Author
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Knight, Alan |
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Submitted to: Journal of British Columbia Entomological Society
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/10/2001 Publication Date: 5/15/2002 Citation: Knight, A.L. 2002. Monitoring the seasonal population density of Pandemis pyrusana (Lepidoptera:Tortricidae) within a diverse fruit crop production area in the Yakima Valley, WA. Journal of the Entomological Society of British Columbia. 98:217-225. Interpretive Summary: Interpretive Summary The population dynamics of the leafroller Pandemis pyrusana was studied in 60 contiguous orchard blocks of mixed fruit production situated in the Yakima Valley, Washington. Larvae from both generations were found in a low proportion of apple, pear, and cherry but not in the peach/nectarine, apricot, or prune orchards. Larval densities between generations increased 5-fold in apple and 10-fold in cherry and non-bearing apple, respectively; however fruit injury was only detected in five apple and pear orchards. Cumulative moth catch was 10-fold higher in sex pheromone than food baited traps and moth catch varied significantly among crops in both types of traps. In general, moth catches were highest in apple and cherry. However, only the cumulative moth catch in both trap types during the first moth flight but not during the second flight was correlated with levels of fruit injury. Several factors likely contributed to the trap's poor predictive ability during the second flight including the efficiency of the trap, moth dispersal among orchards, and different spray practices among orchards. The capture of female moths versus the total of both sexes caught in food bait traps did not improve the prediction of fruit injury. Technical Abstract: Technical Abstract The population dynamics of Pandemis pyrusana was studied in 60 contiguous orchard blocks of mixed fruit production situated in the Yakima Valley, Washington. A grid of sex pheromone-baited and liquid food-baited traps were each placed at a rate of 1 trap per 2 hectares. Trees within 50 m of each trapping location were sampled for overwintering and summer generation larvae, and fruit injury prior to harvest. Larvae from both generations were found in a low proportion of apple, pear, and cherry orchards, but not in the peach/nectarine, apricot, or prune orchards. Larval densities between generations increased 5-fold in apple and 10- fold in cherry and non-bearing apple, respectively. Low levels of fruit injury (< 0.5%) were detected in only five apple and pear orchards. Cumulative moth catch was 10-fold higher in sex pheromone than food baited traps. Moth catch in both types of traps varied significantly among crops. In general, moth catches were highest in apple and cherry. Cumulative moth catch in both trap types in apple and pear during the first flight was weakly correlated with levels of fruit injury. In contrast, moth catch during the second flight was not correlated with fruit injury. The observed low predictive ability of traps was likely due to trap saturation and contamination with non-target moths, a general dispersal of moths among orchards throughout the region, and differential spray programs among growers and across crops. The capture of female moths versus the total of both sexes caught |
