Laboratory And Field Tests Of Entomopathogenic Nematodes Against The Scarab BeetleTemnorhynchus Baal (Reiche), A Novel Insect Pest Of Strawberry In Egypt

• M. M. Shamseldean and A. A. Atwa
• Applied Center for Entomonematodes, Faculty of Agriculture, Cairo University, Giza, Egypt.

Abstract

Entomopathogenic nematodes (EPN) belong to bothSteinernema and Heterorhabditis genera were tested against the scarab beetle, Temnorhynchus baal (Reiche). Results of laboratory experiments indicated that, Steinernema glaseri (Steiner) caused a 100% mortality of 1st and 2nd instar larvae of T. baal. Whereas, mortality of the 3rd instar larvae and adult stages has reached 95% 72 hours after treatment with nematode infective juveniles (IJs). In contrast, Steinernema sp. (EGG4) caused 70, 65, 50, and 55% insect mortality when applied on 1st, 2nd, 3rd, larvae and adult stages respectively. Meanwhile, Steinernema sp. (EBNE) has caused 55, 55, 50, and 45% of insect mortality in 1st, 2nd, 3rd instar larvae and adult stages respectively. While, the Egyptian isolate of S. kushidai (EBN32), has caused 60, 65, 52, and 62% in 1st, 2nd, 3rd instar larvae and adult stages of this scarab pest respectively. However, the Egyptian isolate of S. carpocapsae (EGBX), has caused 45, 30, 28, and 35% of insect mortality in the 1st, 2nd, 3rd instar larvae and adult stages respectively. On the contrary, the Egyptian isolate of Heterorhabditis bacteriophora (EKB20) has caused 45, 30, 28, and 35% of insect mortality in the 1st, 2nd, 3rd instar larvae and adult stages of this scarab beetle respectively. When S. glaseri was tested against T. baal in the field, persistence of EPN was measured by testing the infection of trapped Galleria mellonella larvae in soil samples collected from treated field plots. Nematodes collected from a soil depth of (0-10 cm) has caused up to 30% mortality in the tested G. mellonella larvae, meanwhile no nematode persistence was detected in all treated field plots at the soil depth (10 - 30 cm) after the first three field applications. The data also showed that nematode persistence at a soil depth of (0 - 10 cm) caused up to 65% mortality of G. mellonella after the fourth and fifth field applications. Meanwhile low persistence of nematodes have occurred at the fourth, fifth, and sixth applications causing up to 30 % mortality of G. mellonella placed in soil collected from the depth of (10-30 cm). In contrast, after the seventh and eighth applications, higher persistence of nematodes were recorded in both tested soil depths of 0-10 and 10-30 cm which caused 100% mortality of G. mellonella. Steinernema glaseri tested in the field against T. baal infestation caused population reduction ranging from 89.2% to 96.8% after four field applications. While the overall percentage of population reduction after eight field applications was 96.3% to 99.1%. Although inoculative release for the four and eight field applications gave almost the same degree of population reduction of insect larvae, the repeated treatment with S. glaseri from the 4th to the 8th field application has greatly reduced the numbers of white grubs below the economic injury level of strawberry plants.