OFA Bulletin May/June 2010 : Page 2

OFA Mission Statement To support and advance professional horticulture. OFA – an Association of Horticulture Professionals 2130 Stella Court Columbus, Ohio 43215-1033 USA 614-487-1117 Fax: 614-487-1216 ofa@ofa.org www.ofa.org OFA Bulletin May/June 2010 NUMBER 921 Editorial Staff Stephen A. Carver, Ph.D. Laura Kunkle Editor Contributors Janna Beckerman Bridget Behe Steve Carver Andrew Chow Barbara Crowhurst Julie Fox Kevin Heinz Bob Humm Rob Leeds Bill McCurry Julie Smetzer Grower The “Real” Cost of Fungicides M by Janna Beckerman y grandmother introduced me to the phrase, “Penny wise and pound foolish.” It describes a trap that many people fall into in various aspects of their lives. However, in plant disease control, it is one trap that can be readily avoided. When managing plant disease, it is important to remember that the quoted cost of the fungicide is probably the least economically important piece of information that you as a grower are confronted with. This last fall/winter was a disastrous one for many poinsettia producers. Cooler temperatures can be managed in a greenhouse, but the lack of sun is less manageable. With less sun, plants transpire less, resulting in wet media. As a result, many growers had tremendous outbreaks of Pythium root rot. In choosing a control, especially for something as explosive as Pythium sp., the first concern should be choosing the most effective fungicide. There are many possibilities. Unfortunately, for one grower, he was also battling mefenoxam- resistant Pythium, eliminating Subdue Maxx as a control option. This left us with the following choices: Aliette, Fenstop, Segway DF, and Truban 25EC/30WP. We’re all familiar with the phrase, “You Published Bimonthly Copyright© OFA 2010. Permission is hereby given to reprint articles appearing in this OFA Bulletin provided the following reference statement appears with the reprinted article: “Reprinted from the OFA Bulletin, (phone: 614-487-1117) May/June 2010, Number 921.” No endorsement is intended for products mentioned in this OFA Bulletin, nor is criticism meant for products not mentioned. The authors and OFA assume no liability resulting from the use of practices printed in this OFA Bulletin. 2 do the math.” But how many of us actually take the time do so? And although the math is simple, coming up with the time is the problem! Table 1 shows 35 of the most commonly used greenhouse fungicides, the cost of each product for the average small grower (please note all footnotes below), the recommended label rate, the recommended application interval, cost per application, and the most important piece of information: the per month use cost. All too often, we don’t do the math. This simple (but tedious and time-consuming) math takes into account the cost per treatment, the rate, and the number of applications. When evaluated this way, an “expensive” product that is used at a low rate once per month (or every other week) may be more cost effective than using a high rate of a “less expensive” fungicide on a weekly basis. At first, the above-referenced grower blanched at the recommendation of one of the more expensive fungicides, even when faced with loss of his entire crop. I walked him through the cost breakdown, in addition to the cost of losing his entire crop. He decided to proceed using the “Cadillac” fungicide, rotated with an equally effective fungicide with a different mode of action. We also began the process of correcting some of the underlying cultural problems that predisposed the crop to Pythium root rot by removing severely infected plants, improving drainage issues, and preventing the accumulation of standing water. This reduced the spread of pathogen, allowed the fungicides to work better by primarily preventing disease in new plants, and minimized the fungicide’s role as a curative in a few lightly symptomatic or asymptomatic plants. The end results were a very happy grower and an excellent poinsettia crop. Another area where a deeper consideration of costs should occur is when you are faced with a mixed infection – like downy mildew and black spot of florist’s roses, or Phytophthora blight and Alternaria leaf spot on Catharanthus (Vinca). There are many fungicides with excellent activity against only one of these pathogens; however, using a strobilurin fungicide (Pageant, Cygnus, Compass, or Heritage) would be effective against both pathogens as well as offering some curative/eradicant ability (cure existing infections while protecting against new ones). Tank mixing or alternating with mancozeb would also provide control for both diseases, making it an excellent rotation partner. Hopefully, Table 1 will assist you by providing the cost-benefit and cost-per- month rates and also by showing growers O F A B u l l e t i n

Previous Page  Next Page

Publication List