Susceptibility of Choristoneura rosaceana (Lepidoptera: Tortricidae) to two new reduced-risk insecticides.

The response of field-collected populations of the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), to chlorantraniliprole, spinetoram, spinosad, and azinphosmethyl was assessed using a diet incorporation bioassay. Populations of obliquebanded leafroller were collected from nine orchards in Chelan, Douglas, Grant, and Okanogan counties of Washington. The neonates of the F1 or F2 generation were used in all assays. The parameters of probit regression lines were estimated and lethal concentration ratios were calculated for all populations compared with a susceptible laboratory population. Significant variation was detected in response to all four insecticides including chlorantraniliprole and spinetoram, which had never been used in the field, lethal concentration ratios were 3.9-39.7 for azinphosmethyl, 0.5-3.6 for spinosad, 1.2-5.3 for chlorantraniliprole, and 0.5-4.1 for spinetoram. Correlation analysis indicated possibility of cross-resistance between spinosad and spinetoram, which are both members of spinosyn class. The occurrence of low but significant levels of resistance against chlorantraniliprole and spinetoram in field-collected populations of C. rosaceana before their first field application indicates that the risk of resistance evolution against these two new reduced-risk insecticides exists. However, it is likely that these low levels of resistance can be managed if the insecticides are used judiciously in conjunction with sound resistance management programs. Implications of these results for developing and implementing resistance management strategies are discussed.

Resistance and cross-resistance in populations of the leafrollers, Choristoneura rosaceana and Pandemis pyrusana , in Washington apples.

Insecticide bioassays of the leafrollers, Choristoneura rosaceana (Harris), and Pandemis pyrusana Kearfott (Lepidoptera: Tortricidae), were used to investigate resistance and cross-resistance between azinphosmethyl and other insecticides. Comparisons of field-collected populations with susceptible laboratory colonies of both leafroller species were made in 1996-97, prior to registration and field introduction of several of insecticides, and were re-tested in 2000-2001 following several years of use in the field. Insecticides tested included azinphosmethyl, chlorpyrifos, methyl parathion, tebufenozide, methoxyfenozide, spinosad, indoxacarb, acetamiprid, Bacillus thuringiensis , and azadirachtin. Azinphosmethyl-susceptible laboratory colonies were used for comparison to field populations. Resistance to azinphosmethyl was found in all populations of C. rosaceana (5.2-26.8 fold) and P. pyrusana (8.4-24.9 fold) collected from commercial orchards. Cross-resistance between azinphosmethyl and the insect growth regulators tebufenozide and methoxyfenozide was found in all but one population of the two leafroller species. No cross-resistance was found to chlorpyrifos. Some of the populations tested were cross-resistant to spinosad and indoxacarb, but the responses to these materials were more variable.

A synthesis of the temperature dependent development rate for the obliquebanded leafroller, Choristoneura rosaceana.

The obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), is a serious pest of apples and other tree crops throughout North America. A review of temperature dependent development and models show that five different lower thresholds for development are published and used as the basis of heat-driven phenology models. We present a small lab data set of C. rosaceana development at four different temperatures and combine this with literature-based data into a single meta-analysis. Our analysis shows that the data from the different studies can be lumped together and the combined analysis suggests the lower and upper thresholds for development from egg to adult are approximately 10 degrees C and 30 degrees C, respectively.

Phenology of Lacanobia subjuncta (Lepidoptera: Noctuidae) in Washington and Oregon apple orchards.

The phenology of Lacanobia subjuncta (Grote & Robinson) (Lepidoptera: Noctuidae) was investigated in 30 apple orchards in central Washington state and northeastern Oregon from 1998 to 2001 (57 total orchard-yr). Adult captures in pheromone-baited traps were fit to a Weibull distribution to model emergence of the first and second generations. Initial capture of first generation adults was observed at 216.2 +/- 2.6 degree-days (DD) (mean +/- SEM) from 1 March by using a base temperature of 6.7 degrees C. The model predicted that flight was 5 and 95% complete by 240 and 700 degree-days (DD), respectively. Monitoring of oviposition and hatch was used to establish a protandry plus preoviposition degree-day requirement of 160.0 +/- 7.7 DD, as well as to provide data to describe the entire hatch period. Egg hatch was 5 and 95% complete by 395 and 630 DD, respectively. The start of the second flight was observed at 1217.1 +/- 8.3 DD by using an upper threshold for development of 32 degrees C and a horizontal cutoff. The model indicated that the second flight was 5 and 95% complete by 1220 and 1690 DD, respectively. Second generation hatch was 5 and 95% complete by 1440 and 1740 DD, respectively. A discussion of the potential uses of these detailed phenology data in optimizing management strategies is presented.

Integrated pest management approach for a new pest, Lacanobia subjuncta (Lepidoptera: Noctuidae), in Washington apple orchards.

Bioassays of Lacanobia subjuncta (Grote and Robinson) larvae established baseline LC50 values and identified the potential of reduced-risk, organophosphate replacement and naturally derived insecticides (eg chloronicotinyls, spinosyns, oxadiazines, insect growth regulators, microbial insecticides and particle films) to control this pest. The toxicities of these products were compared with those of organophosphate, carbamate, chlorinated cyclodiene and synthetic pyrethroid insecticides used in the management of lepidopteran pests in Washington apple orchards. Field trials were conducted comparing candidate insecticides to conventional alternatives. Several new insecticides (eg spinosad, methoxyfenozide, indoxacarb and an aluminosilicate particle film) proved to be effective for the management of L subjuncta. We summarize the goals and challenges of developing an integrated pest management program for new and resurgent pests as insecticide tools continue to change, and propose a hypothesis for the sudden increase in pest status of L subjuncta based on organophosphate tolerances. The role of novel insecticides with unique modes of action in resistance management and the encouragement of biological control are also discussed.