Ecology

The main life environment of the entomopathogenic nematodes is soil or substrate. The infective larvae can spread to 90 cm in horizontal and vertical directions for the search of food resource during 30 days. The most active migration takes place during the first 2–4 days, after that their moving slows. The factors influencing on the mobility of the infective larvae are humidity, temperature and the structure of medium.

One of the most important factors is humidity, because the nematodes need water film in the inner space of medium pores for effective movement. If water film becomes too thin (drying out of medium) or space between pores is filled up with water very much, the movement of nematodes is limited.

Various species and strains of nematodes have different optimal temperatures and their limits that influence on nematode survival and mobility. At low temperatures (less than 10–15°C) the nematodes loss their motility but at high temperatures (more than 30–40°C) they reduce their activity. The long exposure of extreme temperatures (lower than 0°C or higher than 40°C) is lethal for the majority of entomopathogenic nematode species. The long storage of the infective nematodes is better to make at 5–15°C. At higher temperatures the infective nematodes have an increased metabolic activity and deplete their energy reserves, shortening by it their lifespan.

The porosity of substrate also influences on the dispersal of nematodes. The less pores become in substrate the worse dispersal of nematodes is. Oxygen is also a limiting factor in water-saturated media with high concentration of organic matter, but pH doesn’t have a strong effect on the survival of infective nematode larvae. The high level of salt concentration in medium doesn’t exert direct influence on nematode survival.

Ultraviolet irradiation (sunlight) is able to kill the nematodes during short time. The problem of ultraviolet irradiation is one of the most important factors for nematode application as a biological insecticide. Direct susceptibility to ultraviolet irradiation can be minimized by the application of the entomopathogenic nematodes in the early morning or evening or by way of the use of sufficient quantity of water to wash the nematodes into substrate.

The entomopathogenic nematodes can spread passively for long distances by water, wind, phoresia (transfer by other organisms), infected hosts, human activity and other.