It takes an observant gardener to detect that a root-eating pest has taken hold of a plant or shrub. These pests hide themselves in the soil while simultaneously causing much damage and sometimes death to plants. However, all is uncovered when you go to remove the damaged or dead plant and find that the roots are half-eaten, tunnelled or covered in squirmy bugs. Luckily, releasing some friendly beneficial insects into the soil will halt these root-eating foes before they can cause any further damage.
The larvae of root weevils feed on the roots of many kinds of shrubs and plants. The strawberry root weevil larvae bore into the roots and crowns of strawberry plants, as well as many other types of plants. Root weevil larvae have white bodies with yellow heads and are up to 1/2 inch long. Release parasitic nematodes, which inject bacteria into harmful pests that kill the host within 24 to 48 hours, or by entering the insect, parasitising and feeding on it.
Vegetable root plants are all susceptible to small yellowish-white legless maggots that hatch from eggs laid in soil crevices or plant stems. The larvae feed on the plant's roots for three or four weeks, causing the plant to turn yellow and have tunnelled roots that eventually rot. The root tunnelling creates ideal breeding grounds for diseases such as black rot. The adult flies, which are similar in appearance to houseflies, are attracted to moist seed beds, where they lay eggs. Cover seed beds with floating row covers to avoid infestations. Parasitic nematodes also offer some control of root maggots.
White grubs are the larvae of May beetles, June beetles or Japanese beetles. They have plump white bodies that curve into crescent shapes, brown heads and three pairs of legs. A plant that suddenly wilts is a sign of a white grub problem because these insects gnaw holes in the plant's roots. White grubs eat the roots of a variety of flowers, fruit and vegetables and grasses. Damage is worse in soils high in organic matter. Suppress white grub populations with the help of parasitic nematodes, and clean up garden debris during the fall.
Three types of mole crickets that are the most damaging are the short-winged, tawny and southern mole crickets. Tawny and southern mole crickets look similar, while short-winged mole crickets differ in appearance because of their short wings. Adults and nymphs tunnel below the soil to feed on roots. At night, mole crickets come above ground to cause further damage by feeding on foliage, stems, seedlings and young plants. They are omnivorous, feeding also on insects and other soil dwellers. Encourage beneficial wildlife that feeds on mole crickets such as toads, parasitic nematodes and parasitic flies.
- "The Organic Gardener's Handbook of Natural Pest and Disease Control"; Fern Marshal Bradley, et al.; 2010
- University of Idaho Extension; Integrated Pest Management Guide for Sugarbeet Root Maggot; E.J. Bechinski, et al.
- University of Florida IFAS Extension; Shortwinged Mole Cricket,Scapteriscus abbreviatusScudder; Southern Mole Cricket,Scapteriscus borelliiGiglio-Tos; and Tawny Mole Cricket, Scapteriscus; John L. Capinera, et al.; 2009
- "American Horticultural Society: Pests and Diseases: The Complete Guide to Preventing, Identifying and Treating Plant Problems"; Pippa Greenwood, et al.; 2000
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