September 25, 2006	Monday	Ramazan 1, 1427

CITRUS fruits rank at the top in world production and trade among tree fruits and comprise about 40 per cent of the total fruits produced in Pakistan and it is cultivated over an area of 185,400 hectares with an annual production of about two million tons.

Average yield of citrus in Pakistan is just 9.076 tons per hectare, while in many other citrus growing countries it is much higher, as average yield of Brazil is 21.64 tons per hectare, USA 25.98 tons and Turkey 26.73 tons. Why is so? The main reason for this is excessive insect pest attack.

The growers are suffering huge losses in yield and quality of citrus crop due to attack of various insect pests and diseases which act as significant limiting factor in increasing its production.

Because of their improper or un-integrated management, the citrus production is low. Citrus crop is easily damaged by pests, so citrus growers are always looking for ways to protect their crops.

The present situation of citrus field, with special reference to Punjab province, needs special attention, where the crop is suffering from an emerging problem of mealy bug pest.

The citrus mealy bug has been recognised as a pest of citrus and ornamental plants in Europe since 1813 (where it is called the greenhouse mealy bug).

Mealy bug Planococcus citri is a small, scaled insect 1/5th of an inch long that gets its name from its appearance, which looks as if it has been rolled in coarse flour. Female adult is approximately 3 mm in length, wingless, and have piercing–sucking mouthparts. A white cotton-like wax covers the female’s reddish body. When punctured, the female’s body fluids are also reddish, but it is important to note that some other mealy bug species may have a similar coloration.

It feeds on the sap of the plant on new as well on old branches and releases toxic substances causing injury, curling and drying of leaves which, damages fruiting and drastically decreases the yield. Mealy bug also attacks the roots just below the level of the soil, especially where the root and the stem meet.

In Punjab, the minor infestation of mealy bug had been reported on citrus crop since last few years. But this year the attack of mealy bug has been observed in early stage of cotton crop in district Faisalabad, Toba Tek Singh, Sahiwal and is spreading very fast. Furthermore it must be remembered that once mealy bug pests become established, it is extremely difficult to achieve acceptable control.

Symptoms mealy bug Infestation: one or more of the following symptoms may be observed: crinkled or twisted leaves and shoots; bunched and unopened leaves; distorted or bushy shoots; white fluffy mass on buds, stems, fruit, and roots; presence of honeydew, black sooty mold, and ants; unopened flowers which often shrivel and die.

Management Options: The mealy bugs produce large amounts of honeydew (similar to that of produced by whiteflies and aphids), which can coat plants and surrounding surface with a sticky or waxy layer of honeydew. Pesticides cannot easily penetrate the heavy wax layers. Therefore, applying pesticides only is an ineffective control technique against this mealy bug pest. However the managements should include following integrated control options.

• Weeds serve as potential host plant for the citrus mealy bug therefore they must be eradicated regularly.

• The severely infested branches must be cut and burnt immediately and field should be ploughed to kill immature stages available in the soil.

• Spray as strong a stream of soapy water solution as the plant can tolerate; this should dislodge most of the bugs. This is the easiest way to control mealy bugs. Repeat if you see new egg sacs.

• Spray with a soap/oil (mix 1 tsp. detergent surf +100 ml neem oil, and 16 litre water in a spray tank) mixture may also give better results.

• The less affected crop at early growth stage should be sprayed with Imidacloprid (120 gram/acre) or Thiamethoxam and may be repeated after 5-7 days followed by water spray. The spray should be done at the crawler stage of mealy bugs, because it is the most fragile stage and the most susceptible to chemical control.

• The foliar spray of Chlorpyrifos, Triazophos, Profenofos, and Bifenthrin may be applied in case of attack at early stages of crop but not later on when fruit has attained reasonable size due to sanitary and phytosanitary (SPS) measures.

• Prior to the spray of Imidacloprid, Chlorpyrifos at the rate of two litres per acre should also be applied through irrigation as to control the root infestation and suppress the pest population in the soil.

• Biological control offers the safest, most economical and long-term solution to this problem. This strategy relies on producing sufficient numbers of tiny wasps (parasitoids) that attack and kill the mealy bug. A number of natural enemies are known, including the coccinellid predator Cryptolaemus montrouzieri and the parasites Anagyrus pseudococci and Gyranusoidea indica which suppress the mealy bug population.