Controlling rice black bug

The rice black bug may be considered one of the most difficult rice pests to control, but this should not be much of a concern in transplanted rice if these parasites are properly managed, results of studies conducted in Agusan indicated. 

This pest infests the rice plants at all growth stages, most especially from maximum tillering to ripening stage.

In studies led by PhilRice crop protection specialist Eliseo H. Batay-an, it was observed that soon after the black bug egg mass population reaches its peak, egg parasitism subsequently reaches its peak also. This indicates that the pest cannot do much damage if much care is done to protect the parasites from chemical sprays.

An experiment was conducted in farmers’ fields in Kitcharao, Agusan del Norte and Esperanza, Agusan del Sur, using NSIC Rc122 and PSB Rc82 as the test varieties since these are among the popular varieties in the Caraga region.

In direct-seeded rice in Esperanza, the rice black bug egg mass population started to increase at eight weeks after seeding and reached its peak three weeks later. The rice black bug nymphs started to colonize the rice plants at nine weeks after seeding and then peaked two weeks later. Similarly, the population of adult black bugs declined from three until seven weeks after seeding, started to increase again after one week, and reached its peak two weeks later.

In transplanted rice, the egg mass population picked up at three weeks after transplanting, then declined until four weeks later, peaked at nine weeks after transplanting, and dramatically decreased thereafter. The population of the nymphs, on the other hand, had four peaks: three, five, nine, and 11 weeks after transplanting, which was the highest peak. The adult population peaked at three, nine, and 11 weeks after transplanting.

However, rice black bug eggs in direct-seeded rice started to be parasitized at nine weeks after seeding. The degree of parasitism gradually increased and reached its peak two weeks later with 18.26 percent parasitism. On the other hand, egg parasitism in transplanted rice had three peaks: five, eight, and 10 weeks after transplanting. 

The results indicated lower egg parasitism in direct-seed rice than transplanted rice. Batay-an said this could be due to the poor searching ability of the adult parasite in locating their host (the eggs) in direct-seeded rice. He added that in transplanted rice, the parasite could easily transfer from one hill to another, leading to higher efficiency in finding their host. –  Sosimo Ma. Pablico