Abstract
The fungus
Alternaria eichhorniae
isolate #5 (Ae5) is being developed as a mycoherbicide agent for controlling waterhyacinth(
Eichhornia crassipes
) in Egypt. Inoculum concentrations above 10% (mycelial wet weight) were all equally e
V
ective in controllingwaterhyacinth at 100% level (weed kill). Fresher mycelial inoculum (4 weeks old) was more virulent than older inoculum (9 or 16weeks old). Applications of Ae5 in an aqueous carrier or in nine di
V
erent oil emulsions were evaluated for the biocontrol of waterhy-acinth, without a post-treatment dew period, under natural outdoor conditions. The oil emulsions were developed to provide mois-ture and to retard evaporation from the applied fungal inoculum so that the fungal propagules could germinate and infect the weedunder relatively dry conditions. All of the invert and oil emulsion formulations induced higher levels of disease on waterhyacinthplants than the aqueous formulation under dew-free conditions. Reducing the oil content in the Ae5 emulsion formulation from 30to 5% had no e
V
ect on the formulation’s e
Y
cacy against waterhyacinth. When applied in the winter under natural conditions inEgypt, Ae5 formulated in cottonseed oil emulsion caused 100% control of waterhyacinth in outdoor
W
eld plots 7–13 weeks afterapplication. Thus, the results con
W
rm the utility and feasibility of oil emulsions as formulating materials that promote the bioherbi-cide’s activity in the absence of dew.
2004 Elsevier Inc. All rights reserved.