TABLE 2. Accumulation of'Kilval' in nuts after injection with 50 ml on one side of trunk (5-8 year old palms). Depth of Injection with 50 ml. of Accumulation of Dye and rfeAticide Pesticide (Northern in Side) 25% 50% 75% o100T of Circu~ference of Trunk 2" 4" 2/5 trees 1/5 trees not seen not seen 4" 6" 5/5 5/5 4/5 3/5 6" above 5/5 5/5 5/5 5/5 corresponding sulfoxide, is more soluble in the plant, it has half the acute toxicity of the parent molecule. The preparation Kilval, containing 300 or 400 g vamidothion per 1, has been effective on the coconut mite in Brazil since 1968. Moreover, the acaricide is miscible with, and is as soluble as, crystal violet. These qualities make it useful for some trials on movement of the pesticide. In paper and thin layer chromatography trials with alcohols and water, the rates of movement are identical. The preliminary studies with the chemical as a systemic pesticide in coconuts involved the following: 1. Observations on the movement towards the fruit and ac- cumulation of the chemical in the inflorescence and fruits after its injection in the trunk, 2. Single tree studies on variable dosages and their effects on mites and possible phytoxicity on the palm, and 3. Back yard studies on small pocket infestations for efficiency in control. Movement of Chemical Palms injected with the formulation Kilval and 1% crystal violet on one side of the tree to a depth between 4-6 in showed an accumulation of the chemical in all the active inflorescences when 50 ml or more of the substance was used. Accumulation was determined by the removal of the calyx from the fruit and the ex- amination for the blue dye (crystal violet) under the pericarp seven days after infection (see Table 2). Variable Dosages with their Effects on Mites on the Tree Most of the mites on all the young nuts were killed by injec- tions over 50 ml of Kilval. Injections were made 4-6 in deep, with a /8 in auger at an angle of 45, on one side of the trunk. Samples of the affected inflorescences were taken from the tree immediately before injection and corresponding samples of nuts from the same inflorescences were taken 14 days after. The cor- responding totals of mites were used as comparisons for a percen- tage kill. Uninjected trees were used as basic controls to indicate any environmental influence on the mite population. A dose of 75 ml or more killed all the mites on the younger nuts and also some (about 30%) in the older affected fruits. When 100 ml were given in two separate doses seven days apart, almost all the mites (98%) were killed after 14 days. The exercise, therefore, revealed that it was better to remove large, edible and ripe nuts containing mites from the tree before the palm was treated. This prevented the older nuts from being a reservoir and leaving a genetic source of residual variability in existing unaffected mite population to develop early resistance to the chemical. The mites are capable of surviving for about two weeks under the calyx of picked green nuts left in the open on the ground unattended. Several pockets of mite infestation were tested with the chemical in backyards where housewives in Trinidad had reported their presence. Accordingly, the older affected nuts were re- moved and the trunks of the trees injected with 100 ml Kilval in two doses. The trees were examined one month after injection to determine the presence of mites on the younger developing fruit. TABLE 3. Variable doses of the 'Kilval' and their effects on mite population on coconut fruits of various ages. Amount of % Killed Che Aic1a After 14 days Cornents (In ml.) 50 62 All mites on young fruits were killed. 75 83 All on young fruit, and some on mature (7 mths.) fruit (30%). 100 94 All on young fruit and some on mature (7 mths) fruit (63%). 50 I. 00 All on young fruit and some on 50 mature (7 mths) fruit (65%). given In two dose3. The results showed, in most cases, that the mites had disap- peared completely. Such control measures could become effective if large areas were done simultaneously to prevent the movement of mites from affected trees which remained untreated. The Development of a Programme for Control in the Island of St. Vincent Following the preliminary studies done in Trinidad, the full scale operation was planned at two large areas of coconuts af- fected with mites (Griffith, 1982). The areas were Peter's Hope with large holdings and Vermont with smaller holdings of less than one acre each. Both areas were operated as a cordon sanitaire to prevent movement of mites from around. The programme of injection began on April 19 and ended on May 21, 1982. A total of 3,729 trees were treated. The area in Peter's Hope was about 65 acres in one block. Each tree received 100 ml of Kilval in two doses at one week intervals. Colour codes were used to indicate the number of treatments. In Peter's Hope the nuts were not removed, but in the smaller areas in Vermont the old affected nuts were taken off prior to treatment. After three months, the treated trees in Peter's Hope showed about 85% of the new and existing nuts on the trees were free from mite damage. In Vermont, where 644 trees were treated on small holdings with the nuts removed, nearly 100% effectiveness was obtained. Another feature was the increased number of fruit per inflores- cence. This feature was generally observed, though not statistical- ly checked. However, the increase in abundance of nuts per in- florescence on the treated trees was very obvious. The Timing of Control Programmes and Mite Eradication From what has been outlined in the foregoing concerning rain- fall and the restriction of mite population development, the effi- ciency of the systemic application increases when the mites are at their survival level towards the end of the rainy season. Based on the principle that infection rate and probabilities of dispersion are at their lowest in the rainy season, any chemicals which might destroy the population under the calyx during that time would, in fact, pave the way for eradication of the mite almost in a single event. This was the underlying principle in attempting to achieve maximum mortality of the mite by utilizing two doses of 50 ml of Kilval at such short intervals. Aided by the suppression of mite movement during the rainy season in Trinidad, control pro- grammes which are properly organized can almost permanently restrict the large-scale development of the coconut mite. The same principle is applicable to any of the islands of the West In- dies or the tropical areas of Brazil and Latin America. Thus, the recommendations for control ought to be followed closely. Older fruits should be removed before treatment of the infected tree in order to ensure an absence of a residual popula- tion which cannot be adequately reach by the chemical. By and VOL. XX-PROCEEDINGS of the CARIBBEAN FOOD CROPS SOCIETY 131