UBC Theses and Dissertations
The agricultural ecology of peachtree borer, (Synanthedon Exitiosa say) Edwards, Linda Lynne
The peachtree borer, Svnanthedon exitiosa (Say), (Sesiidae), was studied to determine factors influencing its distribution, and four possible methods for its control in Prunus orchards in the Okanagan Valley, B.C. A survey for peachtree borer infestation was made by inspecting more than 7000 Prunus trees in 49 orchards, and 34 chokecherry trees, Prunus virginiana L., the native host, at 9 sites. Seventy-five per cent of the Prunus plantings contained peachtree borer. Infestation levels ranged from 0.9-83.3 % of the trees per planting. Young trees were least often attacked. Peach was the most heavily attacked species, prunes and apricots were intermediate, and cherry was the least attacked. Differences in bark texture appeared to be an important factor influencing oviposition behaviour and larval survival and establishment. Trees in clay soil without vegetation around the trunk were more heavily infested than trees in loam or in clay with vegetation. No peachtree borers were found in any of the chokecherry trees examined nor in any abandoned Prunus plantings. Fertilization and irrigation were important in determining borer survival and establishment. More than half of the forty growers surveyed did not know if their orchards were infested with peachtree borer, although all mature plantings where no controls were being carried out contained borers. Four possible control methods were tested in five infested orchards. Two methods, removal of borer larvae by hand and coating the trunk with rubber latex in an attempt to prevent larval entry, were ineffective. Chemical control was more successful but 20 % of the trees sprayed once with endosulfan (Thiodan) at the beginning of the period of adult emergence were successfully attacked during the summer. This was reduced to 7.8 % on trees that received a second spray 4 weeks later. An aluminum cone designed to protect the basal area of the tree trunk that is most susceptible to borer attack was completely successful in preventing infestation. These results are compared with the results of growers' control programs. Conventional endosulfan trunk sprays are very effective when properly applied, but only 5 of 40 growers were using them. The advantages and disadvantages of all methods of control are discussed and the importance of growers' understanding the biology of the insect and compatibility of control methods within the context of the total orchard operation emphasized.
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