Host status of fresh prunes by potential quarantine pests in laboratory tests and evaluation of packinghouse culls

The status of fresh prunes, Prunus domestica L., as a host for codling moth , Cydia pomonella (L.) (Lepidoptera: Tortricidae); peach twig borer, Anarsi a lineatella Zeller (Lepidoptera: Gelechiidae); omnivorous leafroller, Plat ynota stultana Walshingham (Lepidoptera: Tortricidae); oriental fruit moth, Grapholita molester (Busck) (Lepidoptera: Tortricidae); navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae); and walnut husk fly , Rhagoletis completa Cresson (Diptera: Tephritidae), was investigated in l aboratory tests and by examination of packinghouse culls. In laboratory no- choice tests, the mean number of adults reared per fruit was 0.01 for codli ng moth, 0.08 for omnivorous leafroller, 0 for oriental fruit moth, and 1.6 for navel orangeworm. In choice tests the mean number of adults reared per apple or fresh prune was for codling moth, 0.78 and 0.02 (significantly di fferent); for omnivorous leafroller, 0.05 and 0.02; and for oriental fruit moth, 2.07 and 0 (significantly different), respectively. Walnut husk ny ov iposited in fresh prunes in no-choice tests but pupae did not develop from the fruit. In choice tests, walnut husk ny did not oviposit in fresh prunes when caged with its normal host, green walnuts, in which large numbers of pupae developed. Inspection of packinghouse culls for immature insects show ed that fresh prunes with possible larval feeding sites in the form of fras s or fruit gum extrusions were lighter in weight, significantly less firm, similar in color, and had significantly higher soluble solids than noninfes ted fruit. Based on packinghouse cull samples, 1 fresh prune per 133 harves ted fruit would be expected to show possible insect damage. Eleven peach tw ig borer larvae were found in fresh prune cull samples (213.9 kg) removed f rom a 16,744.5-kg harvest. The calculated level of infestation was 1 infest ed fruit per 8,501.8 fruit harvested or per 21.7 cartons of medium-sized pa cked fruit. Based on our results, the risk of infestation of fresh prunes b y the insects in this study would be minimal in fruit exported from the San Joaquin Valley of California.