Effect of Planting Date and Plant Spacing on Field Colonization by Colorado Potato Beetles, Leptinotarsa decemlineata (Say), in New Brunswick

Abstract

Field studies carried out at Fredericton, New Brunswick, Canada, between 1982 and 1984 show that an important proportion of overwintered Colorado potato beetles, Leptinotarsa decemlineata (Say), colonizing the young potato plants in late plantings originate from the earlier plantings. Results of a concurrent insectary test suggest that these beetles have a 15% higher total fecundity than the beetles that stayed on the older plants. Reasons for the relocation of the beetles remain, however, to be fully determined. The late planting was colonized more heavily than the early planting in 1982 and 1983 but not in 1984. The seed spacings of 15 and 36 cm had no effect on the colonization by the beetles. The numbers of adults, egg masses, and larvae were larger in the weed-free plots than in the plots with weeds except in the widely spaced late plantings. The importance of these results for the management of the beetle is discussed.