Texas Plains Pests: Hot, Dry Conditions Keeping Activity Limited

General Status

Not much has changed again this week. We are still in a prolonged extremely hot and dry pattern. We have had a few below triple digit days due to a front that passed through recently. A lucky few did even seen a few rain drops that smelled like rain for a short while but I do not believe any 4-wheel drives were in danger of engagement due to the events. Much more is needed quickly if it is to have any helpful impact on this year’s summer crops.

Pests too are keeping the pressure up similarly to last week. Spider mites and sugarcane aphids are rampaging where they can get away with it until we are forced into treatment for them. At least those treatments are working very well.

Also, on the positive side is that we have seen little to nothing of a large migration of bollworms yet. Outside of post-tasseled corn, this pest remains hard to find, for now.

Cotton

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This week our Plains Pest Management scouting program cotton ranged in stage from 5.4 NAWF (nodes above white flow-er) to absolute cut-out of less than 3.5 NAWF with over 90% of our fields slamming into absolute cut-out in the extreme temperatures for such a protracted time. The plants continued setting fruit pretty well considering the conditions, but all fields have been experiencing a sharp increase in fruit loss as they reach cut-out stage.

We experienced no economic pests in cotton this week again. Bollworms were hard to find, but we did find a few boll-worm eggs in lusher fields far from any later corn. Even when we did find eggs, they were only ranging between 4,000 and 7,000 eggs per acre. We should never treat for bollworm eggs on the High Plains as egg as early instar mortality could be enough in many cases to control a large number of worms.

We are still running a moderate to good population of beneficials in our fields. We only found one field with any live worms and that field only totaled 1,076 bollworms per acre. These hard to find levels are well below our High Plains standard ET (economic threshold) of 8,000-10,000 live worms per acre and hardly detectable on the new 6% harvestable fruit damage method of scouting.

Lygus were a little easier to find this week in our cotton, but only about half our fields held detectable populations. Our highest field held 1 Lygus per 4.5 row feet. This could be a red flag for future issues with Lygus soon, but with natural fruit shed in the heat so high, these Lygus may very well be feeding on fruit already being shed. Cotton aphids were again found in most fields this week, but at levels that average less than 1 aphid per leaf in most cases.

Spider mites were found in more than half our fields this week, but only on 1 or 2 of the uppermost leaves in a few spots so far. With a few cooler and dewy mornings, the mite potential issues should drop significantly as the days shorten for fall. We are still picking up an occasional stink bug in cotton, but this has dropped from already sub-economic levels from earlier this summer.

This up coming week would be perfect to evaluate your fields for verticillium wilt pressure. We are noting most of our cotton fields have this plant disease at some level. Some fields will be high enough to initiate some level of integrated verticillium management plans for fields next year.

Corn

Our program corn this week ranged from VX to 10% starch line with most of the replant corn between pollenating and dough and older corn in dry down that could easily be described as rapid desiccation. As we worked through this rapid dry down issue this week with Dr. Jourdan Bell, Agronomist district 1, a new term might have been coined to describe why so many area older corn fields are falling into this situation. “Lazy Corn Root.”

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All of the fields in this rapid dry down were planted in May and went through that cool, wet period that has now been followed by prolonged heat and drought. Dr. Bell is just describing how plants with plentiful early moisture, particularly those that also experience cool temperatures at the same time, do not develop roots deeply or fully. Add to these factors a limited irrigation capacity that cannot supply these plants and their short, underdeveloped roots need hand-to-mouth and we see exactly what is happening in these fields.

Just as fields should start the natural dry down process, we are seeing rapid desiccation as the soil moisture near these ‘weak’ roots drops to zero, even as pivots deliver all they can at the same time. Just how much this is likely to impact yield remains debatable but some light grain weights and some lodging potential are a possibility. We will be spot checking fields in this situation this next week for fall armyworms (FAW) feeding on the ear shank. If any FAW do move to these ear shanks, the chance of ear lodging increases drastically.

Banks grass mites remain our largest corn pest concern this week, but most of our older corn has rapidly developed, or rather dried, past mite issues. Mites continue to increase in our later planted corn, but still below ET so far. If conditions do not change or mite specific predators to not increase a few fields might reach ET soon.

We did find some of the ‘new’ red mites we discussed last week in our corn locally this week at low levels. These mites are causing more serious issues north of Amarillo than our usual BGM and may need special attention if confirmed in your fields.

We found more indications of western bean cutworms this week in the older corn. This was well below ET, but younger corn should be scouted for this more unique pest this week.

Sorghum

Our program sorghum ranged in stage from VX to late dough this week. All of our program fields, even the very drought stressed ones, have sugarcane aphids present at some level. The pattern continued again this week with the SCA averaging slight but sub-ET population increases until fields reach boot stage. Shortly after, the SCA populations explode to economic levels and beyond.

As fields reach ET, we are conversely recommending treatments that still seem to be working very well. The BGM made larger increases in the drought conditions in some of our older sorghum fields this week without the hinderance of the SCA covering many leaves, but remained just below ET.

Headworms and midge remain hard to find in our fields with the highest populations reaching 0.18 small worms per head and 0.08 midge per head. Whorl stage sorghum does have a substantial population of fall armyworms moving into feed this week. Whorl stage feeding should not be economic below 25% to 35% foliage loss. These are levels rarely if ever found.


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