Larval spatial patterns and sequential sampling plan for pickleworm, Diaphania nitidalis (Stoll) (Lepidoptera: Pyralidae), on summer squash

The pickleworm, Diaphania nitidalis (Stoll), was studied to determine the spatial pattern of its five larval stages within reproductive structures of summer squash and to characterize the spatial pattern of larvae between plants to develop a sampling method for assessing pickleworm populations. Sampling green staminate flower buds greater than 5 cm in length was more reliable for detecting infestations than sampling smaller green staminate flower buds, blooming flowers, and fruit. Flower buds provided a more efficient (large reservoir of larvae), reliable (smaller sampling variance than other sample units), and acceptable (non-marketable plant structure) method of sampling pickleworm populations. Fruit damage was positively correlated with flower bud damage and larval counts. The between-plant spatial pattern was variable between samples but suggested a slightly contagious (overdispersed) larval dispersion. Based on this information, a sequential sampling plan was developed in which the required number of plant samples at a given level of sampling precision for specific larval densities can be calculated