PhilRice supervising science research specialist Dong Arida and his team found out in a three-year study that weekly removal of damaged eggplant fruits and shoots, coupled with less insecticide application, produces more fruits without the worms.
Results of the study showed a net incremental benefit of P128,000 a hectare with the application of this technique. In sharp contrast, the net incremental benefit was reduced to only P60,000 a hectare if removal was done every two weeks.
Arida said the fruit and shoot borer is the most important insect pest of eggplant in South and Southeast Asia. Its larvae can be observed in the field as early as three weeks after transplanting.
Newly hatched worms bore through the shoots and apical buds of the plants in search for food. This activity of the insect causes the shoots to wilt, eventually resulting in reduced fruits of the plants because of reduced number of fruiting branches.
At the fruiting stage, the worms bore through the flowers and enter the fruits just below the calyx. Damaged fruits are not marketable because these look ugly, crooked, and taste bitter even when cooked. Their size is abnormal. The fruits have entry and exit holes made by the borer, which often partially heal and close as the fruits grow, making the fruits look healthy from the outside.
The butterfly of the adult borer is generally brown with white wings containing brown to brownish orange markings. They fly low, are active at night, and prefer to stay at the lower surface of the leaves during the daytime. When at rest, their wings spread outward.
The female butterfly is generally bigger than the male. The female lays its eggs singly on the leaves and buds. Newly laid eggs are creamy white and then turn orange when about to hatch. The eggs hatch in about four days.
Filipino farmers usually spray 56 times during a cropping season to control this insect pest. The frequency of insecticide application increases as soon as the plants start to bear fruits due to the highly visible damage in the shoots and fruits.
This tremendous misuse of pesticides results in higher production costs, longer exposure of farmers and consumers to pesticides, and development of insect resistance to pesticides.
With weekly removal of damaged fruits and shoots, pesticide application is reduced from 56 times for a five-month crop to none at all, Arida said. Thus, this new strategy will surely have tremendous impact on the environment.
The researchers also noted that weekly removal of damaged fruits and shoots is comparable to insecticide application every three weeks. They said that if farmers insist in using insecticides, they would do well to spray only six times in a cropping season and save themselves from the cost and danger of spraying too much insecticide. – Sosimo Ma. Pablico