COCONUT ERIOPHYID MITE

CLASSIFICATION

Distribution & Occurrence:

In India, the first report on eriophyid mite, Aceria guerreronis Keifer. infesting coconut was made during later part of 1997 from Amballur panchayat of Ernakulam district of Kerala. A section of farmers recalled that, similar damage symptoms were seen in 1960 s but at a level not significant enough to cause damage.

By the systematic approach of Scientists from Central Plantation Crops Research Institute, the introduced mite infesting coconut was identified as A. guerreronis . Since their dispersal is by wind, their distribution to the neighboring states of Tamil Nadu, Karnataka, Andhra Pradesh and Pondicherry occurred in a relatively short span of time.

The presence of mites in the nuts is evident round the year with a slight reduction during the rainy season. The continued presence of these mites in the nuts causes an yield loss to a tune of 20 – 30 % (In terms of copra yield). In case of severely infested puny nuts, yield losses are compounded, because the compacted fibers of mesocarp render them unsuitable for coir industry, which would push the yield loss upwardly to 30 – 50 %. Severe infestation also leads to premature nut drop.

Coconut eriophyid mite, A. guerreronis was first reported from Guerrero state of Mexico in 1965, a place that was not reported to be the center of origin of coconut. Hence, it is presumed that they would have moved from unknown host to coconut. Later it spread to Caribbean islands, Latin American Countries and Africa.

Damage

Coconut eriophyid mite, was known to infest only Cocos nucifera, but during 1989 the pest was reported on Lytocaryum weddellianum a cocosoid palm. In case of coconut mite they develop on the upper portion of the developing nut that is covered by perianth. Feeding by mites in this zone causes physical damage to cells (Fig. 1). The feeding sites that grow downward from the perianth appear as longitudinal patches, then they develop to triangular yellow patches, turns brown, develop longitudinal fissures and finally appear as warts (Fig.2).

Bionomics

The adult mite measures about 200 – 250 µ long and 36 – 52 microns wide (Fig. 3). The body is elongated and worm like with an yellowish white color. The adults have two pairs of legs at the anterior end of the body. Intermittent rains followed by short dry spell promote population and growth. Pest infestation is found during the rainy months also. The life cycle is completed in seven days (approximately 4 generations in a month). In a given situation about 2 – 140 mites (in various instars) / 4 Sq.mm area has been reported.

Management:

Periods of water deficit and lower nutrition results in greater yield loss due to coconut mites. The nut growth is slower in dry periods, which in turn results in fruits remaining susceptible over a longer period of time. This demands a close observation on agronomic practices like nutrient and irrigation management of the mite-infested gardens. Enhancing the nutritional strength of palms by inoculation of Azospirillum , application of organic matter and neem cake reduced the incidence of mites.

A Cambodian variety that has a compact perianth is found to be tolerant to this mite damage. Importation of this variety from Cambodia is not desirable in view of the prevalence of the deadly lethal yellowing disease in that country. However this can be taken as a cue that resistance to mites could be available for which detailed observations are necessary.

In India, among the coconut germplasm, Kenthali dwarf was found to be less susceptible (20.0%) to mite infestation as compared to Tiptur Tall (84.0%).

Infested nuts harbor a very low population of natural enemies Viz., Bdella distincta Baker, Amblyseius largoensis Muma, Neoseiulus mumai and N. paspalivorus Deleon.. However, the relatively low number of these bio agents makes it insufficient to cause an impact on eriophyid mite population. Hence, efforts are to be made to multiply and effect innundative release of these bio agents in the infested gardens.

Entomofungal pathogen Hirsutella thompsonii and Verticillium lecanii are reported to be promising in managing the mites. Both the pathogens are mass multiplied by a commercial firm and sold in the market. Further research is underway to make biological control practically feasible.

•  Chemical control:

a). Root feeding of Neemazol 10 ml + 10 ml water is ideal for sandy or sandy loam soils but this method is cumbersome for laterite soils because of the difficulty in tracing of active roots. Care should be exercised to select an active root of pencil size thickness and a polythene bag containing the biopesticide and water mixture should be held tight to the root.

b). Spraying of monocrotophos 4 ml/ lit or triazophos 2.5 ml/ lit. or carbosulfan 2 ml/ lit of water is effective in reducing the mite population. Both the methods (Root feeding and spraying) involving chemical pesticides demands a safe waiting period of 45 days after application till the harvest of nuts as they may harbor residue that would pose health hazard.

In states like Kerala where homestead cultivation under mixed farming with animal husbandry and poultry is in prevalence faulty spray of chemical pesticides will lead to bio magnification. Hence, spraying eco friendly pesticides like neem formulations containing 0.1 % azadirachtin @ 6 ml/ lit. of water and wettable sulphur @ 5 gm/ lit. of water are ideal in such situations.