Predicting the emergence of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae), on a degree-day scale in North America.

BACKGROUND: Codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is a major pest of apple, pear and walnut production in North America. Management programs are based on preventing larval entry into the fruit or nut and are typically timed by heat-driven models that are synchronized to field populations by first capture of overwintering moths in pheromone traps. Unfortunately, trap capture is affected by a range of environmental parameters as well as by the use of mating disruption, which makes detecting first flight difficult, thus complicating implementation of management programs. The present goal was to evaluate data collected from a broad range of locations across North America to see whether average first spring emergence times could be predicted. RESULTS: Average emergence time on a degree-day scale from 1 January was predictable using latitude and elevation. Sites at elevations of <400 m fit a simple quadratic equation using latitude, but, when higher elevations were included, a multiple regression using elevation was required. CONCLUSIONS: The present models can be used to simplify management programs for codling moth in areas where heat-driven models that require extensive trapping to synchronize with emergence are currently used.

Selection for resistance, reversion towards susceptibility and synergism of chlorantraniliprole and spinetoram in obliquebanded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae).

BACKGROUND: Obliquebanded leafroller, Choristoneura rosaceana (Harris), is an economic pest of pome fruits throughout North America. Repeated applications of broad-spectrum insecticides have resulted in the development of resistance, cross-resistance and multiple resistance in this pest. Studies were conducted to determine the possibility of resistance evolution, stability of resistance and the effect of metabolic synergists on toxicity of new reduced-risk insecticides chlorantraniliprole and spinetoram in C. rosaceana. RESULTS: Larvae of C. rosaceana were selected for resistance to chlorantraniliprole and spinetoram in the laboratory. Significant levels of resistance to each insecticide were observed after 12 generations of selection. In the absence of selection pressure, susceptibility of a subset of larvae from both chlorantraniliprole- and spinetoram-selected populations reverted to preselection levels after five and six generations respectively, indicating that resistance to both chlorantraniliprole and spinetoram was unstable in C. rosaceana. In synergist bioassays performed after 12 generations of selection, S,S,S-tributylphosphoro trithioate (DEF) and piperonyl butoxide (PBO) synergized the toxicity of chlorantraniliprole and spinetoram respectively, suggesting the involvement of esterases in chlorantraniliprole resistance and the involvement of mixed-function oxidases in spinetoram resistance. CONCLUSION: These findings suggest that chlorantraniliprole and spinetoram could be incorporated into C. rosaceana resistance management programs by using rotational strategies.

Evaluating aggregation membership and copulatory success in the stink bug, Euschistus conspersus, using field and laboratory experiments.

The aggregation and mating behavior of the stink bug, Euschistus conspersus Uhler (Hemiptera: Pentatomidae) was investigated in a series of field and laboratory experiments. Marking of E. conspersus mating in aggregations in the field demonstrated that both sexes mate multiple times within aggregations on successive nights and with different partners, although ≈ 20% of the individuals of both sexes returned to aggregations but did not mate. Further analysis of mating patterns in caged aggregations revealed that heavy males and light females mated more frequently than their respective counterparts. Data are interpreted in terms of elucidating the function of benefits of multiple mating within aggregations for males and females.

Recapture of codling moth (Lepidoptera: Tortricidae) males: influence of lure type and pheromone background.

Recapture of marked male codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae), released four distances from traps was measured in experiments comparing either lure type or mating disruption. Experiment 1 assessed recapture by 0.1, 1, and 10 mg of codlemone lures. Experiments 2 and 3 assessed moth recapture in orchard plots with 0, 500, or 1,000 Isomate C Plus dispensers per ha. Moths were released 1, 3, 10, and 30 m downwind of the trap in experiments 1 and 2, and 3, 10, 30, and 45 m in experiment 3. Lure type did not affect recapture, however, significantly more moths were recaptured at 3 m compared with 10 or 30 m. Most moths recaptured < or = 10 m of the trap were recaptured by day 3, whereas most of the moths recaptured > or = 10 m were recaptured after day 3. Thus, 0.1-, 1-, and 10-mg lures, have an attractive range of between 10 and 30 m in orchards lacking mating disruption. Both mating disruption rates greatly reduced moth recapture, and moths recaptured under a 1,000 dispenser per ha rate were recaptured from < or = 10 m and within the first 2 d after release. Similar results were observed when release points were expanded to 45 m. Thus, results suggest that pheromone dispenser technologies and placement strategies that maximize disruption of males that arise within 10 m of a female are needed to markedly improve mating disruption.

