KERALA AGRICULTURAL UNIVERSITY
Coconut mite Aceria (Eriophyes) guerreronis (Keifer) of the family Eriophyidae has been posing serious problems to the production of coconut in Kerala from 1997 onwards. From an infestation which was confined to a few plantations in Ernakulam District in 1997, the pest has now spread extensively in the State. The attack has caused drastic reduction in coconut production, playing havoc to the coconut based economy of Kerala.
Coconut perianth mite is a microscopic organism, 0.20 - 0.25 mmlong, elongared and cylindrical. To a naked eye the mite colonies look like white powder sprinkled here and there.
The pest is infesting the young buttons in the post-fertilization period. The mites which settle at the interspace between the perianth and button feed on the sap of the perianth and button. Thelife cycle of the mite is completed with in 8 - 10 days. The population of the mite increases 100 fold in about 10 days and in a matter of less than a month, the population will be enormous.
The symptoms are manifested about one month after the initial colonisation. At this time, a small yellow halo develop around the edge of the perianth covering the button. In many cases, when the perianth is removed, a pinkish band can be seen on its inner side. A few days later, the halo develops into triangular wellowish discoloration pointing towards the distal end. The discoloration can also take the shape of thin stripes. Within two months after pollination, the hallow fully develops and becomes conspicuous. During this period, some buttons show browning and necrosis on the periphery of the perianth. The yellow discoloration later turns brown and results in warty shrinking of the husk. At this stage, the husk develops cracks, cuts, gummosis and frckles. When the infestation is severe, nut fall may occur. The nuts which continue to remain in the bunches are undersized and malformed, the degree of malformation varying with infestation. At maturity the husk of the nut is very tight and shrunken causing difficulty in dehusking.
When the infestation is set in, spraying of acaricides is recommended. It can be an organic acaricide like neem-garlic-soap emulsion or synthetic acaricide, Dicophol. Both are found to control the mite effectively.
For 10 litres of emulsion, the following materials are required :
The garlic must be well ground either manually or using a mixie / grinder, adding sufficient water. The garlic paste is then sieved through a cloth to get the extract. The specified quantity of soap is cut into small pieces and then dissolved in hot water. This solution also should be sieved through a cloth. The soap solution is then mixed with neem oil and stirred well to make a good emulsion. This is further mixed well with the garlic extract and then made upto 10 litres by adding water and stirring well to make the neem-garlic-soap emulsion for spraying.
6 ml of the commercial formulation of Dicofol (containing 18.5 % a.i.) per litre of water is used to make the spray solution.
Either rocker sprayer or hand sprayer can be used for spraying coconut trees. If a rocker sprayer is used, the quantity of spray solution required is about 1.5 litres. If a hand sprayer is used, the spray solution required is only about 500 ml. The workers engaged in spraying have to climb on the top of the crown and direct the spraying only on the bunches so that the drift and fall out of the acaricides can be reduced to the minimum.
Dicofol is less toxic to honey bees and other pollinators, predatory and parasitic natural enemy complex and microbial agents. It is also more bio-degradable and has a less acute toxicity to mammalian systems.
Before spraying, the crown has to be cleaned. Drinking water sources should be covered during spraying.