Excerpt from the University of Maryland Research & Education Center
Landscape and Nursery IPM Report
Sept. 3, 2021
Fall Armyworm- Hyperactivity
By: Stanton Gill
Wow, the flood of emails on armyworm really came in after our Special IPM Alert on Monday. We had reports of fall armyworm activity in Williamsburg, VA, Arlington Cemetery in Northern VA, North Carolina, Ohio, Illinois, Kansas, Texas and Tennessee. In Maryland, we received reports from throughout the state including activity in Washington County and Garrett County. In Garret County, they were not only damaging turfgrass but also hay fields.
Now, the question is… will fall armyworm continue to be a problem in September? Most of the pictures I received were later instar stages of the fall armyworm. They go through 6 larvae instars then pupate, as I reported in the Monday report. They will pupate in the soil, then adults could emerge and start to mate. This should put potential egg laying from mated adult females at the end of September in Maryland. Since the caterpillars chew on the tops of grass plants, I suspect we should not see the large turf loss we saw in August. In late September, the temperatures should cool down and cool season grasses should be growing vigorously, producing new leaf sheaths and tillers rapidly. This growth should outpace any feeding injury from the fall armyworms. You should examine turfgrass for the small larvae that are greenish with black head capsules in the early instars. If larvae are present, you could apply Spinosad, Provaunt, Mainspring, or Acelepyrn and get very effective control. I
spoke with Nancy Rechcigl at Syngenta Company and she said at 4 oz of Mainspring /100 gallons, you should get 4 – 6 weeks of protection.
The caterpillars feed on the blades and stalks of the grass. The roots and crown should still be intact, and once cool weather is here with rains, the grass should start to produce new replacement shoots. When looking at an area of brown lawn, it is upsetting and the immediate reaction is you should do something right now. The problem is the damage is done. Now you need to be patient and wait for the lawn to recoup. You can reseed in September. Keep in mind that Oregon and Washington State are the two big grass seed producing states.
The weather last year and this year was less than ideal for seed production. This year they had drought, a thermal inversion, and excessively high temperatures. As a result, many seed heads are aborting and dropping prematurely to the ground. The result is seed supplies may be limited this fall. Prices have already shot up 20 – 40%. A bag of seed that was $70 in the spring is now $130 for the same size bag. Again, do not panic and start stocking up on grass seed. The established turfgrass will likely resprout with new shoots as the weather cools down, combined with the rains accompanying all of the tropical storms blowing in from the south.