Toxicity and residual efficacy of chlorantraniliprole, spinetoram, and emamectin benzoate to obliquebanded leafroller (Lepidoptera: Tortricidae).

Studies were conducted to determine the residual toxicity of spinetoram, chlorantraniliprole, and emamectin benzoate to obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). Larvae were exposed to apple (Malus spp.) foliage collected at different intervals after an airblast sprayer application at the manufacturer-recommended field rate and half the field rate. A mortality of 100% was recorded at field rate applications of spinetoram, chlorantraniliprole, and emamectin benzoate through 59, 38, and 10 d after treatment (DAT), respectively. Significantly less foliage was consumed by C. rosaceana larvae surviving in the emamectin, chlorantraniliprole, and spinetoram treatments compared with those exposed to untreated foliage. Third-instar C. rosaceana exposed to fresh residues on terminal foliage showed 100% mortality after 5-d exposure to spinetoram residues and after 10-d exposure to chlorantraniliprole and emamectin benzoate. The effects of larval movement from foliage with fresh residues was examined by transferring neonate larvae from foliage treated with spinetoram, chlorantraniliprole, or emamectin benzoate to untreated foliage after various exposure intervals. An exposure of 1, 3, and 6 d was required for spinetoram, chlorantraniliprole, and emamectin benzoate to cause 100% mortality at the field rate, respectively. The higher the concentration of chlorantraniliprole and emamectin benzoate, the less exposure time was necessary to cause high levels of mortality in C. rosaceana neonates. Our results indicate that these novel insecticides are highly toxic to C. rosaceana larvae. Implications of these results for C. rosaceana management programs are discussed.

Assessment of resistance risk in obliquebanded leafroller (Lepidoptera: Tortricidae) to the reduced-risk insecticides chlorantraniliprole and spinetoram.

Obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), is a major pest of pome fruit in Washington. The use of broad-spectrum insecticides for decades has led to the development of insecticide resistance in C. rosaceana. Recently registered insecticides with novel modes of action, such as chlorantraniliprole and spinetoram, have provided effective C. rosaceana control, but resistance remains a threat. The risk of insecticide resistance development in a pest can be assessed by artificial selection in the laboratory. Subsequently, this information can be valuable in developing strategies to retain susceptibility in the field. A laboratory population of C. rosaceana was selected after repeated exposure to chlorantraniliprole and spinetoram to determine the risk of resistance evolution. After six generations of selection, 6.58- and 3.64-fold increases in LC50 were recorded for chlorantraniliprole and spinetoram, respectively. The realized heritability (h2) of resistance was estimated as 0.17 for chlorantraniliprole and 0.18 for spinetoram by using threshold trait analysis. The rates of resistance development were compared using the response quotient (Q), which was estimated as 0.11 and 0.07 for chlorantraniliprole and spinetoram, respectively. Projected rates of resistance evolution indicated that if h2 = 0.2 and 80% of the population was killed at each generation, then a 10-fold increase in LC50 would be expected in less than six generations for chlorantraniliprole and 10 generations for spinetoram. These results indicate that the risk of resistance development in C. rosaceana exists to both of these insecticides but that resistance development in C. rosaceana would be slower against spinetoram than chlorantraniliprole.

Lethal and sublethal effects of an insect growth regulator, pyriproxyfen, on obliquebanded leafroller (Lepidoptera: Tortricidae).

The obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), is one of the most destructive pests of tree fruit in Washington. The development of insecticide resistance in C. rosaceana has led us to explore new management tactics. The use of very low doses of insecticides that have strong sublethal effects represents an environmentally friendly option to improve existing integrated pest management (IPM) strategies. We tested the insect growth regulator pyriproxyfen to determine its lethal and sublethal effects on growth and development of C. rosaceana. A leaf-disk bioassay was used to test seven concentrations of pyriproxyfen ranging from 0 to 30 ppm on fifth-instar C. rosaceana. Male and female larvae were assessed separately for mortality as well as other parameters of growth and development. The LC, values for males and females were 2.4 and 4.8 ppm, respectively. The response to pyriproxyfen was concentration-dependent: only 5-6% of the larvae treated with the highest concentration emerged as morphologically normal adults compared with 86% emergence in the controls. The pupation and adult emergence was significantly delayed at concentrations higher than 1 ppm. The weights of C. rosaceana pupae and adults were significantly increased, whereas fecundity and fertility were significantly reduced at a sublethal concentration of 0.3 ppm. We conclude that both lethal and sublethal effects might exhibit significant impacts on the population dynamics of C. rosaceana in tree fruit orchards treated with low concentrations of pyriproxyfen.

