1a. Objectives (from AD-416)
Objective 1: Determine the comparative efficacy of alternative chemicals to methyl bromide and develop methods that keep alternative fumigants as well as methyl bromide out of the atmosphere following postharvest fumigation. • Sub-objective 1.A. Determine efficacy, practicality, and product quality (phytotoxicity) of alternative fumigants such as phosphine, sulfuryl fluoride, propylene oxide, ozone, and others to control postharvest commodity pests. • Sub-objective 1.B. Determine the efficacy of sulfuryl fluoride as an alternative to methyl bromide for use in flour/rice mills by direct comparison in laboratory and field experiments. • Sub-objective 1.C. Test absorbent materials to find more efficient materials than coconut-based activated carbon to recapture methyl bromide and other fumigants. • Sub-objective 1.D. Develop stacking and airflow techniques to maximize the efficiency of capturing methyl bromide from airstreams following commodity fumigation. Objective 2: Electrophysiological and behavioral responses of pests to host compounds • Sub-objective 2.A. Cigarette beetle host attractant identification and behavioral evaluation. • Sub-objective 2.B. Navel Orangeworm host attractant identification and behavioral evaluation. Objective 3: Develop combination quarantine treatments for foreign and domestic hay exports including timothy, alfalfa, oat, Bermuda, and Sudan grass hays and rye straw that utilize hay harvesting and postharvest handling procedures, and apply chemical fumigants to minimize human exposure. Objective 4: Develop models to accurately predict damage to nuts by navel orangeworm and determine the feasibility, accuracy, and precision of these predictions. • Sub-objective 4.A. Develop models for damage in Nonpareil and pollenizer almonds in Kern County based on previous year’s damage, harvest date and/or sanitation efficacy and then determine if these models can be extended to the entire almond belt • Sub-objective 4.B. Determine if the methodologies or models developed for almonds can be used to predict navel orangeworm damage in pistachios • Sub-objective 4.C. Develop models for almonds relating navel orangeworm damage to males captured in pheromone traps within the same year
1b. Approach (from AD-416)
Develop alternative chemical controls and quarantine fumigations for stored product insects. Develop equipment and investigate the feasibility of controlling fumigant emission to the atmosphere by trapping and destruction. Develop combinations of fumigants with other technologies to reduce the dosage of fumigant required to control or eradicate stored product and quarantine insects in durable and perishable commodities. Develop non-chemical control approaches for stored product pests of commodities to reduce the use of methyl bromide. Develop methods to detect infestations by detecting volatile emissions from insects and/or commodity. Develop methods to enhance or maintain quality of perishable commodities and ensure that treatments developed do not reduce quality of persihable commodities or shorten shelf-life. Formerly 5302-43000-030-00D and 5302-43000-028-00D (12/07)
3. Progress Report
Sulfuryl fluoride, ProFume®, is proposed as an alternative to methyl bromide (MB) for treating walnuts infested with navel orangeworm (Amyelois transitella) eggs and diapausing codling moth (Cydia pomonella) larvae. We developed treatments for these under both atmospheric pressure and vacuum using multivariate design strategies. We reported the influence of dose, pressure, temperature, and exposure duration on both insect mortality and residue levels of SF2O2, FSO3 1-, and F 1-. Data were collected on the toxicity of ProFume® to Indianmeal moth and dried fruit beetle, two economically important insect pests of raisins, dates, and dried plums and also to the red flour beetle. Insect eggs exposed to various doses of MB or ProFume® showed that MB was toxic to many insect species eggs at lower dosages. The perforation area of sheets used to pack grapes from Chile was not significantly different in allowing the penetration of MB and thus, sheets with less area could be used which would help retain sulfur dioxide and lengthen shelf life. Quarantine fumigation of cherries showed that size made no difference in the CxT achieved with MB and thus would allow shipment of small cherries of a variety to Japan. Phosphine treatment at low temperature was shown to be a potential replacement for MB in artichoke, peach and nectarine fumigations. Phosphine as a viable alternative to MB would impact the industry’s most important markets for fresh fruit, Canada, Mexico and Taiwan. Hessian fly mortality was evaluated after exposure of puparia to a phosphine/carbon dioxide mixture at different dosages and durations. Preliminary data were developed for Hessian fly survival at different temperatures and photoperiods simulating postharvest conditions in hay fields in the northern U.S. Data were collected comparing navel orangeworm (NOW) harvest damage to almonds with earlier numbers of eggs on egg traps and males on pheromone traps baited with live females. There was a significant association with subsequent harvest damage for the number of eggs on egg traps in first flight and of males in pheromone traps in second flight. Related data shows that the relationship of the proportion of traps with eggs and the mean numbers of eggs per trap differs between the high egg numbers typical of first flight and the low numbers typical of second flight. Adult activity patterns were assessed by trapping males, and both the density of unharvested almonds (mummies) and their infestation level were determined in Madera County at a site containing 5 varieties of almonds. Comparison studies were initiated with collaborators at UC Davis who are evaluating these factors in the Sacramento Valley. Part of the predictive model was published in a refereed journal. Volatile collection devices and procedures for collecting host volatiles were refined and used to elucidate odors that attract NOW and other insects. EAD methods were refined as our first line of bioassays for biological activity of collected volatiles. Bioassay methods to assess attractiveness of host volatiles were improved for rapid discrimination among actual hosts and host volatiles, by test insects.
