Submitted to: Western Orchard Pest and Disease Management Conference
Publication Type: Abstract only
Publication Acceptance Date: 12/15/2003
Publication Date: 1/14/2004
Citation: Knight, A.L. 2004. Development and testing of a new female-based phenology model for codling moth. Western Orchard Pest and Disease Management Conference. p.15. Interpretive Summary: Abstract only; please refer to technical abstract section
Technical Abstract: The use of the DA lure to establish a female moth Biofix followed by 155 degree-days was found for a third year to be roughly equivalent to the current use of male catch in pheromone traps plus 250 degree-days to predict the beginning of codling moth egg hatch. A color-coded Biofix system based on three-day periods of maximum daily temperatures was successful in assigning the Biofix dates for males and females in all eight sites plus in a similar study conducted in Medford. This approach, on average, did not improve the standard Biofix selection protocol that is based on weekly counts of moth catches in traps. Moth flight and egg hatch were found to continue throughout the summer in unmanaged orchards. A decline in activity (no cessation) occurred between 900 ' 1,000 degree-days after Biofix. Unhatched codling moth eggs were found in these orchards every week during the season. A new predictive phenology model was developed for codling moth that includes the nonlinear effects of daily degree-day accumulations to control the rate of female mating and the number of eggs laid. These curves were generated from a series of laboratory tests conducted under fluctuating temperatures in environmental chambers. The new model improved the prediction of cumulative fruit injury during the first generation in four of the five sites fully evaluated. The model delays the accumulation of fruit injury compared with the WSU model due to the restraining influence of cool spring temperatures. The accumulation of 20% of the total fruit injury was approximately 110-150 DD later than that predicted by the WSU model. In addition the distribution of injury over the entire generation was shifted later with 80% of the cumulative injury occurring 190-230 DD later than predicted by the WSU model. The current WSU model was more accurate than the new model for one site that can be characterized by three important factors: establishment of a rather late Biofix (13 May), the orchard was neither sprayed with insecticides or treated with sex pheromones, and the moth population was highly susceptible to Guthion (population originally derived from field-releases of the USDA laboratory colony). A significant delay in the occurrence of fruit injury was found in three orchards treated with a full rate of Isomate-C+ dispensers (400/acre). The first detection of fruit injury in these sites was 4-8 d later than predicted by the male Biofix. Similarly, the distribution of fruit injury was delayed in an orchard with a Guthion-tolerant population.