I am glad folks are paying attention to what is
happening in other areas. I had a few calls regarding bollworms this week--mostly
in response to the hubbub in Central and South Texas. So far, worm pressure in
cotton have remained light for the most part with some areas (e.g. parts of
Swisher, Floyd, and Hale counties) just starting to show increase in numbers.
Our Bt sentinel research plots at Texas A&M
AgriLife Research and Extension center in Lubbock are showing a few worms in non-Bt
plots—no activity has been spotted in any of the Bt technology plots so far. As
the season progresses, we may see increase in moth flights and the egg lay.
I wouldn’t spray for bollworm egg lay in West Texas cotton
as very few eggs make it to worms (thanks to beneficials!). Treatment decisions
should be made based on the amount of fruit injury and the presence of live
worms in both Bt or non-Bt fields. Since newly
hatched larvae must feed on the plant for the Bt toxin to be effective, delay
decision making until you can determine the survivorship of larger worms. The
threshold level before bloom is 30 percent or more damaged squares with worms
present. After boll formation, the threshold is 6 percent or more damaged
fruit with worms present.
Many of you are aware of the situation of worms breaking
through some of the Bt traits across various cotton producing regions including
the parts of Texas. We may experience similar events in the High Plains cotton
if it turns out to be a heavy bollworm year. For now, let’s hope it remains a quiet one but don’t let your guard down. Irrespective of what Bt traits you have, keep
scouting and be on the lookout. Remember,
once worms increase in size and dig into the lower plant canopy, it’s hard to get
them even with the most effective diamide insecticides.
