Battle of the Bugs!
Staff and students at the school’s farm think they have worked out why Gooseberries are not a commonly grown fruit around Gympie. These delicious little berries don’t just taste good to us but to a plethora of hungry bugs as well! So fierce is the competition for ripe Gooseberries that we have been forced to try a new approach…
To avoid applying a cocktail of chemical sprays to control mites, beetles, aphids and the like, Mr Bob Leitch, our Agriculture Coordinator, sought a far more sustainable and chemical-free alternative. Last week, over 500 Lacewing larvae were released amongst the Gooseberries in special boxes to wage war on the insect pests decimating our crop.
As their common name implies, adult green lacewings (Mallada signata) are green, with four clear wings. Adult female lacewings live for approximately three or four weeks and lay up to 600 eggs. Each egg sits on the end of a slender stalk, which elevates it from the ground and decreases the chances of predation by ants. The eggs take approximately four days to hatch.
Larvae range in size from 1 mm at first emergence up to 8 mm just before they pupate. They have small spines on their backs upon which they impale the remains of prey. This provides a form of camouflage and allows the larvae to appear inconspicuous amongst the prey. Larvae pass through three moults over a period of 12 days before pupating inside a silken cocoon. Adults emerge after nine days and start laying eggs seven days after emergence.
Larvae of the green lacewing are wide-ranging predators that will attack and eat almost any small insects or eggs. Lacewing larvae are particularly effective at controlling aphids and can consume 60 aphids in an hour. They will also attack mealybugs, greenhouse whitefly, thrips, two-spotted mite, small caterpillars and moth eggs.
Now that the Lacewing larvae have been released, students will monitor their effectiveness over the coming months. If all goes well with this biological control strategy, the number of pest species amongst our Gooseberries will be reduced to below economic injury levels and more luscious berries will be available for sale.