Effects of moisture stress on annual bluegrass weevil ovipositional behavior and larval survival

Annual bluegrass weevil, Listronotus maculicollis (Coleoptera: Curculionidae) is a pest of golf turfgrass that overwinters during cold seasons and becomes active in the spring. Females chew on basal stems within grass sheaths to lay their eggs which hatch and dig into individual stems. Larval feeding can cause detachment of the stem from the roots. L. maculicollis damage ranges from causing discoloration to necrosis of the plant.

Weevils prefer Poa annua turf and display high fecundity, increased egg laying and larval survival when compared to other grass hosts. But what influences their movement once they arrive in golf courses? Spatial studies have shown that L. maculicollis adults tend to aggregate on the perimeter of infested areas, but what influences their host choice remains unknown. Through this research, we attempt to determine whether soil moisture has an effect through greenhouse and behavioral experiments.

In greenhouse conditions, turf cores were maintained at three different soil moisture levels: dry, moist, and fully saturated. Once moisture levels were attained, two female and male adults were released within grass cores. Larval count was recorded after 7 days and after 30 days. In behavioral experiments through EthoVision, we presented adult females with a combination of turf cores with the following levels of moisture: 65%, 75%, 85%, 100% during which choice and behavior was recorded for 10 minutes.

Understanding how the annual bluegrass weevil moves in the field and what influences its host choice and dispersion in golf courses could help in developing more targeted management plans.