HEATHER-LYNN’S HABITAT: Fierce battle of the bugs on
THERE ARE TINY BATTLES playing out on the leaves of your plants and your crops every day.
Pests, some no bigger than a millimetre, others as large as a pinhead, are sucking the life sap from foliage and flowers.
But they themselves are under attack from predators who delightfully feast on their larvae, their eggs and the adults.
It’s the world of biological control outlined by senior agricultural officer and head of the Entomology Section of the Ministry of Agriculture, Ian Gibbs.
He gave an example of how local entomologists fought the Sago Palm scale which killed off those palms all over the island. He said his department investigated and found the pest had two natural enemies – a tiny parasitic wasp and a predatory beetle.
“We went up to Florida and we collected both species and brought them back here and released them on a palm that had not been sprayed with insecticide, because we wanted them to be as free of pesticide so they could become established.
“And, how well they established. That beetle is only the size of a pinhead and we managed to only collect 25 or so in Florida. We released them on a tree down by Maynards, St Peter. Within a year, we were able to collect in excess of 25 000 from that tree and distribute them all across Barbados,” Gibbs remembered.
He said the wasps were also “pretty well established” but hastened to add that they posed no threat to humans since they were only the size of “two pin heads”.
In addition, there was a wide variety of ladybird beetles attacking the pests that attacked plants.
One such ladybird beetle was that which feasts on the pests which attack crotons.
“Croton scale is a relative newcomer to Barbados. It loves crotons. You see all the scales attached to the mid-rib of the plant and now they have developed a nice taste for our mangoes,” Gibbs noted.
He added while the scale looked unsightly, it did no damage to the fruit of the mango tree. “It just makes the mango look a little ugly.”
The scale also attacked peanuts and pigeon peas.
“When they got onto things like peanuts, peanuts just stopped growing. They just came to a full stop and would not grow anymore so it became a real problem,” he said.
“Fortunately, we found that however they got in here, the natural enemy happened to come with them. But it did a lot of damage to crops. l remember in pigeon peas, I saw a crop down in St Lucy and you would see the whole stem covered in these things.”
Gibbs said sucking pests were especially prevalent in the dry season and this was as a result of plants, in reacting to drought conditions, producing more of the nitrogen compounds which the pests loved.
“The scales and other sucking pests say, ‘yeah boy, nuff food’ and they go on the plants and their population just blooms.
“They then poop it out and it comes out in tiny little droplets of what we call honeydew because it is very sweet. And when this honeydew falls on the leaves, it spreads out and fungi grows in it – that black stuff that Bajans call Black Blight or sooty mould is a complex of different fungi growing in sweet layers excreted by the sucking pests.
“And invariably when you have problems with these sucking pests on your plants, you get ants and why? Because the ants are feeding on that sweet honeydew.”
The problem, he added, was that when people saw signs of infestation in plants, “they run for a spray can”, not only killing off pests but good bugs as well.
Gibbs explained that pest control by natural means was as simple as a dishwashing liquid/cooking oil/water solution.
“Or you can go and spend nuff money and buy a systemic insecticide which will do an excellent job of killing them (pests), but will also do an excellent job of controlling the natural enemies as well, which we don’t want.”