By STACY CAMPBELL
Cottonwood Extension District
Ok, I know I have already had an article on chinch bugs, but I thought I would wrap it up with a quick overview and summary of some keys points to ponder for farmers when facing them again next year.
Chinch bugs in Kansas are a perennial pest of just about any type of grass. Since they are true bugs, chinch bugs may attack any grass where they insert their mouthparts into the plants and suck out the juice.
They have caused problems in turf farms, golf courses, and lawns. In crops, they mainly affect sorghum and sorghum/sudan hay fields, but are occasionally problematic in corn and wheat.
Primarily, it is because of timing. As wheat is quickly maturing, chinch bug nymphs, which have been feeding on the wheat until the plants started drying, move elsewhere, seeking a new food source. Often, this is seedling sorghum or sorghum/sudan planted adjacent to those wheat fields that are now maturing, but in which the chinch bugs were perfectly happy feeding. This is called the walking migration because these nymphs can't fly or jump. They walk out of the maturing wheat seeking succulent grass to feed on. However, these small nymphs can only live a few days without food and can only walk about 50 yards without finding a suitable food source, says Jeff Whitworkh K-State Extension Entomologists.
Furthermore, it needs to be noted that the first generation of chinch bug nymphs migrating out of the wheat will not migrate through the entire sorghum field, and thus that is why you get the edge effect, of anywhere between 6 to 16 rows, give or take, of plants being affected.
There are two generations of chinch bugs in Kansas each growing season. But the first generation that is coming out of mature wheat fields and feeding on young seedling sorghum or sorghum/sudan plants is the main concern. Generally, by the time the second generation of chinch bugs nymphs are hatching and feeding, the sorghum and sorghum/sudan plants are big enough to withstand the feeding and will continue to grow well.
Insecticide-treated seed also helps as the nymphs seem susceptible. However, the bugs need to feed on the plant juice to get the toxin, and if there are too many bugs inserting their mouthparts and sucking out the fluid, especially on seedling plants or plants under less than ideal growing conditions, this may kill the bug, but also kill the small plant.
Last year, in 2023, much of Kansas experienced large populations of chinch bugs, so there were potentially large numbers going into the fall/winter. And this year, sure enough the number of chinch bugs was probably in all estimations the largest we have seen to date.
Also, because they float, says Withworth, chinch bugs do not generally drown in heavy rain. So, water running off infested wheat fields moves chinch bugs, often accumulating wherever runoff water pools. Good growing conditions really help plants withstand chinch bug feeding though. So once sorghum plants get bigger they can withstand the feeding of the chinch bugs without killing the plants.
The first generation of nymphs produced now has most likely became adults. Then they mate and start the process all over again for another generation, (two generations in KS each year) which will then move to fall-planted wheat, then on to overwintering sites. They overwinter in bunch grasses then move to wheat in the spring to deposit eggs and start all over again.
For more information, please refer to the following KSRE publications. Sorghum Insect Pest Management 2024 MF742, and Chinch Bugs MF3107, or give me a call in the Cottonwood Extension District Office in Hays at 785-628-9430.
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at [email protected] or by calling 785-628-9430.