Tuesday, May 31, 2011

Cool soils promote seed/seedling pests

This week, several soil-dwelling pests have been reported throughout the state. Typically early-season seed/seeding pests can be problematic with slowly developing plants growing in cool soils. Examples of these pests include wireworms, millipedes, slugs and corn cornseed maggot. 

Millipedes are generally beneficial to have in soil because they break down organic matter. However they can become pests when planting into cool, wet soils because they feed on seeds and seedlings. They are especially prevalent in reduced tillage fields of corn and soybean. Sometimes they can chew  through the soybean hypocotyl and kill the plant. There are no registered pesticides for millipede control. In some severe cases, grower may need to replant in order to get a desired plant population. 

 Millipedes are insect relatives with two pairs of legs per segment. 
Photo credit Marlin E. Rice.

Seedcorn maggots have been reported in southeastern Iowa.. This isn’t a big surprise considering the cool, moist soil conditions this year. Like millipedes, the maggots typically feed on organic matter. But they will feed on corn, soybean and many horticultural plants The maggots feed on seed and often just leave the shell behind. There are no rescue foliar treatments available for seed corn maggot control.

Seedcorn maggot are immature flies that can destroy seeds/seedlings.
Photo credit Purdue Extension Service.

Whenever feasible for persistently infested fields, avoid planting in cool, wet soils. In some cases, insecticidal seed treatments can help suppress feeding, but will not provide complete control. Shallow planting and late planting will encourage quick germination to avoid seed/seedling feeding. 

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