Response of grey slug to entomopathogenic nematodesABSTRACT
Biological control using entomopathogenic nematodes (EPNs) is known as an ecofriendly strategy in integrated pest management. The terrestrial slug Parmacella ibera is a major pest of vegetables and citrus trees in north of Iran. The heavy costs and environmental concerns of synthetic molluscicides led the study to use EPNs, against the slug P. ibera. The present study was arranged to evaluate and compare the performance of EPNs, Steinernema feltiae, S. carpocapsae and Heterorhabditis bacteriophora on P. ibera population (mortality rate) and the feeding rate in vitro, and also its damage (seedlings establishment rate) in vitro. Phasmarhabditis hermaphrodita, as a slug parasite nematode, and also the metaldehyde, as a molluscicide, were used as positive controls. The results of the study showed that the highest mortality rate (%) and the seedlings establishment rate (%) of the slug population were observed in S. carpocapsae, S. feltiae and H. bacteriophora treatments, respectively. The feeding rate (%) of the slug declined in the treatments with H. bacteriophora, S. feltiae and S. carpocapsae, respectively. The mortality rate of the pest was enhanced by extending the exposure time and increasing levels of the nematodes. Therefore, it can be concluded that the EPNs S. carpocapsae, S. feltiae and H. bacteriophora are able to control the slug P. ibera population.
Key words biological control; Parmacella ibera ; Steinernema feltiae ; Steinernema carpocapsae ; Heterorhabditis bacteriophora
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The letters a, b, c, d, e, f, g, h and i correspond to days 1, 2, 3, 4, 5, 6, 7, 8 and 9, as exposure times, respectively. Defined doses at the X axes (I, II, III, IV and V) respectively correspond to 250, 500, 1000, 2000 and 4000 IJs·qm-2 for the nematodes; and 1, 2, 4, 8 and 16 g·m-2 for the molluscicide metaldehyde. Means with the same letters on the curves are not significantly different (p < 0.05; n = 5).
The letters a, b, c, d, e and f correspond to days 1, 2, 3, 4, 5 and 6, as exposure times, respectively. Defined doses at the X axes (I, II, III, IV and V) respectively correspond to 250, 500, 1000, 2000 and 4000 IJs·m-2 for the nematodes; and 1, 2, 4, 8 and 16 g·m-2 for the molluscicide metaldehyde. Means with the same letters on the curves are not significantly different (p < 0.05; n = 5).
The letters a, b, c, d, e and f correspond to days 2, 4, 6, 8, 10 and 12, as exposure times, respectively. Dose levels I, II, III, IV and V correspond to 250, 500, 1000, 2000 and 4000 IJs·m-2 for the nematodes; and 1, 2, 4, 8 and 16 g·m-2 for metaldehyde, respectively. Ctrl correspond to the treatment including the slug and without the control agents; the containers free of the slug and the control agents was considered as Ctrl+. Means with the same letters on the curves are not significantly different (p < 0.05; n = 5).