–by Dr. Jeff Whitworth
New KSU extension publication available from KSU co-authored by Dr. Holly Davis and Jeff Whitworth.
Month: August 2019
Sorghum Update
–by Dr. Jeff Whitworth
The 1st sugarcane aphids have been detected in Kansas (i.e., Mr. Jeff Seiler, et al., reported finding colonies (see pic) on 30 July in Sumner County). Most sorghum is in the whorl to boot stage throughout south central and north central Kansas and thus this situation needs to be closely monitored throughout the rest of the season. Unfortunately, “headworms” will just be hatching, probably at pretty good infestation levels, about the same time as these sugarcane aphids will probably be trying to colonize. Fortunately, however, there are a pretty good number of beneficial insects which seems to have really helped control the aphids the last couple of years.
Predator eating an aphid (picture by Jeff Seiler)
Soybean Update
–by Dr. Jeff Whitworth
The usual soybean defoliators, i.e., thistle caterpillars, garden webworms, green cloverworms, etc. have just started feeding again as small larvae. However, soybeans should have enough foliage, and the growing conditions are good enough, that this feeding should be negligible. Please note, Ms. Rene Hessel, a soybean researcher for KSU, and a soybean aphid detector extraordinaire, reported finding the first soybean aphids in Riley Co. on 7 August (see pic). Soybean aphids have migrated into Kansas every year since 2002, however, there has only been a couple years in that time that conditions were conducive enough to allow the aphid populations to build up to treatable levels. Most conventionally planted soybeans are in the early reproductive stages throughout south central and north central Kansas, so these aphids warrant periodic monitoring.
Also, just FYI. There seems to be a healthy number of stinkbugs (see pic) in most soybean fields at the present time. Remember, when pods are filling, the beans are vulnerable to both “podworms” and these stinkbugs.
Soybean aphid (photo by Rene Hessel)
Adult Green Stinkbug
“Bugs” To Be On The Look-Out For
–by Dr. Raymond Cloyd
Green June Beetles: lots still flying around. This has been one of the best…or worst years…depending on your perspective.
Japanese Beetle Adults: many are feeding on fruit trees and roses.
Bagworms: time is running-out in regards to applying insecticides…you have about two to three more weeks…and then it is too late.
Mosquitoes: with all the rain and moist conditions, mosquitoes (adults) are very prevalent.
Milkweed Aphids: many milkweed plants are literally covered with the milkweed aphid. Simply use a forceful water spray to dislodge them from plants.
Squash Bugs: eggs have hatched and nymphs are looking for suitable feeding sites…on the leaf underside.
Mimosa Webworm
–by Dr. Raymond Cloyd
Mimosa webworm (Homadaula anisocentra) larvae (=caterpillars) are now feeding and creating protective habitats on honeylocust (Gleditsia triacanthos) and mimosa (Albizia julibrissin) trees, which are quite noticeable in the Manhattan (KS) area. The larvae (=caterpillars) are 1/2 inch long when fully-grown (Figure 1),
Fig 1. Mimosa Webworm Caterpillars Feeding On Leaves (Auth–Raymond Cloyd, KSU)
Fig 2. Mimosa Webworm Webbing On Branch End (Auth–Raymond Cloyd, KSU)
Webbing commonly starts at the tops of trees and serves to protect caterpillars from natural enemies (parasitoids and predators) and insecticide spray applications. Heavily-infested trees are brown or scorched in appearance (Figure 3) as the caterpillars skeletonize the leaf tissue. Caterpillars eventually fall from trees on a silken strand before pupating. Mimosa webworm pupates in bark crevices or pupae are glued to structures (e.g. buildings).
Fig 3. Mimosa Webworm Feeding Damage (Auth–Raymond Cloyd, KSU)
In regards to controlling mimosa webworm infestations, it is probably too late although initial damage may be minimal. Insecticides that can be used to suppress mimosa webworm populations, in which the caterpillars are exposed, include: acephate (Orthene), Bacillus thuringiensis subsp. kurstaki (Dipel), spinosad (Conserve), and several pyrethroid-based insecticides (e.g. bifenthrin, cyfluthrin, and permethrin). Read the label of each product to ensure that “webworms” are listed. High-volume spray applications are required to contact the caterpillars inside the protective webbing. If trees are already heavily-infested with webbing then it is too late to apply an insecticide. If possible, selective pruning can quickly remove isolated or localized infestations of mimosa webworm.