Perimeter spraying can sometimes reduce the rate at which aphids progress into the crop. Pirimor is effective against aphids whilst still being safe for bees. Slugs Slugs become active with the break of the season. Slugs surviving from the previous season do most damage, and eat two or three times their weight daily. The paddocks after pasture in a high rainfall zone are prone to slug damage.
Granules work best on a smooth flat surface with low stubble residue.
In years when large Heliothis larvae are present as the crop is maturing, serious damage may occur. Larvae over 15 mm may enter pods and consume the seed. It is essential to sample crops using a sweep net to determine grub numbers because in a dense canola crop the grubs are very difficult to detect. Thresholds for heliothis are also lower than those for DBM, see table 10. DBM is a major vegetable pest over the warmer months and is difficult to control as it breeds prolifically and develops resistant to insecticides quickly.