There has been an age-old practice of adding manures to the soil to improve soil fertility and crop productivity. Manures provide necessary macronutrients and several micronutrients while increasing organic matter. Manures can range from plant to animal wastes. The most commonly used manure in J&K is cow manure i.e., cow dung. It has relatively less nitrogen than some other manure, hence can be added directly to the soil without damaging plants. It also adds abundant amounts of organic matter and beneficial microbes. However, raw cow dung or fresh cow manure when added to the soil directly without decomposing fully may contain harmful micro-organisms, weed seed, too much salt for dry soil & simultaneously may form a breeding habitation for White grubs.
White grubs are the immature forms of scarab beetles also known as root grubs or June beetles or chafer beetles which are soil-inhabiting polyphagous pests. They mostly feed on organic matter in soil as well as the root system of various economic crops. The crops that are mostly affected include Apples, Cherries, Peaches, Pears and Plums and also wreak havoc in vegetable gardens. These pests in recent years have posed serious and alarming situation at regional as well as national levels and is designated as a ‘National Pest’.
The grubs damage the rootlets, causing wilting of the plants and yellowing of the canopy. In severe case, the plants may even die and can be easily pulled out from the soil. Initially, the crops do not exhibit any symptom but in the long run, their lifespan is reduced and consequently the yields are also reduced. In annual plants, sudden wilting of plants is the most primitive symptom, later followed by premature defoliation. Affected plants are yellowish in color and wilted and mostly die in patches.
In a Nutshell:
The symptoms are mainly caused by a group of white grubs of the genus Holotrichia spp. Both adults and larvae can damage the plants by feeding on their roots. The adults are dark brown about 20 mm long and 8 mm wide and feed on the foliage of plants. Within 3 to 4 days, after the onset of rains, they emerge from the soil during night time, feed on the surrounding plants and reenter soil to hide and lay eggs. The larvae are whitish yellow in color, translucent, almost 5 mm long and ‘C’ shaped. They feed on organic matter like cow dung which when semi decomposed consists of cellulose and is a favorable breeding place for grubs. Since the roots are also rich in cellulose, the grubs feed on the roots of the plants severing plants at or above the crown.
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