1. Methyl Bromide Alternatives for Insect Control in Walnuts. Sulfuryl fluoride-treatments of insect pests were explored for the navel orange worm and the coddling moth, which are both detrimental to California walnut growers targeting export markets. An ARS scientist in Parlier, CA, used multivariate experimentation to probe Probit 9 mortality scenarios to expedite the development of quarantine fumigation schedules. Empirical tests were then used for confirmation. Furthermore, the marked predictive and confirmatory power of multivariate experimental techniques in streamlining the development of biocidal treatments for structural, perishable, or durable commodities was reported for the first time in the context of postharvest chamber fumigation. The information will be used by both the walnut industry and government when considering future methyl bromide critical use nominations.
2. Effect of Size on the Concentration by Time (CxT) Product and Sorption of Methyl Bromide by Cherries. Exporting cherries to Japan requires methyl bromide fumigation for the commodity to be accepted. Japan sets CxT product standards for acceptance that must be adhered to. ARS scientists at the San Joaquin Valley Agricultural Sciences Center in Parlier, CA, determined that neither the CxT product achieved nor the sorption of methyl bromide was affected by the size of cherries exposed to the fumigation. These results will open trade of different sized cherries to Japan without further testing.
3. The Toxicity of Profume to Insect Eggs as Compared to Other Life Stages of Insect Species. Insect eggs can sometimes be the most difficult stage to kill and care must be taken to ensure a fumigant’s effectiveness on this life stage. ARS scientists from the San Joaquin Valley Agricultural Sciences Center in Parlier, CA, assayed indianmeal moth, red flour beetle, and dried fruit beetle to determine the toxicity of Profume to the active life stages and the eggs to assess whether or not the egg stages could be killed by doses that kill active life stages. It was determined that eggs were in all instances the most tolerant stage of the insect and that some species required very high doses to kill the eggs. This will therefore make Profume expensive to use in some cases and render it not efficacious in others.
4. The Effect of Perforated Area on the Penetration of Methyl Bromide Through SheetsWrapping Table Grapes Imported into the U.S. Table grapes shipped from Chile with wrappers require an area of perforations equal to 0.9% for methyl bromide to penetrate into the grapes. However, that requirement allows sulfur dioxide to aerate from around the grapes, allowing premature decay of the berries. ARS scientists at the San Joaquin Valley Agricultural Sciences Center in Parlier, CA, showed that perforation areas reduced to 0.3% allow an adequate penetration of methyl bromide while retaining enough sulfur dioxide to inhibit decay. These data will allow longer shelf life of grapes in markets.
5. Development of Quarantine Strategies to Control Hessian fly in Exported Hay. China, Hong Kong, South Korea, and South Vietnam are emerging markets for U.S. hay exports, and regulatory agencies seek new methods to ensure that Hessian fly, a domestic pest, is not accidentally introduced through hay shipped from the western states. ARS scientists with the San Joaquin Valley Agricultural Sciences Center in Parlier, CA, developed novel fumigations using a carbon dioxide and phosphine gas mixture and simulated hay drying conditions on the resistant stage of the insect as control techniques to reduce the risk of infestation in exported bales. The National Hay Association supported further research of these hay handling procedures as potential quarantine treatments for Hessian fly. This work helps protect the U.S. hay export market valued at more than $600 million annually.
6. Improving Navel Orangeworm Monitoring with Egg Traps. Egg traps are standard means of monitoring navel orangeworm, and there is interest in increasing the effectiveness of these traps. An ARS scientist from the San Joaquin Valley Agricultural Sciences Center in Parlier, CA, in collaboration with Paramount Farming Company, showed that the difference in the number of eggs laid on different baits is insignificant at low egg numbers. Since the number of eggs per trap and the proportion of traps with eggs are related, when there are few eggs, presence-absence analysis of traps could be used to increase the number of traps that can be monitored and the precision of sampling. This finding can improve protection of almonds against insect infestation.
7. Development of a Predictive Model for Navel Orangeworm Damage to Nonpareil Almonds. Navel orangeworm is the primary pest of California almonds. ARS scientists at the San Joaquin Valley Agricultural Sciences Center, Parlier, CA, and collaborators at Paramount Farming Company, assessed the relative contribution of harvest date, previous year crop residue, and proximity to pistachios as contributors to its damage in Nonpareil almonds. A learning tool was developed enabling growers and county farm advisors to change these levels and predict damage. This information will improve control of navel orangeworm and reduce damage in this important almond variety.
8. Identify Risk Factors for Navel Orangeworm Damage in Pistachios. The navel orangeworm is the primary pest of pistachios in California. There is substantial information available that can be used to determine both the pattern of damage and identify risk factors, yet this information is not utilized. In 2007 and 2008 ARS scientists at the San Joaquin Valley Agricultural Science Center, Parlier CA and industry collaborators obtained gradesheets representing more than 65% of the entire harvest and determined the relationships between harvest date, shell integrity, and pistachio maturity. The information obtained will be used to improve control of this important pest.
9. Collection of Host Volatiles for Attraction of Navel Orangeworm. The almond oil volatiles that are currently used in traps to monitor navel orangeworm in the field are not always effective. This is at least partially due to a competition of the traps with host nuts in the field once the nuts become susceptible to infestation. ARS scientists at the San Joaquin Valley Agricultural Sciences Center in Parlier, CA collected volatiles from susceptible and non-susceptible nuts and analyzed them chemically and by behavioral bioassays to determine which compounds are attractive to navel orangeworm females. Isolation and characterization of these host volatiles will lead to better monitoring and/or direct control for this serious nut pest by inducing oviposition on unsuitable hosts.
Walse, S.S., Alborn, H.T., Teal, P.E. 2008. Environmentally Regulated Abiotic Release of Volatile Pheromones from the Sugar-based Oral Secretions of Caribflies. Green Chemistry Letters and Reviews. 1(4):205-217.