James D. Hansen

Dielectric properties of fruits and insect pests as related to radio frequency and microwave treatments.

Information on dielectric properties of commodities and insect pests is needed in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave energy. Dielectric properties of six commodities along with four associated insect pests were measured between 1 and 1800 MHz using an open-ended coaxial-line probe technique and at temperatures between 20 and 608C. The dielectric loss factor of fresh fruits and insects decreased with increasing frequency at constant temperatures. The loss factor of fresh fruits and insects increased almost linearly with increasing temperature at 27 MHz radio frequency, but remained nearly constant at 915 MHz microwave frequency. Both dielectric constant and loss factor of nuts were very low compared to those of fresh fruits and insects. The temperature effect on dielectric properties of nuts was not significant at 27 MHz. The large difference in the loss factor between insects and nuts at 27 MHz suggests possible differential heating of insects in nuts when treated at the same time in a RF system.

High-temperature-short-time thermal quarantine methods

Abstract In this paper, kinetic models are discussed with respect to their uses in describing the intrinsic thermal mortality of insect pests. A unique heating block system was used to obtain kinetic information for the thermal mortality of codling moth larvae. The kinetic data demonstrated the possibility to develop high-temperature-short-time thermal treatments to control codling moth and reduce thermal impact on product quality. Equations are presented to evaluate cumulative effects of any time–temperature history on the thermal mortality of target insect pests and on the quality of host materials. Computer simulation results demonstrated that the cumulative thermal effects on product quality during the heating period in conventional hot air or hot water treatments are much more important than the cooling period. Radio frequency (RF) heating or microwave heating is suggested as an alternative to reduce adverse thermal impact to treated commodities during the heating period. A case study is presented to demonstrate the effect of RF heating in a high-temperature-short-time thermal treatment to control codling moth larvae in in-shell walnuts.

Radio frequency treatments to control codling moth in in-shell walnuts

‘Diamond’ Walnuts (Juglans regia L.) in the shell were treated with radio frequency (RF) energy in a 27 MHz pilot-scale system to determine the treatment effect on third- and fourth-instar codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), mortality and walnut quality. After 2 and 3 min of RF treatments, infested in-shell walnuts were heated to 43 and 53°C. The corresponding insect mortality reached 78.6 and 100%. The fatty acid (FA) concentration of treated walnuts was not affected by RF treatments. The FA values were B 0.1% after accelerated storage times up to 30 days at 35°C, simulating storage at 4°C for up to 3 years. The effect of RF treatments on walnut oil peroxide values (PV) was not significant. The PV value of walnuts was less than 1.0 meq:kg (the upper limit for good quality walnuts), after 20 days storage at 35°C that simulated 2 year storage at 4°C. The PV was about 1.2 meg:kg after 30 days storage at 35°C. RF treatments can, therefore, potentially provide an effective and rapid quarantine security protocol against codling moth larvae in walnuts as an alternative to methyl bromide fumigation.

Process protocols based on radio frequency energy to control field and storage pests in in-shell walnuts

A practical process protocol was developed to control insect pests in in-shell walnuts using a 27 MHz pilot scale radio frequency (RF) system. Fifth-instars, that had been determined to be the most heat resistant life stage for navel orangeworm (Amyelois transitella [Walker]) using a heating block system, were selected as the targeted insect in the protocol development. RF heating to 55 °C and holding in hot air for at least 5 min resulted in 100% mortality of the fifth-instar navel orangeworm. Rancidity, sensory qualities and shell characteristics were not affected by the treatments. The process slightly reduced the moisture content of the walnut kernels, which could prove an additional benefit by providing even nut moisture content and reducing the growth of microorganisms. If this method can be economically integrated into the handling process, it should have excellent potential as a disinfestation method for in-shell walnuts.

Development of a saline water immersion technique with RF energy as a postharvest treatment against codling moth in cherries

‘Sweetheart’ sweet cherries (Prunus aium L.) immersed in 0.15% saline water were treated with radio frequency (RF) energy. The dielectric and ionic conductivity properties of the immersion water and that of fruit were matched to obtain a relatively uniform temperature distribution within and among fruits during RF heating. With immersion in saline water of 0.15% NaCl, the mean temperature of the water and that of the cherries differed by 0.6 °C, while the maximum temperature variation within and among fruits determined within 1 min after RF treatment completion was 1.0 °C of the set temperatures of 48 and 50 °C. The saline water immersion technique helped overcome the markedly high temperature differential problem within and among fruits, normally associated with treatments in air (without immersion) during RF heating. More than 99% mortality of the 200–400 codling moth larvae or 589–624 eggs was obtained at 50 °C when treated for between 7 and 10 min (heating 2–5 min and holding 5 min). Most quality parameters analyzed were better, or are comparable with methyl bromide fumigated fruit. Saline–water-immersion treatment in RF may be used to overcome the problem of slow conventional hot air or water heating, as well as the non-uniformity of temperature associated with electromagnetic heating in air, for developing alternative quarantine treatment for fruits.

