Beneficial Nematodes For Vegetable Gardens

Beneficial nematodes, also called Entomopathogenic nematodes, can be used majorly to control soil-borne insect pests than controlling other pests found in the vegetable garden. Members of the Steinernematidae and Heterorhabditidae families are beneficial nematodes for gardening purposes; they are colorless roundworms that are non-segmented, elongated in shape, and usually microscopic and commonly found living within the soil.  

Beneficial nematodes can be used as gardening insect control measures; they can be used to control insect pests like Caterpillars Cutworms, Crown borers, Grubs, Corn rootworms, Crane flies Thrips, Fungus gnats, Beetles. There are also bad nematodes and the difference between good nematodes and bad ones are simply which host they attack; bad nematodes, also called non-beneficial, root-knot, or “plant-parasitic” nematodes, cause damage to crops or other plants.

Activities of Beneficial Nematodes

Beneficial nematodes as a biological pest control measure will attack soil-borne insect pests without causing any detrimental effects on earthworms, plants, animals, or humans; it is eco-friendly. Beneficial nematodes are morphologically, ecologically, and genetically more diverse than any other animal group except for arthropods. With over 30 species of existing entomopathogenic nematodes, each with a unique host, finding a suitable nematode to aid in pest control is not only a biological solution of integrated pest management but a simple one as well.

Beneficial nematodes have a lifecycle made up of egg, four larval stages, and an adult stage. The third larval stage is the most important in the lifecycle of beneficial nematodes; during this period, the nematodes seek a host, usually insect larvae. The nematode gets into the host through the mouth, anus or spiracles. The nematode goes along with the bacteria called Xenorhabdus sp., which is subsequently introduced into the host through any of the aforementioned channels; the introduction of the bacteria into the host causes the death of the host within 24 to 48 hours.

The Steinernematids develop into adults and multiply within the host; however, the Heterorhabditids produce hermaphroditic females. Both nematode species feed on the host’s tissue until they mature to the third juvenile phase and then they leave the remains of the host body. Using beneficial nematodes for gardening pest control strategy has become an increasingly popular method for several reasons: beneficial nematodes have an incredibly wide range of hosts; this makes them ideal to control numerous insect pests.

Entomopathogenic nematodes kill their host quickly, within 48 hours. Nematodes may be cultivated artificially, making a readily available and inexpensive product. Beneficial nematodes can be stored for a long time at temperatures within 60-80 F. or 15-27 C., for up to three months and if refrigerated at 37-50 F. or 16-27 C., they may last six months.

Beneficial nematodes are tolerant of most insecticides, herbicides, and fertilizers. They are resilient and durable; the juveniles can survive for some time without any food. There is no insect immune to the Xenorhabdus bacteria, although beneficial insects often escape being parasitized because they are more active and apt to move away from the nematode. The nematodes not being able to develop and multiply within vertebrate pests, make them extremely safe and environmentally friendly.

Management and Storage Beneficial Nematodes

Beneficial nematodes used for gardening reside in sprays or soil drenches. To enhance their survival, it is important to create a perfect environmental condition needed for their survival; a warm and moist environment is suitable for their survival. Both before and after introducing the nematodes, irrigate the application site and only use them when the soil temperature is within the range of 55-90 F in filtered sun. The nematode product must be used within the year and do not store in areas of high heat. Remember, these are living creatures.

Nematodes That are Beneficial in A Garden

Each species of beneficial nematode targets specific pests. For instance, one species (S. carpocapsae) is very effective on larval stages of some insect pests like, armyworm, weevils such as black vine, caterpillars, cutworm, and sod webworm.  Another species (S. feltiae) is used against larvae of cabbage maggot, onion maggot, raspberry crown borer, and thrips.  Both species are effective on larvae of codling moth, corn earworm, and cucumber beetle. You will want specie (H. bacteriophora) of the other nematode for larvae of tree and vine borers, European chafer, Colorado potato beetle, corn rootworm, flea beetles, and grubs including those of the Japanese beetle.

How to Apply Beneficial Nematodes To Plants and Soil

Once you know which nematode species is appropriate, it must be applied properly to ensure effectiveness.  Timing is important in the application of beneficial nematodes, as the vulenrable stage of the target pest needs to be present for the nematodes to work on them.  Late summer into early fall is the best time to target many grubs of plants, crops, and lawns, as they are usually small, feeding on grass roots near the soil surface, and have thin skins that the nematodes can easily penetrate.  This is also the time when armyworms fall to the ground to change stages (pupate).

Nematodes are living organisms, so they should be applied immediately after they are gotten.  They like moisture, so if it does not rain, water thoroughly before and after application, or apply when it is raining.  If your nematodes arrive on a wet sponge, rinse them from the sponge into the cool water, and then spray on plants according to directions on the label.  Soils must be kept moist by irrigation for a week to 10 days after application.

Rainy period or cloudy weather is good for nematode application for some reason; nematodes are quite sensitive to ultraviolet sunlight and can be killed within a minute or two if exposed to it.  That’s why you would read from the recommendation label to apply in the early morning or late evening.  Beneficial nematodes are sensitive to temperature too; apply them with ideal temperatures between 45 and 100 degrees (F).

For prevention, nematodes can be applied 2 to 3 times a year, such as in spring, summer, or fall.  For control of existing pests, apply every 2 weeks until the infestation lessens or goes away.

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