Improved analysis of propylene oxide, propylene chlorohydrin and propylene bromohydrin: Presentation

The benefits and deficiencies of several methods of analysis for PPO and PXH, including the aqueous extraction used in ASTA method 23.1 and the MTBE extraction method previously reported by the authors, will be discussed. Novel methods utilizing dynamic headspace extraction and solid phase microextraction (SPME) will also be reported with particular emphasis on preventing artefactual effects. Preliminary experiments have found that dynamic headspace sampling can lower detection limits by up to 3 orders of magnitude.The benefits and deficiencies of several methods of analysis for PPO and PXH, including the aqueous extraction used in ASTA method 23.1 and the MTBE extraction method previously reported by the authors, will be discussed. Novel methods utilizing dynamic headspace extraction and solid phase microextraction (SPME) will also be reported with particular emphasis on preventing artefactual effects. Preliminary experiments have found that dynamic headspace sampling can lower detection limits by up to 3 orders of magnitude

Sublethal exposure, insecticide resistance, and community stress

Insecticides are an invaluable pest management tool and anthropogenic stressors of widespread environmental occurrence that are subject to biased perceptions based on the targeted application, market value of use, and regulatory requirements. As a result, short-term and simplistic efforts focusing on lethal effects toward individual species and populations prevail. Holistic and comprehensive studies exploring rather common sublethal insecticide exposures are rare, particularly considering their potential role in structuring populations and communities in diverse environmental settings and potentially interfering in a range of ecological interactions. Studies on insecticide resistance, for example, do not go beyond population-based studies, disregarding temporal and spatial effects in the associated community, and rarely considering the whole of sublethal exposure. Some of these knowledge gaps are here recognized and explored

Sublethal exposure, insecticide resistance, and community stress

Insecticides are an invaluable pest management tool and anthropogenic stressors of widespread environmental occurrence that are subject to biased perceptions based on the targeted application, market value of use, and regulatory requirements. As a result, short-term and simplistic efforts focusing on lethal effects toward individual species and populations prevail. Holistic and comprehensive studies exploring rather common sublethal insecticide exposures are rare, particularly considering their potential role in structuring populations and communities in diverse environmental settings and potentially interfering in a range of ecological interactions. Studies on insecticide resistance, for example, do not go beyond population-based studies, disregarding temporal and spatial effects in the associated community, and rarely considering the whole of sublethal exposure. Some of these knowledge gaps are here recognized and explored

Postharvest treatment research at USDA-ARS: stored product fumigation: Presentation

The overall goal of this USDA-ARS research is to ensure the protection and quality of stored product foodstuffs. The results of this research directly enhance production, distribution, and safety of foodstuffs, promote and retain access of United States-grown crops to domestic and foreign markets, and protect the United States and trading partners from the agricultural, ecological and economic threat posed by quarantine and invasive pests. In general, USDA-ARS research related to the fumigation of stored products focuses on the development of techniques to rapidly disinfest raw products of field pests, control pests in processed products amenable to reinfestation and microbial infection, and reduce reliance on fumigation as a stand-alone measure for postharvest disinfestations and disinfections. Specific research objectives include: comparative evaluation of alternative fumigants to methyl bromide in postharvest applications, development of novel technologies to reduce and eliminate atmospheric emissions from chambers used in postharvest fumigation, and design production strategies that allow for a more strategic postharvest use of methyl bromide and alternative fumigants. Recent research findings will be presented and discussed, including: exposure requirements of phosphine on key stored product pests (as related to resistance management), the establishment of efficacy and experimental criterion for quarantine applications, and the development of models to quantitatively understand the underpinnings of fumigations and related phytosanitary treatments.The overall goal of this USDA-ARS research is to ensure the protection and quality of stored product foodstuffs. The results of this research directly enhance production, distribution, and safety of foodstuffs, promote and retain access of United States-grown crops to domestic and foreign markets, and protect the United States and trading partners from the agricultural, ecological and economic threat posed by quarantine and invasive pests. In general, USDA-ARS research related to the fumigation of stored products focuses on the development of techniques to rapidly disinfest raw products of field pests, control pests in processed products amenable to reinfestation and microbial infection, and reduce reliance on fumigation as a stand-alone measure for postharvest disinfestations and disinfections. Specific research objectives include: comparative evaluation of alternative fumigants to methyl bromide in postharvest applications, development of novel technologies to reduce and eliminate atmospheric emissions from chambers used in postharvest fumigation, and design production strategies that allow for a more strategic postharvest use of methyl bromide and alternative fumigants. Recent research findings will be presented and discussed, including: exposure requirements of phosphine on key stored product pests (as related to resistance management), the establishment of efficacy and experimental criterion for quarantine applications, and the development of models to quantitatively understand the underpinnings of fumigations and related phytosanitary treatments

Postharvest Fumigation of Fresh Citrus with Cylinderized Phosphine to Control Bean Thrips (Thysanoptera: Thripidae)

