Curcumin and Quercetin as Potential Radioprotectors and/or Radiosensitizers for X-ray-based Sterilization of Male Navel Orangeworm Larvae.

Two natural compounds (quercetin and curcumin) were tested as sensitizing or protecting agents for Navel Orangeworm (NOW) larvae under x-ray sterilization, with the aim to reduce required doses and thus facilitate the substitution of x-ray for radioisotopes. The compounds were added to NOW diet at concentrations between 0 and 1.0 mmol kg-1 and subsequent reared male larvae were subjected to x-ray irradiation (90 keV, 9 mA) to doses up to 15 Gy. Upon emergence as adults, surviving male NOW were paired with colony virgin females and placed in isolation for observation of deformity, mortality, and fertility. Treatments included rearing larvae on infused diet before irradiation, after irradiation, and both. Results were tabulated as percentage of insects that were dead/deformed, infertile, or fertile and subjected to chi-squared analysis. While insect populations subjected to quercetin treatments were not found to be significantly different from control at any x-ray dose, all curcumin treatments yielded significant differences at an absorbed dose of 10 Gy, both in terms of decreased mortality and fertility. While none of the treatments resulted in acceptable mortality/deformity rates, the observed effects strongly support the need for continued testing of natural compounds for their efficacy to reduce required dose levels for sterilization.

Addition of Pear Ester With Sex Pheromone Enhances Disruption of Mating by Female Codling Moth (Lepidoptera: Tortricidae) in Walnut Orchards Treated with Meso Dispensers.

We evaluated the low-density application of 50 dispensers per hectare, in contrast to the traditional >800 dispensers per hectare in apple orchards, to achieve disruption of communication of adult codling moth, Cydia pomonella (L.), in walnuts, Juglans regia (L.), using several methods. These methods included cumulative catches of male moths in traps baited with sex pheromone (Ph) or codlemone, (E,E)-8,10-dodecadien-1-ol, or a combination of codlemone, pear ester (PE), ethyl (E,Z)-2,4-decadienoate, and acetic acid, and by examining the mating status of females. These data were collected from 2011-2014 in nontreated plots and in similar plots treated with Meso dispensers loaded with codlemone (Ph Meso) or codlemone and PE (Ph + PE Meso). Male moth captures in both the Ph and combination lure traps reduced by 88-96% and 72 to 77%, respectively, compared with traps in the nontreated plots. A significantly higher proportion of female moths were nonmated in plots treated with Ph + PE Meso dispensers (33%) than in plots treated with Ph Meso (18-26%), or left nontreated (13%). In addition, significantly fewer multiple-mated females were trapped in the Ph + PE Meso-treated plots (6%) than in either Ph Meso-treated (13-18%) or nontreated plots (23%). These data suggest that the addition of PE can effectively improve Ph-based disruption of C. pomonella in walnut orchards. In addition, these data suggest that the use of low-density hand-applied dispensers can be an effective and lower-cost approach to manage this pest in the large canopy presented by walnut orchards.

Control and Monitoring of Codling Moth (Lepidoptera: Tortricidae) in Walnut Orchards Treated With Novel High-Load, Low-Density "Meso" Dispensers of Sex Pheromone and Pear Ester.

Low-density per ha "meso" dispensers loaded with pear ester, ethyl (E,Z)-2,4-decadienoate, kairomone and codlemone, (E,E)-8,10-dodecadien-1-ol, pheromone of codling moth, Cydia pomonella (L)., were evaluated versus meso dispensers loaded with pheromone alone for mating disruption control in walnut orchards receiving no insecticide sprays. Meso dispensers loaded with codlemone alone (Ph meso) were applied at 50 ha-1 and compared with mesos combining codlemone and pear ester (Ph + PE meso) at 25 and 50 ha-1. Various lures containing pear ester (PE), Ph-PE combo, and an experimental codlemone plus (E)-4,8-dimethyl-1,3,7-nonatriene lure were tested alone and with acetic acid (AA) lures for moth capture efficacy. Male moth capture in pheromone traps was significantly reduced by 88% in Ph meso plots and 96% in Ph + PE meso plots versus control plots. Moth capture in Ph-PE combo traps was significantly reduced for both sexes in all meso plots. Harvest damage by both the codling moth and the secondary pest, navel orangeworm, Amyelois transitella (Walker), was significantly lower in all meso treatment plots compared with damage in control plots. Nut injury level with the Ph + PE meso treatment (50 ha-1) was significantly lower than in Ph meso plots for both codling moth and combined pest injury. Regression analysis suggested that nut infestation levels by navel orangeworm were influenced by codling moth levels. In all meso plots, the most effective lures attracting both codling moth sexes were PE & AA or Ph-PE combo & AA. Demonstrated disruption and control efficacy of these pheromone plus PE-meso dispensers applied at low densities supports development of the meso dispenser tactic for practical pest management use in walnut orchards with inherent low planting densities.

