Cabbage white
Pieris brassicae
Role in the garden
The green-yellow caterpillars quickly devour the leaves of cabbages and other Brassicaceae, sometimes down to the veins.
Practical guide
Where to find them
Cabbages, turnips and nasturtiums mainly, and more broadly the whole Brassicaceae family.
Prevention
Set up an insect net from the start of the crop to stop the females laying on the leaves.
Early signs
Holes in the leaves; plants can be reduced to their stems in a few days. Risk of confusion with slug damage: look closely to spot the green caterpillars or the clusters of yellow eggs under the leaves.
Action / control
Gather the caterpillars and the egg clusters you spot every day. Release trichogrammas for preventive parasitism. Bacillus thuringiensis as a last resort.
Sources
- RHS (Royal Horticultural Society) : Cabbage caterpillars (rhs.org.uk/biodiversity/cabbage-caterpillars)
- Parker, J.E., Snyder, W.E., Hamilton, G.C. & Rodriguez-Saona, C. (2013). Companion planting and insect pest control. In Weed and Pest Control: Conventional and New Challenges. InTech.
- UC IPM (université de Californie) : Less Toxic Insecticides (ipm.ucanr.edu)
Favourite plants / resources
Related plant entries
Radish
A brassica with an ultra-short cycle (3-4 weeks in spring), the best row-marker for slow sowings (carrot, parsnip). Lets you occupy a space while waiting for the main crop. To be avoided before cabbage (same family, common clubroot).
Cabbage
A brassica with a long rotation: 4 to 5 years between two brassicas, 8 to 10 years after a clubroot attack (Réussir Fruits & Légumes, 2022), whose spores (Plasmodiophora brassicae) can contaminate the soil for up to 20 years (RHS). Very greedy (nitrogen, calcium, water). To be planted after a legume to benefit from the nitrogen.
Turnip
A fast-growing root brassica (5 to 8 weeks): ideal as an intercrop between two longer crops, or in succession after peas to use the fixed nitrogen.
Brussels sprouts
A late long-season brassica: occupies the soil from April to February. An excellent autumn and winter transition plant, to be earthed up for stability. Pinching out the head ('topping') in late August encourages the sprouts to swell evenly. Frost converts starch into sugars: the sweetest harvest is after the first frosts.