BY RICHARD DRASIMAKU
ARUA: TUESDAY, MAY 10, 2022
On a tall mango tree in his samba, Emmanuel Ajedra, an experienced fruit farmer and entrepreneur hangs a yellow tape.
It is a sheet laced with sticky gum on both sides incorporating pheromone as an insect lure to trap the male fruit flies.
“Pheromone is a sex attractant,” Ajedra says. “It stimulates the male fruit flies to think that there is a female fly eager for mating and combined with the yellow bright color of the sheet the insects get attracted and trapped by the gum. This leads to decline in the population of fruit flies by disrupting the reproduction cycle.”
Each sticky sheet costs between sh30,000 to sh50,000 in Uganda depending on where you purchase it from and is effective within a radius of 50 metres for at least three months.
Migratory fruit flies are a typical nightmare for fruit farmers in West Nile and Uganda leading to serious losses of fruits during the ripening stage.
The flies migrate from the North following the rift valley in search of humid climatic conditions, according to Ajedra’s assertions.
“There are certain climatic conditions that naturally curtail fruit flies from thriving. For example when it is too hot such as during dry season, fruit flies die and when it is too cold like when there is constant raining, the eggs will not hatch,” he said.
He added that the most important thing is for farmers to master the behavior of the fruit flies so as to control them.
Impregnated female fruit fly lays eggs on the warmer side of a ripening fruit and after few days the eggs hatch into maggots that feed on the fruit. When fully developed, the maggots flip out of the fruit onto the ground or leave the fruit when it falls down due to the damage.
They burrow their way into the ground to pupate before metamorphosing into adult fruit fly.
Ajedra says because mangoes are one of the most valuable fruits easily damaged by fruit flies, farmers can use alternative crops to divert them away from the mangoes if they are unable to acquire the yellow sheets.
He recommended guava saying that because guavas mature and ripen before mangoes, all the fruit flies will head for the guavas, leaving your mangoes free from destruction.
Another effective method would be using pheromone solution without the sticky traps but this would require government commitment due to the expenses involved in buying pheromone.
“Entire West Nile only needs 10 litres of pheromone for the whole year. This means one drum of 200 litres of pheromone is enough to serve the whole of Uganda for two years,” he added.
On the application at farmers’ level, Ajedra says what one needs is to make three small drops of pheromone on the ground, sit on your stool or chair armed with broom and wait for the male fruit flies to gather.
“Then after 30 minutes or an hour you hit them with the broom. You could kill 50 at a go and in one day you could kill over 200. Now that greatly reduces the population of fruit flies,” he explained.
He said alternatively farmers can apply pheromone on the lead of a bottle. You pour a small amount of insecticide inside the bottle so that when the male fruit flies enter the bottle, they fall to the bottom and get killed by the insecticide.
However Ajedra said there is a local tree species known as Albizia whose stem bark extracts can be used instead of insecticide to kill fruit flies.
During the dry season, people use the Albizia stem bark extracts for fishing in the drying swamps but they would be doing more good than harm if they were using it in pheromone laced bottles to kill the menacing fruit flies.
In the absence of all the above, farmers still have options such as burning dry grass based on the direction of the wind. The smoke from the burning grass would chase away the fruit flies from the garden but this practice must be repeated every two weeks because the fruit flies will keep coming back.
Ajedra suggested that other more subtle approaches like catching and sterilizing male fruit flies and then releasing them into the wild like the Israeli’s do would be applicable at an East African Community or African Union level since fruit fly menace knows no boundaries.