Effects of X-Ray Irradiation on Male Navel Orangeworm Moths (Lepidoptera: Pyralidae) on Mating, Fecundity, Fertility, and Inherited Sterility.

Male adult navel orangeworm, Amyelois transitella (Walker), were irradiated using a laboratory scale x-ray irradiation unit to determine the required dose for complete egg sterility of mated female moths and inherited sterility of F1 and F2 generations. Adult male A. transitella were irradiated in two separate experiments at 100-300 Gy and 50-175 Gy. Mating frequency, fecundity, and fertility of normal females crossed with irradiated parental males was compared with the mating of nonirradiated moths. Mating frequency was 100% for females crossed with nonirradiated control males. At male treatment doses of ≥150 Gy the percentage of females found unmated increased, while multiple-mated females decreased. Female fecundity was not affected while fertility was affected in a dose-dependent relationship to exposure of parental males to x-ray irradiation. Embryonic development of eggs to the prehatch stage and egg eclosion did not occur at radiation doses ≥125 Gy. Emergence of F1 adults was low and occurred only for progeny of parental males exposed to doses ≤100 Gy, with no emergence at ≥125 Gy. Though fecundity appeared similar for control and irradiated F1 females, no F2 eggs hatched for the test exposures of 50-100 Gy. Based on our results, a dose of ≥125 Gy had efficacy in inducing both primary parental sterility in treated male moths and inherited sterility in F1 male and female moths. Results suggest that A. transitella might be considered a candidate for the sterile insect technique using adults irradiated at these relatively low x-ray exposure doses.

Spread of Aspergillus flavus by Navel Orangeworm (Amyelois transitella) on Almond.

Navel orangeworm (NOW) damage to almond is correlated with increased incidence of aflatoxin contamination caused by Aspergillus flavus. However, no reports demonstrate a causative relationship between NOW feeding and A. flavus infection. To demonstrate the potential of NOW to act as a vector of A. flavus on almond, NOW eggs were dusted with A. flavus and incubated in microchambers adjacent to but not touching agar plates or almond kernels. Following egg hatch, A. flavus colonies developed on agar along trails left by NOW larvae. Almond kernels damaged with A. flavus-carrying NOW showed higher incidence of A. flavus colonization and aflatoxin contamination than control treatments. Interestingly, levels of aflatoxin in NOW-damaged, A. flavus-infected almond were significantly higher than control treatments, even in the absence of visible fungal growth. Commercial almond orchards had a relatively low level of contamination with Aspergillus section Flavi in spring and early summer and a high level during summer, corresponding with the higher level of NOW infestation of the crop. Our study demonstrates that NOW is capable of vectoring A. flavus to almond, and that monitoring and sorting of almond kernels for insect damage is warranted to limit aflatoxin contamination potential both before and after harvesting.

Adding microencapsulated pear ester to insecticides for control of Cydia pomonella (Lepidoptera: Tortricidae) in apple.

BACKGROUND: The possibility of improving the efficacy of various insecticides for codling moth, Cydia pomonella (L.), by the addition of a microencapsulated formulation of pear ester, ethyl (2E, 4Z)-2,4-decadienoate (PE-MEC, 5% AI), was evaluated in field trials in apple from 2005 to 2009. RESULTS: The addition of PE-MEC (<3.0 g AI ha(-1) ) significantly lowered fruit injury with low rates of organophosphate and neonicotinoid insecticides. The addition of PE-MEC (1.48 g AI ha(-1) ) to maximum label rates of insecticides with moderate activity for codling moth, such as ebamectin benzoate, spinosad and methoxyfenozide, significantly improved their effectiveness. However, PE-MEC did not consistently improve the activity of maximum label rates of either rynaxypyr or spinetoram. The addition of PE-MEC with seasonal spray programs of acetamiprid and azinphos-methyl in combination with the use of sex pheromones for mating disruption provided the most effective control. CONCLUSION: The addition of PE-MEC can improve the effectiveness of some insecticides for codling moth in apple. Insecticides active via dermal toxicity are more strongly improved by the addition of PE-MEC. Season-long use of PE-MEC can also augment the effectiveness of mating disruption. Adding PE-MEC to variable integrated management programs for C. pomonella should be further investigated.

