Comparison between inoculative and inundative release for controlling scarab beetles in strawberry using entompathogenic nematodes under field conditions

Laboratory bioassay indicated that, Steinernema glaseri (NJ strain) (Steiner) caused a 100% mortality of the 1. t and the 2. d instar larvae of T. baal. Whereas, 94% mortality of the 3. d instar larvae and 96% mortality of the adult stages three days after nematode treatment were obtained. In contrast, Heterorhabdis bacteriophora (HP 88) (poinar) strains caused 68, 62, 60, and 58% insect mortality when applied on the 1. t, 2. d and 3. d, larval instars and adult stages of T. baal respectively. The current data suggest that, S. glaseri was the most virulent nematode on the all stages of this scarab pest more than H. bacteriophora. Under field conditions, the inoculative release was effective (F value, 3.47, mean square (M.S.), 1.65; P¡Ü0.05 after three inoculate release) more than the inundative release (F value, 2.61, M.S., 1.26; P¡Ü0.05 after the first inundate release). Furthermore, the data of both the six and second applications for the inoculative and inundative releases respectively showed the same trend with S. glaseri. On the other side, there was a strong host population reduction according to the application strategy mentioned reporting a highly significant variation of both strategy : (F = 3.71; M.S. = 1.41; P¡Ü0.05 after the first three inoculative release) while, (F = 11.15; M.S. = 2.49; P¡Ü0.05 after the first inundate release) with H. bacteriophora. However there was no significant variation between the two methods of application with H. bacteriophora after inocultive and inundative release. In the present study, the nematodes S. glaseri was highly effective when applied on the soil surface at a concentration of 200001J/m. more than H. bacteriophora with the same concentration in both methods of application inundative and inoculative release. Inoculative release was effective more than the inundative release for controlling T. baal in strawberry fields in Egypt.