Cereals processing technology

24 Cereals processing technology
Despite the advances made in plant breeding and the adoption of appropriate
husbandry strategies, control of the main cereal pathogens by non-chemical
means are unlikely to provide total disease control. However, over reliance on
chemical control measures is equally unacceptable as it can lead to the overuse
of fungicides to the detriment of the environment and over time reduce the
fungicidal properties of the chemical itself. For example, populations of
Erysiphe graminis have developed resistance to some of the older mildewicides
which has resulted in these products losing their effectiveness in controlling
barley powdery mildew. The development of this kind of resistance has
promoted the development of more integrated disease control strategies, where
chemical control measures are combined with other measures to combat the
pathogen.
2.7 Pest control
Cereals are susceptible to a wide range of pests. Some such as rabbits, birds and
slugs attack a wide range of crop plants, whilst others such as wheat bulb fly, frit
fly and cereal cyst nematode are specific to cereals. Plants at the seedling stage
of growth are particularly vulnerable to pest damage when the green area of the
crop is small. The established plant during the phase of active tillering is better
able to compensate for moderate pest attacks, but crop damage can again be very
significant after ear emergence. For the majority of crops, pest attacks are less
threatening than disease outbreaks; therefore effective control strategies are
based on early identification of the pest, an assessment of the population relative
to the growth stage of the crop and the application of an appropriate pesticide.
The aim must be to forestall epidemics at an early stage when a worthwhile cost
benefit can be obtained from the control measure adopted.
Pest incidence in cereals varies according to crop species, soil type, farming
practice and the weather pattern. Unlike diseases, variety resistance to pests is
unlikely to be an important factor in the control strategy. An exception can be
found in winter oats where certain varieties show resistance to stem eelworm
(Dtylenchus dipsaci), whilst others are susceptible. Cereal cyst nematodes
(Heterodera avenae) are frequently found to attack spring sown cereals sown on
light, well drained soils often in areas where high quality malting barley is
grown.
Intensive cereal production systems have often resulted in an increase in the
incidence of pests, whilst the introduction of crops such as oilseed rape into the
rotation may increase the incidence of slugs in the following cereal crops. There
is some evidence that set-aside can provide a convenient green bridge which can
aid the survival of some pest species between non-consecutive crops. Wheat
bulb fly (Delia coarctata) may be more prevalent after set-aside if adults are
able to lay their eggs on bare soil in the summer.
Weather patterns are known to influence the scale of future pest problems, for
example high autumn rainfall preceding a mild winter is known to favour high