I - --ii

30 24 18 12 6
Temperature (°C)
t6
3s3
9
8
72
Figure 3. Ascochyta disease intensity in relation to temperature and wetness duration during the
infection period.
temperature data during rain periods or recorded wetness periods, when completed,
might provide further evidence that a slow infection was possible in February
but the epiphytotic did not spread before mid-March. Based on these findings it
seems possible to identify locations of specific high or low disease incidence
probability.
Role of Infected Pl'int Debris in Disease Initiation
In the 1980-81 season, soil was infested in five microplots within an isolated field
plot and disease incidence and spread was then monitored on a single-plant basis.
Figure 5 shows the trend of disease development between February 25 and
March 25. Obviously, primary infection occurred only in one microplot and only
11 plants wcre diseased by February 25. Though all seeds were hand selected for
freedom of Ascochyta sym.ptoms, it cannot be excluded that some seeds passed
through as symptomless carriers. Thus, one may conclude that the role of plant
debris for disease initiation is very limited, as massive soil infestation can only
occur on highly infected fields, where chickpeas are not likely to follow again in
39