In recent weeks, local farmers and backyard gardeners have noticed a dramatic increase in the number of caterpillars feeding on their trees, crops, ornamental and flowering plants.
The Department of Agriculture has received several phone calls from residents concerned about this situation, as well as questions on dealing with the problem, states a GIS press release.
‘There is nothing to be overly concerned about,’ assures Graduate Research Assistant Sasha Fredrick. ‘This is a natural phenomenon resulting from the passage of Hurricane Ivan last year. The storm left the island’s natural dynamic severely unbalanced, as many of the caterpillar’s natural predators did not survive the hurricane or starved in the following weeks. Normally these predators, particularly birds and bats, are able to hold the caterpillar population to manageable levels’.
Birds feed directly on the caterpillars, while bats are instrumental in controlling moths, the adult stage of some of the most destructive local caterpillar species.
‘This year, more caterpillars are surviving into adulthood. More adults mean more caterpillars, thereby perpetuating and compounding the problem.’ Ms Fredrick explains.
But the imbalance is already beginning to correct itself. Birds are having a bumper year with lots of caterpillars to eat and to feed their young.
Likewise, bats have many moths to catch at night. With the predators eating so well, they are in turn producing more offspring, which will eventually allow them to regain the numbers that keep the caterpillars in check.
However, this does not mean farmers and homeowners should sit idly by and watch their plants being destroyed.
There are effective measures they can take to protect their crops and ornamental plants. Key to this is the concept of Integrated Pest Management, promoted by the Department of Agriculture.
Integrated Pest Management is an environmentally sensitive approach to pest management that relies on a combination of common-sense practices, natural control measures and the judicious use of environmentally friendly pesticides to manage such problems.
Central to the IPM strategy is careful observation of your plants. If caterpillars are caught at an early stage they can be controlled before causing much damage.
‘We call this regular checking of plants for pests and disease scouting’. There are also some techniques that will help farmers and homeowners better scout their plants when looking for caterpillars and other pests:’
Check plants for holes in the leaves every other day, if not, daily;
Check thoroughly: It is not effective to just look the plants over quickly and assume that everything is fine. To catch the insects when they are still at an early stage you must make sure to turn the leaves over; many insect pests hide on the underside of leaves;
Un-wrap any folded leaf margins to find caterpillars rolled up in the leaves;
Search for caterpillar droppings, called frass, which appears on the leaves as little greenish pellets.
When caterpillars are found in sufficiently low numbers, they can be picked of the plant by hand and dropped into a container of alcohol to kill them.
Pesticides are another control option and if caterpillars are detected early, DipelTM which is available at the Department of Agriculture, is effective in keeping the population at low levels.
However, it must be applied regularly.
Specifically for caterpillars, Dipel is a natural insecticide that is completely environmentally friendly and non-toxic to all other living organisms.
Should the caterpillar population reach high levels where extensive damage is being caused; rapid control can be achieved through the use of pesticides containing Pyrethrin as the active ingredient.
Available at most plant nurseries, such pesticides quickly kill caterpillars and are relatively safe to use around people and pets. Make sure to always follow the instructions on the label and follow all safety precautions suggested by the manufacturer.
Weeding is another important aspect of IPM and caterpillar control. Many local weeds are the food of choice for caterpillars and attract butterflies and moths which will lay their eggs on them.
Problems can occur when the caterpillars have eaten all the weeds and then have to find another food source; if your plants are nearby they will most likely be next on the caterpillar menu.
Good weed management will therefore certainly reduce the amount of caterpillars you see around your plants.
The Department of Agriculture has collected specimens of caterpillars and is rearing them for identification. This will enable staff to determine whether any are newly introduced in Cayman or confirm whether those that were already present pre-Ivan are behaving outside of the norm for that particular type of insect.