Thermal-death kinetics of fifth-instar Amyelois transitella (Walker) (Lepidoptera: Pyralidae)

Information on kinetics for thermal mortality of navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), is needed for developing post-harvest phytosanitation thermal treatments of walnuts. Thermal-death kinetics for fifth-instar navel orangeworms were determined at temperatures between 461C and 541C at a heating rate of 181C min � 1 using a heating block system. Thermal-death curves for fifth-instar navel orangeworms followed a 0.5th-order of kinetic reaction. The time required to achieve 100% mortality (N0 ¼ 600) decreased with increasing temperature in a logarithmic manner. Complete kill of 600 insects required a minimum exposure time of 140, 50, 15, 6, and 1 min at 461C, 481C, 501C, 521C, and 541C, respectively. The reaction rate (k) was affected by treatment temperatures following an Arrhenius relationship. The activation energy for thermal kill of fifth-instar navel orangeworms was

Use of hot water treatment to control codling moths in harvested California ‘Bing’ sweet cherries

Preharvest gibberellic acid-treated California ‘Bing’ sweet cherries ( Prunus avium L.) were treated with hot water baths (46–58 ◦ C for 0.25–18 min), followed by hydrocooling. The fruit were then stored to simulate either air shipment or sea shipment to overseas markets, both followed by 15 h of shelf life at 20 ◦ C. In separate experiments, cherries were also infested with codling moth larvae and subjected to similar hot water bath heating. The quality attributes showed different sensitivity to the combinations of temperature and time used for hot water bath treatment. Pitting was more common in fruit treated at lower temperatures for longer times, while stem browning was more common in fruit treated at high temperatures. Berry browning, stem color, and pitting were the quality attributes most affected by heat treatment. Browning of cherry stem color was a crucial factor in determining whether a combination of temperature and time for hot water bath treatment was successful. All cherries stored at 0 ◦ C for 14 days to simulate sea shipment were of unacceptable quality after shelf life. Hot water bath treatments that provided 100% codling moth mortality and maintained overall acceptable fruit quality were very limited and included treatments at 50 ◦ C for 10 min and at 54 ◦ C for 6 min. Delaying the hot water bath treatment after fruit harvest, even if the cherries were kept at 0 ◦ C, resulted in a greater loss in fruit quality compared with those treated on the harvest day. Using hot water baths as a quarantine treatment for codling moths (Cydia pomonella) on sweet cherries may be feasible if fruit are air shipped at 5 ◦ C for 2 days, but not suitable if

History and use of heat in pest control: a review

This review describes the history and use of heat in the management of a wide range of agricultural and structural pests. Definitions and concepts used in heat treatments are discussed as well as possible mechanisms of thermal lethality. Factors used in determining treatments are availability, costs, complexity, and other constraints. Heat can be used separately in multiple forms or in combination: fire, water-based and atmospheric, steam, vapor heat, dry heat, forced hot air, high temperature controlled atmospheres, electric fields, and electromagnetic energies. The early research into each of these strategies is presented, including design, temperature ranges, and target pests. An understanding of the development of thermal treatments will increase efficacy of pest control and adaptability, and will reduce duplication.

Effect of Cold Treatment on Survival and Development of Codling Moth (Lepidoptera: Tortricidae) in Cherry

Abstract ‘Bing’ cherries, Prunus avium L., were obtained from an organic orchard and a conventional commercial orchard. The two groups were examined separately in replicated tests infested with each fruit initially infested with a first-instar codling moth, Cydia pomonella (L.). To simulate commercial postharvest holding conditions, the treatments were 0 (control), 1, 2, 4, 7, 10, and 14 d cold storage at 3.3°C. The fruits were examined three or more times to determine larval survival, life stage, fruit condition, and fungal disease. Survival of first instars was affected only by cold storage durations of ≥7 d. When infested with codling moth larvae, both organic and conventionally grown cherries quickly deteriorated from fungal diseases. The rate of moth development was estimated from the surviving larvae and was significantly different between organic and conventionally grown cherries for all instars except the second.

Trapping hop looper moths, Hypena humuli Harris (Lepidoptera: Erebidae), in hop yards with acetic acid and 3-methyl-1-butanol

Hop looper moths, Hypena humuli Harris, in commercial hop yards (Humulus lupulus L.) were captured in traps baited with a combination of acetic acid plus 3-methyl-1-butanol (AAMB). The two chemicals were synergistic in attracting hop looper moths. In a comparison of the lure chemicals, most moths were trapped with AAMB as the lure, while very few moths were captured in traps baited with acetic acid alone or 3-methyl-1-butanol alone. Female and male hop looper moths were trapped with AAMB, with an overall sex ratio through the year of 44% females to 56% males. Moths were trapped in all months of the growing season, from April into October. From April through September, most females captured in traps were mated, whereas in October most females trapped had been unmated. Most of the mated females, we trapped contained one spermatophore, indicating a single mating. The numbers of moths trapped were low from April through June, and increased greatly in July, and at one site again in late August. AAMB-baited traps may be a useful tool for monitoring hop looper moths in commercial hop yards, to determine their presence, and potentially to assess the risk of damaging infestations.