Hi, this is Jack Bacheler, Extension Entomologist at NCSU with the Wednesday Cotton Insect Update. Today is Wednesday, August 23.
The next bollworm moth flight began this past weekend in our southern counties. However, only a few late maturing cotton fields will likely be impacted by this flight. Female bollworm moths have largely turned their egg laying mission elsewhere, for example soybean and other hosts. However hard as it may seem to the rest us in our largely droughty state, some areas have good moisture levels and cotton has not bloomed out the top. For scouts who are only monitoring upper very small and bloom tagged bolls, be sure to raise the bollworm threshold by three or four fold, say to the 8 to 12% live worm level.
Stink Bug Damage
In our widely scattered stink bug tests, damage to quarter sized bolls is dropping to well below threshold levels. Additionally, in many cotton field, most bolls are now beyond the stink bug safe stage of 3 ½ weeks old. For cotton fields showing 3 or less nodes above first position white flower, damage thresholds can probably be raised to the 20 to 40% level without a noticeable yield loss. A few widely scattered, rapidly growing cotton remain susceptible to bug damage though they're getting few and far between.
Spider mites are showing up throughout much of the state as this dry weather continues. In most cases, cotton is too far cut out to justify treatment. However, there also appears to be a couple of close treatment calls - that is very high mite and egg levels in some less mature cotton with significant reddening and large scale defoliation. If this is the case throughout much of a cotton field, treatment may be justified. If treatment is needed, Kelthane (now sold as generic dicofol) at a quart of product per acre appears to be the best bet here, although another product Oberon has shown promise in some 2005 tests. It would appear that treatment would be justified in very few situations.
At this point, our insect year appears to be thankfully winding down. What we need now is some rain to fill out upper bolls.
I hope you plan on attending the September 14 Cotton Field Day at the Upper Coastal Plain Research Station near Rock Mount.
In case we have a surprise or two, we'll have another cotton insect report next Wednesday, August 30. See you then.