In May of this year I wrote my original post in this trial, if you haven’t read it, see here: The Keep Out Cabbage White Butterfly Cage Trial.

I’m now writing the update in August for this trial and it’s been an interesting few months. The cabbage white butterflies have been active in the garden since July but not really taken much interest in the cage until a sudden surge of growth in the Brussels sprouts meant that temporarily their leaves were bulging out the side of the netting and the butterflies were like a moth to a flame, exploiting my error in not being quick enough to maintain the cage.

Cabbage White Butterflies 1 vs Me 0

This error was small and caused no damage, I.e no butterfly eggs have been seen on the leaves as I have opened the netting, removed two plants which led to overcrowding and trimmed the leaves back on the plant where the leaves hit the side of the netting.

Whilst I was in the cage I noticed the leaves had some white rings on the underside and white flies where fluttering around, this is cabbage whitefly. It is a little annoying pest but doesn’t affect the crops and can be cut off or squished with your fingers to remove them (with gloves on).

I also shook the plant to check for caterpillars, they will drop to the ground so you can remove them, there was only a few.

To prevent the leaves from touching the netting again, I have devised a cane structure to hold back the plants and I have also mounded up the plants with earth to keep them grounded and secure.

Hopefully the plants can survive with fewer leaves, this is all an experiment to see if I can actually get some Brussels sprouts at the end. My husband is still hopeful that he might get some from our garden!

I’ve been doing my research on the cabbage white butterfly to see what they are capable of and what is available to eradicate them. I will discuss all options however I follow the organic gardening route and don’t use any chemicals hence this is why this trial came about to see if netting worked as a preventative measure.

All About the Cabbage White Butterfly

The Problem

There are two types of cabbage white butterfly in the UK, one smaller than the other but both given half a chance could devastate any brassicas related crop like kale, cabbage, Brussels sprouts, cauliflower, broccoli, swede and turnip.

The problem is not the butterflies themselves, the problem is the eggs they try to lay inside the mesh or netting on your brassica leaves. These yellow eggs in clusters on the underside of brassicas leaves turn into very hungry caterpillars who then munch everything in sight so your plants will just look like a stalk.

Yellow eggs = Hungry caterpillars within days

If you see small yellow eggs in clusters on the underside of brassica leaves, remove them straight away. Squishing with fingers in gloves is the best method or remove the part of the leaf they are on. If you don’t do this within days then it’s game over for your brassicas.

Solutions

• Netting or mesh covered brassicas, make sure no leaf comes in contact with side of your netting or when you life your mesh/netting no butterfly gets trapped inside.
• Check underside of brassica leaves regularly for yellow eggs and remove them.
• Remove the caterpillars by hand. Shake the plant to see if anymore drop onto the soil.
• If the caterpillar is green, it has come from the smaller cabbage white butterfly and these tend to bore into the heart of any young leaves I.e. at the top of the Brussels sprout plant or into the heart of the cabbage.
• If you see black hairy caterpillars, this is from the larger cabbage white butterfly and can somewhat be controlled by nematodes if you are quick enough to reaction to the breakout.
• Nematodes for Caterpillars – Nemasys do a fruit and vegetable protection of nematodes for when the caterpillars have hatched. You may need to apply this several times for a resolution.
• Bacillus thuringiensis is a naturally occurring bacterium but can be bought in a spray version, it kills the caterpillars only and not other insects when sprayed all over the leaves.
• Avoid bright coloured flowers near brassica cages – avoid growing brightly coloured flowers in the area of your brassica cage as it attracts the cabbage white butterfly to this area. This would include marigolds which I planted near the cage, oops.
• Try growing nasturtiums away from your cage to lure the butterflies to lay their eggs on these plants and not near your brassicas. The particularly like the bright orange and red varieties.

I’m concluding at mid way through the growing season:

Does the netting for cabbage white butterflies work by keeping them out?

Yes if you keep checking that your leaves don’t hit the sides of the netting and keep checking the underside of leaves in the cage.

Stay tuned to see if I actually get Brussels sprouts this year in October to December.