Upper Coast IPM: Plant Bugs and Aphids

Howdy,

There are still cotton fleahoppers around this week. Treatments have been made for them in all three counties, and I was picking up more nymphs this week than I was last week. Threshold is 15 - 20% plants with fleahoppers. Cotton is beginning to bloom in all three counties. Fleahoppers will no longer be a pest of concern once a field reaches the first week of blooming. Once a field is blooming, we need to start watching out for other plant bug pests, like the verde plant bug, lygus bugs, and stink bugs. In the Rio Grande Valley, Dani has reported a few verde plant bugs moving into cotton as well as a few bollworms. I found a couple of lygus bug nymphs in a Matagorda county field this week.
Prior to peak bloom it's recommended that a sweep net be used for sampling for lygus. Using a standard 15 inch sweep net, make 15 - 25 sweeps at a time, concentrating on a single row. The number of sweeps you will be able to make is dependent on the amount of foliage that accumulates in the net. Avoid letting the net accumulate too much debris, since it will prevent you from getting an accurate sample. Try to take at least 100 total sweeps from 4 - 6 locations in the field.

http://cottonbugs.tamu.edu/fruit-feeding-pests/lygus-bugs/

We did receive approval for a section 18 for use of Transform in cotton for control of plant bugs. This section 18 expires October 31, 2017. When using Transform to control plant bugs the rate per application allows for 1.5-2.25 oz/acre, with no more than a total of 8.5 oz/acre per year. Remember not to apply within 14 days of harvest, make applications less than 5 days apart, or make more than two consecutive treatments per field. The full section 18 label can be found here.

Cotton Flower
Photo: Kate Harrell

This week sugarcane aphid populations are on the rise. If you need the scouting guide, it can be found here. Threshold for these insects begins at 50 aphids per leaf if field conditions are warm and dry. The two products available to spray for the sugarcane aphids are Sivanto and Transform. Use Sivanto at 4-5 oz/acre, do not go lower than 4 oz for good residual. When applying with a ground rig use at least 10 gal per acre to get the chemical into the lower canopy. If the canopy cover is pretty dense, you may need to go to 15 gal. For Transform use at 1-1.5oz/ acre, and do not go lower than 1 oz for good residual.

Full Reference Material

In the Rio Grande valley, Dani has been finding rice stink bugs and sorghum midge. We need to be watching for those pests as well. Midge is a problem in sorghum during bloom, the female midge lays eggs in the florets, where the maggots consume the developing fruit. To check for midge, beat the flowering grain head around inside a bucket or jar. Any midge will wind up smeared on the side of the container. Check at least 20 heads per 20 acres of field. If the fields are smaller than 20 acres, check 40 heads. The threshold for midge can be calculated by this calculator or:

Number of midges (cost of control in $ per acre x 33256)
per flowering head = (Value of grain in $ per cwt x number of flowering heads)

I saw a few rice stink bugs starting to show up in fields in Matagorda county this week. Use the same bucket technique used for midge to check for rice stink bugs, but check at least 30 plants or 1 sample per acre in larger fields. This calculator will help determine threshold for rice stink bug.
Keep in mind that treatments for rice stink bug or midge can knock back predator populations and flare aphids. That doesn't mean that you shouldn't treat if you find stink bugs or midge at threshold, but it does mean that you should check aphid populations after treatment and be ready to treat with Transform or Sivanto afterward if populations do flare.

Wasp Mantidfly
Photo: Kate Harrell

This week's insect is the wasp mantidfly. The adults are predatory, and will hang out near flowers. They grab and eat whatever flies by with their raptorial forelegs. Their color pattern and shape mimics that of a paper wasp, which keeps things that would be predators away, since they are mistaken for something that stings. The larvae of this insect species are parasitoids of spiders, and eat their host from the inside out before pupating and emerging as adults.

On Wednesday I got a call about some interesting feeding activity near the edge of a field in the Crescent area. The damage was beside a house with a couple of trees around it. The photos below show some cotton plants that appear to be gnawed off at the base of the plant. Leave a comment with what you think happened!