Early Emergence of Soybean Gall Midge Raises Concerns for Growers

Soybean growers in certain regions of Nebraska are urged to begin scouting for the soybean gall midge, a pest that has already emerged earlier than usual this year.  Justin McMechan, a crop protection and cropping systems specialist at the University of Nebraska, is part of a multi-state monitoring network that has reported the presence of soybean gall midge adults at several trapping sites.  

McMechan explains that the tiny flies lay their eggs on young soybean plant stems, and the hatched larvae feed on the stem tissues, causing disruption to nutrient and water movement.  Infested plants may wilt, break off at the feeding site, or even die, resulting in significant yield reductions, especially at field edges. 

The vulnerable plants are typically at the V2 growth stage, characterized by small cracks or fissures at the base of the stem, which serve as entry points for egg-laying females.  

This year, concerns arise due to delayed plant development caused by early cold weather and subsequent hot, dry conditions. McMechan points out that early planted soybeans in the region may be at higher risk of infestation, as they remain in the susceptible window for potential injury and plant death.  

Managing soybean gall midge has proven to be challenging. While chemical control has shown some effectiveness, foliar-applied insecticides have yielded inconsistent results across locations and years. Growers should consider treatment only if they have a history of soybean gall midge issues and observed the pest in neighboring fields the previous season. A combination product containing a pyrethroid is recommended. 

Given that soybean gall midge primarily infests field edges, McMechan suggests treating the first 60 to 120 feet of the edge as sufficient. He emphasizes focusing on the first four rows where larvae are most likely to be found. Pre-V2 foliar treatments are unnecessary as plants have not developed the fissures or cracks at the base of the stem. 

An alternative control method involves covering the base of soybean plants with soil, a practice known as "hilling. This technique has shown high efficacy in controlling soybean gall midge, but it can be challenging to implement when plants are small. 

Growers are advised to remain vigilant, regularly scout their fields, and implement targeted management strategies to mitigate potential damage from soybean gall midge infestations.