Hull split and damaged almond volatiles attract male and female navel orangeworm moths.

A blend of volatiles derived from the emissions of almonds at hull split and mechanically damaged almonds was compared to almond meal, the current monitoring standard for the insect pest navel orangeworm (NOW). Field trapping studies were performed to determine the blend's ability to attract adult NOW. The blend comprised racemic 1-octen-3-ol, ethyl benzoate, methyl salicylate, acetophenone, and racemic (E)-conophthorin. Ethyl acetate was used as a solvent with a blend component concentration of 100 mg/mL. The blend attracted both sexes of NOW when tested in five 2-week intervals spanning the first three flights of NOW in commercial almond orchards in the southern Central Valley of California. The blend demonstrated consistently higher capture rates for female NOW throughout the evaluation period, but unlike almond meal it significantly attracted males. Reported is a survey of the major and minor volatiles emitted from almonds at hull split, the key period of vulnerability to NOW infestation. Also reported is the attractancy of a formulated test blend based on the host plant volatile emissions, electroantennographic screening experiments, and field trapping studies. The results of this test blend highlight progress toward a host-plant-based attractant for NOW, a major insect pest of California tree nuts that presently lacks an adequate monitoring tool.

Behavior of codling moth (Lepidoptera: Tortricidae) neonate larvae on surfaces treated with microencapsulated pear ester.

Codling moth, Cydia pomonella (L.), larvae cause severe internal feeding damage to apples, pears, and walnuts worldwide. Research has demonstrated that codling moth neonate first instar larvae are attracted to a pear-derived kairomone, ethyl (2E,4Z)-2,4-decadienoate, the pear ester (PE). Reported here are the behavioral activities of neonate codling moth larvae to microencapsulated pear ester (MEC-PE) applied in aqueous solutions to both filter paper and apple leaf surfaces that were evaluated over a period of up to 20 d of aging. In dual-choice tests the MEC-PE treatment elicited attraction to and longer time spent on treated zones of filter papers relative to water-treated control zones for up to 14 d of aging. A higher concentration of MEC-PE caused no preferential response to the treated zone for the first 5 d of aging followed by significant responses through day 20 of aging, suggesting sensory adaptation as an initial concentration factor. Estimated emission levels of PE from treated filter papers were experimentally calculated for the observed behavioral thresholds evident over the aging period. When applied to apple leaves, MEC-PE changed neonate walking behavior by eliciting more frequent and longer time periods of arrestment and affected their ability to find the leaf base and stem or petiole. Effects of MEC-PE on extended walking time and arrestment by codling moth larvae would increase temporal and spatial exposure of neonates while on leaves; thereby potentially disrupting fruit or nut finding and enhancing mortality by increasing the exposure to insecticides, predation, and abiotic factors.

Electroantennographic bioassay as a screening tool for host plant volatiles.

