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Weather Forecast

Feb 8, 2017

Blacklands Pest Update

Wheat in Hill and McLennan Counties ranges from Feekes stage 2 through Feekes 5, just before noding (see chart below for reference). We have good soil moisture and no standing water issues, and the wheat is tillering well. Temperatures fluctuate week to week, with near freezing to in the 80's within a few days. Such is Texas weather!


Disease
Low levels of leaf and stripe rust can be found just about everywhere, but are restricted to the lower leaves and are much reduced in fields that were sprayed with fungicide at topdress. Fungicide residual control, depending on the product and environmental factors, usually lasts about 3 weeks.

Stripe rust is a light yellow color and can typically be seen in long stripes following the leaf veins.

Leaf rust on wheat. Leaf rust pustules are a dark orange color and scattered about the leaf.

Flecking (the light spots on this leaf) can indicate a resistant response to disease. The plant cells around the fungal pustules die, preventing them from spreading. Flecking occurs naturally on some varieties and may not always be a sign of disease.

No signs yet of septoria or tan spot, which don't usually cause concern here in the Blacklands, or powdery mildew.

Insects
Several fields that didn't receive insecticide at topdress have larger populations of the bird cherry-oat aphid (BCOA). This aphid does not inject a toxin as it feeds, like the greenbug, but can spread barley dwarf virus.
BCOA can be recognized by their dark green color and distinct reddish spot on their abdomen. Photo from Oklahoma State University Extension.

It takes a rather sizeable infestation of BCOA to justify a spray: Oklahoma State entomologits suggest a threshold of 20 per tiller on average. It's also reasonable to use the same thresholds for greenbugs here, though greenbugs cause considerably more damage as they feed. Wheat can typically tolerate BCOA feeding very well, and their populations are usually controlled by predators and parasitoids.

Speaking of which, ladybeetles and parasitized aphids (mummies) abound in their infested fields as well.

A rather cheeky ladybeetle laid a cluster of eggs on this henbit. Good thing that the newly hatched larvae can travel a short distance to find food.
Weeds
We seem to have fairly typical levels of weeds in wheat with no resistance problems or herbicide failures reported so far. Common weeds in the scouting program fields include henbit and ryegrass, which are being controlled as topdressing continues.

If you have any questions or need help with pest issues, don't hesitate to contact your local AgriLife office via e-mail or phone.

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