Texas Plains Cotton: Thrips Resurgence; Scout for Fleahoppers, Lygus

General Status

Showers continue to cross our region, the latest round this week leaving the gift of between 0.3” and nearly 2” with most of our fields getting around 0.75”. Slowly but steadily fairly frequent rainfall events (or almost rain events in many cases) through June has tried to relieve our extreme environmental conditions.

The situation was so dry coming into June and weather between these rain events so hot, dry, and windy little headway has been made for most fields. Failed dryland fields are widespread while hard fought but lightly populated cotton fields common.

Pests remain on the light but not absent side this week while weeds remain a concern as many of our crops look to make the jump to the next important stage.

Cotton

Weather has prevented us from making full rounds on our scouting program so far this week. So far, our scouting program fields range in stage from emerging to pin head square stage. Now that fields have established, our attention fully turns toward insect and weed pests.

Thrips made a resurgence this week with a few spotty fields overtaking the 1 thrips per true leaf stage economic threshold. Our thrips populations ran from 0 to 1.51 thrips per true leaf with most fields over the economic threshold being north of Plainview and the majority of fields running around 0.5 per true leaf.

A few of our earliest fields have starting squaring and now sport pin head squares. Immediately, we need to be on the look out for fleahoppers and Lygus in these situations so that we protect our earliest 1st position square set. The economic threshold for early squaring cotton (too young for dropcloths) should be 35% fleahopper infested plants or 8% Lygus infested plants for whole plant inspections with 8 – 15% plant bug caused square loss.

AgFax Weed Solutions


Established thresholds are always best applied with field situational data and some field experience to make a correct judgment call. A light plant populated cotton field might require treatment with a lower percent infested rate.

In our fields this week, we found no fruit drop and no plant bugs. Beneficial populations remain very light.

Corn & Sorghum

Our sorghum and grain crops continue to develop, enjoying the sparse but frequent rainshowers but feeling the heat in-between rain events. Our program corn ranged in stage from V8 to V9 while we have not been able to return to our sorghum fields yet. So far we have found no pest of note in our grain crops this week.

We may expect to start finding fall armyworm whorl feeding soon based upon moth trapping data this week. This type of damage is cosmetic but rarely, if ever, economic. Studies have shown that 35% of the foliage would need to be removed before any treatment would be justified.

Our wireworm “X-File” field found in sorghum last week has been replanted. In that field we noted a large population of adult false wireworms move in to the seed milo field and heavily reduce stands to below a profitable level with serious root zone loss added.

We noted that this species of ‘wireworm‘ looked to be the culperit for reducing stands in cotton also. Our recommendation was to replant with an improved combination of insecticidal seed treatments and, because we were dealing with adult false wire-worms, treat over the top with an insecticide spray.

I eagerly await the establishment of this field and urge you to be mindful of any fields you may have in a similar situation.

So far, we do have some results about this odd situation. The following was returned to me from Dr. Pat Porter, District Entomologist, in an e-mail.

The mysterious beetle causing stand loss in cotton might be identified.

Both Adam (Adam Kesheimer, lab tech, cotton extension entomology lab) and I keyed out the beetles Jim brought to family Tenebrionidae. I then went through a stack of old insect ID reports that Pat Morrison saved from TAMU Insect Museum identification requests back in the 80s and early 90s. One ID was for Blapstinus fuscus. Your beetles are too small to be B. fuscus.

I looked at the genus on Bugguide and saw there are several species that are very small, and they look quite like the ones from you. So, we are going to call this Blapstinus spp. for now. Adam and Suhas (Dr. Suhas Vyavhare, district cotton entomologist) will mount some specimens and figure out to whom they should be sent.

Ed Riley’s ID and report to Carl Patrick (Ext. Entomologist in Amarillo, who sent in the original ID request in 1990) says, “These beetles are normally scavengers feeding on dead organic material. Usually very common on surface of the soil in AM or late afternoon and night. We have several records that indicate it is an occasional pest of crops. It eats around the base of plants (corn, cotton, watermelons, sorghum) causing plants to fall; some reports indicate that beetles feed on leaves also. South Central and West Texas. Probably one generation per year, but I don’t have anything specific on life history.”

Carl Patrick wrote the following:

“In a single field of dryland sorghum (6-8”) near Washburn (15 mi. SE of Amarillo) these beetles were causing considerable stand reduction (average about 50%, and in some spots, 100%). Sorghum plants would have 1-15 beetles feeding at the base causing damage as described by Ed Riley.”
Pat

Thanks Pat!


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