Native parasitic wasps
Twenty days after transplanting, monitor the plants by looking for the window-like leaf damage created by the early larval instars. Do this twice a week in order to detect the larvae before they move into the center of the growing plant.
If the percentage of the plants infested with the larvae exceeds 15%, it becomes more efficient to do control measure on the entire field.
Cultural and management practices
- Remove by hand the egg masses and larvae during the monitoring activity. For example, it takes more or less than 3 hours/2000 plants/person to monitor and remove the larvae at the same time.
- Do spot spraying with Bt with visible larvae 40 days after transplanting. Once the larvae are inside the plants, spraying is not effective.
- Plant Indian mustard (Brassica juncea) as a trap crop every 15 rows of cabbage to attract most Cabbagehead caterpillar (CHC) moths and some Diamondback moth (DBM) adults (Parker, et. al., 1995). Planting of trap crops can be done 12 days before transplanting and/or 25 days after transplanting or both. Mustard attracts almost the entire population of CHC and 80% DBM (CABI, 2000). Remove the trap crops
when these are heavily infested with the pests or else these pests will transfer to the main crop.