Body Condition Category and Harvest Process Affect Contamination of Alfalfa by Epicauta occidentalis Werner (Coleoptera: Meloidae)

Abstract

Forage harvesters equipped with mechanical conditioners are known to cause significant mortality of blister beetles inhabiting hay. Studies also have documented that a large part of the mortality associated with the use of the sicklebar mower is caused by tractor-tire traffic over the swathed hay. Our study was designed to evaluate the likelihood that beetles with swathed alfalfa may become incorporated within and dislodged from hay during harvesting. Results indicated that the blister beetle back-to-hay effect was related to the body condition category of the beetles. Living beetles had the greatest chance of being incorporated into hay from a ground-surface position. Nondried beetles (freshly killed or living) on the ground had a significant chance of being crushed and incorporated into the hay. Dead dried beetles located on the ground under the windrow were more likely to be crushed but had little chance of being incorporated into the hay. Tractor tires running over the alfalfa returned ≍10% of the beetles on the ground to the hay. Beetles located above the alfalfa were more likely to be killed or crushed by tractor tires and to become stuck to the alfalfa than were those on the ground. Raking significantly reduced the number of beetles incorporated in the hay. Baling did not change Significantly the quantity of beetles remaining in the hay after raking. Fingerprint powder, applied to the beetles as a marker, did not alter the rates of beetle crushing, dislodging, or incorporation.