Long, Garrell E.

Xu, Guomin

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Section IIFoliage 8t Seed-Feeding 8c Mining InsectsHost Selection by First Generation Adults ofColorado Potato BeetleGuomin XuandGarrell E.LongDepartment of Entomology, Washington State UniversityPullman, WA 99164-6382The Colorado potato beetle, Leptinotarsa decemlineata (Say), is one of the mostimportant pests of potatoes in Washington. Overwintered adults colonize commercialpotatoes in spring, and develop the first summer generation. Mark-recapture techniquesverified that many adult beetles of the first generation move out of potatoes to anotherhost plant, hairy nightshade. Egg densities of second summer generation on the weedwere as much as 5-foid higher than on potato. Larval densities, consequently, weremuch higher on the weeds.To determine the host preference by first generation adults, no choice and free choicetests were set up in lab experiments on colonization, feeding and oviposition. In thecase of colonization trials, both potato and nightshade foliage were provided fornewly-emerged beetles. Daily observations were made to record host colonized by thetest beetles. Results from this experiment indicated that first generation adultsapparently (p=0.01) preferred nightshade to potato.Feeding is necessary for proper development of newly-emerged beetles. Starved adultsdid not harden their elytra, and more than 94% of them died within 9 days afteremergence. Hardening of elytra took 7 days if beetles were fed potato foliage at 26* C oftemperature, and 16/8, L/D photoperiod. The developmental interval from emergence tooviposition was shorter when beetles were fed potato foliage only. The period waselongated when beetles were fed nightshade. The total foliage consumed during thisperiod did not vary much, no matter which foliage was supplied. Beetles provided withboth plants developed intermediately. However, beetles significantly preferred feedingon leaf disks of potato to that of nightshade, in free-choice tests.The oviposition preference of first generation adults was examined by countingdailynumber of egg masses and eggs. Results indicate that adult beetles of the firstgeneration significantly preferred nightshade foliage for oviposition. Many more eggmasses were found on nightshade than potato, and more than 70% of all eggs were laidon nightshade.21

Host Selection by First Generation Adults of Colorado Potato Beetle

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Host Selection by First Generation Adults of Colorado Potato Beetle

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