230 – II.3. BRASSICA CROPS (BRASSICA SPP.)
Phyllotreta spp. – Flea beetles
Flea beetles feed on spring-sown seedlings and in some years the second generation
may attack green foliage and pods in the fall. Several species of flea beetles occur in
different Brassica-growing areas of the world. Damage by these small beetles is
characterised by feeding holes in cotyledons and first true leaves and is most severe under
warm, dry conditions. Some Brassicaceous species (e.g. Sinapis alba, B. villosa) avoid
damage due to the presence of hairs (trichomes) on cotyledons, leaves and stems.
Attempts at biological control have not been successful, but research is underway to
develop B. napus plants expressing large numbers of trichomes as a means of defence
(Gruber et al., 2006). The primary control measure is insecticidal seed dressings.
Psylliodies chrysocephala – Cabbage stem flea beetle
This beetle is one of the most important pests of oilseed rape in Europe (Ekbom,
1995). Eggs, laid by adults in the soil at the base of seedlings, produce larvae that eat into
leaf stocks and later into the stem and base of the biennial plants, where the larvae
overwinter. Feeding damage results in weakened plants, resulting in reduced yield and
winter kill. Control is dependent upon insecticide sprays.
Ceutorhynchus spp. – Stem weevils
Both C. napi and C. quadridensare are important pests in continental Europe.
The weevils overwinter as adults and lay their eggs on leaf petioles of overwintered
Brassica plants. The larvae eat into and feed in the stems resulting in weakened and
broken plants. Insecticide sprays are used for control.
Aphid species
Three species of aphids can be of economic importance on Brassicaceous plants
(Ekbom, 1995). Lipaphis erysimi and Brevicoryne brassicae prefer Brassicaceae hosts
while Myzus persicae is polyphagous. On the Indian sub-continent L. erysimi is a very
serious pest capable of reducing oilseed mustard yields by 50%. In temperate zones,
B. brassicae is a common pest of vegetable Brassicas and occasionally of oilseed crops.
Suction feeding causes a direct loss of vigour and yield. M. persicae also causes indirect
damage as a vector of beet western yellow virus (BWYV) (Hill et al., 1991). Insecticide
sprays can be used for control but care must be taken not to kill beneficial insects present
during flowering.
Lepidoptera species
The lepidopteron pests occur sporadically and can have more than one generation per
year. The eggs are laid on the leaves where the larvae feed. In Canada, a second
generation of the diamondback moth (Plutella xylostella) may also attack pods of oilseed
rape. The diamondback and Pieris brassicae (the large cabbage white butterfly) are also
important pests of vegetable crops, where their leaf damage affects market value.
Chemical control is applied where populations warrant.
Meligethes species
Pollen beetles are important pests of both spring and winter oilseed rape in Europe.
Adult beetles move onto the crop from unrelated early flowering plants to feed on pollen
from open flowers and to lay eggs in unopened buds. The larvae emerge and eat the
