Abstract
Entomopathogenic nematodes (EPNs) can provide a substantial control, especially of the root feeding larval pests. The objective of the present study was to examine beneficial traits of an indigenous entomopathogenic nematode species, Heterorhabditis bacteriophora Poinar (Hb-EG strain), and to identify superior biocontrol candidates for suppression of the scarab beetle Temnorhynchus baal (Reiche & Saulcy) (Coleoptera: Scarabaeidae: Dynastinae) larvae as serious pests of strawberry in Egypt. The nematodes were applied to infect the greater wax moth, Galleria mellonella L. cadavers, to represent natural emergence from the host in laboratory and under field conditions. Its average yield was 49604 infective juveniles (IJs) per G. mellonella larva. Overall averages of nematode-induced mortality in G. mellonella larvae were (4.63, 3.12, and 1.92) at 4, 8, and 12 weeks, respectively, after continuous weekly baiting with 5 cadavers. Nematode capability for infection and reproduction ranged from 72 to 26% one to five months, respectively, after field inoculation of the infected larvae into the strawberry rhizosphere. The number of IJs, moved to the North of the rhizosphere, was significantly (P ≤ 0.05) less than that moved to the South or the East as reflected by the numbers of infected insects. The factors that may have a marked influence on EPN foraging behavior, persistence, and movement direction with implications for harnessing them as biological pest control agents were discussed.
Highlights
White grubs are serious pests of strawberry (Shehata et al 2019)
The mean number of infective juveniles (IJs) emerged from H. bacteriophora-infected G. mellonella larvae was compared with IJs for each of 2 groups, comprising 23 and 15 H. indica populations emerging from the scarab grub, Temnorhynchus baal (Reiche & Saulcy) (Coleoptera: Scarabaeidae: Dynastinae) in a previous study (Shehata et al 2019), using the two-tailed Student’s t test
The corresponding average of 15 populations (Shehata et al, 2019) related to Egyptian H. indica IJs emerged from the infected scarab grub, T. baal (Coleoptera: Scarabaeidae), in sandy soil, 46,960 IJs/grub, was not significantly (P ≤ 0.05) different from that of Hb-EG strain reported (t = 0.99; df = 33)
Summary
White grubs (larvae of scarab beetles) are serious pests of strawberry (Shehata et al 2019). Control recommendations for the white grubs currently consist solely of applications of chemical insecticides (El-Shemy et al, 2013). Entomopathogenic nematodes (EPNs), in the two families Steinernematidae and Heterorhabditidae, are potential environmentally friendly biological alternatives. They possess virtually many attributes of ideal biological control agents. Dozens of important insect pests are susceptible yet non-target populations are mostly undisturbed (Abd-Elgawad et al 2017). Despite their high pathogenicity to insects, their lack of threat to the environment facilitated their commercialization without registration requirements in many countries
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