ment systems favour mite development. Experimental work on
various cooling systems is being conducted by individual farmers
for use as a pest control strategy and to increase flower set. Mites
of the genus Tetranychus infest a wide range of ornamental
plants. Many home gardeners cultivate tomatoes as a back yard
crop in close proximity to such ornamentals, thus increasing the
probability of mite outbreaks. Within recent times, there has
been quite a trade in ornamentals, many of which are cultivated
in glasshouses in which serious mite outbreaks have occurred.
This is undoubtedly a sure means of dispersal. Because of their
small size, mites are wind bourne and, thus, easily transported
from home gardens to commercial farms. They also find their way
into commercial farms via.seedlings which have been produced by
the Speedling method at greenhouses. When those seedlings are
already heavily infested, the farmer initiates a pest problem upon
transplanting. Much stricter control of plant distribution centers
seems advisable and controlled environment systems which have
been designed for tomato cultivation in cooler climates must be ac-
cordingly modified to suit local conditions. Most tomato farmers
still farm in open fields where pest populations are variable, but
not alarmingly high. Good field sanitation, crop rotation and pro-
vision of Polistes shelters are good control strategies.

Breeding and Selection Currently, the most widely cultivated
tomato varieties are all imported into the island. The local plant
does, however, appear to be most tolerant to disease and pest at-
tack, and is generally early flowering and high yielding. A par-
ticular "Larcario" selection has produced very large fruits even
under wet season conditions. Consumer preferences have been for
large fruit with good keeping quality, but generally the local fruit
is small, irregularly shaped and sometimes too ugly for fresh table
use. Its high high seed content makes it unsuitable for process-
ing. Some of the smaller fruits are very cherry-like, but the skins
are soft and a great deal of cracking occurs. Thus, despite
tolerance for disease and pests, the local tomato plant is not very
popular. In experiments conducted at Piarco during the period
1981-1984, the more disease tolerant and earlier maturing
varieties, local and Roma, consistently gave the highest yields in
both wet and dry seasons. Both these varieties also produced the
most leaves and harboured the most pests.
 A sound selection and breeding program aimed at producing a
tomato variety which has improved fruit quality while maintain-
ing tolerance to pest and disease is highly recommended. Low
tomato yields in tropical countries have been attributed to the
fact that unadapted varieties are being cultivated (Villareal,
1979); yet seed breeding programs for tropical countries are exis-
tent only at the Asian Vegetable Research Centre and Southern
Tomato Exchange Programme, U.S.A. Certainly, there is need
for Trinidad and the wider Caribbean region to begin to address
the problem of breeding insect and disease resistant tomato
varieties which can be marketed.
Biological Control and Pesticide Application The tomato
ecosystem contains a wide range of natural enemies including
many hymenopterans and Aranidae, which perhaps accounts for
consistently low level infestations. Serious pest outbreaks are
sporadic and appear to be pesticide induced. The most recent
group of insecticides, the synthetic pyrethroids, are most exten-
sively applied to vegetable crops because of their relatively low
mammalian toxicities, reduced persistence, and specificity to
lepidopterans, one of the most significant groups of vegetable
pests. Their abuse has, however, led to serious mite outbreaks,
with resultant higher losses.
 A management strategy utilizing B. thuringiensis is being pro-
posed for the tomato ecosystem in Trinidad, since fruit infesta-
tion by lepidopterans in experimental plots was reduced by
68.7% for 1983, with a resultant yield increase of 32.66%


(Tables 1 and 2). Further research is being directed at increasing


178


the effectiveness of this pesticide through use of adjuvants,
overhead irrigation and late evening applications. By reducing
use of insecticides which are toxic to hymenopterans and
Araneidae, it is hoped that the biological balance within the
system would favour pest reduction with consequent increase in
yield. Fruit-piercing bugs which caused 1.7% fruit damage in
combined treated and untreated plots in 1983 are not affected by
B. thuringiensis treatments and must be controlled by applica-
tion of chemical insecticides. Since these bugs tend to infest close
to the time of the first harvest, timely application may reduce the
number of sprays required for control.

CONCLUSION
 Lepidopterans are by far the most serious tomato pests in
Trinidad, but infestation levels are not very high and insurance
spraying often leads to more serious problems. Leaf damage does
not appear to have very significant effects on yield, and caterpillar
species which bring about fruit damage fluctuate considerably. In
1981, highest fruit damage was inflicted by Heliothis followed by
Spodoptera, whereas in 1982, Spodoptera did greatest damage,
followed by Keiferia. In 1983 and 1984, Heliothis and Keiferia
fruit damage was almost equal, Spodoptera damage being quite
low. B. thuringiensis has given some measure of control of all
three lepidopterans and it is being further investigated for in-
creased effectiveness. Mite outbreaks, which are fairly recent,
have not yet occurred in experimental plots in which B. thur-
ingiensis has been used continually. This pesticide is being con-
sidered as one of the major inputs into a pest management
package for the tomato ecosystem.


TABLE 1. Percent fruit infested by Lepidopterous pests at Corn and Soya,
Piarco, Trinidad, during the dry season of 1982-1984.


 YEAR UNTREATED TREATED % REDUCTION
 1982 5.85 3.70 36.6
 1983 4.95 1.50 69.7
 1984 1.10 0.49 63.6





TABLE 2: Marketable yields (tonnes/ha) of tomatoes at Corn and Soya, Piarco,
for 1983 and 1984.


 YEAR UNTREATED TREATED
 1983 27.61 39.92
 1984 32.0 33.93





TABLE 3: Percent fruit infested by Lepidopterous pests at Corn and Soya,
Piarco, 1983-1984.


 K. lycopersicella S. eridania H. virescens
 YEAR Untreated Treated Untreated Treated Untreated Treated
 1983 1.89 0.69 1.15 0.36 1.84 0.44


1984 0.81 0.17 0.11 0.005 0.68 0.12




 PROCEEDINGS of the CARIBBEAN FOOD CROPS SOCIETY-VOL. XX