Phaedon Betulae
(Mustard Beetle). This beetle is about 1/8in. long, oval, of a glossy violet or brilliant blue, sometimes greenish; the head and thorax are minutely punctate; wing-cases punctate-striate; lower surfaces of body, legs, and antennae black. The eggs are laid on the backs of the leaves. The larvae are flattened. The body is broadest about the fifth segment, and tapers slightly to each end. It is of a smoky-yellow colour, spotted with black; the head is black. Each segment is prolonged at the sides into a conical protuberance. There are a few scattered hairs on the body. The insects are believed to pupate in the soil. There are two broods in the year, and the beetles that emerge in autumn hybernate. In "Farm Insects," p. 104, Mr. Curtis attributes to this species damage done to Turnips; and, in 1881, Mr. Fryer drew attention to it as destructive to Mustard and Cabbages. In Ormerod's "Report" for 1882, pp. 74-76, there is an account of the ravages of these insects in the Fen District of England, especially around Whittlesea, where the beetles prove so destructive to cultivated Mustards, Cress, Rape, and Cole, "that, in six or seven days, they will completely destroy a field of twelve acres, and leave nothing but the bare stalks." To garden produce of the same sort, they are also very hurtful. They are common in most parts of Britain, frequenting plants of various kinds in damp places; and, possibly, it will be found that they are dangerous to farm and garden produce only in damp distrits, like the Fens in England.
Remedies. Burning stubble, and rubbish of all kinds, is one means of destroying many of the beetles in their winter retreats. A change of crop for a year or two is recommended, with a view of starving out the insects; but, since they are common on Brooklime, Bittercress, and other plants inhabiting damp localities, this method can hardly be fully successful, except under special conditions. Probably, dressings such as have been found useful in attacks of a similar kind by other insects on Turnips, &c., would be found useful, e.g., gas lime, soot, or sulphur, scattered alone or mixed, while the dew is on the plants, or after a shower. Probably, hand-picking would suffice to protect garden produce from serious injury. Anything that promotes vigorous, healthy growth is of much value in enabling the plants to resist injury from the attacks of the larvae.