Issue 596 - April 28, 2015

​This time of year, I receive many questions about what fungicides to apply. I get fewer questions about how to apply fungicides. Below, I will try to address how to apply fungicides. Many years ago, I was told that to successfully use fungicides on vegetables, one must use high spray pressures and hollow cone nozzles. However, I had trouble finding any research on this topic, just rumors. So, I did my own research. Dennis Nowaskie, Superintendant at the Southwest Purdue Agricultural Center (SWPAC) built a single row sprayer that could be used to vary nozzle types between flat fans and hollow cones and spray pressures from 30 to 150 PSI. We used the sprayer to conduct experiments on Alternaria leaf blight of muskmelon during three years of field tests. The fungicide we used to try to manage this disease was the contact product chlorothalonil (trade names include Agronil®, Bravo®, Echo® and Terranil®). Phillip Harmon, now[Read More…]

​Since the season of applying fungicides to vegetable crops has arrived, below I have listed 10 rules that will help vegetable growers apply fungicides effectively and safely. Apply fungicides prior to the development of disease. Although many fungicides have systemic (“kick back”) action they will not completely eradicate diseases after they have started. And by the time a single disease lesion is observed in the field, many more lesions too small to observe are already working at your crop.  Most systemic fungicides move less than an inch toward the tip of the plant or may just move from the upper to the lower side of the leaf.  Use shorter spray intervals during weather conducive to plant disease. Each plant disease has its own “personality” and thus prefers different weather. However, most plant diseases require leaf wetness. Therefore, during periods of rain and heavy dews, more frequent fungicide applications are a[Read More…]