Plant volatiles play an important role in plant-insect interactions. Herbivorous insects use plant volatiles, known as kairomones, to locate their host plant. When a host plant is an important agronomic commodity feeding damage by insect pests can inflict serious economic losses to growers. Accordingly, kairomones can be used as attractants to lure or confuse these insects and, thus, offer an environmentally friendly alternative to pesticides for insect control. Unfortunately, plants can emit a vast number volatiles with varying compositions and ratios of emissions dependent upon the phenology of the commodity or the time of day. This makes identification of biologically active components or blends of volatile components an arduous process. To help identify the bioactive components of host plant volatile emissions we employ the laboratory-based screening bioassay electroantennography (EAG). EAG is an effective tool to evaluate and record electrophysiologically the olfactory responses of an insect via their antennal receptors. The EAG screening process can help reduce the number of volatiles tested to identify promising bioactive components. However, EAG bioassays only provide information about activation of receptors. It does not provide information about the type of insect behavior the compound elicits; which could be as an attractant, repellent or other type of behavioral response. Volatiles eliciting a significant response by EAG, relative to an appropriate positive control, are typically taken on to further testing of behavioral responses of the insect pest. The experimental design presented will detail the methodology employed to screen almond-based host plant volatiles by measurement of the electrophysiological antennal responses of an adult insect pest navel orangeworm (Amyelois transitella) to single components and simple blends of components via EAG bioassay. The method utilizes two excised antennae placed across a "fork" electrode holder. The protocol demonstrated here presents a rapid, high-throughput standardized method for screening volatiles. Each volatile is at a set, constant amount as to standardize the stimulus level and thus allow antennal responses to be indicative of the relative chemoreceptivity. The negative control helps eliminate the electrophysiological response to both residual solvent and mechanical force of the puff. The positive control (in this instance acetophenone) is a single compound that has elicited a consistent response from male and female navel orangeworm (NOW) moth. An additional semiochemical standard that provides consistent response and is used for bioassay studies with the male NOW moth is (Z,Z)-11,13-hexdecadienal, an aldehyde component from the female-produced sex pheromone.

Monitoring codling moth (Lepidoptera: Tortricidae) in sex pheromone-treated orchards with (E)-4,8-dimethyl-1,3,7-nonatriene or pear ester in combination with codlemone and acetic acid.

Traps baited with ethyl (E,Z)-2,4-decadienoate (pear ester) or (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) in two- or three-way combinations with the sex pheromone (E,E)-8,10-dodecadien-1-ol (codlemone) and acetic acid (AA) were evaluated for codling moth, Cydia pomonella (L.). All studies were conducted in apple orchards, Malus domestica Borkhausen, treated with sex pheromone dispensers during 2010. Septa were loaded with codlemone, DMNT, and pear ester individually or codlemone with either DMNT or pear ester together (combo lures). Polyethylene vials loaded with AA were added as a co-lure. Residual analyses of field-aged combo lures and weight loss of the AA co-lure were conducted. AA vials lost 50-150 mg wk(-1). Weekly weight loss was not affected by field aging, but was closely correlated with the daily mean temperature. Pear ester was released from septa at a slightly higher but nonsignificant rate than codlemone. DMNT was released at a significantly higher rate than codlemone, and lures were effective for 4 wk. The addition of codlemone to traps baited with either host plant volatile plus AA had either no effect or significantly increased total moth catches. The addition of AA significantly increased the catch of female moths with either combo lure. Total moth catches in traps baited with pear ester or DMNT combo lures and AA did not differ and were either significantly higher or similar to the pear ester combo lure. These data suggest that codling moth may be more effectively monitored in sex pheromone-treated orchards with multi-component lures, including codlemone, AA, and host plant volatiles.

Microencapsulated pear ester enhances insecticide efficacy in walnuts for codling moth (Lepidoptera: Tortricidae) and navel orangeworm (Lepidoptera: Pyralidae).

The efficacy of combining insecticides with a microencapsulated formulation of ethyl (2E,4Z) -2,4-decadienoate (pear ester, PE-MEC) was evaluated in walnuts, Juglans regia L., for codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), and navel orangeworm, Amyelois transitella Walker (Lepidoptera, Pyralidae). Two types of studies were conducted to compare the use of insecticides with and without PE-MEC. In the first study, PE-MEC in combination with reduced rates of insecticides, including chlorpyrifos, phosmet, methoxyfenozide, and codling moth granulovirus were evaluated in single tree replicates. PE-MEC was tested at one to three rates (0.6, 1.8, and 4.4 g active ingredient ha(-1)) with each insecticide. In the second study, seasonal programs including sprays of esfenvalerate, chlorpyrifos, and ethyl parathion at full rates were evaluated in replicated two ha blocks. Significant reductions in nut injury occurred in the single-tree trial with treatments of PE-MEC plus insecticide compared with the insecticides used alone against both pest species; except with methoxyfenozide for navel orangeworm. Similarly, nut injury in the large plots was significantly reduced with the addition of PE-MEC, except for navel orangeworm in one of the two studies. These results suggest that adding pear ester as a microencapsulated spray can improve the efficacy of a range of insecticides for two key pests and foster the development of integrated pest management tactics with reduced insecticide use in walnut.

