Among the factors contributing to the maintenance of the "Balance of life" in nature, the availability of food is a most potent one. With the spread of intensive cultivation and the practice of growing the same crop continuously in large belts, condition have been set for an unrestricted multiplication of certain injurious insects associated with them.
One most recent example to this effect is the resurgence of the mealy bug on cotton crops in the prime cotton belt of Nara canal in District Sukkur. During the Kharif-2005 season this year, cotton crop on about 300 acres at Salehpat in District Sukkur, belonging to the two different adjoining growers, were seen badly damaged by the mealy bug.
When enquired, the haree [tenant] of one of the growers concerned reported to this scribe that in the beginning if September he observed a white waxy covering on the branches and leaves of some cotton plants. Out of ignorance of this new menace he neither bothered about it nor reported it to his landlord.
But when this menace assumed serious proportion and spread in to the entire block it came to the notice of the very landlord, who applied different pesticides recommended for pests of cotton but none of the pesticides proved effective, and ultimately the entire standing cotton crop, on about 300 acres, sustained severe damage by this new mealy bug menace.
This very writer, when he visited the mealy bug outbreak site at Salehpat, on 4th October 2005, it was surprising to see the devastation caused by this new menace. The entire cotton crop was virtually littered with a white waxy covering on the branches, fruiting parts, leaves and stems of the plants.
However, since the sowing of cotton had been undertaken early in the first week of May, the mature bolls had managed to open but the honey due be secreted by the mealy bug on the fruiting parts, and twigs may cause stickiness in the cotton fiber during the picking, damaging the very quality of the seed cotton[phutty].
Here it would be proper to mention that according to the weekly bulletin of the Pest Warning Division of the Agriculture Department, Government of Punjab, for the period ending 7th September 2005, sporadic occurrences of mealy bug, covering over 100 acres, were observed in different cotton growing areas of Punjab this year, which was a new phenomenon. According to the said bulletin the most haunting aspect of this new phenomenon was that the pesticides, recommended for the cotton pests control in the country, failed to contain the spread of this new menace.
Regarding the species of the mealy bug, the insurgence of which was observed on the cotton crop at Salehpat in District Sukkur,close observation revealed that the female bodies of this mealy bug were pink in colour with white waxy covering.
Apparently, it looked similar to those species of the mealy bug which is found on the thorny keeker plant[ Prosopis julipholia ].Here it would be proper to mention that the perennial keeker is found in abundance in the desert as well as in the entire Nara canal cotton belt. For the sake of information of our reader, the mealy bugs are cottony looking insects with piercing/sucking mouthparts. They suck the fluids from the leaves and stems, robbing the plants of essential nutrients.
Mealy bugs feed on all parts of the plant but specially on the tender new growth. Leaves wither and yellow, and on the crop plants the fruits may drop prematurely. The irony of the fact is that cotton is the highest foreign exchange earning cash crop as well as a major source of edible oil production in the country, yet the very incidence of mealy bug on the cotton crop goes unattended both at the provincial and federal levels.
Moreover, since the outbreak of mealy bug was of a localized nature, it is quite possible, that the very incidence might be the case of resurgence, following the use of either some adulterated substandard pesticides or highly toxic pesticides. This is because natural enemies often have a lower tolerance to many pesticides.
According to the entomologist of the Federal Plant Protection Department, Muhammad Ziauddin based at Khairpur, aerial spray undertaken with moderately toxic organophosphate pesticide on the sugarcane crop for Pyrilla [a sucking pest] control in District Naushero Feroze, Dadu and Khairpur in 1980/s, on thousands of hectare, had led to the resurgence of sugarcane mites in many areas, especially those facing water stressing during the campaign.
A review of literature has also revealed that the use of some new chemical brings a disruption in the stages of the life cycle of long-established natural enemies, allowing the resurgence of some new pest problem.
For example, in the USA, the cottony cushion scale remained harmless in citrus production, more than 100 years after its successful suppression by the vadelia beetle [an imported, introduced natural enemy] . But when the insect growth regulator (IGR) was used to control the California red scale on the citrus it caused flare up of the cottony cushion scale.
This is because the IGR caused the disruption of vadelia beetle pupation and egg hatch[Graftan Cardwell and Gu 2003]. Reportedly, the most effective programme involving the periodic release of commercially produced natural enemies in tree fruit and nut crops is the use of the parasitoid Aphytis melinus, for the control of California red scale in citrus[Collier and Van Steenwyk 2004].
SUGGESTIONS: determine the species of the mealy bug in question, the concerned department of the government should arrange its proper identification. In case, the mealy bug species is the same one found on Keeker plants of the area, Pakistan Agriculture Research Council [PARC]should come forward to launch its biological control with the help of natural enemies, either endemic or exotic, using augmentation techniques.
However, since biological control of any pest is a long term process, the use of selective pesticides should be advocated in the outbreak area to preserve the naturally occurring biological control which will certainly be the single most effective approach against the newly added potent menace of our precious foreign exchange earning cash crop.