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The brown olive scale (Saissetia akar) occurs throughout the State on a wide variety of host plants. It is best known as a pest of citrus but also commonly infests olives, passion vines, and many different ornamental shrubs, including oleanders. This scale may occasionally he found in large numbers on more succulent hosts such as watermelon vines and geraniums.
Large numbers of eggs are deposited beneath the adult female scale and individuals may lay up to about 2,000 eggs which appear like little heaps of fine sand. The six-legged "crawlers" move from under the parent scale and settle usually on the leaves along the veins. After about four to six weeks the young scale moults and withdraws the feeding organ and migrates to the stem of the plant, where it remains for the rest of its life. After another four to six weeks moulting again occurs, and the insect reaches the "rubber" or early adult stage, when an "H" formation on the back becomes evident. The female commences to deposit eggs a little later and these hatch in two to three weeks.
The period from settling to the commencement of the next hatch of eggs is about three to four months. Some overlapping of broods occurs, but peak hatch periods can he distinguished in September, December and March. Whilst the older stages usually infest the stems and twigs it is not uncommon to find adults maturing on leaves and on the fruits of citrus.
The injury caused by this scale as a direct
result of sap feeding is not usually great. As they have the habit (like some other scales, aphids and mealybugs) of excreting a sweet sticky "honeydew". infested plants may become heavily coated with this material. A sooty mould fungus grows on this excretion and, as a result, the plants become covered with this "black smut". This not only renders them unsightly, but by interference with the natural processes of the plant causes general weakening.
This honeydew on infested plants attracts ants in large numbers, and in their constant movement over the scales, the ants frighten off the small wasp parasites which help to keep the scale under natural control.