Texas Plains Cotton: Lygus Remain Most Prominent Pest

    Tarnished plant bug, aka lygus bug. Photo: Lisa Ames, University of Georgia, bugwood.org.

    General Status

    Hot and dry week. That is just what the doctor ordered for the late, lush cotton fields that received so much rain last week but not what the grain fields trying to fill grain. It is hard to have it both ways, especially across the turnrow. As the crops are coming in a touch late, so it seems are several of the pests. There is still a lot of activity in our area fields and scouting remains paramount a bit longer in the season this year.

    Cotton

    We are still running several dozen fields behind schedule in the PPM scouting program, but all fields have been scouted in the past 8 days. We still have almost 30% of our fields have not reached absolute cut-out of 3.5 NAWF yet. This is at least 10% higher than my assumptions from last week. These fields are mostly late planted and under the heavy rains of 2+ inches early last week.

    Most fields reached that milestone and stopped trying to set nearly impossible to make at this point bolls. Several, including our dryland fields, are entering multiple weeks post absolute cut-out. One field in southern Hale was already sporting the very welcome sight of an open boll today.

    While this is peak bollworm season in cotton, Lygus remain our most problematic and only economic pest in cotton this week. We had 6 fields we had to treat for Lygus populations. In these fields the Lygus were all under 1 Lygus per 2 row feet and were causing fruit drop of thumb sized bolls and larger in substantial numbers.

    These bolls should mature in time and make good lint. We should be very careful about deciding to make Lygus treatments this late. We had at least twice as many fields with similar populations, but feeding was limited almost exclusively to young fruit that were naturally shedding anyway post absolute cut-out.

    While they were harder to find again this week, bollworms were certainly still in the mix, but we found no field at ET in the last 8 days. There are 2 non-Bt fields that were close 8 days ago that are slated for my eyes tomorrow that I am concerned about. Our highest bollworm population topped out at 5,037 worms per acre and our highest egg lay came in at 4,429 eggs per acre.

    A slim majority of our fields came back with no worms or eggs found with most moths being attracted to corn as a preferred host plant. Cotton aphids continue to pop up in most fields at very low levels. Our highest exception came in with 13 aphids per leaf after leveling at less than 3 last week. This late field had recently been given a late nitrogen application, factors that are known to cause cotton aphids to flare.

    The ET for cotton aphids ranges from 50-100 aphids per leaf until open bolls are found in field. Once open cotton is found, the ET drops to 12 per leaf to prevent sticky cotton. Until then, on late fields, a moderate aphid populations might actually help draw the plants down quicker resulting in a bottom line benefit that pre-vents outright rankness. Stink bugs continue to be found at sub-ET in most fields again this week.

    Corn

    Our oldest corn has started forming a starch line and should start drying for harvest successfully. Our youngest fields have all entered silk stage. We have not had any corn field reach ET for any pest yet. We are still watching Banks grass mites gradually increase through a good beneficial population to threaten fields later in the calendar year than ‘normal’ but right on time for the stage of corn under the weather conditions we are seeing.

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    All disease pressure seems caped for now with no increases noted. Bollworms, or in case referred to as corn earworms are easily found in all our fields, but feeding remains limited to tip feeding only, where it is of none or very limited economic impact, unless the field is sweet corn intended for vegetable production.

    Sorghum

    Our oldest sorghum field is in late dough stage with our youngest just starting to show a few flag leaves here and there. Sugarcane aphids were our only economic sorghum pest this week with several more fields gradually moving into economic issues. So far, we have had to treat just over half our fields for the aphids with more issues expected.

    Aphid populations seem to hold steady until boot before they begin to outpace beneficial populations to reach ET with just a few exceptions. These exceptions are moving both ways and include some fields at dough stage with populations that seem to be dropping and populations that had to be treated at flag leaf.

    Headworms (bollworm/corn ear-worm and fall armyworm) continue to be found in most fields. Here too beneficials, and perhaps the corn draw of the moths, are holding most fields below economic levels in our fields. Our highest population this week came in at 0.56 small worms per head and 0.46 large worms per head.

    In most fields, FAW account for less than 30% of the population. BGM can be found in most sorghum fields at sub-ET levels again this week while Lygus and stink bugs are beginning to find the maturing grain attractive. Our highest population of Lygus came in at 0.9 Lygus per head while stink bugs were even less at 0.3 per head, both well below ET. Midge should still be a concern for any blooming sorghum.




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