Texas Plains Pests: Migratory Bollworms Remain an Uncertainty

Trap with Bollworm - Corn Earworm - CEW moths. Photo: Gus Lorenz, Extension Entomologist, University of Arkansas, Division of Ag

General Status

Very little has changed over the past week in weather or pest status with crops, mites, and aphids only getting ‘hotter.’ A change in the weather during crunch time and peak water use for so many of our fields would give a great aid, if the rain would come gently. Some of our neighbors from not too far away received some of that damaging wind and hail that devastated already hard fought over fields.

Meanwhile, we are still expecting the arrival of the migratory bollworm population that may or may not arrive and may or may not be an issue when they get here. If cotton continues on its rapid crash into absolute cut-out that it is currently on, there might not be much to feed on except tough bolls or late corn.

Cotton

This week our scouting program cotton ranged in stage from absolute cut-out of 3.5 NAWF (nodes above white flower) or less back to 6.2 NAWF with most fields hovering around 4 NAWF.

The rapidity that many of the later fields are racing from 7 NAWF down to 4 or less, undoubtedly a factor of the heat and irrigation capacity, are leaving many plants with a limited plant structure and fruiting sites to set is a concern. Yet the percentage of fruit set remains relatively good.

These plants are holding and converting as many squares to bolls as we can possibly expect.

In our cotton, we had no economic pest issues this week. We did find a few bollworm eggs in areas not near late corn or sorghum, a few scattered Lygus, cotton aphids are in most fields at light levels, and spider mites (two-spotted only) are not an uncommon find.

We continue to recommend diligence in scouting all Bt technologies for bollworms, but as our moth trap numbers elude us, no major migration of bollworms has started yet. The few bollworms we are currently dealing with are moving from older corn, and so far, they vastly prefer to find the later corn currently early in ear development.

There remains a notable beneficial population in our cotton, targeting the aphids primarily for now, that could prove helpful if the bollworms arrive in time to damage this cotton crop.

Corn

Our program corn ranged in stage from VX to full dent this week with most of the first late planted fields tasseling and pollenating this week. Control of the BGM (Banks grass mite), which had increased rapidly in the heat despite good mite predators, in our older corn is adequate to good. BGMs are now increasing in most of our younger corn shortly after tassel stage and we are watching them closely.

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In our fields (of any crop) we have not seen any of the red mites to date that are causing issues north of Amarillo, but they are in the area on a wide range of hosts including lawns and trees. Crop diseases are sub-economic and seem steady in most fields. We found a few more ears damaged by western bean cutworm, but those were the only signs of any ear feeder other than bollworms or corn ear worms.

Many of our older corn fields are experiencing a rapid and slightly premature dry down. While some sections of particular fields are at this time mysteriously ahead of other sections, we have been digging roots looking for a cause. All of the fields we have noted drying down prematurely in late dent stage all have shallow roots.

According to Dr. Jourdan Bell, Agronomist District 1, this was likely caused by the cool and wet May that allowed the corn to draw moisture from near the soil surface. Now the plants do not have the depth of root needed to keep pace with these extreme temperatures over this extended period of time and premature dry down is the result. Just how much this is likely to impact yield is debatable, but some light grain weights and some lodging potential are distinct possibilities.

Sorghum

In our program sorghum fields the stage ranged from V9 to dough. The sugarcane aphid (SCA) remains the pest of note by far this week. Control looks adequate to superb in fields already treated for SCA. The pattern remains that the aphid slightly increases in population while infested fields are in the whorl stage, then increases rapidly once boot stage and later are reached. In most cases, fields were not at 50% bloom before the aphid reached economic levels.

There remain some very early fields in the area now at late dough, nearing black line that seem to have escaped any heavy damage or infestation, but these are the exception. 100% of our May or later planted sorghum seems to be following the SCA pattern.

BGMs remain a concern for most of our sorghum fields. Thus far, we have only treated for the SCA and a hefty population of predators have shifted to the BGM holding them from getting out of control.

We do have sorghum in bloom which is at risk for the sorghum midge. Our highest population only reached 0.22 midge per head. Headworms, of any species, are also a rarity in sorghum so far. Our highest headworm population was 0.2 small worms per head.


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