What is in this article?:
- Kudzu bug expected to be statewide in Alabama by 2014
- Threshold questions
- Check fields closely
- Kudzu bugs could be a statewide issue for Alabama soybean producers in 2014.
- Heavy pest pressure this year was limited to the central part of the state.
- Research has found a wasp parasite that does a good job on the insect pest.
AUBURN UNIVERSITY EXTENSION Entomologist Tim Reed scouts a soybean field in northeast Alabama for kudzu bugs. Reid expects the insect pest to be statewide on Alabama soybeans in 2014.
At the beginning of the growing season, Reed says his threshold was based on data from counterparts in Georgia and South Carolina who had been fighting the kudzu bug for a couple of years.
“They were saying to wait until you have one adult per sweep and immature present. That’s not really a good threshold to use because you can have a few adults and then have a few immatures, and you’ll get that in a sweep net or just looking on the plant. But I really think you need a pretty respectable number, and five per sweep is a threshold that worked in one study in Georgia where they sprayed every week starting June 28, on early planted beans.
“They sprayed at R1, at R2, at one per sweep, two adults per sweep. When they had about five per sweep with two adults and three immatures together, they got a yield reduction of about five bushels per acre. That’s one of the best tests I’ve seen in terms of thresholds.”
One thing he’s encountering, says Reed, is that just about every field has kudzu bug in it, but you might not pick up but one per sweep, or one per 20 or 25 sweeps.
“In a lot of fields, you’ll pick up enough that you’re a little bit concerned about them, and you’re picking up a stink bug about every 10 sweeps or maybe two stink bugs per every 10 sweeps. You’re also picking up three-cornered alfalfa hoppers, a few loopers, green cloverworms, and you’re thinking about spraying a fungicide.
The critical decision comes when you’ve got disease and insect problems in a field, says Reed.
“You might make a decision to spray a fungicide and bide your time to see what the disease does. That’s when it becomes more difficult to make a decision to apply an insecticide. If they’re R4 or early R5 soybeans, there’s still time for worms to get bad, and if you spray and kill all of your residuals, it may increase the worm problem.”
Some consultants are cautious about spraying soybeans with sub-threshold levels of insects because of podworms, he says. “If podworms get down in the bottom, you can’t get them with a sweep net, and they’ll chew on the beans and hurt yield.”