THE cotton crop has been facing a number of problems like the leaf-curl-virus, drought, reddening of leaves etc. Last year new menace pink mealy bug emerged which is gradually increasing in Sindh and Punjab.

The pink mealy bug, maconellicoccus hirstus, is a source of worry for the farmers’ community and the scientists.

During 2005, the sudden appearance of the pest damaged crops in Multan, Sanghar, Mirpurkhas and Tando Allahyar. Many control measures with pests were applied to control the bug population, as the pests destroy the crop in few days.

The insect weakens the plants by sucking the sap from leaves, twigs, stems, and sometimes from the roots. The attack mostly occurs on branches and leaves. Serious attack results in retarded growth and late opening of bolls, affecting the yield badly. It feeds on soft tissues and injects saliva that causes curling and contortion of leaves.

The entire plant may be stunted and shoot tips develop a bushy appearance. The production of bolls is deformed, fewer, and small in size. The mealy bug also secretes a sweet substance called honey dew which encourages the development of black sooty mould due to adverse photosynthesis activity.

High population of this bug results in the death of a plant with more susceptibility among weaker plants as it has a high reproductive rate with a female laying up to 600 eggs and producing up to 15 generations per year. The bug has the ability to spread rapidly once introduced.

The pink hibiscus mealy bug is a serious threat to many plants in tropical and subtropical parts of the world and can attack on 300 species. In fruits, it attacks papaya, golden apple, pigeon pea, carambola, soursoap, cherry, passion fruit, avocado, mango, plum, grape, citrus, bread fruit, guava and banana.

The ornamental plants, it strikes, are hisbiscus, croton, allamanda, anthuricum, heliconia, lantana, bougainvillaea, nerium, ixora, ficus and is equally bad for vegetables such as tomato, pumpkin, okra, lettuce, beans, cucumber, peppers, cabbages, squash etc.

The pink hibiscus mealy bug differs from other types due to the presence of toxin (i.e., plant damage); pink to reddish brown in colour; no lateral filaments; two short candle filaments; loose cotton ovisac and pink eggs.

Adults are pink in body colour but are covered with white mealy wax like substance. The waxy filaments are short and usually obscure females. When a large mealy bug is crushed, its body fluid is also pink. Female bug passes through three stages i.e., egg, nymph/crawler and adult while male passes through four stages i.e., egg, nymph/crawler, pupa and adult.

The adult female is approximately 3mm long and 1.5mm wide, oval shaped and wingless. It has two short inconspicuous wax caudal filaments and covered with white mealy powder, hence looks whitish in colour and is less active than crawlers. It has an ovisac in which she lays eggs. Females die shortly after depositing eggs.

From the sac of eggs many nymphs/crawlers emerge. The crawlers are very active and agile, and pale in colour. In the early stage red eyes of crawlers are conspicuous. Later on, they get covered with white powder. Newly hatched crawlers prefer the apical and tender regions of a host plant but under field conditions, older parts of plants may harbour large populations.

Only male nymphs/crawlers of this bug after three stages pass into pupa. Adult males are smaller than females, have one pair of wings. Males have two long waxy “tails”. They have non-functional mouth parts and live only for few days.

Management of this bug is difficult due to its wide host range; easily spread to other areas; wax coating on body; dense colonies; nature of hiding in cracks and crevices on the bark; and crawling off the host plants. Besides, its feeding distorts the foliage providing some protection from pesticides.

As the body of this bug is covered with white waxy powder, it is difficult to control them with pesticides. Certain techniques may help in giving good results. Pesticides suppress its population to a specific level.

Trials with chemical pesticides indicate that profenofos and chorpyrifos@ 1000mls/acre give satisfactory control for up to five days and a second application should be repeated to suppress the bug’s population at a maximum level.

Both these chemicals were sprayed using @ 125 litres per acre. The plants were washed thoroughly (stem and leaves) as well as the soil. A delay of spray by seven days increased the population at a maximum level. High volume spray drops the nymphs of this pest on ground and after second day climb up to the plant. Therefore, it is necessary that soil around the plant is also sprayed.

The lady bug cryptolaemus montrouzieri (coccinelidae), a predator (red head lady beetle) feeds on all stages of the mealy bug which suppresses the high pest population. Cryptolaemus larvae are covered with a white flocculent secretion and may be confused with pink hibiscus mealy bugs, but are important predators and should not be destroyed.

Several effective parasitoids are known in Asia and elsewhere. One parasitoid angyrus kamali completes a generation in less than half the time required for its host. It suppresses pink hibiscus mealy bug population. This parasitoid has been released on Islands in the Caribbean and appears to be providing sustainable control. Anagyrus kamali and gyranusoidae indica parasitoids are long-term control solution.

Following points should be noted for the control of mealy bug:

* Water should be used @125 litres per acre for cotton and double for other crops.

* Stems should also be sprayed along with the leaves.

* Soil around the stem must be sprayed.

* Second application should be applied as soon as possible.

* Most affected plants should be uprooted and burnt.

* Land should be thoroughly prepared, so that eggs may be destroyed.

* Weeding should be done on time.

* In initial stages all the affected plants and its parts should be destroyed by burning.

* Chloropyrephos at the rate of two litres per acre should be applied through water.

* This pest mostly spreads in other areas of field during the picking time, therefore, cotton pickers should be guided accordingly.