Texas Plains Pests: Cotton Quiet; Sugarcane Aphids, Banks Grass Mite Active in Grains

Sugarcane aphids cluster on the underside of grain sorghum leaves. The pest decreases yields and secretes a sticky waste called “honeydew” that gums up combine harvesters. (Texas A&M AgriLife Extension Service photo by Dr. Raul Villanueva)

This week has been both very quiet and manic at the same time. Not much has developed on the pest side for cotton this week, while sugarcane aphids and Banks grass mites have been very busy in our reproductive stage grain crops.

All have been subjected to continued hot and dry conditions with just a few scattered showers for a select few fields with a 0.2” or so to alleviate conditions for a few hours at best. Irrigation systems are running hard and ‘crunch time’ is upon us, ready or not.

Cotton

Our program cotton is a bit of a mixed bag of outcomes this week. Our stag-es came in between 3.9 and 7.2 NAWF with most fields hovering just above 5 NAWF. This would be almost on time to reach 5 NAWF, which is also peak-bloom and peak-water use. Many of these fields got off to a late and rough start.

While boll set has been pretty good, these plants just have not had the time to build much plant to sup-port very many fruiting sites. So, in this heat, we have many fields rushing to absolute cut-out of 3.5 NAWF with a disappointing number of fruiting sites. These diminutive plants are hanging onto as much fruit as we could possibly expect as they move from bloom to boll.

We also have other fields at the other end of the spectrum still running at a little behind 6 or 7 NAWF setting bolls as they continue to develop. It is no secret that soil moisture, whether from heavier rainfall and deep moisture or higher irrigation capacity is the difference in these fields but, fields with ‘easier’ starts do seem to be trending along the more developed fields.

Cotton pests have been hard to find in our cotton this week, with the exception of one isolated Lygus field. We have picked up a few two-spotted spider mites, a few cot-ton aphids, a few stink bugs and a lonely bollworm egg. We should be on alert for all of these pests.

We have reports from areas not too far away with any one or several of these at ET. The annual arrival of the migratory bollworm population is due any day now. While our trap numbers have been very light with almost all worms going to corn, this can change quickly and has for some of our neighbors.

Corn

Our program corn ranged in stage from V10 to full dent stage this week with the earliest replants just going into green silk. Or, if you prefer, a stage when corn ears get too tough for bollworms, just in time for younger fields to be their prime target.

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Pressure so far has been remarkably light, even in corn where the worms should not be an economic concern. Hopefully, most of the expected bollworm migratory population that caused so many problems to our south will sink into our younger corn too.

For several weeks our spider mite specific beneficials have held populations in check, despite triple digit temperatures and our older corn making sugars to fill ears that send the mites into overdrive. That has come to an end. Several of our program fields reached ET for BGM just as they came to dent stage.

A few more weeks and perhaps we could raise our ET levels as corn matures out, but today, the mites would rob far too much yield and possibly weaken stalks causing lodging if they are allowed to thrive over our research proven ET levels. Almost half of our older fields needed treatment this week and the other are nearing ET.

Mite populations remain low in our younger corn but deserve monitoring. ET for all mite species remains at 3.5 to 4 on the Texas A&M 0-10 mite damage rating scale. This ET equates to mites on 35% to 40% of a healthy corn field’s leaves, usually starting from the lower leaves and moving up the plant.

Sorghum

Our program sorghum ranged in stage from V8 to soft dough. The sugarcane aphid again took the majority of our focus with most of our program fields reaching ET for the aphid shortly following boot stage. The aphid seems to again be increasing relatively slowly but steadily during whorl stages, then increases rapidly post-boot.

While there are some sorghum fields in the area, mostly dryland, that somehow did get a legitimate early start that are now going into hard dough with only light populations of SCA, this pattern seems to be holding true for all fields established later or are at a later stage.

We picked up our first headworms in our program sorghum this morning, both were bollworms. These were the first headworms we had noted this year on post-boot sorghum. Banks grass mites continues to be a nuisance in our program sorghum also with a few fields nearing ET alongside the SCA.

So far, we have only treated for the SCA and the beneficials have then cornered the mites and few surviving aphids, but each situation and field should be evaluated for each pest need.

We have been able to place a BGM efficacy trial in a hot-pocket of mites within one of our program’s seed milo fields with hopes of getting you the latest product efficacy data in case the BGM issue in sorghum spreads and becomes economic in the near future. Today, we completed our 10 DAT counts.

The trial consists of all labeled products that might be used in this area. These three products and an UTC were arranged into a small plot-CRBD with treatment made via backpack CO2 sprayer at 16.2 GPA.


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