When growing broccoli it is very disappointing to find you crop infested with aphids or more commonly the white cabbage moth larvae or loppers those pale green grubs that always seems to find the best hiding places in your broccoli plants and much away happily all day and night. They can reduce a young plant to nothing over night or infest your broccoli heads by the hundreds if the plants are a cropping stage.
This can be very disheartening.
However with a few clever tactics we can diminish the damage to acceptable level.
1. Know thy enemy- white cabbage moth do not like cooler temperatures, in fact larvae eggs will not hatch or will die if temperatures get below 8 degrees which is why plants do well during the cooler months in temperate regions.
One of the easiest ways to protect plants, especially seedlings is to cover with some kind of exclusion barrier. I use a second hand gauze window screen folded in half length ways. I have tried netting and aviary mesh but these are too large and the adult moths can either fly in or lay eggs through the openings.
2. Confuse them – The adult white cabbage moths are almost blind and find braccicacia plants by smell and the distinctive shape of these plants. We need to try confusing the moths to prevent them finding our crop .Make sure you do not plant a whole row of Brassicaceae plants (cabbage family).This is like putting in an aircraft landing strip saying “here is the smorgasbord”. So confuse the adult moths by planting our broccoli plants in between other plants with different coloured foliage and different growth habit such as silver beet. We can further confuse them by planting them near strong smelling plants which can mask that distinctive cabbage smell of this family. I have had lots of success planting coriander plants around my broccoli.
3. Physcially remove them – Check plants every day and rub off eggs and hand pick the loppers off the plants to reduce damage. Make sure you check the underside of the leaf.
If all this doesn’t work but your plants still produce a crop with the head infested with loppers, try placing your heads in a sink of warm salty water for a few minutes this will kill all the loppers, and one good bang against the edge of the sink will dislodge the loppers from the head so it can then be cooked and eaten.
So just to go over this again:
• Protect plants with a Physical barrier.
• Confuse the adult moth by planting broccoli in between other plants, especially strong smelling herbs.
• Hand pick off any grubs everyday.
Check out my module on protecting your crops from pest and disease for more information.
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