Back to the other Hotline tapes

This is Jack Bacheler, Extension Entomologist at NCSU with the Wednesday cotton insect update. This is Wednesday afternoon, July 15, 2009.

Although we continue to have a scattering of treatable levels of plants bugs, spider mites and cotton aphis, to our knowledge, none of these pests is causing general widespread damage. Most of our cotton acreage is short on water, with demand increasing daily now that boll production is generally underway across the state.

The bollworm moth flight seems to be just now getting underway in our southern most counties, perhaps a few days earlier our historical average. The next week or so should provide us with an indication of the size of this year’s flight. On our few remaining non-Bt cotton acres, the arrival of the flight in an area provides an opportunity to intensify scouting to twice a week, focusing in bollworm eggs in terminals and fruit. With most of our cotton acreage either Bollgard II, and to a lesser degree WideStrike and Bollgard, bollworm thresholds, if met, typically occur approximately one to two weeks after flight initiation in an area. Although Bollgard II and Widestrike cotton fields often do not often reach the threshold of three, 1/8-inch bollworms on fruit, our lower spray environment has opened the door for stink bugs - so scouting is just as important with Bt technology.

Stink bug levels appear to be higher than in 2007 or 2008, with brown stink bugs dominating the scene over greens up to this point. Stink bug damage to cotton can vary from miniscule to significant, and also routinely varies from field to field. Remember to follow the suggested dynamic threshold of 50, 30, 10, 10, 10, 30 and 30% internally damaged bolls by week of bloom. That means that producers should be following the protective threshold of 10% during weeks 3 through 5 of blooming, the time of maximum crop susceptibility to stink bug damage. In a series of 49 stink bug threshold tests conducted in NC, SC and GA, the dynamic threshold was shown to be more profitable than either the 10% or the 20% static threshold at all levels of stink bugs, and resulted in more than $30/acre net returns compared to the 20% threshold under high stink bug pressure.

We’ll have much more on stink bug levels and potential damage in three coming weeks with threshold tests underway in all four of our major cotton production regions of the state. Just a reminder that you can keep up with several of our light traps on line by clicking on the picture of the light trap at our Cotton Insect Corner web page.

See you next Wednesday on July 22.