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APHIDES

In winter the shiny black aphis eggs lie in crevices of the bark and round dormant buds. With the first warmth of spring the eggs hatch; the aphides of this first brood are all females. They are remarkable in reproducing without fertil­ization, that is by parthenogenesis. They do not lay eggs, but give birth to living young. The second generation is identical with the first, and well within another forty-eight hours a third generation is produced in the same viviparous manner. Each female may live many weeks reproducing at the same phenomenal rate. One investigator claims to be conservative in stating that the progeny of one aphis may reach, within three weeks, the astounding figure of one quintillion-that is, 1 followed by 30 ciphers. The weight would exceed that of five hundred million stout men! These calculations ignore the activities of the natural enemies of the aphides.

As the aphides hatch they migrate to young growth and cluster round the sappy tips. Most of the early aphides are wingless, followed soon by winged specimens that fly to other plants. The appearance of young males seems to be in response to bad weather conditions. Subsequent reproduction is by the laying of eggs that can withstand extreme climatic changes -the aphis has become oviparous.

In early summer the winged insects fly to other plants, and very few aphides are to be found on roses again until March, or later. Then they return to feed, breed, and deposit their eggs, which hatch in the following spring.

With curiously constructed beaks, aphides do tremendous damage by withdrawing great volumes of plant sap. They will distort flowers, cause bud-drop, mar foliage, and even stunt the bushes. We believe, but have not proved it, that they can transmit rose wilt. They secrete a colourless sticky substance called honey-dew {Vumagine), which attracts ants and serves as a medium on which "sooty mould" grows.

In controlling aphides the attack can be made on either the egg or the insect. Tar distillate or E605 will destroy every egg it reaches, and so all spring aphides can be eliminated, but there is no such easy means of control for the autumn multi­tudes. Spraying with organic phosphates, a product containing the gamma isomer of benzene hexachloride (BHC), or a twenty to twenty-five per cent DDT preparation with a white-oil or wax or "mayonnaise" base is effective at any season. DDT in a water base is not effective against aphides. Pespruf Emulsion (No. 20), Rulene and Rucide are all DDT preparations that have given me good results. The first and second are in the form of white-oil or "mayonnaise" emulsions with the insecti­cide added; the third has an advantage over other DDT pre­parations in being less easily washed off by rain. It has a pro­prietary base other than white oil, and needs to be heated in preparing for use, but do not boil it. In many preparations, other emulsifying agents are used with the white oil, and the base is then called a "mayonnaise" type.

Enthusiastic references to organic phosphate preparations (Systox, HETP and E605) are unavoidable in discussing con­trol of insects of all kinds, caterpillars, and other rose pests, for they are, undoubtedly, the most potent sprays, for such pur­poses, that have ever been produced.

Unfortunately they are extremely toxic to human beings, and it has been found impossible to rely on people being suffici­ently cautious, in using them, to avoid tragedies. In conse­quence, legislation has been enacted recently, in some Austra­lian States, imposing conditions that render the use of organic phosphates practicable only for users of large quantities, but virtually impossible for home gardeners. However, we now have other sprays available that partly compensate for the pro­hibition of the use of organic phosphates. These new prepara­tions contain Chlorparacide (p-Chlorobenzyl p-Chlorophenyl sulphide), and it is compatible with both DDT and the gamma isomer of BHC. By mixing Chlorparacide with either of these other products one obtains a spray that is superior to the organic phosphates in some ways, and inferior to it only in that it is slower in killing aphides. As the gamma isomer of BHC kills quicker than DDT, I would recommend it instead of DDT. Lindane is a name given commonly to the gamma isomer of BHC, and it is not merely a proprietary name for a commercial preparation.

There is, already, on the market at least one proprietary preparation (called Spraymate) wherein DDT and Lindane are combined with ovicides similar to Chlorparacide. This spray is compatible with TMTD and Zineb, and, when mixed with either, gives control of fungi as well as insects and arach­nids. Spraymate is, of course, not nearly as toxic to human beings as E605, yet it does the same work almost as effectively, and so it is the best safe insecticidal and miticidal spray avail­able for most gardeners. In addition, it is not very expensive.

These sprays supersede all preparations such as nicotine sulphate, Clensel, and soapsuds. Washing off aphides with the hose jet and killing them by squeezing between finger and thumb have been widely advocated. Such methods require no apparatus and no spraying material, but are so comparatively ineffective as not to warrant consideration when spraying is so easy, so simple, so inexpensive, and so infinitely more successful.