Historically, field applications of bio-control nematodes have primarily focused on purchasing commercial strains of entomopathogenic nematodes (EPN) and applying them as a biopesticde. Long term establishment of nematodes in the soil profile for long-term pest suppression through pest recycling is not a focus because commercial suppliers want to sell producers nematodes every year. For commercial nematodes to be successful for insect control, they must be applied at rates around 1 billion nematode IJs per acre. The relatively low value of alfalfa and clover per acre and the high cost of commercial nematodes that would require an annual application strongly suggest that the use of commercial nematodes as a biopesticde is not economically viable.
The use of nematodes in a more classical biocontrol approach requires the nematodes to persist in the environment for several growing seasons by establishing them as part of the soil fauna where they will seek out prey (soil insects), increase their population, spread into adjacent areas and persist in the field for a number of years. Focus then shifts to an area wide biological program using entomopathogenic nematodes as a means to control the ASB infestation in northern NY. Using this strategy, nematode persistence under NY conditions is a key component and is one of the main reasons why we use native NY nematodes which have the ability to persist under NY conditions. To establish these persistent nematodes in a field, applicators drive the entire field using stream nozzles six ft. (6’) apart providing application coverage to 33% of the field.
Using this management strategy, application rates of nematodes range from 20 million to 25 million nematodes per acre and nematodes spread throughout the entire field will occur in 1-year based on nematode movement in the soil. A review of research data and rearing experience indicated that the best combination were the two Steinernema sp.
Application Strategies and Cost Saving
Unlike a pesticide application, nematodes are alive, will move with time throughout the field and will persist for many years. Farming activities involving the movement of soil throughout the field enhance the natural movement of these biocontrol nematodes.
Farmers have the option to treat all of their acreage directly for faster results at $80/acre. The approach is similar to a pesticide application where nematodes are applied to entire fields in application streams every two ft. (2’). However, we recommend utilizing the skip nozzle method to reduce costs and allow natural movement of the nematodes to fill in the areas where nematodes were not applied. Natural movement includes the physical dispersal of the nematodes, movement of infected insects before they die and the movement of soil with nematodes to other parts of the field during farming practices. Nozzles applying nematodes spaced every six ft. (6’) will allow only every third nozzle to apply nematodes allowing for 33% of the field actually being treated at a cost savings of $26/acre. Some farms have further reduced costs by applying nematodes to 16% of the field by spacing the stream nozzles 10 ft. (10’) apart at a cost savings of $13/acre.
Full field application and the 33% application rate are recommended for fields with large to moderate populations whereas the 16% application rate is best used for fields with low insect pressure.
When applying nematodes, enough water needs to be used to penetrate the plant canopy and deposit the nematodes on the soil surface so they can enter the soil profile. In our work, this water application rate should be at minimum 50 gpa.
Biocontrol nematodes used for control of alfalfa snout beetles are easily applied through slightly modified commercial pesticide sprayers. Application equipment varied from large commercial pesticides sprayers with all screens and filters removed and nozzles changed to fertilizer steam nozzles (006-0015), smaller sprayers with open nozzle bodies dribbling a stream of water and home-made gravity dispersed applications composed of water tank and a pipe with holes in it.
Please refer to the sprayer requirement manual which provides the necessary steps for your application of nematodes.