Time to control aphids

Press, 15 October 1976, Page 8

Time to control aphids

Close inspection of young rose leaves and even swelling buds may reveal them to be thickly populated by aphids — yes, even so early in the season. Other plants where they may be found now include peach and nectarine trees, citrus, new 1 y-emerged potato shoots, plums and members of the cabbage family.

As the weather becomes wanner so these sap-suck-ing insects increase. More than 20 generations are possible in one year of some species.

Colonisation of growing points causes various deformities of growth and stunting; it can lead to ruination of the crop for consumption; the loss of flowers; the development

of sooty mould; but, most serious of all, many aphids are vectors of a number of now eradicable virus deseases which they transmit to the plants from which they suck the sap.

It is important to provide advance control for these pests before they reach plague proportions, such as is frequently to be seen of the black bean aphid on broad beans. The home gardener has really only two aphicides available to him, namely maldison and menazon. Maldison is a short-term control with a three-day waiting period and a residual life of about one week. Apart from its predominantly “contact” control of aphids, maldison also has some effects on caterpillars. Manazon is specifically an aphicide. It is systemic, which means that it is absorbed by the plant and carried throughout its system. This material has a much greater residual life (2 to 3 weeks) and harvesting of crops must be withheld until 21 days after spraying.

It is important to note that both these insecticides are toxic to bees and must therefore be applied only to plants which are not in flower.

Spraying should be done as close to flower bud opening as possible so as to give the maximum protection during the blossoming period.