Controlling the false spider mites

Mites are considered minor pests of coconuts as these are predominantly observed only in nurseries. However, an outbreak in the island of Camiguin [Philippines] in 1994 affected 90-08 percent of the coconut palms and reduced yield from 63 percent to 87 percent. Hence, from 1999 to 2005, as a pioneering work on the pest, Gallego (PCA) studied its biology and ecology and developed an integrated pest management scheme against the false spider mites. In 1996, the mite was identified and recorded as a new genus and species (Rarosiella cocosae Rimando) under Family Tenuipalpidae, Order Acarina. Mites were found in large numbers on undersurface of the leaflets. Both nymphs and adults were destructed as these sucked the plant sap. In young palms, the damage started from the tip of the leaflets as tiny lesions, which later discolored and dried up the leaf surface from the tip downwards. On mature bearing palms, the damage started from the lowest mature fronds and progressed upward. Closer examination of infested leaflet showed irregular lesions with necrotic centers and water-soaked borders that later coalesced and formed blights. In severe cases, both young and mature mite-infested palms appeared as burnt from a distance. Quarterly monitoring of R. cocosae Rimando populations showed that the mites were present throughout the year in coastal and inland zones in Camiguin Island. Mite population declined when average rainfall increased, but there was no correlation with relative humidity and temperature. Eggs of the false spider mites were minute, oval, and reddish measuring 0.07 mm wide and 0.10 mm long. Incubation period ranged from 3 to 10 days. The nymph has three instar stages with a total nymphal period of 10-25days. Adults lived from 13 to 54 days. Both female and male had similar bodies - broadly oval or round and magenta red, except that the female was larger than the male. The total development cycle from egg laying to death of R. cocosae Rimando ranged from 35 days to 78 days, with an average of 49.84 days. About 10-27 eggs were laid in the entire life of the mite, with 95 percent hatchability. The destructive stages were from first nymphal instar to adult, implying that each individual mite fed on the leaf for 42.71 days. Three natural enemies were observed to prey on the false spider mites. These were voracious feeders of the mites eggs, nymphs, and adults. These natural enemies were: Amblyzeius largoensis (Muma), and Armascirus taurus (Kramer), both mite species, and Telsimia ephippiger Chapin, a coccinellid beetle. The role of the two predatory mites still needs to be further investigated. Based on the survey, alternate hosts, of the mites were the red palm, ivory palm, phoenix palm, ordinary palmera, coffee, cacao, papaya, banana, mahogany, Flimingia macrophylla, and 'Kamias'. The following were the integrated control strategies developed and recommended for adoption. Biological studies on the biology of the beetle, T. ephippiger, showed that it voraciously fed on different stages of the mites for 59.83 days. Its total development period from egg laying to death was 72.95 days. This meant that the predator devoured an average of 56.68 mites/day or a total of 3,470 mites throughout the predatory beetle's lifespan. Thus, the beetle was a potential biological control agent ideal for its short life cycle, ease in handling, high predatory capacity, and availability of the hosts. Mechanical. As a preventive measure, pruning of severely infested leaves in coconut seedlings or young plants was done every quarter. Mite population was lower in pruned palms than in unpruned ones. However, pruning was only feasible in coconut seedlings and in young plants, and not economically feasible in tall palms. Chemical. Among four commercially available pesticides tested in the laboratory, Triazophos and Dimethoate proved highly effective with total knockdown-effect in all dilutions 48 hours after tyreatment. Standard dilution of Lamdacyhalothrin was also effective 72 hours after application. Botanical pesticides. As an alternative to the commercially available chemical pesticides, Derris sp. ('tubli') and Azadirachta sp. (neem) were also tested in the laboratory. Pure tubli root extract proved to be the most effective at 24, 48, 72, 96, and 240 hours after spraying. Neem seed extract showed significant effect against mites only at 24 hours after application. These botanical pesticides can be used in young plantings and seedlings in the nursery. The use of chemical pesticides may also have adverse effect on the natural enemies and thus result in recurrence of mite population outbreak. Hence, the use of biological control was a more sustainable option.