Gardening – Moth menace

The warming weather of spring brings with it an increasing invasion of pests in the garden. Many pests, for example aphids, cause minimal damage for a short period of time. They can largely be ignored or treated to a quick blast of soap spray. There are some, though, that cause major crop loss in the home garden.

Codling moth is one of these, and they will soon be on the prowl for tender young apples. In fact, the larvae will be active just after flowering. The lovely sprinkling of petals on the lawn is a good reminder to take action. Doing nothing means you can expect at least half of your fruit to become infested. Unfortunately, here in the north, there is a second generation of codling moth which occurs about mid-November. It is less prolific but almost as destructive.

Codling moth traps are available in most garden centres. Spray foliage with Kiwicare Organic Caterpillar Biocontrol or Success Naturalyte about a week to 10 days after a spike in moth numbers in the traps. The sprays are only effective while the caterpillars are on the outside of the fruit, which is a fairly short period, so timing is everything.

More limited, but less time critical control can be achieved with trunk traps, comprising a band of corrugated cardboard or cloth with a grease band underneath. These trap larvae as they crawl down the tree at the end of the season to pupate for next year. Burning or disposing of the bands at pruning time kills the pupae. However, only a proportion will be caught. Some will pupate in branch crevices and some will land on the ground and pupate near the base of the tree. If your neighbour’s tree is infested, this control is mostly ineffective. Picking up or mulching infested fruit also has limited success.

A technique that I’ve yet to use but is reported to be quite successful is milk bottle traps. These work in a similar way to pheromone traps by attracting the male moths before they mate with the females. Using a two-litre milk bottle, cut a flap in the shoulder opposite the handle. This keeps the rain out while allowing the moths to fly or crawl in. Make up a solution of 1 cup cider vinegar, 1/3 cup dark molasses (or treacle, or 1/3 cup sugar with 1 tsp vegemite), 1/8 tsp (5 drops) ammonia and 1 ½ litres  water. This is enough for 10 or so traps. Hang in the trees from flowering until the end of November, replacing the solution every two weeks or so. If all else fails, use the fruit to make stewed apples.

Andrew Steens