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How to use beneficial nematodes for insect pest control? What do you need to consider when applying beneficial nematodes?
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Beneficial nematodes are being used in both agricultural and horticultural crops and have proven effective against insect pests such as white grubs and black vine weevils. For gardeners as well, beneficial nematodes are attractive as a non-toxic pest control method. Their advantages include no side effects nor resistance, no residues remaining in the soil and the treated areas can be accessed at any time. But what are nematodes, how do they work and how do you use them correctly and efficiently?
Nematodes: Useful Helpers in the Fight Against Pests
Nematodes are naturally occurring roundworms, which can either be useful or harmful. Those who do not know yet these organisms as effective against insect pests often associate them with pests that attacks carrots and potatoes in vegetable gardens.
Some species of the genera Steinernema and Heterorhabditis are parasites of insects and are referred to as entomopathogenic nematodes—commonly termed as beneficial nematodes. They are being used to control soil-dwelling stages of insect pests. These nematodes are very small (<1.5 mm) and can be easily observed with a hand lens.
Some commercially available beneficial nematode species include: Heterorhabditis bacteriophora, Steinernema feltaie and Steinernema carpocapsae. In the following table, you can find information about some targeted insect pests for those three commercially available nematodes—this is not an exhaustive list.
Heterorhabditis bacteriophora | |
|---|---|
Banana weevil Billbugs Black vine weevil Citrus root weevils Clearwing borer moths Corn rootworms Cranberry rootworm Diaprepes root weevil Fifth flies | False Codling moth Fungus gnats Root weevils Scarab grubs Sugarbeet weevil Sweet potato weevil Tomato leafminer |
Steinernema feltiae | |
Armyworms Banana weevil Black vine weevil Clearwing borer moths Codling moth Corn earworm Fifth flies Flat-headed rootborer Fungus gnats Leafminers | Shore flies Sciarid flies Sweet potato weevil Strawberry root weevil Tomato leafminer Turnip cutworm Western flowers thrips |
Steinernema carpocapsae | |
Armyworms Artichoke plum moth Banana weevil Billbugs Black cutworm Black vine weevil Cranberry girdler Carpenter worms Codling moth Corn rootworms Corn earworm Cranberry rootworm Crane flies Crown borers Cutworms Clearwing borer moths Flea bettles Fruit flies Fungus gnats Leafminers | Leopard moth Navel orangeworm Peach borer moth Pecan weevil Red palm weevil Rootworms Root weevils Stem borers Strawberry root weevil Sugarbeet weevil Sweet potato weevil Tomato leafminer Turnip cutworm Webworms Western flowers thrips White grubs |
How Beneficial Nematodes Work
In the soil, nematodes locate and penetrate the larva of the pest through body openings —mouth, respiratory orifices and anus. Then they release their toxic bacteria, which can cause rapid insect death within 24-48 hours. Subsequently, they multiply until food depletion and their life cycle is complete in a few days. Hundreds of thousands of new infective juveniles emerge from the cadaver in search of another host and the life cycle is repeated.
How To Use Them Correctly
Nematode application rates vary depending on the crop, and the rates of nematodes recommended by the supplier should be used. For example, nematodes are usually applied with water at a typical rate of 500 000/m2 on lawns, turfs, and pastures. Nematodes can be applied with most commercially available spray equipment, including watering cans, hand or ground sprayers, mist blowers, aerial equipment on helicopters, and irrigation systems. Application times should coincide with the most susceptible stages of the insect and soil optimal temperatures. Other important factors to consider in the application of nematodes are:
Soil temperatures between 15 and 30°C are considered favorable for applying most beneficial nematode species. Direct sunlight or dry conditions can inactivate and kill nematodes within minutes. Applying nematodes to outdoor areas in the morning or evening and using enough water would allow nematodes to move into the soil.
Nematodes can be applied under field conditions with many agricultural chemicals.
The shelf life of nematode products is limited to a few months. If the product cannot be used immediately, it should be refrigerated at 2-10°C or according to the label instructions.
Nematode viability should be checked before application by examining a small amount of the formulated material in water using a hand lens or a microscope. Live nematodes will be seen in movement or will revert to a typical "J"-shape, whereas dead nematodes will be straight.
Learn more about beneficial nematodes here. Find out more about the use of beneficial nematodes for pest control here.