MSU Extension Floriculture & Greenhouse Crop Production

Applying beneficial nematodes is an effective method for managing soil-dwelling pests, such as fungus gnats and western flower thrips, in greenhouse production areas. Nematodes are a diverse group of tiny roundworms that occur naturally in a wide range of environments. Several of these species have been selected for commercial production as biological control agents for their ability to reliably attack and kill insect pests. Beneficial nematodes are easy to integrate into any pest management program and are safe for use around employees & pets. Products containing the species Steinernema feltiae are a top choice among growers and used extensively across the industry to control both thrips and fungus gnats in growing media. The nematodes are easy to apply. Tonya Powell is the head grower of herbs and perennials at Kalamazoo Specialty Plants in Kalamazoo, Michigan. With growing edibles, I am very limited on the type of chemicals I can use. So instead of doing several different applications of different chemicals, I can go throughout the entire seed house with the nematodes and get good coverage. Like most biological control agents, nematodes should be applied soon after the shipment arrives. If immediate application is not possible, they can be stored in a refrigerator until their expiration date. Beneficial nematodes are available from several suppliers and are commonly packaged in trays or sachets with sizes ranging from 50 to 250 million nematodes. These products are mixed with water to create a suspension that can be applied with standard application equipment, including sprayers, injectors, and irrigation booms. When preparing equipment, remove screens and filters from intake and spray lines, ensure the nozzle opening is large enough for the nematodes to pass through, and keep the pressure under 300 psi. If using an injector, set the dilution rate to 1:100. For soil application, beneficial nematodes are most effective when applied early in the crop cycle. A typical initial application rate is 50,000 nematodes per square foot, which can be adjusted based on experience and pest pressure. Follow-up applications usually occur every one to two weeks as needed. When preparing the application suspension, allow nematode trays to warm up to room temperature to avoid inducing heat shock. Fill the stock tank or spray container with half the desired amount of cool clean water, add the nematode trays, and mix thoroughly while adding the remaining water. Maintaining the product suspension is crucial for satisfactory results. The mixture should be constantly agitated, otherwise they will drop out of suspension in the spray tank, resulting in an uneven application. Aerating the solution is also important. Although nematodes require moist environments, they're not aquatic animals. Aeration provides adequate oxygen to the stock tank mixture to keep them in good condition. Conveniently, both aeration and agitation can be accomplished by using a submersible water pump. Once the water and nematodes are mixed together, we will add a pond pump and the pond pump agitates the nematodes, it keeps them in suspension while we are using the injector. If you do not use the pond pump, they're all going to sink to the bottom. It's good to have the aeration in there too, so they're not drowning. Keep in mind that nematodes are susceptible to desiccation and ultraviolet light. Avoid these negative effects by ensuring the growing media is moist and by applying them in the early morning, evening, or on an overcast day. The first thing you want to do when applying nematodes is to choose a cloudy, not bright, sunny day, preferably cool. So I like to do it in the morning or later in the evening. If it is sunny and I have to make the application, I'll close the shade. Once the environment is correct, mixing the nematodes, I will take my injector and remove any filters, and then we will add the nematodes to the stock bucket. Once all the preparations are complete, gently water the nematodes into the growing media. Apply enough of the mixture to soak the substrate, but not to the point where water leaches from the container. Best results come when the grower is able to distribute the product evenly across the entire treatment area. Once in the soil profile these nematodes can provide pest suppression for weeks under favorable environmental conditions. More information on 
beneficial nematodes, biological control, and many other topics in floriculture production can be found online at the MSU Extension floriculture website.