Agriculture Reference
In-Depth Information
different agents, including many that are not pathogens. For example, the
symptoms may be a result of mechanical injury, improperly applied fertilizers
and pesticides, or frost. Often the only way to pinpoint the cause is by find-
ing the signs
of the particular disease agent—such as fungal spores and myce-
lium or bacterial ooze. Many pathogenic disease agents, including some
fungi, bacteria, and nematodes, may have to be positively identified by an ex-
pert with access to sophisticated laboratory procedures. However, other
pathogenic diseases occur regularly on specific agricultural, ornamental, and
forestry plantings and the appearance of specific symptoms is enough to cor-
rectly identify the cause.
Figure 3.10
Life cycle of a disease-causing nematode.
C.
CONTROLLING PLANT DISEASE
At present, plant disease control measures are mainly preventive. Once a
plant or plant product is infected and symptoms appear, few control methods,
including pesticides are effective.
1.
In Greenhouses
In greenhouse production, the keys to prevention of plant disease buildup
are:
•
host resistance—use of disease-resistant varieties
