Predicting Larval Stage Distribution of Lobesia botrana (Lepidoptera: Tortricidae) at Three Constant Temperatures.

European grapevine moth, Lobesia botrana (Denis and Schiffermüller), is an invasive pest species subject to regulatory control under the International Plant Protection Convention. An extensive infestation of this insect detected in California vineyards in October 2009 resulted in the initiation of postharvest research intended to ensure continuing trade of California table grapes by preventing the unintentional introduction of L. botrana to uninfested export destinations. Having the ability to accurately predict and confirm the particular stadia of larval development of insects obscured from direct observations, such as those being mass-reared in diet for use in phytosanitary control experiments, is necessary to be able to ensure that the most tolerant life stage is accurately targeted. Lobesia botrana were reared from egg to eclosion at three different temperatures: 16, 20, and 24°C (60% RH; 16:8 [L:D] h). Daily samples (≥15) were taken of larvae and pupae to determine the chronological distribution of life stages until daily samples comprised 100% pupae, after which only adults were counted. Head capsule measurements of all sampled larvae were taken (n = 2,820) and analyzed using nonlinear least squares (NLLS) fitting to Gaussian curves to describe stadia-specific head capsule demarcations and the probability of misclassifying instars due to overlapping life stage distributions.

Activated carbons from end-products of tree nut and tree fruit production as sorbents for removing methyl bromide in ventilation effluent following postharvest chamber fumigation.

End-products of tree nuts and tree fruits grown in California, USA were evaluated for the ability to remove methyl bromide (MB) from ventilation effluent following postharvest chamber fumigation. Activated carbon sorbents from walnut and almond shells as well as peach and prune pits were prepared using different methods of pyrolysis, activation, and quenching. Each source and preparation was evaluated for yield from starting material (%, m/m) and performance on tests where MB-containing airstreams were directed through a columnar bed of the activated carbon in an experimental apparatus, termed a parallel adsorbent column tester, which was constructed as a scaled-down model of a chamber ventilation system. We report the number of doses needed to first observe the breakthrough of MB downstream of the bed and the capacity of the activated carbon for MB (%, m/m) based on a fractional percentage of MB mass sorbed at breakthrough relative to mass of the bed prior to testing. Results were based on a novel application of solid-phase microextraction with time-weighted averaging sampling of MB concentration in airstreams, which was quantitative across the range of fumigation-relevant conditions and statistically unaffected by relative humidity. Activated carbons from prune pits, prepared either by steam activation or carbon dioxide activation coupled to water quenching, received the greatest number of doses prior to breakthrough and had the highest capacity, approximately 12-14%, outperforming a commercially marketed activated carbon derived from coconut shells. Experimental evidence is presented that links discrepancy in performance to the relative potential for activated carbons to preferentially sorb water vapor relative to MB.

Postharvest treatment of fresh fruit from California with methyl bromide for control of light brown apple moth (Lepidoptera: Tortricidae).

Methyl bromide (MB) chamber fumigations were evaluated for postharvest control of light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), in fresh fruit destined for export from California. To simulate external feeding, larvae were contained in gas-permeable cages and distributed throughout loads of peaches, plums, nectarines (all Prunus spp.), apples (Malus spp.), raspberries (Rubus spp.), or grapes (Vitis spp.). Varying the applied MB dose and the differential sorption of MB by the loads resulted in a range of exposures, expressed as concentration x time cross products (CTs) that were verified by gas-chromatographic quantification of MB in chamber headspace over the course of each fumigation. CTs > or = 60 and > or = 72 mg liter(-1) h at 10.0 +/- 0.5 and 15.6 +/- 0.5 degrees C (x +/- s, average +/- SD), respectively, yielded complete mortality of approximately 6,200 larvae at each temperature. These confirmatory fumigations corroborate E. postvittana mortality data for the first time in relation to measured MB exposures and collectively comprise the largest number of larval specimens tested to date. In addition, akinetic model of MB sorption was developed for the quarantine fumigation of fresh fruit based on the measurement of exposures and how they varied across the fumigation trials. The model describes how to manipulate the applied MB dose, the load factor, and the load geometry for different types of packaged fresh fruit so that the resultant exposure is adequate for insect control.

Quantifying host potentials: indexing postharvest fresh fruits for spotted wing Drosophila, Drosophila suzukii.

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), Drosophila suzukii 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 ( (mean)HPIvaried  = 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 ( (mean)HPIvaried  = 232.4±3.21; rank 7 of 7) having the least potential.

Field and laboratory evaluation of persistence and bioavailability of soil termiticides to desert subterranean termite Heterotermes aureus (Isoptera: Rhinotermitidae).

Control information for the desert subterranean termite Heterotermes aureus (Snyder) (Isoptera: Rhinotermitidae) is limited, despite being one of three major termite pests in the United States. Annual control information comes from field evaluations by the USDA-Forest Service. This partial assessment of termiticide efficacy is likely deficient without concurrent residual analysis and laboratory bioassays of termiticides. In this study, six termiticides were evaluated using exposed and covered field plots in Tucson, AZ, over a 5-yr period for persistence and efficacy by using both residue analysis and laboratory bioassays. All the termiticides degraded significantly during the study. Termiticide degradation seemed to be consistently slower in covered plots than in exposed plots, although this trend was not statistically supported. A comparison of yearly degradation rates showed the three classes of termiticides degraded at different rates. Chlorpyrifos, the organophosphate, degraded quickest at a rate of 68.9% for each doubling of time, whereas chloronicotinyls and pyrethroids degraded at much slower rates (50.4 and 48.4% for each doubling of time, respectively). Bioassays showed termites tunneled 1.26 +/- 0.61 cm deeper in uncovered plots than in those that were covered. Mortality rates in bioassays from covered treatments were 16.13 +/- 9.87% higher than in uncovered treatments. Our study demonstrated that the termiticides evaluated could remain effective against H. aureus for at least 4 yr after application, particularly under covered conditions. Additionally, it is anticipated that retreatments may be necessary before the 5-yr warranty expires when using final grade applications to stem walls in warmer parts of Arizona.