Red Orange Scale (Chrysomphalus aurantii).—The red orange scale is distributed throughout the world, and is especially abundant in tropical and sub-tropical regions, the most southern limit being New Zealand. As a major pest it is peculiar to citrus, but infests to a minor extent other plants—e.g., plum, apple, pear, quince, grape, fig, euonymus and rose. So far it has been found only on citrus in New Zealand, it being well established in the Auckland province, and also in the South Island on Banks Peninsula. It is very often found on imported oranges and lemons.
This scale is a circular one, with a central pimple-like prominence, as in the case of the San José, but is flatter, about half as large again, and is of a characteristic reddish colour. The damage done to citrus trees by this insect is of a serious nature, as the entire tree or part of it may be killed in severe infestations. A characteristic feature of this species is that no honey-dew is secreted, and hence there is a total absence of sooty mould on infested trees.
Like the San José scale, the red scale is viviparous, and over-winters as partially mature adults, completing development in early spring, when the young insects make their appearance. An average of about 55 young is produced by each female, and development to maturity takes from two or two and a-half months; about one month later young are produced, and their production continues over a period of one or two months; climatic conditions, however, have a direct influence on development.
An important natural enemy is the steel blue ladybird (Orcus chalybæus), imported from Australia; but the most efficient control is cyanide fumigation, or spraying with red oil or lime-sulphur.
The Black Scale (Chrysomphalus rossi).—Foliage of palms, oleander and citrus is often infested by this reddish-black to black circular scale ([Fig. 7], 3); it is almost flat, with a central whitish spot, and measures up to one-tenth of an inch in diameter; when many individuals are crowded together, their outline becomes irregular. This species is not especially injurious, though common.
Oleander Scale (Aspidiotus hederæ).—This cosmopolitan insect occurs on orchids, oleander, ivy, camellia, palms, citrus, coprosma, and karaka, infesting stems, leaves and fruit. In the case of citrus, this insect delays colouring of the fruit, which becomes blotched with yellow or green. The insect may be so numerous, that it completely covers the whole plant, giving to the latter a white appearance; this is due to the preponderance of white male scales, the female being slightly yellow, with a purplish tint.
The female scale is almost circular ([Fig. 7], 7), having a diameter of from one-twenty-fifth of an inch to two-twenty-fifths of an inch, and is rather flat; the male is more oval and of the same size, and in both cases there is a central orange-yellow spot. The eggs are comparatively large, and hatch soon after being deposited. The insect reaches maturity in from four to six weeks.
Greedy Scale (Aspidiotus rapax).—This European insect is now widespread, and in New Zealand is common on apple, pear, quince, and wattle; it has a wide range of hosts. The adult female scale is convex and of a general grey colour, though sometimes yellowish. The winter is passed in all stages of development.
Rose Scale (Aulacaspis rosæ).—This is a very common insect, forming white incrustations on the bark of roses, briar, raspberry, loganberry, blackberry, and sometimes pear. The adult female ([Fig. 7], 8), which is from one-twelfth of an inch to one-eighth of an inch in diameter, is rather thin and flat, circular or oval in outline, but irregular when crowded; the general colour is white or slightly yellowish. The male ([Fig. 7], 9) differs, in being elongated and narrow. This insect can withstand severe winters, and is to be controlled by the use of red oil.