Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2007
Publication Date: 12/10/2007
Citation: Knight, A.L. 2007. Adjusting the Phenology Model of Codling Moth (Lepidoptera: Tortricidae) in Washington State Apple Orchards. Environmental Entomology 36:1485-1493.
Interpretive Summary: A simple predictive model, developed nearly 30 years ago, continues to be widely used by growers to time their use of insecticides to manage codling moth in apple and pear. Recently many growers and consultants have noted that the model’s output no longer seems to match the timing of adult flight or egg hatch seen in many orchards. Field studies conducted by researchers at the Yakima Agricultural Research Laboratory examined the seasonal pattern of adult activity and egg hatch of codling moth over four years to see if the model needs to be updated. These data showed that the old model is inaccurate in predicting the timing of egg hatch, particularly during the first moth generation. The potential impact of this error on the effectiveness of current spray timing programs was demonstrated.
Technical Abstract: Studies were conducted in eight apple orchards in Washington State from 2003-2006 to characterize the seasonal cumulative curves of codling moth flight and the occurrence of fruit injury. Data from each generation were fit to logistic curves and these data were compared to a current widely-used model. No difference in phenology was found for codling moth in orchards either treated with or without sex pheromone. The major difference found in the new versus the old model was for the cumulative curve of egg hatch during the first moth generation. Data from the four-year study found that the peak in egg hatch occurred much later than previously predicted. The importance of knowing the correct shape of the cumulative curve of egg hatch is emphasized by comparing several hypothetical pest management scenarios using either the old or new model. Several modifications in the current pest control program for codling moth are suggested.