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Minimize corn silage loss.

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Spider mites can be a major corn pest in western regions of the United States. Mite infestations damage corn by removing photosynthates from the leaves, resulting in loss of leaf tissue, stalk breakage, kernel shrink and premature death. Damage from spider mites may lead to yield or tonnage loss and poor quality silage with low relative feed value.

Factors to Consider

  • Insecticide programs
  • Irrigation schedule
  • Dust
  • Additional treatments

Action Plan

  1. Plan insecticide programs before planting. Be proactive and determine the insecticide program and spraying schedule before planting. In corn, mite infestations frequently include a mixture of species, including two-spotted spider mite; banks grass mite, Pacific spider mite and strawberry spider mite. The two-spotted spider mite is most common. During warm conditions, spider mites move rapidly within the colony area. A new generation may hatch in as few as five to seven days in midsummer, or in a month during cool periods.
  2. Avoid drought stress by scheduling irrigations. Spider mites thrive in hot and dry conditions and are most prevalent under dryland or surface irrigation. They do not like moist environments; schedule timely irrigations to create humid microenvironments. If not controlled, spider mites will damage corn by removing moisture from plant leaves, causing premature drying. This results in a loss of leaf tissue, stalk breakage and kernel shrinking. Damaged leaves become yellowish and stippled on the upper surface. Webbing on the undersurface of the leaves also will cause a grayish color.
  3. Manage dust on field roads to eliminate mite problems. Dust control on roads in or near fields can play an important role in the control of spider mites. Infestations commonly begin in field edges near dirt or gravel roads. Spider mites spread among fields by climbing to the top of a plant and spinning tiny strands of silk. When dust is caught by the wind, mites travel on the dust and drift to new host plants. Female spider mites then lay their eggs on the underside of plant leaves.
  4. Consider increased treatment for a longer period of protection. When spraying for spider mites, be sure to use adequate amounts of water for good plant coverage. Follow the guidelines in Table 1 for more treatment information.


In western regions of the United States, plan insecticide programs before planting corn to prevent spider mite damage. Provide timely irrigation to help eliminate a large infestation. Manage the edges of fields near dirt or gravel roads that have the potential to pick up more spider mites. Consider increased treatment rates and multiple insecticide applications to improve the degree of mite suppression. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

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