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Cabbages and other brassicas can be extensively holed by caterpillar feeding by the end of summer.
Common names Large cabbage white, small cabbage white and cabbage mothScientific names Pieris brassicae, Pieris rapae, Mamestra brassicaePlants affected All brassicas, including cabbage, broccoli and Brussels sprout, some ornamental plants in the Cruciferae family, and nasturtiumsMain symptoms Holes in the leaves and presence of caterpillarsMost active May-October
Caterpillars are the larval stage of various butterflies and moths. There are several species of caterpillar that feed on cabbages, other brassicas and other plants including turnip, swede, horseradish and nasturtiums. Large cabbage white butterfly caterpillars are yellow and black with obvious hairs on their bodies (see picture above). Those of small cabbage white butterfly are pale green and covered in short, velvet-like hairs. Cabbage moth caterpillars are yellowish green or brownish green, with no obvious hairs on their bodies.
Holes are eaten in the outer leaves of all brassicas and damage may also be seen on the inner leaves of cabbages when the heart is cut through. Caterpillars and their excrement are often found on the plants.
There are three common caterpillar culprits:
All three may be present at the same time. Caterpillars of cabbage moth and small white butterfly are more damaging as they bore into the hearts of cabbages, whereas the yellow and black caterpillars of the large cabbage white stay mostly on outer leaves.
Spray with insecticides containing pyrethrum (considered organic e.g. Bug Clear Gun for Fruit and Veg, Defenders Bug Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Bayer Provado Ultimate Fruit & Vegetable Bug Killer) or Cypermethrin (e.g. Py Bug Killer). Pyrethrum has a one-day harvest interval and no restrictions on numbers of applications. For lambda-cyhalothrin, deltamethrin and Cypermethrin, read and follow the label instructions regarding each crop in general there is a seven-day harvest interval and a maximum of two applications can be made during the growing season (up to three applications for deltamethrin on cauliflower, broccoli, kale or Chinese cabbage)
Plants in flower should not be sprayed due to the danger to pollinating insects.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Biological control suppliers (Adobe Acrobat pdf document listing biological controls available to gardeners).
Brassica downy mildewBrassica white blisterCabbage moth (UK moths information)Cabbage whiteflyFlea beetles on brassicas and allied plantsInsect-proof meshLarge cabbage white (UK butterflies information)PigeonsSmall cabbage white (UK butterflies information)
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Mrs A Noble on 12/08/2014
I have my brassicas covered with netting but wonder if fleece would be better, would the plants struggle for light they are a bit drawn with the netting
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