Factors Affecting Disruption of Navel Orangeworm (Lepidoptera: Pyralidae) Using Aerosol Dispensers

Diel Periodicity in Males of the Navel Orangeworm (Lepidoptera: Pyralidae) as Revealed by Automated Camera Traps

Navel orangeworm, Amyelois transitella (Walker), is a key pest of walnuts, pistachio, and almonds in California. Pheromone mating disruption using timed aerosol dispensers is an increasingly common management technique. Dispenser efficiency may be increased by timing releases with the active mating period of navel orangeworm. Past work found that the peak time of sexual activity for navel orangeworm females is 2 h before sunrise when temperatures are above 18°C. Inference of male responsiveness from data collected in that study was limited by the necessity of using laboratory-reared females as a source of sex pheromone emission to attract males and the inherent limitations of human observers for nocturnal events. Here we used camera traps baited with artificial pheromone to observe male navel orangeworm mating response in the field over two field seasons. Male response to synthetic pheromone exhibited diel patterns broadly similar to females, i.e., they were active for a brief period of 2-3 h before dawn under summer conditions and began responding to pheromone earlier and over a longer period of time during spring and fall. But contrary to the previous findings with females, some males were captured at all hours of the day and night, and there was no evidence of short-term change of pheromone responsiveness in response to temperature. Environmental effects on the response of navel orangeworm males to an artificial pheromone source differ in important ways from the environmental effects on female release of sex pheromone.

Pheromone Deployment Strategies for Mating Disruption of a Vineyard Mealybug

The mealybug, Planococcus ficus (Signoret), is a primary vineyard pest in California and other grape-growing regions throughout the World. Mating disruption programs are commercially available to manage Pl. ficus, but widespread adoption has been limited, in part, by high costs compared with insecticide programs. To improve mating disruption economic effectiveness, different deployment technologies (passive, aerosol, and microencapsulated formulations) were individually examined. Adult male Pl. ficus captures in pheromone traps and categorical ratings of vine infestation or crop damage suggest that all deployment strategies lowered mealybug densities or damage. Using passive dispensers, deployment rates of 310 and 465 per ha lowered Pl. ficus crop damage similar to 615 per ha, a rate commonly used in commercial operations; reduced rates would lower product and deployment costs. Meso dispensers, containing more a.i., deployed at 35 per ha did not have a treatment impact, but a microencapsulated formulation and aerosol canisters lowered male flight captures and/or crop damage. Male mealybug flight activity was greatest from 0500-1100 hr, which coincided with temperatures >16° and <32°C. These restricted times and temperatures suggest programable dispensers might allow pheromone deployment to coincide only with flight patterns. A large field trial using passive dispensers found greater treatment separation after 3 yr of pheromone deployment. Discrepancies in results among vineyards may be related to Pl. ficus density, but combined results from all trials suggest that different deployment technologies can be used to impact Pl. ficus densities and damage, even at reduced rates, especially with continued use over multiple seasons.

Diel Rhythmicity of Field Responses to Synthetic Pheromone Lures in the Pine Sawyer Monochamus saltuarius

Simple Summary

Monochamus saltuarius is a vector of pine wood nematode (PWN) in Korea and eastern China. The diel rhythmicity of M. saltuarius in response to an aggregation pheromone and attractants (PA) was studied with the aid of a spray device controlled with an electronic timer. Our study revealed that the flight activity of M. saltuarius in response to PA was diurnal. The results improve the understanding of the behavioral biology of M. saltuarius, allowing the development of pest management strategies to prevent the spread of PWN and control its vector.

Abstract

The pine wood nematode (PWN), Bursaphelenchus xylophilus, causes lethal pine wilt disease (PWD) in Asia and Europe and has become a serious threat to global pine forest ecosystems. In Korea, Monochamus saltuarius transmits PWN not only to Pinus densiflora, but also to Pinus koraiensis, which is widely distributed across eastern Asia. The diel rhythmicity of M. saltuarius in response to its aggregation pheromone was studied with the aim of providing reliable data for the prevention of PWD and control of Monochamus spp. Using a spray dispenser controlled with an electronic timer, M. saltuarius pheromone and attractants (PA) were sprayed to determine the diel rhythm of the response to PA. The spraying period was divided into four time periods: 05:00–11:00 (time period A), 11:00–17:00 (time period B), 17:00–23:00 (time period C), and 23:00–05:00 (time period D). The largest number of M. saltuarius was caught in time period B, followed by A, C, and D. It could be concluded that the flight activity of M. saltuarius in response to PA was diurnal. The results of this study improve the understanding of the behavioral biology of M. saltuarius, allowing for the development of pest management strategies to prevent the spread of PWN and control its vector.

