Alfalfa-weevil damage on second-cutting alfalfa.
Unusually warm weather has attracted insects to hayfields a mite earlier than usual. These regions are reporting pests that growers may want to monitor:
Armyworms In Pennsylvania, New York: Arkansas isn’t the only place true armyworms are making unwanted appearances this year (see “True Armyworms March In Arkansas”).
“From nearly every portion of Pennsylvania, we have heard of true armyworms chewing up cornfields, clipping the heads in wheat fields and marching into grass hayfields. It is certainly the most substantial influx of armyworm in years,” says John Tooker, Penn State University entomologist. Growers should be looking for damage now, he urges.
True armyworms are at threshold levels in winter wheat in western New York and have been sighted in the eastern part of the state as well. The levels are the highest in several years, reports Nathan Herendeen, Western New York Crop Management Association consultant. The pests can be found in grass hay in several fields in New York’s Washington and Schenectady counties, adds Aaron Gabriel, a Cornell Cooperative Extension agent. Although larvae are still small, he speculates the pest is widespread and urges growers to monitor fields before it spreads further.
Grasshoppers In Southern Great Plains: Warm weather in Oklahoma and Texas has increased grasshopper feeding and the threat of significant damage for forage producers, says David Annis, soils and crops consultant at the Noble Foundation.
“Grasshoppers can quickly devastate a field,” Annis warns. Thirty pounds of grasshoppers can consume as much forage in a day as a 600-lb steer.
Warmer and drier conditions in the Southern Great Plains – ideal conditions for grasshopper nymphs – are expected the next three months, according to the National Oceanic and Atmospheric Administration Climate Prediction Center.
The economic threshold for grasshoppers is seven to 10 insects per square yard, Annis adds. “Now is the time for producers to scout pastures and discuss potential treatment options with their local agricultural professionals. It would also be good to work with neighbors when treating for grasshoppers. This joint effort will lengthen the life and effectiveness of treatments.”
Alfalfa Weevils Attack Second-Cutting Growth In Michigan: Alfalfa weevils are finding first-cutting alfalfa regrowth in much of Michigan rather tasty. And that will likely affect second-cutting yield, reports Phil Kaatz, Michigan State University Extension educator.
An alfalfa weevil development model is one tool for predicting possible insect damage. It predicts when weevil damage is expected based on growing-degree-day accumulations calculated from data recorded at Enviro-weather stations. Click here for more information.
Potato Leafhoppers In Ohio: Potato leafhoppers have been sighted in Ohio alfalfa fields earlier than expected, alerts Ron Hammond, Ohio State University Extension entomologist.
“Normally, we’d see these pests more in the mid- to later part of June. The alfalfa just grew a lot quicker to begin with,” he says. Hammond urges growers to start scouting for them when alfalfa regrowth is the right height for sweep-net sampling. The pests stunt alfalfa plants, cause a yellowing of leaves and significant yield loss as well as impact the plants’ nutritional value.
To determine if insecticide treatment is warranted, scout and sample fields, taking 10 sweeps of a sweep net as one sample. When the average number of adults and nymphs in a sample is equal to or greater than the average height of the alfalfa stand, treat the area, he suggests.
“For example, if alfalfa is 6” tall and the average number of leafhoppers is six or higher, insecticide treatment is warranted.” If that average is lower, resample in a few days.
In glandular-haired, leafhopper-resistant alfalfa, the economic threshold is three times the normal threshold, or three leafhoppers per inch of growth. “However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding.” After that, a three-times-the-normal-level threshold should be used.
Click here for more information on potato leafhoppers.