 per 6 ft of row with an unacceptable square set, which is usually considered near 75% square set or lower.
The fleahopper populations are remaining active in the squaring fields this week. The heaviest population I found was near our fairgrounds, with 18% of plants with fleahoppers present. The threshold for fleahoppers is 15- 20% present on squaring cotton.
I am still finding fleahopper nymphs in fields in all three counties, but most are closer to hatchling size, and probably emerged after a good number of fields were treated.
Dry conditions have still been favoring spidermites. Their populations are continuing to thrive in a few areas. They tend to be more common near grassy pastures or ditches, places with drying grass or near dusty margins. I was still picking them up the heaviest in the blue creek area, but have found them in other places in all three counties as well.
My concern with these arthropods is not just their presence, but that their numbers can be flared if a field is treated with acephate for thrips. Keep an eye on younger fields with thrips and double check for spider mites. For more information on spider mites, go to page 21 of the new Cotton Insect Guide.
Thrips are still present in smaller cotton in all three counties. The threshold for thrips is 1 per true leaf per plant. Once the plant reaches 5 true leaves, it’s large enough that thrips are no longer a concern.
If you do have a thrips problem, keep an eye out to see if you have spider mites in the field. Treating thrips with acephate can flare spider mite populations. Bifenthrin has some effect on spider mites as well as thrips, but is not normally a first choice for treatment of either pest individually.
I am participating in a study to look at the Bt resistance in cotton bollworms in our area. The study requires me to collect caterpillars out of refuge corn. If you have heavy populations of corn ear worm in your corn, please give me a call.