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How to apply nematodes

Insect-parasitic nematodes can be easily applied using conventional pesticide and fertilizer sprayers that have up to 300 PSI pressures.  However, nematodes will be easily damaged, if they are agitated through excessive recirculation of spray mix or if the temperature in the tank increases beyond 86 degrees F. Nematodes can also be applied through different types of irrigation systems but pumps should have proper pressure to avoid damage to nematodes and screen sizes should be larger than 50 mesh so that nematodes will pass through them live. Watering cans are used to apply nematodes in small areas including vegetable and ornamental gardens.

How many nematodes should be applied

For the suscessful control most of the soil dweling insect pests, the optimal rate of 1 billion infective juvenile nematodes in 100 to 260 gallons of water per acre is generally recommended.

Optimal soil and environmental condtions to apply nematodes

All nematodes require proper soil moisture for their optimal movement and infectivity. The activity and infectivity of nematodes can be enhanced by maintaining optimum moisture levels in the soil before and after their application.  In case of nematode application in turf, turf should be irrigated immediately after applicationwith at least 1/2 inch of water to rinse off nematodes from the folliage and move them into the soil and thatch. As nematodes are very sensitiv to heat and cold, their infectivity will be reduced if soil temperature is below 4 degrees C and above 35 degrees C. Soil temperatures between 20 to 30 degrees C are considered favourable for application of majority of nematode species and their virulence.  Nematode survival and activity also influenced by soil type.  Both survival and activity of nematodes is higher in sandy-loam soils than in heavy clay soils.

When to apply nematodes

Since nematodes are very sensitive to UV light, they will die within a minute or two when exposed to full sun. Therefore, nematodes should be applied early in the morning or late in the evening to avoid exposure to UV light.

Nematodes are defined as thread-like microscopic, colorless, unsegmented round worms found in almost all habitats especially in soil and water. Nematodes may be free-living, predacious and parasitic. Nematodes that are considered our friends include entomopathogenic nematodes, insect-parasitic nematodes, slug-parasitic and free-living nematodes.

Nematodes are called free-living because they are not parasitic to either plants or animals, live freely in soil and can play an important role in nutrient cycling in the soil food web. These nematodes are currently used as bio-indicators of soil health because they have diverse feeding habits, some of them can survive harsh, polluted, or disturbed environments better than others, and some have short life cycles and can respond to environmental changes rapidly.

Nematodes are called insect-parasitic because they benefit for their development and reproduction at the insect host’s expense. The best examples are the members of the family Mermithidae.

Nematodes are called slug-parasitic because they benefit for their development and reproduction at the slug’s expense. These nematodes nematodes are mutualistically associated a bacterial smbiont, which is capable of causing disease and killing several species of slugs. Example is Phasmarhabditis hermaphrodita, which belongs to a family Rhabditidae in the order of Rahbdita and symbiotically associated with a gram-negative bacterium, Moraxella osloensis .

Nematodes are called entomopathogenic because they are mutualistically associated with a species specific pathogenic bacterial symbiont, which are capable of causing disease in insect hosts. All the entomopathogenic nematodes are members of two families Steinernematidae and Heterorhabditidae in the order of Rhabdita.

In this blog, I will be providing the information on only entomopathogenic nematodes/insect-parasitic nematodes.