Individual and Additive Effects of Insecticide and Mating Disruption in Integrated Management of Navel Orangeworm in Almonds

Simple Summary

Mating disruption is an increasingly important part of pest management for the navel orangeworm Amyelois transitella. Industry groups have long supported mating disruption research and development with the divergent objectives of both minimizing damage from this key pest and reducing insecticide used on these crops. It is therefore important to know whether the benefits of mating disruption and insecticide are additive or, alternatively, if using both together provides no additional benefit over either alone. Ten years of data from research trials in a large commercial almond orchard found that the benefits of mating disruption are generally additive with lower damage if both are used together than either alone. Substantial year-to-year variability in navel orangeworm damage was also evident, even with stringent management. These findings indicate that the combination of mating disruption and insecticide can reduce the impact of navel orangeworm damage on the almond industry. Further improvements in monitoring and predictions of navel orangeworm abundance and damage are necessary for mating disruption to effectively contribute to the industry goal of reduction of insecticide use by 25%.

Abstract

Damage from Amyelois transitella, a key pest of almonds in California, is managed by destruction of overwintering hosts, timely harvest, and insecticides. Mating disruption has been an increasingly frequent addition to these management tools. Efficacy of mating disruption for control of navel orangeworm damage has been demonstrated in experiments that included control plots not treated with either mating disruption or insecticide. However, the navel orangeworm flies much farther than many orchard pests, so large plots of an expensive crop are required for such research. A large almond orchard was subdivided into replicate blocks of 96 to 224 ha and used to compare harvest damage from navel orangeworm in almonds treated with both mating disruption and insecticide, or with either alone. Regression of navel orangeworm damage in researcher-collected harvest samples from the interior and center of management blocks on damage in huller samples found good correlation for both and supported previous assumptions that huller samples underreport navel orangeworm damage. Blocks treated with both mating disruption and insecticide had lower damage than those treated with either alone in 9 of the 10 years examined. Use of insecticide had a stronger impact than doubling the dispenser rate from 2.5 to 5 per ha, and long-term comparisons of relative navel orangeworm damage to earlier- and later-harvested varieties revealed greater variation than previously demonstrated. These findings are an economically important confirmation of trade-offs in economic management of this critical pest. Additional monitoring tools and research tactics will be necessary to fulfill the potential of mating disruption to reduce insecticide use for navel orangeworm.

Management of Navel Orangeworm (Lepidoptera: Pyralidae) Using Four Commercial Mating Disruption Systems in California Almonds

The navel orangeworm, Amyelois transitella (Walker), is the most significant pest of California almonds. Direct feeding on the kernel by the larvae causes reductions in salable crop, crop quality, and exportability. Pheromone mating disruption (MD) targeting navel orangeworm is a relatively new technique with the potential to improve management. In 2017, we used replicated ~16-ha plots to compare the efficacy of four commercial MD systems (CheckMate, Cidetrak, Isomate, and Semios) for their relative impacts on the number of navel orangeworm in monitoring traps and crop quality. From 2017 to 2018, we conducted nine direct comparison studies in 16 to 40 ha almond orchards to compare conventional pest management programs to programs incorporating pheromone MD systems. Across all studies, MD reduced male moth captures in pheromone traps by >94%. In the efficacy study, use of mating disruption led to 35% and 53% reductions in kernel damage in Nonpareil and pollinizer cultivars, respectively, and an average increase in crop value of $370 ha-1. In the direct comparison, kernel damage to Nonpareil and pollinizer cultivars was reduced by 65% and 78%, respectively, resulting in an average increase in crop value of $357 ha-1. Economic analyses showed that increases in crop returns exceeded the costs of implementing MD systems with the break-even point ranging from 0.86 to 1.06% of kernel damage. These results suggest that adding MD to an existing navel orangeworm management program is a cost-effective way to reduce damage while promoting sustainable pest management practices.

Persistence of Mating Suppression of the Indian Meal Moth Plodia Interpunctella in the Presence and Absence of Commercial Mating Disruption Dispensers

The Indian meal moth Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), is controlled by commercial mating disruption dispensers using passive release to emit high concentrations (relative to females or monitoring lures) of their principal sex pheromone component, (9Z,12E)-tetradecadienyl acetate. Since P. interpunctella is sexually active throughout the scotophase, an assay system was developed to determine the importance of direct interaction of the male with the dispenser, and whether exposure to mating disruption early in the night is sufficient to suppress mating throughout the night. Exposure to mating disruption dispensers in the mating assay chamber for the first two hours of a 10-h scotophase significantly reduced mating when females were introduced four hours later. Mating was also reduced to a lesser degree in a concentration-dependent manner based solely on re-emission of pheromone, and when males were exposed outside the mating assay chamber. These results indicate that the commercial mating disruption dispensers can suppress mating throughout the night based on interaction with the dispenser early in the night. Desensitization resulting from attraction to a high-concentration pheromone source is important to this suppression, but other factors such as re-emission from the environment may also have a role. These observations imply a non-competitive mechanism for P. interpunctella with the product studied, and suggest that effectiveness of the mating disruption dispenser might be augmented by using them in conjunction with another formulation such as an aerosol or micro-encapsulated product.