Wearing a grim face, Andres Savella looks around his 1,000-square meter onion field. Disheartened, he tells himself that there’s no solution to his problem. A certain kind of insect feeds inside the onion leaves, and no amount of insecticide can kill it.
The problem of this 62-year-old farmer is the onion leafminer, a yellowish insect with a black spot on its back is suspected to have been accidentally introduced in the Philippines through imported cut flowers, according to Dong Arida, supervising research specialist at the Philippine Rice Research Institute (PhilRice). The insect was first collected in 1997 from onion fields in Central Luzon by Dr. Sonja J. Scheffer of the Agriculture Research Service, US Department of Agriculture. Based on laboratory-reared flies that she collected, Scheffer identified the leafminer as Liriomyza trifolii (Burgess).
The larvae of the insect eat the inner portion of the leaves, and by the time the mines are noticed, the leafminer larvae are already well protected by the leaf cuticle from insecticidal spray.