Egg and larval survivorship of Carposina sasakii (Lepidoptera: Carposinidae) in apple and peach and their effects on adult population dynamics in orchards.
Egg and larval survivorship of Carposina sasakii Matsumura in fruits was investigated, and its effects on adult population dynamics was examined by comparing the seasonal adult population trends in apple and peach orchards. Egg survivorship was relatively high and did not differ among fruits, cultivars, and seasons. However, larval survivorship in fruits was very low according to fruits, cultivars, and seasons. In late apple ('Fuji'), no larvae survived inside fruits during mid- to late June, and larval survivorship in mid-July was very low (2.0%). In early apple ('Tsugaru') and early peach ('Kurakatawase'), larval survival was 18.1 and 43.7% during mid- to late June, respectively. However, in late peach ('Hakuto'), it was much lower (4.5%). The mean numbers of degree-days between the first and the last adult flight peaks were significantly different among different orchard systems. Significantly more degree-days occurred in apple (1029.8 DD) and apple-peach adjacent orchards (939.2 DD) than in peach orchards (681.0 DD). This could have been caused by high larval mortality in apples during the early season, and a mixture of both multivoltine and univoltine components contributing to C. sasakii overall population dynamics. Implications for management of C. sasakii in diverse fruit systems are discussed.