Brassica plants take a while to grow and it can be heart breaking to see the precious crop you have carefully nurtured gradually wilt from Cabbage Root Fly, or find the leaves stripped or shredded by Cabbage White Butterfly caterpillars overnight.
It is best to take preventive action early and a little time spent initially will save hours in the long run. We use simple biodegradeable Cabbage Root Fly collars around the base of each brassica plant to aid against Cabbage Root Fly and fine netting held up with bamboo canes and rubber ball connectors to prevent Cabbage White Butterflies laying their eggs on the plants. It is easy and cheap to put up and works very well for us.
Left image - shows Cabbage White Butterflies on the underneath of a cabbage leaf.
Top Right Image - Small Cabbage White Butterfly Caterpillars. Small green abour 2cms long.
Bottom Left Image - Large Cabbage White Butterfly Caterpillars. About 4cm long, hairy with yellow & black markings.
The Small variety lays her eggs from Feb-April and again in late summer whereas the Large Variety sows from April to May. So watch out for these little devils as they have most months covered through the growing season.
Cabbage Root Fly..
The flies of Cabbage Root Fly lay their eggs at the base of brassica stems and when the larvae hatch they feast away on the roots. This causes the plant to wilt and eventually die, sometimes in the early stages it can appear the plant is lacking water and it droops but failure to perk up when watered may show it has been eaten away and has nothing to support it in the ground. Unfortunately once wilt has started there is nothing to do but remove plant and put in council bin for them to take away or burn it...
'Prevention is better than cure' so net up your brassicas and pop a collar round their necks, it certainly saves a lot of time and heartache if pests attack.