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Aphids & Weeds in Wheat

Rome Ethredge (Grain & Soybean Agronomy) –

“Aphids can cause direct feeding damage and transmit disease in small grains. Today (Jan 3, 2022), in Seminole County, I found Bird cherry-oat aphids reproducing in wheat, see the female and 6 young offspring in [photo below]. Although all aphids can potentially transmit barley yellow dwarf virus, infections in the Southeast US are mostly associated with infestations of bird cherry-oat aphid and rice root aphid. 6 per row foot is the treatment threshold for this growth stage, tillering. We are about at that level in this field and grower also needs to apply a herbicide now, so he will treat both pests together.”

Bird Cherry-Oat Aphids on Wheat – Rome Ethredge, Seminole Co, GA, 2022
Aphids (from left): English grain aphid, bird cherry-oat aphid, greenbug and corn leaf aphid

Dr. David Buntin, UGA Entomologist:

“A single, well-timed insecticide application of the insecticide lambda cyhalothrin (Warrior II, Silencer, and similar products) or gamma cyhalothrin (Declare) also can control aphids, reduce the incidence of BYD, and increase yields. The best time for treatment in northern Georgia usually is about 25 – 35 days after planting, although an application in the winter until full tiller also may be beneficial. In southern Georgia, the best treatment time usually is at full-tiller stage in late January to mid-February. But, scout fields for aphids at 25 – 35 days after planting and during warm periods in January to determine if an insecticide application is needed.

A lambda cyhalothrin or gamma cyhalothrin treatment at full tiller can be applied with top-dress nitrogen. Two new insecticides, Sivanto Prime and Transform WG, also will provide useful control but its effect on BYD infection has not determined. OP insecticides, such as dimethoate, also will control aphids but are not effective in preventing barley yellow dwarf infection.  To sample aphids, inspect plants in 12 inches of row in fall and 6 inches of row in winter. In spring, inspect 10 grain heads (+ flag leaf) per sample. Count all aphids on both the flag leaf and head for making control decisions. Sample plants at 5 to 10 locations per field.”

Thresholds from UGA Pest Control Handbook:

Rome:

“It’s a good time for weed control in most wheat fields. The Wheat Weed guide by Dr. Stanley Culpepper is below and here. https://site.extension.uga.edu/colquittag/files/2021/11/2021-2022-Wheat-Circular-002.pdf

I’m seeing Wild mustard in many fields which is the main reason for spraying. Also seeing Chickweed and Henbit in abundance and wheat has a few tillers on it, so it’s a good time for a Harmony extra and MCPA mix in many fields. This is much better than the old standby 2,4-D , which has a very narrow spray time interval or it can hurt your yield and doesn’t do as much on the variety of weeds we have.”