No description available.

In a survey conducted in Zimbabwe in 1993, waterhyacinth was present in seven out of the eight provinces. No control measures were imposed on 35% of the infested dams and 61% of the infested rivers, while in 47% of the infested dams and 11% of the infested rivers control of waterhyacinth was being attempted with a combination of 2,4-D and mechanical control methods. The population of Neochetina eichhorniae and N. bruchi declined during the period 1993 to 1995 in the Hunyani River system. Several fungi were isolated from diseased waterhyacinth, and Fusarium moniliforme (isolate 2ex 12), F. solani (isolates 5a ex25 and 2a3), and F. pallidoroseum (isolate 3ex1) were found to be the most pathogenic. Large numbers of viable conidia were produced in shake-flask liquid fermentation with modified Richard's medium and in solid fermentation with food grains. Conidia production in straw was poor with the exception of waterhyacinth straw. Host range studies conducted in pots and in the field indicated that Commelina benghalensis was moderately susceptible to both isolates of F. solani in the field, while Setaria verticilata grown in pots was moderately susceptible to isolate 2a3. Brassica rapa and Crotalaria juncea grown in pots were moderately susceptible to F. moniliforme but they showed no infection in the field. Fifty-nine additional plant species of ecological and agricultural importance were not susceptible to the Fusarium species. When F. solani, F. pallidoroseum and Neochetina spp. were used individually in ponds, they did not control waterhyacinth. When the fungi were combined with Neochetina spp., the area covered by waterhyacinth and the volume of waterhyacinth were significantly reduced.