Abstract
The barley chafer grub, Coptognathus curtipennis, is an important field pest
of barley, wheat and linseed seedlings at Tikur Inchini district of theWest
Shewa zone of Ethiopia in Ormoia regional state. Two entomopathogenic
nematodes (EPN; Heterorhabditis bacteriophora and Steinernema yirgalemense,
strains ANEPN21, ANEPN22, respectively) and three entomopathogenic fungal
isolates of Metarhizium anisopliae (MM, EE and PPRC66) were compared
separately at different rates of concentration for their effect against C.
curtipennis in laboratory bioassays. Heterorhabditis bacteriophora and M.
anisopliae isolate MM were found to be the most pathogenic to C. curtipennis
at 1000 infective juveniles (IJ)/grub and 108 conidia (g soil)–1
concentration, causing 88.7% and 88.6% mortality, respectively, after 3-4
weeks exposure. These two most effective entomopathogens were further tested
against the same insect in simultaneous and sequential combination with each
other. Insect larvae were exposed to optimal concentration of H.
bacteriophora and M. anisopliae isolate MM, which caused 50% larval
mortality, i.e., 380 IJ/grub and 1.7 × 107 conidia (g soil)–1, respectively,
as observed in the first experiments. The combined application increased
larval mortality in an additive and synergistic manner. To achieve a strong
synergistic effect, larva had to be exposed to M. anisopliae isolate MM 3
weeks before the addition of nematodes. The result of the whole experiment
suggests that the damage caused by barley chafer grub can be controlled or
managed by applying EPN and/or fungi. Furthermore, the combined use of M.
anisopliae with nematodes may offer an integrated approach to increase the
efficacy of EPN for C. curtipennis control and perhaps other insect
pests.
Control of melon thrips, Thrips palmi Karny, on greenhouse cucumber with the combined use of a red insect-proof net, Amblyseius swirskii, and Metarhizium anisopliae