The Disadvantages of Biological Control with Nematodes


Applying beneficial nematodes to lawns where the larvae of Japanese beetles feed and destroy turf, or to gardens and nurseries with infestations of immature soil-dwelling insects such as weevils and rootworms, is a method that is becoming an increasingly popular way to get rid of these pests in your landscape. Nematodes are microscopic organisms that feed on and destroy the larval stages of other insects, such as Japanese beetle larvae. These tiny critters, which resemble worms, serve as a biological control agent, which means that they help remove insects without the use of chemicals, which may be hazardous to the environment. Beneficial nematodes, like any other kind of pesticide, have several downsides that may reduce how effective they are.


Beneficial nematodes, when used in a garden, may assist in the management of certain insect pests; however, these worms need to be specifically targeted to the pest species that you want to suppress.

Timing Must be Precise

Nematodes may be applied to the landscape using a garden hose and sprayer, but gardeners can’t just do it whenever they feel like it and expect them to be effective. Nematodes must be introduced into the soil in a certain way. Because nematodes feed on the larval stage of most insects, you will need to get familiar with the signs that indicate the presence of larvae. Grubs often make their appearance in the late summer or early autumn on the grass, where they feed on the roots. Nematodes should only be applied during the early morning or late evening hours, since prolonged exposure to the sun’s powerful UV rays may be fatal to them.

Pests Must be Targeted

According to Sciencing, the dynamic between a prey animal and its predator is very contextual in many situations. When it comes to nematodes in particular, you have to make use of a certain species in order to target a particular problem. The nematode enters the host via a naturally occurring entrance in its body, consumes a bacterium that it carries, and then passes on the bacteria to its offspring. Because of this, they need to be a certain size and have other properties that enable them to come into touch with the pest in a manner that is natural to the environment.

Proper Storage and Handling is Required

Because of their short shelf life, live nematodes should be used as soon as possible in order to achieve the highest potential level of effectiveness. They have a shelf life of up to several months in a refrigerator if they are properly maintained there. Be wary of the circumstances under which you store the nematodes, though, since temperatures that are too high might either kill them or make them useless. Be sure that the nematodes you have kept don’t become exposed to temperatures that are higher than 90 degrees Fahrenheit, and don’t let them go below freezing.

Environmental Conditions Play an Important Role

The degree to which nematodes are effective against insect pests is also influenced by a variety of environmental factors. The presence of an adequate amount of moisture is the most critical factor, since nematodes need water in order to move about and locate their host insects. They are susceptible to death if they get dehydrated. Sandier soils with larger pore areas are more conducive to the movement of nematodes than clayier soils. A lack of adequate mobility into the soil may also be caused by excessive accumulations of thatch, leaves, and other types of detritus. According to a study paper published by the Food and Agriculture Organization of the United Nations, nematodes go dormant when the temperature of the soil is at least below 62 degrees Celsius (54 degrees Fahrenheit). These parasites may also become ineffective if the salt level is high, the pH is high, or both. Nematodes are susceptible to the toxicity of some pesticides, such as those that include carbaryl. Before applying any herbicides to your grass, you should inquire with your nursery about whether or not the chemicals are harmless to nematodes.

Results and Cost

Because nematodes execute their job below the surface of the soil, gardeners can not see dead insect carcasses; this makes it difficult to quantify the effectiveness of worms. It can take as long as a month for the plant’s health to start to improve. When dealing with persistent infestations, it’s possible that you’ll need to apply the treatment more than once. This will almost certainly result in higher expenses than chemical treatments.