Texas Cotton: Bollworms Still Bear Watching In Hale, Swisher Counties

Owen Taylor
By Blayne Reed, Texas AgriLife, IPM Extension Agent, Hale and Swisher Counties August 24, 2013

Last week’s rains and cooler temperatures slowed much of our area cotton from reaching that absolute cut-out stage (3.5 NAWF) this week. I feel we had done a pretty good job of managing our later planted cotton this season so that most fields were not ‘late.’

Now there are several cotton fields with varying levels of late concerns. With a typical fall, we should be able to count on an August 24th bloom making a harvestable boll in Hale and Swisher Counties seven out of ten seasons, but not much after that date.

This makes managing fields at 4 our 5 NAWF this week difficult to manage, especially as our sub-moisture remains short and our September heat unit accumulation is in question. It remains a tightrope act with irrigation – stressing cotton into timely cut-out, avoiding stress that triggers harvestable fruit shed and all the while preventing ‘junk’ fruit production from ruining an otherwise good field.

Our program fields so far this week have ranged from well cut-out with no new blooms noted to 5.7 NAWF. All fields avoiding recent hail events have a solid boll load ranging from a late field with 2.7 ‘made’ bolls per plant to a finishing up 10.2 ‘made’ bolls per plant.

Most were reaching absolute cut-out (3.5 NAWF) this week with 5 to 7 ‘made’ bolls per plant. Boll set has been relatively high and later fields have plenty of squares and potential, but limited time.

Actual field pest pressure remains light, but we remain on alert for multiple pests. For the first week in nearly a month, we had no new fields reach ET (economic threshold) for Lygus. Although several cotton fields remain at risk for Lygus damage many other fields are developing past economic Lygus concerns via heat unit accumulation and boll development. Lygus populations remain very spotty.

We noted in our blog earlier this week that a suspected large bollworm moth flight had begun and that most moths appeared to be drawn more to our large amount of late corn and sorghum rather than cotton.

This trend seems to be continuing as the only bollworm eggs we are finding in cotton are not near any corn fields. Our fresh bollworm egg lay ranged from 0 to 8,250 eggs per acre in cotton this week. This remains light by any standard and predators are expected to take a toll on eggs and small worms.

The ET for bollworms is roughly 10,000 to 12,000 worms (not eggs) per acre, crop stage depending. It is quite likely that some area non-BGII cotton will need to be treated this week or next for a late population of bollworms, matching the still at risk ‘lateness’ of our crop.

Owen Taylor
By Blayne Reed, Texas AgriLife, IPM Extension Agent, Hale and Swisher Counties August 24, 2013

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