Abstract
In laboratory experiments, we investigated how media with varying ratio of peat:sand and two levels of compaction influence dispersal success of entomopathogenic nematode (EPN) species with different foraging strategies: Steinernema carpocapsae (ambusher), Heterorhabditis downesi (cruiser) and Steinernema feltiae (intermediate). Success was measured by the numbers of nematodes moving through a 4 cm column and invading a wax moth larva. We found that both compaction and increasing peat content generally decreased EPN infective juvenile (IJ) success for all three species. Of the three species, H. downesi was the least affected by peat content, and S. carpocapsae was the most adversely influenced by compaction. In addition, sex ratios of the invading IJs of the two Steinernema species were differentially influenced by peat content, and in the case of S. feltiae, sex ratio was also affected by compaction. This indicates that dispersal of male and female IJs is differentially affected by soil parameters and that this differentiation is species-specific. In conclusion, our study shows that organic matter: sand ratio and soil compaction have a marked influence on EPN foraging behaviour with implications for harnessing them as biological pest control agents.
Highlights
Soil is a complex biomaterial (O’Donnell et al 2007) that serves as a reservoir of a wide range of insect pathogens and parasites, such as viruses, bacteria, protozoa, fungi and nematodes (Klingen and Haukeland, 2006)
Entomopathogenic nematodes (EPN) that have been categorized as cruising foragers, such as Heterorhabditis and some Steinernema species, are allegedly better suited to control soil-dwelling insect pests, whereas nematodes that are categorized as ambush foragers, such as Steinernema carpocapsae (Weiser), are traditionally recommended for use against soil surface active pests (Campbell and Gaugler, 1993; Kaya and Gaugler, 1993)
The mortality (= parasitism) of Galleria larvae was on average 53·9, 95·3 and 50·1% for S. carpocapsae, S. feltiae and H. downesi, respectively
Summary
Soil is a complex biomaterial (O’Donnell et al 2007) that serves as a reservoir of a wide range of insect pathogens and parasites, such as viruses, bacteria, protozoa, fungi and nematodes (Klingen and Haukeland, 2006). Some of these parasites have soil-transmitted infective stages that need to find hosts, and soil properties modulate biotic interactions between these parasites and their hosts. More recently, it has become clear that S. carpocapsae may be effective against distant, immobile hosts (Dillon et al 2006; Martinez de Altube et al 2008)
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