Characterization of microencapsulated pear ester, (2E,4Z)-ethyl-2,4-decadienoate, a kairomonal spray adjuvant against neonate codling moth larvae.

Codling moth (CM), Cydia pomonella (Lepidoptera: Tortricidae), is the key pest of apples, pears, and walnuts worldwide. The pear-derived kairomone, ethyl (2E,4Z)-2,4-decadienoate, the pear ester (PE), evokes attraction and arrestment of CM larvae. Microencapsulated PE formulation (PE-MEC) enhances the control efficacy of insecticides when used as a spray adjuvant. Characterization of the microencapsulated kairomone, including microcapsule size, concentrations, emission rates, and larval response, was performed. Microcapsule diameter ranged from 2 to 14 mum, with 68% of capsules being 2-3 mum, and the concentration of microcapsules averaged 25.9 x 10(4) capsules per mL of field spray solution. Headspace collections showed emission of PE was related to PE-MEC concentration and was best described as first-order power decay. Neonate larvae responded to PE-MEC applications aged through 14 days. These results demonstrated that application of PE-MEC concurrent with insecticides may increase neonate foliar wandering, thereby disrupting host location and enhancing mortality by prolonging its exposure to insecticide.

In situ seasonal study of the volatile production of almonds (Prunus dulcis) var. 'Nonpareil' and relationship to navel orangeworm.

Nonpareil almonds, Prunus dulcis , account for the largest percentage of almond varieties grown in the Central Valley of California. Several studies have investigated the various nonvolatile and volatile components of various plant parts; however, the volatile organic compound (VOC) emission of almonds from a single cultivar has not been studied over the course of a growing season. This aspect is particularly relevant to research concerning the navel orangeworm (NOW), a major insect pest of almonds and other tree nuts. Despite the continued presence of NOW, the identification of particular VOCs and their relationship to NOW have not been addressed. The VOC emission of Nonpareil almonds was collected in situ over the course of a growing season by solid-phase microextraction (SPME). The VOCs (Z)-hex-3-enyl acetate, (Z)-hex-3-enyl butyrate, undecan-2-ol, beta-bourbonene, and tetradecane were present for the majority of the days investigated. Several VOCs exhibited positive electroantennographic signals from male and/or female NOW moths.

Specificity of codling moth (Lepidoptera: Tortricidae) for the host plant kairomone, ethyl (2E,4Z)-2,4-decadienoate: field bioassays with pome fruit volatiles, analogue, and isomeric compounds.

Codling moth, Cydia pomonella (L.), is a severe pest of apples, pears, and walnuts worldwide, and new approaches for precise monitoring and management would be beneficial. Ninety-two pome fruit volatiles were formulated in 23 distinct blends, of which a single 4-component blend of 10-carbon esters showed the only significant attraction of moths in field bioassays conducted in both walnut and apple orchards. A single constituent of this blend, ethyl (2E,4Z)-2,4-decadienoate--the "pear ester", was the major contributing attractant. The pear ester attracted both male and female moths in combined numbers that were comparable to the attractiveness of conspecific sex pheromone. Structure-activity tests were conducted in a series of orchard trials to determine the specificity of attraction of codling moths to the pear ester kairomone. No analogue 10-carbon alcohols, aldehydes, acetates, or other esters elicited significant moth capture responses. Tests with various analogue esters with alcohol chain length moiety substitutions of the (2E,4Z)-2,4-decadienoic acid elicited differential capture responses, with the ethyl exceeding the propyl, methyl, butyl, and hexyl analogues. The (E,Z) geometric isomers of this series of (2E,4Z)-2,4-decadienoic acid esters far exceeded the attractiveness of the (E,E) isomers. The pear ester is a potent attractant of both males and females, and codling moths are highly discriminating and specific in their structure-activity-based attraction to this pear-derived kairomone. These specificity attributes should allow this host plant kairomone to contribute to new abilities for female monitoring and the potential of development of novel and highly selective control practices that should decrease the current dependence on the use of broad-spectrum insecticides.

Insect chemical ecology research in the United States Department of Agriculture-Agricultural Research Service.

This multi-author paper reviews current work by USDA-ARS scientists in the field of chemical ecology. Work with pheromones, the discovery and development of the codling moth kairomone, studies on insect-plant interactions and chemically mediated tritrophic plant-insect interactions have led to practical methods for control of important insect pests.