Butterflies, Moths and their Larvae
A few aphids are not a problem. Only if their numbers grow beyond the point that their sap-sucking habits are damaging the plants you have so lovingly cared for are they a pest. Caterpillars are only a problem when their voracious feeding is on the vegetables you were hoping to make dinner with.
Gardens are not natural habitats, they are controlled by the gardener. The gardener is attempting to create a pleasant place, coaxing nature to combine habitats that would not normally be found together. Striking the balance between encouraging beneficial insects and controlling the pests that can get out of hand is the responsibility of the gardener.
We all love butterflies, even the cabbage white butterfly adds to the beauty in a garden. It is only the knowledge that the white butterfly caterpillars will be devouring the cabbages, cauliflowers and sprouts that you planted that make them less wanted. The gardener will want to protect the vegetable patch without harming the beneficial insects that he or she wants to encourage.
For white butterfly caterpillars, this is relatively easy with the use of Organic Insect Control applied late in the day. This product contains the naturally occurring pyrthrum and there is only a 1 day withholding period.
Monarch butterflies, with their long lopping flight are a joy, to see swooping around the flowers in the garden. Many gardeners actively encourage these butterflies by planting the favourite food of their caterpillars; swan plant also known as milkweed.
The monarch caterpillars are striking in their own right, with strong yellow, black and white stripes. They will grow to 3-4cm before forming a green chrysalis (cocoon, pupa) hanging from a twig or skeleton of an eaten leaf. In the chrysalis the caterpillar metamorphoses into the adult butterfly. This process is an education for children and adults alike and can be followed easily on the swan plant.
Swan plants are often attacked by plagues of aphids and if the aphids are not controlled the swan plant will be a reservoir of aphids that will then infest other plants in the garden. Manual control of aphids by squashing them is possible if they have not been allowed to get out of hand. But if the aphid infestation is heavy it may be necessary to use other methods. First, collect caterpillars from the swan plant and put them in a sealed container with some swan plant leaves. Then spray the parts of the swan plant affected by aphids with Organic Super Spraying Oil.
The oil kills the aphids by blocking their spiracles (breathing holes) and suffocating them. It is therefore important to cover the aphids in the spray. The oil does not contain an insecticide and will not harm the caterpillars when they are returned to the plant but the oil and dead aphids should be washed off the swan plant before returning the caterpillars. Return the caterpillars after a day or two when the aphids are dead.
For more information on monarch butterflies and how to encourage them in your garden go to the Monarch Butterfly NZ Trust.