Semester

Spring

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Horticulture

Committee Chair

Yong-Lak Park.

Abstract

The Japanese hornfaced bees, Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae), is a key pollinator of spring blooming fruit crops such as apple, pear and blueberry. To maximize pollination efficiency, two implications must be considered. First, diapause termination of overwintering O. cornifrons adults needs to be synchronized with the bloom of the target trees because adult bees are active as pollinators for only a few weeks. Patterns of temperature-dependent diapause termination of O. cornifrons were modeled and simulated with linear and non-linear regression analyses. Results of the study indicated the upper and lower developmental thresholds, as well as the optimum temperature for diapause termination. This study provides a framework for manipulating diapause termination of O. cornifrons adults to synchronize their emergence with pollination periods of target crops. Second, O. cornifrons is associated with the hairy-footed mite, Chaetodactylus krombeini Baker (Acari: Chaetodactylidae), which can impede the propagation of O. cornifrons. This study was conducted to evaluate formic acid and wintergreen and determine if these compounds would effectively control C. krombeini. This study was conducted in two bioassays: to investigate O. cornifrons tolerance of formic acid and wintergreen and to find the lethal concentration of formic acid and wintergreen needed for mite control. Results of this study showed that the time and dosage required to induce C. krombeini mortality with either formic acid or wintergreen was significantly less than the time required to produce O. cornifrons mortality. Estimates of the LC50 and LC90 for C. krombeini hypopi treated with wintergreen were ca. five times lower than those with formic acid, indicating that wintergreen was a more effective chemical that can control the mites. This study provides evidence that C. krombeini can be managed effectively with formic acid and wintergreen without inducing mortality in O. cornifrons .

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