- Trichogramma japonicum.
Release T. japonicum 30 days after transplanting and once a week thereafter. Place .25 grams eggs in a plastic cup. Hang cups on/from bamboo or wooden stakes in the rice field at a distance of 20 meters in between each cup. Look for parasitized eggs to make sure that the wasps are working. T. japonicum controls the population of stem borer by parasitizing the eggs. The parasitized eggs turn black in color. Development of the larvae and pupae takes place inside the egg host. Life cycle is 3- 5 days. (DA, 2002). Ask for assistance from the local agriculturist office for the procurement of T. japonicum
- Eulophid wasps are naturally found in wet and dry rice fields. Eulophid wasp parasitizes stem borer eggs and pupae. A female wasp lays one egg in each stem borer egg. Eggs take 1- 2 days to hatch. Development of the larva takes place inside the egg host. Once the egg is consumed, the larva moves out from the egg and locates another egg host. Each larva needs three eggs to complete its development. Adult appears 1- 2 days later. Eulophid wasp can produce 10 to 60 new wasps (IRRI, 2001).
- Ladybird beetle
- Weaver ant
rice stem borer. Select 10 hills randomly. Walk diagonally across the field. Count the number of dead hearts, larvae, adults, and egg masses per hill. Do nothing to control the pests when there is an abundance of beneficial insects in the paddy. The economic threshold levels
are: 10% of the hills are affected
and 4 egg masses are found per hill during booting stage. However, when damage is seen, it is usually too late to benefit from using control measures. It is impossible to predict the level of damage at the reproductive stage based on the level of damage at vegetative stage. Rice plants can compensate up to 1 tiller per hill damaged, if other management practices are adequately implemented (Reissig; et. al., 1986: pp. 128-140).
Management and cultural practices
- Grow healthy rice plants. Transplant only healthy rice seedlings. Remove and destroy seedlings infested by borers and seedlings bearing egg masses. Healthy plants can compensate for any stem borer damage like deadhearts and whiteheads (IRRI, 2003).
- Plant resistant and early maturing rice varieties. The stem borer completes fewer generations in early maturing varieties. Improved semi-dwarf varieties are generally more resistant to stem borers than the tall traditional ones.
- Harvest at the very base of the plants. This will remove most larvae of all stem borer species.
- Plow the field. Then flood it. These are 2 most effective ways to destroy the stem borers remaining in the stubble. Most of the stem borer population remains in the stubble between crops.
- Good field sanitation is essential in stem borer management. Let water buffalos or carabaos and cows feed and graze on the straws and stubbles, then burn whatever plant debris remains.