What is in this article?:
• There’s always something new and different in the world of crop insects.
• There are sporadic and incidental pests and then there are others that can be counted on to cause problems every year.
AUBURN UNIVERSITY EXTENSION Entomologist Ron Smith, shown here during a field day this past summer, says there are always new things to talk about in the world of crop insects.
New scouting techniques, thresholds
Sweep nets, says Smith, have proven to be a good insect survey tool in peanuts, soybeans and even in cotton for those who want to look for live stinkbugs rather than damaged bolls.
The more drilled beans you have, the more you’ll need a sweep net, he says.
This past year, Smith says Extension began promoting a new threshold for making foliar sprays for cotton thrips.
“The first true leaf stage is the ideal time to apply foliar sprays. We want to do that especially where cotton is planted before May 10, because that would be in the heavy thrips window. This is based on multi-year, multi-state research from Alabama to Virginia.”
As the pigweed problem continues to spread, and growers increasingly move to residual herbicides, some of those herbicides will stunt the growth of cotton and inhibit root growth, says Smith. “Anything that inhibits growth below ground also impacts it above ground and keeps it in the susceptible thrips window for a longer period of time.”
Smith says he thinks stink bugs remain the greatest potential economic insect of cotton, particularly in central and south Alabama.
“Populations have been low in the last couple of seasons, but I don’t think they’ll always be low. We think the colder winters of 2009 and 2010 repressed stinkbug populations during those growing seasons, and the extreme heat and drought in June of 2011 suppressed the populations.”
It’s important to remember that stink bugs have two key reproductive periods, he says.
“Corn and other non-pod hosts are used by stink bugs in the spring, and then there’s a late-summer population explosion on soybeans. They don’t do much reproducing on peanuts, and they do a limited amount on cotton.
“It seems that in wet seasons, stink bugs carry more boll rot organisms on their snouts, which they use to penetrate and get into the bolls. So you get more boll damage in wet seasons than in dry seasons.”
When scouting for stink bugs in cotton, pull a random boll sample, advises Smith.
“Looking for stink bug damage on bolls is the best tool for cotton. We want to pull one boll per acre and no less than 25 per field. Then, we want to crush those bolls and look for any signs of warts or deteriorated tissue.
“Early on, there aren’t a lot of bolls at risk, and this threshold changes as we get into summer. Stink bugs cause the most damage at about week three through six of bloom, about a four-week period.
“Use a 10-percent damage of internal boll threshold. Crushing bolls takes a lot of time, so crack the bolls until you reach a threshold. If you pull 25 bolls, after you reach the third one with internal damage, you’re over 10 percent, so you throw away the rest of them. That’ll save a lot of time.”