Resistance to Diaphania hyalinata (Lepidoptera: Crambidae) in Cucumis species.

Diaphania hyalinata (L.), the melonworm, causes economic damage in cucurbit species in the Caribbean region. To control larvae feeding on leaves, frequent pesticide applications are needed, but this favors outbreaks of other pests. We looked for plant resistance to D. hyalinata in Cucumis melo L. and two wild Cucumis, C. metuliferus Meyer and C. pustulatus Naudin. Fifteen genotypes were observed using a 1-81 damage scale during 8 wk in two field trials in Guadeloupe, French West Indies. Among the C. melo genotypes, we observed different levels of damage (scores of 32-74 at the maximum damage date) ranging from partially resistant to susceptible genotypes. Both wild species scored <20 at the maximum damage date, and were more resistant in the field tests than the tested genotypes of C. melo. Five C melo genotypes and one C. pustulatus genotype were tested using a detached leaf test. Under controlled conditions, newly hatched larvae were fed with leaves from plants that were 5-9 wk old. Duration and mortality of immature stages were highly correlated. Strong antibiosis (long development and high mortality) was expressed by PI 140471 and Concombre Chien (two C. melo genotypes). For both genotypes, mortality was at least 87.9 versus 34% for Védrantais, a susceptible genotype. Because antibiosis and field resistance were not correlated, we hypothesize that some genotypes expressed antixenosis in the field trials. In addition, possibilities of breeding for C. melo resistance to D. hyalinata is discussed.