II.3. BRASSICA CROPS (BRASSICA SPP.) – 231
stamens, causing buds to abort. The final instar larvae fall to the ground and pupate with
the new generation emerging in July into August (Ekbom, 1995). Pyrethroids are the most
commonly used chemical control.
Ceuthorhynchus assimilis – Seed pod weevil
This weevil occurs in both Europe and North America. It has one generation per year,
emerging from over-wintering sites in the late spring to feed on the crop. The main
damage is done to the seed pods. The adults make small holes in the pods to feed on the
seeds within and to lay eggs. The larvae eat their way out of the pods, drop to the ground
and pupate. The weevil has only recently invaded the oilseed rape growing area of
western Canada. Control is by chemical sprays.
Dasineura brassicae – Pod midge
The pod midge is a European pest that uses the small holes in the pods made by the
seed pod weevil for oviposition. The larvae eat the developing seed and cause the pods to
open, losing their seed. The larvae over-winter in cocoons in the soil, pupate in the late
spring and fly to the plants to oviposition, living only a few days (Ekbom, 1995). Early
spraying for the pollen beetle can provide control of pod midge and other pod pests.
Beneficial insects
The interaction between bees, both farmed and wild, and Brassica plants are mutually
beneficial. The bees aid fertilisation and receive nectar and pollen in return. Where
grown, oilseed rape and mustard provide productive bee pasture while the fertilising
activities of the bees are essential for the production of hybrid seed and tend to increase
seed yields of commercial fields.
Animal interaction
Succulent Brassica plants attract many foraging animals including rabbits, rodents
and deer to name a few. Winter oilseed rape is an important winter pasture for wild deer
and other animals. Ruminant animals, both wild and domestic, under certain
circumstances, can become ill from grazing kale or winter oilseed rape crops (Marquard
and Walker, 1995). The toxic compound responsible is dimethyldisulphide that arises
from the breakdown products of glucosinolates and S-methylcysteine sulphoxide
(SMCO), also known as the kale anaemia factor (Maxwell, 1981). Birds often feed on
fall-germinating seedlings and on the developing seed in the pod.
Soil microbial interaction
The genetic makeup of crop plants can influence the composition of the soil microbial
community in which they grow. However, the interaction between plants and their
residues with the soil microflora is not well understood (Dunfield and Germida, 2004).
The soil microbial communities associated with the growing of conventional spring
oilseed rape (both B. napus and B. rapa) and transgenic HR B. napus were investigated in
western Canada plot trials. The soil microflora in the plots of the glyphosate resistant
variety Quest differed significantly from that found in both conventional and transgenic
glufosinate resistant varieties, particularly at the flowering stage. However, although the
microbial diversity was altered, the effects varied by test site and plant growth stage.
In addition, the change in the microbial community was temporary as no differences were