Bean thrips (BT), Caliothrips fasciatus (Pergande), is a pest of concern to certain countries that import fresh citrus fruit from California, USA. A series of laboratory-scale exploratory fumigations with phosphine at 4.9 ± 0.3 °C (mean ± 2 SD; x¯±2s) were conducted to evaluate the postharvest control of adult BT. Models of the duration–mortality response predicted ca. 99% mortality of BT populations when headspace concentrations of phosphine, [PH3], are maintained at levels ≥0.4 g m−3 (250 ppmv (µL L−1)) and ≤1.5 g m−3 (1000 ppmv (µL L−1)) for 12 h, with the duration representing the lower bound of the 95% confidence level (CL). Confirmatory fumigations, each lasting 12 h, were then conducted using BT-infested sweet oranges, Citrus sinensis (L.), at pulp temperature (T) ≤ 5 °C to corroborate the exploratory results. Three formulations of cylinderized phosphine were used: 1.6% phosphine by volume in nitrogen, VAPORPH3OS®, and ECOFUME®, all applied at two levels, ca. 1.5 g m−3 (1000 ppmv (µL L−1)), as well as 0.5 g m−3 (300 ppmv (µL L−1)). Collectively, across the formulations, an applied dose of ca. 1.5 g m−3 (1000 ppmv (µL L−1)) resulted in 0 survivors from 38,993 (probit 8.60, 95% CL; probit 9, 72% CL) treated BT, while an applied dose of 0.5 g m−3 (300 ppmv (µL L−1)) resulted in 0 survivors from 31,204 (probit 8.56, 95% CL; probit 9, 70% CL) treated BT. Results were discussed in the context of commercial and operational features of quarantine and pre-shipment (QPS) uses of phosphine to treat fresh fruit and, specifically, the control of BT in fresh citrus exported from California, USA, to Australia

Quantifying Host Potentials: Indexing Postharvest Fresh Fruits for Spotted Wing Drosophila, <i>Drosophila suzukii</i>

<div><p>Novel methodology is presented for indexing the relative potential of hosts to function as resources. A Host Potential Index (HPI) was developed as a practical framework to express relative host potential based on combining results from one or more independent studies, such as those examining host selection, utilization, and physiological development of the organism resourcing the host. Several aspects of the HPI are addressed including: 1) model derivation; 2) influence of experimental design on establishing host rankings for a study type (no choice, two-choice, and multiple-choice); and, 3) variable selection and weighting associated with combining multiple studies. To demonstrate application of the HPI, results from the interactions of spotted wing drosophila (SWD), <i>Drosophila suzukii</i> Matsumura (Diptera: Drosophilidae), with seven “reported” hosts (blackberries, blueberries, sweet cherries, table grapes, peaches, raspberries, and strawberries) in a postharvest scenario were analyzed. Four aspects of SWD-host interaction were examined: attraction to host volatiles; population-level oviposition performance; individual-level oviposition performance; and key developmental factors. Application of HPI methodology indicated that raspberries (<i>^meanHPI_varied</i> = 301.9±8.39; rank 1 of 7) have the greatest potential to serve as a postharvest host for SWD relative to the other fruit hosts, with grapes (<i>^meanHPI_varied</i> = 232.4±3.21; rank 7 of 7) having the least potential.</p> </div

Spinosad-induced stress on the maize weevil Sitophilus zeamais: Presentation

Although seldom considered, sublethal insecticide exposure may lead to harmful, neutral, or even beneficial responses that may affect (or not) the behavior and fitness of the exposed insects. Intriguingly, little is known about such effects on stored product insect pests and even less is available regarding the bioinsecticide, spinosad. Thus, we assessed the sublethal effects of spinosad on walking, feeding, drinking and mating behaviors of maize weevils (Sitophilus zeamais), also assessing their survival, reproductive output, and grain loss compared with maize weevils exposed to the pyrethroid deltamethrin (as positive control), and water only (negative control). Both spinosad and deltamethrin were able to effectively control the insects, although the latter caused a faster mortality than the former. Behavioral pattern changes were caused by both insecticides, especially deltamethrin, triggering irritability (i.e., avoidance after contact). Different feeding and drinking responses were also detected with significant avoidance to deltamethrin, but not to spinosad. Maize weevil couples sublethally exposed to deltamethrin and spinosad exhibited altered reproductive behavior, a likely consequence of their altered activity, but deltamethrin caused greater behavioral changes. Curiously, higher progeny emergence and grain loss were observed in deltamethrin-exposed insects, suggesting that this pyrethroid insecticide elicits hormesis in maize weevils that may compromise control efficacy by this compound. In contrast, such effect was not detected with spinosad, which did not elicit avoidance allowing the intended weevil exposure and control.Although seldom considered, sublethal insecticide exposure may lead to harmful, neutral, or even beneficial responses that may affect (or not) the behavior and fitness of the exposed insects. Intriguingly, little is known about such effects on stored product insect pests and even less is available regarding the bioinsecticide, spinosad. Thus, we assessed the sublethal effects of spinosad on walking, feeding, drinking and mating behaviors of maize weevils (Sitophilus zeamais), also assessing their survival, reproductive output, and grain loss compared with maize weevils exposed to the pyrethroid deltamethrin (as positive control), and water only (negative control). Both spinosad and deltamethrin were able to effectively control the insects, although the latter caused a faster mortality than the former. Behavioral pattern changes were caused by both insecticides, especially deltamethrin, triggering irritability (i.e., avoidance after contact). Different feeding and drinking responses were also detected with significant avoidance to deltamethrin, but not to spinosad. Maize weevil couples sublethally exposed to deltamethrin and spinosad exhibited altered reproductive behavior, a likely consequence of their altered activity, but deltamethrin caused greater behavioral changes. Curiously, higher progeny emergence and grain loss were observed in deltamethrin-exposed insects, suggesting that this pyrethroid insecticide elicits hormesis in maize weevils that may compromise control efficacy by this compound. In contrast, such effect was not detected with spinosad, which did not elicit avoidance allowing the intended weevil exposure and control