By Dr R. A. Khan and Dr M. Ahsan
THE mealy bug is one of the most damaging insect pests severely attacking mango crops throughout the Subcontinent. The insect lays eggs on soil close to mango trees. The hatching of eggs starts with the rise in temperature in January-February. The emerging lice like tiny nymphs travel via stem to reach the fruiting parts to suck the sap. This causes immature fruit falling, and in severe cases makes the trees completely devoid of fruits. At maturity, the winged insects copulate with females at feeding sites and then the egg-carrying females travel via stem to ground in April-May for laying eggs.
The measures used previously were only one way effective and could not control the pest completely. The devise discussed here is new and is effective both ways and controls the insect pests completely.
This trap is prepared using a narrow strip (8-10 inches wide and 6-12 inches loose than the girth of the tree) made of thick, smooth and transparent “Shesha plastic”. For its installation, the upper margin of plastic strip is erected like a funnel around the tree while the lower margin is systematically rumpled (to reduce its length) and tightly fixed on stem with nails. The lower fixed margin is afterward covered with mud to arrest chances for the nymphs to escape up through cracks and cervices on stem (See Fig.A). The traps are fixed on tree stems almost 3-4 feet above the ground level.
During field research, this innovative technique has been proved to be the most effective barrier against mango mealy bug nymphs crawling up the trees and successfully entrap the egg-carrying females (each female carry 350-400 eggs) while crawling down for egg laying in the soil during May. Powdered un-slaked lime (2-3 inches layer) is placed in funnel of the trap has been found to effectively kill the entrapped egg-carrying females.
The mango mealy bug some times directly fall on the ground due to shaking wind therefore the trap should be kept active for two consecutive seasons from January to May in order to achieve the best results. The funneled part of the trap can be strengthened by passing a thin spring wire through narrow fold made along upper margin of the funnel to fix it in position if the tree bole is of larger size ( Fig.A).
Newly designed permanent funnel type slippery trap (made of stainless steel) will soon be available in the Forestry Department of Faisalabad Agricultural University.. These are made flexible to be fixed around the tree and will get loose accordingly as the stem will gain width with the passage of time.
Previously used technologies “sticky band” (Fig.A 1) have become totally ineffective for mango mealy bug since the passing over nymphs stick on glued area in line, making a bridge for their companions to cross and reach the fruiting parts. Accordingly the “slippery plastic band” (Fig.A 2) has been observed to arrest only 60-70 per cent of the crawling up nymphs while the remaining 30-40 per cent reaches the tree crown causing enormous fruit losses.
Fig.A : Position of funnel type slippery trap on the mango stem. Slippery and sticky traps are also shown below. __
The effectiveness of this mechanical technique is wonderful since it works both-ways. Studies have revealed that almost 84 per cent of the nymphs fall down while crawling up over the wall of funnel type slippery trap. The escaped 16 per cent insects reach fruiting bodies, mature there and copulated by winged males. These 16 per cent insects are highly important since each of them carry 350-400 eggs. Funnel type slippery trap have edge over the old control techniques as it entraps all these egg carrying females on their way back to the ground.
Courtesy: The Dawn