Scattered Insect Observations from Around the State
This article was originally published on May 31, 2012 and expired on June 30, 2012. It is provided here for archival purposes and may contain dated information.
of Illinois professor of entomology and crop sciences Extension coordinator
Mike Gray usually gets the first reports of the emergence of adult western corn
rootworm during the July 4 festivities.
on May 29, Joe Spencer, an entomologist with the Illinois Natural History
Survey, observed second instar corn rootworm larvae northeast of Urbana in his
research plots. Spencer anticipates that the first beetle emergence will occur
in approximately two weeks (June 11-12), which is very early.
the hot and dry weather persist in areas of the state more prone to corn
rootworm damage --the northern two-thirds of Illinois -- heavy infestations of
larvae could take their toll on small root systems," said Gray.
"Because of the early hatch and accelerated development of larvae this
spring due to very warm temperatures, even Bt hybrids may sustain more root
injury than expected. The lack of soil moisture in many fields will speed up
larval development due to the more rapid heating of dry soils."
during the last week of May, adult Japanese beetles were observed in southern,
southwestern, and south-central Illinois. Ron Hines, a former University of
Illinois Extension employee and crop consultant, saw Japanese beetles in Massac
County on May 28. Robert Bellm, University of Illinois Extension commercial
agriculture educator, observed Japanese beetles in Fayette and Madison counties
over the Memorial Day weekend. He estimates that these sightings are about two
weeks ahead of normal.
suggested economic threshold for Japanese beetles in soybeans is based upon a
defoliation level of 30 percent before bloom. Soybean fields that are under
severe moisture stress may suffer greater yield loss due to defoliation, and
this needs to be considered in making treatment decisions. Japanese beetles
tend to concentrate their numbers along field margins. Scouts are encouraged to
examine plants in five separate areas of the field's interior.
base rescue treatment decisions on quick looks of defoliation in border
rows," Gray advised. "With the mild winter we experienced followed by
the hot and dry spring, I anticipate overall good survival of Japanese beetles
and encourage vigilant scouting for this insect throughout the growing
also notes that potato leafhoppers are now frequently observed in stands of
alfalfa and should be monitored using a sweep net. These insects can inflict
significant yield losses, especially in dry years. Field perimeters are often
the first areas to shown signs of injury. The regrowth of stands following a
cutting should be examined carefully for leafhoppers because as few as 0.2
leafhoppers per sweep in alfalfa 0 to 3 inches high can significantly stunt
further plant growth.
assume that the dry weather is solely responsible for delayed plant development
following a harvest," Gray said. He recommends consulting the information
about the life cycle, biology, and management of the potato leafhopper on the
Department of Crop Sciences Extension website: http://extension.cropsci.illinois.edu/fieldcrops/alfalfa/potato_leafhopper/.
producers are observing higher-than-normal numbers of beet and yellowstriped
armyworms in both corn and soybean fields during the late days of May, probably
due to the mild winter, warmer than average spring, and suitable migratory
conditions this spring. Gray recommends scouting of both corn and soybean
fields for these species for the next several weeks.
species are associated mainly with damage to corn and wheat. However, in the
Handbook of Soybean Insect Pests published by the Entomological Society of
America (ESA), the fall armyworm, beet armyworm, and yellowstriped armyworm are
listed as occasional pests of soybeans. ESA's suggested economic threshold for
these armyworm species in soybeans is "when larvae threaten to reduce
stands below the optimum plant population, typically to six or fewer plants per
row-ft (19.7 per row-m)."
Black, an insect and plant disease technical manager at Growmark, Inc.,
observed beet armyworms on corn in western and northwestern Illinois on May 29.
The threshold for armyworms in seedling corn is when 25 percent of plants are
damaged, larvae are three-fourths of an inch long or smaller, and some plants
are being killed. The economic threshold for armyworms in seedling corn
suggested by the ESA in its Handbook of Corn Insects is "when stand loss
exceeds 10 percent."
handbook also states that "the yellowstriped armyworm seldom is a serious
pest of corn in the Corn Belt. Control with insecticides is not economical
unless feeding would cause heavy damage (defoliation greater than 50
Source: Michael Gray, Professor and Assistant Dean for Agriculture and Natural Resources Extension, email@example.com
Pull date: June 30, 2012