STUDIES ON SCALE INSECTS AND MEALY BUGS OF DECIDUOUS AND EVERGREEN FRUIT TREES IN NORTHERN WEST COAST OF EGYPT AND THEIR NATURAL ENEMIES

Abstract

Fruit trees are very useful since they produce edible crop that anyone can eat or use as ingredient of a thousand of food recipes. The agricultural industry has boomed a lot of economies because fruit producing trees can very well become one's stable source of income. Not only are fruits very useful in food preparation, they can also be use since they contain a lot ofvitamins and minerals as health supplements and as a diet to treat certain diseases. ·

The production of fruit yield is an astonishingly complex process dependent on a wide variety of factors and processes. Fruit yield depends on certain factors such as number· of plants in the orchards, plant maturity, plant structure, number of flower clusters, the percentage of set and proportion that matures. Processes that affect fruit yields include pruning, irrigation, fertilization and pollination. Environmentai factors that affect fruit yield include the occurrence of frost, amount of sunshine, length of the growing season, insect pests and diseases. Actual yield is a result of solving pests problems and orchard management. Correctly, identifying pest species and stress symptoms is fundamental for choosing the most appropriate management strategy.

Numerous insects and mites inhabit fruit trees orchard. Some of them actually play a beneficial role in the orchard system performing activities such as pollination, feeding on organic debris, or feeding on pests (Parasitoids and predators). The others cause economic damage to the crop. Of them, the scale insects and mealy bugs hich cause dan:tage to the plants in different ways (Talhouk, 1969).

Scale insects and mealy bugs are phytophagous, feeding by sucking plant juices through set stylets. Individual species can infest one or more organ ( leaves, fruit, branches, main stems, trunks or roots). They are widely distributed throughout the world with the exception of the cold extremes of the Arctic and Antarctic (Miller, 2005). They are considered by many authors to be part of the order Hemiptera, sub order Stemorryncha, super family Coccoidea (Gullan, 2001). They are generally small and cryptic creatures that cause major problems in agricultural and fruit ecosystems. They are commonly transported on plant materials and because of their small size and habit of feeding in concealed areas, they are frequent invasive species (Millar et a/., 2005) causing billions of dollars in damage annually (Kosztarab, 1990).

In addition to physical damage caused to the plants, many scale insects and mealy bugs such as long- tailed mealy bug Pseudococcus Longispinus and fig scale, Ceraplastes rusci are known to carry plant viruses (La Notte eta/., 1997). Some mealy bugs such as the pink hibiscus mealy bug infect a toxic saliva which results in malformed leaves and shoot growth, stunty and occasionally death. Leaves show a characteristic curling similar to damage by viruses. Heavily infested plants have shortened internodes leading to a "bunchy top" appearance (Todd, 1999).