Both two-spotted spider mites and Banks grass mites affect the corn population. Proper mite identification is important because the two-spotted spider mite is much more difficult to control.
Two-spotted spider mite females have a well-defined spot on each side of the body.
Banks grass mites have blackish-green pigmentation extending the full length of the body. Banks grass mites appear earlier in the season on lower leaves, while two-spotted spider mites appear later in the season and may spread rapidly over the entire plant. (SOURCE: University of Nebraska, Management of Spider Mites in Corn, Bob Wright, Gary Hein, Jack Campbell, July 29, 1996)
Facts about Spider Mite
Spider mites feed on the undersides of leaves, eventually killing the leaf and leaving it with a scorched or burned appearance. The opposite side of the leaf from the mite colony is usually yellow.
A common cause of mite infestation is hot, dry weather, and the pest is often a problem in drought-stressed corn.
Life Cycle of Spider Mite
The mites overwinter as females and may lay some eggs during prolonged warm spells.
Generation times depend on temperature and are typically 10 to 20 days.
Under laboratory conditions, populations can increase 70-fold in one generation.
Management of Two-Spotted Spider Mite
Be aware that certain insecticides for European corn borer, western bean cutworm and other pests also reduce populations of beneficial insects, making fields more susceptible to spider mite infestations.
Use of hybrids containing Bt is an effective option that has less harmful effects on the spider mite's natural enemies.
Banks grass mites are more susceptible to the available miticides than two-spotted spider mites.
Dimethoate is still effective against Banks grass mites, but not against two-spotted spider mites.