Solid-stemmed wheat does not affect overwintering mortality of the wheat stem sawfly, Cephus cinctus

Area of Science:

• Agricultural Entomology
• Plant-Insect Interactions
• Pest Management

Background:

• The wheat stem sawfly (Cephus cinctus) is a significant pest in North American wheat production.
• Solid-stemmed wheat cultivars are the primary method for managing this pest through host plant resistance.

Purpose of the Study:

• To assess the impact of novel and traditional solid wheat hosts on the overwintering mortality and cold-hardiness of the wheat stem sawfly.
• To determine if solid-stemmed wheat cultivars affect the survival of wheat stem sawfly larvae during winter.

Main Methods:

• Field studies were conducted from 2003-2005 to monitor overwintering mortality.
• Supercooling points and cold tolerance of wheat stem sawfly larvae were measured.
• Overwintering microhabitat temperatures were recorded in relation to ambient conditions.

Main Results:

• Overwintering mortality averaged 8% across different wheat cultivars and was not influenced by host plant type.
• Wheat stem sawfly larvae exhibited significant cold-hardiness, with high survival rates at -20° C.
• Supercooling points remained consistent regardless of the wheat host.
• The overwintering microhabitat near the plant crown provided insulation, maintaining temperatures approximately 20° C above ambient minima.

Conclusions:

• Winter mortality appears to be a minor factor in wheat stem sawfly population dynamics.
• Solid-stemmed wheat cultivars, while impacting larval weight and adult fitness, do not enhance larval survival during winter.
• Current host plant resistance strategies may not be fully effective in reducing overwintering populations of wheat stem sawfly.