Alot of activity this week in the insect world… This is a long post with of information about false chinch bugs in soybean, Japanes beetles in corn and soybean, yellow-striped armyworm in beans and turtles and rice stink bug in rice – if you don’t have time to read it all, you know what is there so you can scroll the parts you are interested in.
I received a couple of phone calls about false chinch bugs on seedling soybeans – even when seed was treated with an insecticide. Dr. Scott Stewart at the University of Tennessee in Jackson did a recent blog post about false chinch bugs. The blog post mentions Dr. Stewart’s experience with false chinch bugs and the best products available. This pest can be difficult to control, not necessarily because of insecticide resistance but exposure issues because they spend a lot of time underground.
We are also hearing about yellow striped armyworm in beans. Thresholds are based on defoliation not a number of insects per sweep. Treatment is warranted when you reach 30% defoliation in the vegetative stages (V) and drops to 20% when in the reproductive stages (R1 to R6.5). See the picture below for an idea of what 20% and 30% looks like; remember this depicts one leaflet on a soybean leaf (three leaflets make up a leaf) so each leaflet on each leaf needs to average 20-30% defoliation to have reached threshold.
A couple of weeks ago, I had a post on Japanese beetles. They are out in full force now and their range has expanded. For soybean thresholds are based on defoliation (see above). In corn, they clip silks similar to corn rootworm adults. There needs to be an average of 3 or more beetles per ear during pollination. Additionally, silks need to be at least ¾ inch long for successful pollination; so silk clipping that leaves less than ¾ inch is problematic. Japanese beetles are only pests during pollination and pollination is usually completed in 3-5 days – so it is important to understand the relationship of the crop development and the insect. After pollination has occurred, Japanese beetles are not considered a pest. For more information on pollination in corn click on this link.
Today I received a phone call about rice plants being clipped off and the tops of plants floating in the water. It appears that turtles are the likely culprit of this damage and there isn’t much that can be done about them. There isn’t alot of information on this, but here is a recent article about this problem in Arkansas.
Also, we have posted a couple of times about high numbers of rice stink bugs found in wheat earlier in the season. We are on track for a bad rice stink bug year. I got a call about high numbers of rice stink bug in sprangletop in a rice field. The rice is a couple of weeks away from heading – so they are not a problem at this time. I heard reports from Arkansas that rice stink bugs are above threshold in clean rice fields but the rice is a couple of weeks from heading there also. Both of these cases are situations to WATCH but NOT treat. Until rice heads, rice stink bugs are not a pest of rice. It is likely that the stink bugs will leave before panicles emerge and you can avoid the cost of an application if that happens.
And as a last note: One advantage of early planting is letting plants get ahead of the insects before the insects have a chance to build. This year, there have been a lot of late plantings so insect problems should be expected to be worse on the later planting. Along those lines, cutworms are still impacting young beans. Insect problems will likely be persist with late planted crops – so be on the lookout.
For recommendations for pesticides, check out the MU Pest Management Guide.