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.

A web-based decision support system to enhance IPM programs in Washington tree fruit.

BACKGROUND: Integrated pest management (IPM) decision-making has become more information intensive in Washington State tree crops in response to changes in pesticide availability, the development of new control tactics (such as mating disruption) and the development of new information on pest and natural enemy biology. The time-sensitive nature of the information means that growers must have constant access to a single source of verified information to guide management decisions. RESULTS: The authors developed a decision support system for Washington tree fruit growers that integrates environmental data [140 Washington State University (WSU) stations plus weather forecasts from NOAA], model predictions (ten insects, four diseases and a horticultural model), management recommendations triggered by model status and a pesticide database that provides information on non-target impacts on other pests and natural enemies. A user survey in 2008 found that the user base was providing recommendations for most of the orchards and acreage in the state, and that users estimated the value at $ 16 million per year. CONCLUSIONS: The design of the system facilitates education on a range of time-sensitive topics and will make it possible easily to incorporate other models, new management recommendations or information from new sensors as they are developed.

Tree fruit IPM programs in the western United States: the challenge of enhancing biological control through intensive management.

The seminal work of Stern and his coauthors on integrated control has had a profound and long-lasting effect on the development of IPM programs in western orchard systems. Management systems based solely on pesticides have proven to be unstable, and the success of IPM systems in western orchards has been driven by conservation of natural enemies to control secondary pests, combined with pesticides and mating disruption to suppress the key lepidopteran pests. However, the legislatively mandated changes in pesticide use patterns prompted by the Food Quality Protection Act of 1996 have resulted in an increased instability of pest populations in orchards because of natural enemy destruction. The management system changes have made it necessary to focus efforts on enhancing biological control not only of secondary pests but also of primary lepidopteran pests to help augment new pesticides and mating disruption tactics. The new management programs envisioned will be information extensive as well as time sensitive and will require redesign of educational and outreach programs to be successful. The developing programs will continue to use the core principles of Stern and his co-authors, but go beyond them to incorporate changes in society, technology and information transfer, as needed.

Field and laboratory responses of male leaf roller moths, Choristoneura rosaceana and Pandemis pyrusana, to pheromone concentrations in an attracticide paste formulation.

Male leafroller moths, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) and Pandemis pyrusana (Kearfott), were evaluated for responses to a paste formulation loaded with a range of concentrations of the two species' pheromone blends and evaluated in a laboratory wind tunnel and in the field. Response criteria were flight, flight towards the pheromone source, and contact with the pheromone source for the wind tunnel assays, and capture of moths in traps for the field tests. In the wind tunnel and field, responses of males of both species to the paste generally increased as the pheromone concentration in the paste was increased. There was little response by either species to paste with less than 0.16% pheromone. The relationship between pheromone concentration and response for P. pyrusana was linear and for C. rosaceana was sinusoidal over the range of pheromone concentrations tested. These patterns were seen both in the wind tunnel and in the field. Initial release rates from the paste of (Z)-11-tetradecenyl acetate, the main component of the pheromone blends of both species was 3.6-3.8 ng/h. Inhibitory thresholds for responses were not reached for either species, using pheromone concentrations as high as 16%, in either the wind tunnel or the field. For both species, response of males to rubber septa with one mg pheromone loads was similar to the response to the paste with pheromone at concentrations greater than 3-4%. For C. rosaceana, rates of contact with the paste in the wind tunnel were statistically similar to rates of contact in response to conspecific females, with paste pheromone concentrations above 1.6%. Response rates for males of P. pyrusana were significantly lower to the paste than to conspecific females at all paste pheromone concentrations tested. Overall, the optimum pheromone concentration in the paste for moth attraction to contact was 3.2 % for C. rosaceana and 8% for P. pyrusana.

Is biofix necessary for predicting codling moth (Lepidoptera: Tortricidae) emergence in Washington State apple orchards?

