Texas High Plains Cotton: Plant Bugs Widespread and Building

    Tarnished plant bug nymph on cotton bloom. Photo: Virginia Cooperative Extension

    General Status

    This week we have had several isolated but beneficial rain clouds move through our area. These provided great relief without much damaging weather, but coverage was not very widespread. Even along the edges of where these storms passed remains bone-dry.

    Our irrigated crops continue to progress with tired irrigation systems. Most of our agronomic plant measurements we take through our scouting program indicate serious drought stress looming without additional help soon. Yet, peak water use is just around the corner for most fields.

    Pests remain light with a few cotton field exceptions. Our bollworm moth trap numbers remain ridiculously light, but it was clear all that all of the moths trapped were fresh and likely the front runners of a new flight beginning to arrive.

    How large this new flight will be and how many acres of crops they will threaten remain to be seen.

    Cotton

    This week our Plains Pest Management scouting program cotton ranged in stage from match head square wild cat cotton up to 5.4 NAWF (nodes above white flower) with the vast majority of fields entering their 2nd week of consistent blooming. Our NAWF average has developed significantly from last week’s 7 to 9 NAWF average to this week’s 6 NAWF average.

    Fruit retention remains high with our drop mostly hovering around 12% and early bolls setting well. However, our plants are still generally very small statured and rushing into peak bloom and peak water use at 5 NAWF a touch early.

    Typically, we would like to see this developmental stage reached around August 5th,but most of our fields will be at 5 NAWF or less by next week without substantial moisture help very soon.

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    Most of the cotton belt now considers this 5 NAWF level as cut-out. While this is a very important milestone, and the plant is not likely to ever substantially build much fruiting structure past the 5 NAWF point, I do not feel this works for the Texas High Plains.

    Typically, our High Plains cotton fields will go into 1st bloom at 7 to 9 NAWF. This places more than half of our yields typically being set after the 5 NAWF point. Depending upon water availability, and numerous other input factors, our High Plains cotton could exhibit 2 or even 3 weeks of harvestable boll setting between 5 NAWF and absolute cut-out of 3.5 NAWF.

    On the other hand, if water and additional inputs are severely limited, hindered, or otherwise short, our High Plains cotton can race from 5 NAWF to absolute cut-out in a matter of days shedding most setting bolls along the way.

    The next 10 days will be critical for this year’s cotton crop. If a field is already short and no help comes, the growing season for that field will be effectively over without reversal very soon.

    Plant bugs have been our only pest issue in cotton still through this week. All but a handful of our latest fields are finally past economic fleahopper concerns. Without much lax time, Lygus has taken over as our main pest of concern. We can find Lygus at some measurable level in about 60% of our fields.

    Only 1 field required treatment for this pest this week with 1 Lygus per 2.3 row feet and an increased fruit loss of 24% after being 8% last week. We have several fields on our watch list as borderline with Lygus hovering at less than 1 per 6 row feet and drop above average, but still less than 20%.

    Lygus are highly mobile as adults that are capable of shifting host plants at will. With so many of their better preferred host plants either having recently been cut, controlled, or desiccating rapidly, and a fairly robust population in the environment, any cotton field in the region could be at risk.

    Often adult Lygus will travel through a field, leaving a quick increase in fruit drop that seems unexplainable but not quite economic. Unfortunately, they often leave their eggs behind that hatch 7 to 14 days later.

    These skittish but less mobile wingless nymphs can then do some serious economic fruit damage to cotton if left unchecked during boll set stages. While we regularly scout our fields utilizing drop cloths and whole plant inspections (for fruit loss counts and bollworm checks), drop cloths do not always capture adults.

    Often if we are finding an increase in fruit loss to economic levels and not enough Lygus to account for the loss, I will insist upon changing to the sweep net method. Using a sweep net will find the flighty adults if they are still in the field and have not just passed through.

    The ET for Lygus remains about 1 Lygus per 2.5 row feet with a prov-en increase in plant bug feeding induced fruit loss.

    Corn & Sorghum

    This week our oldest corn reached early dough stage and our youngest is still a few weeks away from tasseling. Our sorghum ranged between V4 and 50% bloom. Pests of any flavor remain hard to find in our grain crop fields. A very few sugarcane aphids were found in some sorghum and even fewer mites were found in our corn fields.

    We are not seeing that many bollworms/corn earworms in our corn ears yet. Fall armyworms feeding on whorl sorghum remains our most active pest and this feeding is far below ET.

    We started midge checks in our blooming sorghum fields this week with none found. We also did not pickup any headworm pressure from any species in booted sorghum.

    Beneficial populations have been enough to hold our scouting fields in check so far and the dry environment has not been overly conducive to disease development or spread.

    Much like cotton, many of our grain fields are also small statured and either in or nearing peak water use.




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