X-Ray-Based Irradiation of Larvae and Pupae of the Navel Orangeworm (Lepidoptera: Pyralidae).

The suitability of adult male the navel orangeworm, Amyelois transitella (Walker) for Sterile Insect Technique (SIT) has been reported for both high energy gamma (>1 MeV) and low energy x-ray (90 keV) sterilization. However, research regarding sterilization of NOW larvae and pupae by gamma irradiation indicated nonsuitability due to high mortality. Here, NOW larvae and pupae were irradiated to doses up to 50 Gy with 90 keV x-rays, then paired with nonirradiated colony mates. Sterility of surviving insects was determined by the presence or absence of hatched neonates. While presence of offspring does not guarantee viability, the absence does guarantee sterility (as is appropriate for SIT) and was thus the measure used here. Early stage larvae experienced 77% mortality at a dose of 30 Gy, versus 20% for nonirradiated control. At 40 Gy, mortality reached 98%. Of surviving early stage larvae at 30 Gy, 29% of moth pairs produced offspring. For late stage larvae, no offspring were produced at 40 Gy, but mortality was 73%. For pupae, mortality reached 53% at 30 Gy with 13% still producing neonates, while mortality reached 98% at 40 Gy. These results are consistent with reported results for gamma irradiation of NOW larvae where sterility was observed somewhere between the 30 Gy and 60 Gy data points, but mortality was high. This further confirms the lack of suitability of NOW irradiated in the larval stage, whether by gamma or x-ray, and supports the hypothesis that x-ray and gamma treatments are biologically equivalent at equal doses.

Sample preparation and presampling of pistachios.

A theory has been developed to quantify the reduction of subsample variance of aflatoxin contamination, which is observed when granular materials are wet slurried, rather than dry ground, during subsample homogenization. A coefficient of variation, based on particle size distribution, subsample size, and probability of contamination, is predicted. The theory is tested with dry ground and with wet slurried pistachios, and excellent quantitative agreement is obtained. A 32% increase in the mean aflatoxin level is observed as well when wet slurrying is applied. Although no statistical explanation for this effect can be found, it is suggested that it is related to physiochemical binding between the nut matrix, which is (partly) broken by wet slurrying, and aflatoxin, making the extraction of more toxin possible. Other parameters that may affect slurrying results have been investigated as well.