The heat-driven phenology model used for initiating codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), management in Washington state was examined to determine the need for using the capture of the first moth as a method of synchronizing the model and phenology of field populations (= biofix). We examined trap catch data taken at 1-2-d intervals from two research orchards; one data set encompassed a 28-yr period and the other data set a 4-yr period. We also examined consultant-collected data taken at 7-10-d intervals from 15 sites (N = 81), mostly between 2001 and 2005. At the two research sites, we found the mean biofix occurred at 96 degree-days (DD) (DD Celsius by using 10 degrees C lower threshold and 31.1 degrees C horizontal upper threshold) after 1 January (SD = 14.4; min. = 68, max = 122). After correcting for longer sampling intervals in the consultant data set, the biofix at the nonresearch sites occurred at 97 DD (N = 50, SD = 14.4; min. = 74, max = 120), nearly identical to that at the research sites. We also examined the performance of the codling moth model at predicting moth flight and egg hatch using a biofix and by just accumulating heat units from 1 January. The model performance was similar in both generations regardless of whether a biofix was used. The elimination of biofix simplifies management and eliminates mistakes associated with poor trap catch, particularly in low-pressure situations where mating disruption reduces trap efficiency.

Comparison of delayed female mating on reproductive biology of codling moth and obliquebanded leafroller.

Delay of mating was examined as a possible mechanism for population decreases associated with mating disruption for codling moth, Cydia pomonella L., and obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). We examined the effect of delaying female mating 0, 2, 4, or 6 d while holding male age constant on life table parameters of both species. We found that increasing delays in mating were accompanied by two responses: (1) an increase in the percentage of sterile pairs and (2) a reduction in net reproductive rate and population growth unrelated to sterility. On a percentage basis, obliquebanded leafroller population growth was more strongly affected than codling moth. However, the net fertility rate of obliquebanded leafroller was nearly eight-fold higher than that of codling moth, so that obliquebanded leafroller females that experienced a 4-d delay in mating had nearly the same reproductive rate as codling moth females that experienced no delay. Leslie matrix simulations using life tables with field-based adult longevity estimates showed that codling moth females experiencing >2-d delay in mating resulted in decreases in population density or extinction within two generations. In contrast, obliquebanded leafroller females delayed <6 d showed rapid population growth that decreased as female age at mating increased; only the 6-d delay treatment resulted in decreased population levels. Our results indicate that obliquebanded leafroller females must on average experience a much longer delay in mating to significantly reduce population growth compared with codling moth females, suggesting that delay of mating likely plays a greater role in codling moth mating disruption than for obliquebanded leafroller.

Factors influencing mate choice in Euschistus conspersus Uhler (Heteroptera: Pentatomidae).

The patterns of mating and possible factors influencing mate choice in the consperse stink bug, Euschistus conspersus Uhler, were studied in a series of laboratory experiments. Males were found to transfer a significant percentage of their body mass during the initial mating. Mating was also found to reduce male longevity by 37.8% but had no significant effect on female longevity or fecundity. There was no evidence of male or female choice based on weight of potential mating partners. There was assortative mating based on experience, however, with males mating preferentially with virgin females and females preferring mated males when given the choice. The implications of these findings within the mating dynamics of this aggregating species 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.

Instar-specific phenology of Pandemis pyrusana and Choristoneura rosaceana (Lepidoptera: Tortricidae) in Washington apple orchards.

Head capsule width was used to determine the instar specific phenology of the leafroller Pandemis pyrusana Kearfott and the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), attacking apple in Washington state during 2001-2003. In total, 7012 P. pyrusana and 6122 obliquebanded leafroller larvae were measured from apple orchards from mid-March to mid-September. Degree-day accumulations from each site were paired with the head capsule data to determine the periods during which different instars were present in the field. The implications of this work for pest management and biological control of leafrollers is discussed.

Evaluation of pheromone release from commercial mating disruption dispensers.

Pome fruit growers and crop consultants have expressed concerns about the seasonal release performance of commercial codling moth mating disruption dispenser products. Because of these concerns, we developed a laboratory flow-through volatile collection system (VCS) for measuring the volatile release of the codling moth sex pheromone, codlemone, from commercially available hand-applied dispensers. Under controlled air-flow and temperature conditions, the released vapor was trapped onto a polyurethane foam adsorbent followed by solvent extraction, solvent reduction, and GC/MS determination. Method recovery and breakthrough validations were performed to demonstrate system reliability before determining codlemone release from commercial dispensers field-aged over 140 days. The volatile collection was carried out in a consistent manner among five dispenser types most commonly used by growers, so that direct comparison of performance could be made. The comparison showed differences in the amount of pheromone released and in the patterns of release throughout the season between dispenser types. The variation in release performance demonstrates the need for routine evaluation of commercially marketed mating disruption dispensers. We believe that the simple and cost-effective volatile collection system can assist pheromone dispenser manufacturers in determining seasonal dispenser performance before new products are introduced into the commercial market and in rapidly verifying dispenser release when field-aged dispenser efficacy is in question.

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.