This is Jack Bacheler, Extension Entomologist at North Carolina State University with the Wednesday Cotton Insect Update. Today is Wednesday, June 6.
Things are much improved since last week, with both our cotton crop and with the thrips situation, as much of our state received significant rainfall this past weekend. Accumulation in many areas was in the 1 to 2” range. At our moisture-friendly Rocky Mount and Tarboro thrips test sites, and hopefully elsewhere, migrating adult thrips levels have dropped off markedly since last week at this time. Additionally, cotton seedlings are now growing off rapidly, with far less thrips damage evident in the new terminal growth. All and all, however, this will likely go down as another rough thrips year for many North Carolina cotton producers, given the very dry weather and high thrips levels of the past few weeks.
Several additional thrips samples sent into the NCSU Disease and Insect Diagnostic Clinic have revealed that western flower thrips were part of the high thrips survival following foliar insecticides on some farms, thus helping to explain some of our control difficulties.
In the coming weeks, especially in younger cotton, be sure to check terminal buds for new growth. If the tiny new leaves look shiny and have less than 2 or 3 immature thrips on two to three leaf cotton, a foliar application is not needed. Also, 5 true leaf cotton with adequate moisture is probably safe from further economic damage from thrips.
With some luck, the threat of spider mite buildups has probably eased off some, but if our predicted upcoming 95 to 100 degree weather is accompanied by another bout of dry weather, spider mites still could become a problem and warrant watching. Spider mites can also sometimes build up under good moisture conditions, most commonly in reduced tillage cotton fields on which a foliar insecticide was used for thrips and/or plant bugs.
It appears that stink bug levels, and perhaps plant bugs, may be down this year, although the extent of possible economic bug damage to small bolls this year will begin to reveal itself approximately 2 weeks into the bloom period.
So far cotton aphids appear to be present at low levels. Remember though that cotton aphids can build quickly and on average develop into treatable population on approximately 7% of our acreage.
Meanwhile, continued good soil moisture levels would get us beyond remaining possible thrips problems and lessen the odds of spider mite outbreaks.That’s it for this week. See you next Wednesday, July 13.