Zoologists have warned that giant mealybug, which is difficult to control using traditional insecticides and chemicals, may end up destroying plants and crops in epidemic proportions.
According to a report prepared by a group of entomologists from the Sher-e-Bangla Agricultural University, mango, jackfruit, citrus, papaya, brinjal, guava, tarmarind and rain-trees are most vulnerable to mealybugs.
Although the report said the pests did not pose any massive threat to the human body, zoologists claimed that exposure could cause skin infections.
The exotic pests recently infested the campus of the College of Home Economics at the capital’s Azimpur, triggering panic among students and prompting the authority to keep the college shut.
The three-member group of entomologists, led by Prof Dr Md Razzab Ali, prepared the report after visiting the college campus on Wednesday. It will be presented before media in a conference at the Education Ministry today.
The scientific name of mealybug is “drosicha mangiferae.” It is more commondly known as the mango mealybug, giant mealybug or monophlebids.
The report said giant mealybugs lay purple-coloured eggs in loose soil within a 2-3m radius around the infested trees. Hatching of eggs starts with a rise in temperature and the nymphs crawl to the succulent shoots and base of fruiting parts. The nymphs and female bugs suck sap from inflorescence, tender leaves, shoots and fruit peduncles.
As a result, the affected inflorescences dry up. Rigorous infestation affects the fruit set and causes fruit drop. They exude honey dew over the leaves, on which sooty mould fungus develop.
“Mealybug is difficult to control by insecticides and the use of chemicals has been inefficient. Sticky bands along with burning and burying treatments significantly reduced the frequency of infestation of mango mealybug. Burlap bands reduced population of mango mealybug nymphs by 78.98%. Stem injection can achieve a very high level of mortality of sucking insects [98%]. The mortality rates achieved with insecticide sprays were up to 55%,” said the report.
They occur in all zoogeographic regions but seem to be most diverse in tropical areas especially oriental regions. It can be found in India, Pakistan, Mayanmar, China, and the African countries.
The report suspects that the bugs travelled to Bangladesh from the African countries. Prof Razzab told the Dhaka Tribune that the pests might have travelled along with the baggage of the Bangladeshi soldiers returning from UN peacekeeping missions.
He suspected that there had not been enough checking and quarantining arrangements at the airport for baggage, vehicles and other items brought back by the returning peacekeepers.
Recently, the mealybugs were found at a naval base in the country.
Razzab said the authorities or departments concerned should pay great attention about the spread, bio-ecology, the nature of damage, economic importance and control measures for the giant mealybugs.
He also recommended intensive research to emphasise the control of the pest.
Nishat Parvin, vice-principal of the College of Home Economics, told the Dhaka Tribune the campus would reopen on April 27.
“The decision has been taken in consultation with experts. They have prescribed some pesticides to get rid of the insects,” she said.