Ontario field study showed copper can make disease pressure worse
CHATHAM-KENT, Ont. — North American tomato growers have been questioning the efficiency of copper-based bacterial disease control for years.
It turns out their skepticism is warranted.
“Not only did the copper do nothing in our trials, sometimes the disease pressure was worse,” Mary Hausbeck, a vegetable disease specialist at Michigan State University, told the recent Tomato Day.
“We are rethinking this control strategy. I am not recommending copper for the field any more.”
Cheryl Trueman, a vegetable pathologist with the University of Guelph who has been involved with Ontario trials for the past five years, has come to similar conclusions.
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Trueman said copper is helpful when blended with Actigard, which stimulates plant defences. However, the treatment may not provide an economic yield benefit because it only suppresses disease and is expensive.
Copper appears to have already fallen out of favour among Ontario growers. Trueman said a large percentage of those who responded to a survey last year reported they did not use the material, apparently with little ill effect.
The situation leaves Ontario tomato growers who supply three large processing plants and a handful of smaller companies with little in their bacterial disease control arsenal beyond sanitary protocols and measures taken to contain spread of the problem.
Three bacterial diseases affect tomatoes: spot, speck and canker. The main avenue of infection for field growers is from greenhouse-produced seedlings.
Hausbeck said most tomato seed is produced overseas because of the high cost of hand pollination. Many of the seed producers are farm families working with small acreages.
North America producers use seed treatments and take other steps in the greenhouse and field, but the effectiveness of those measures is limited.
Infected plants combined with humidity, temperatures and excessive rainfall have occasionally led to 100 percent losses.
“The biggest disaster that can happen is when the plants leave the greenhouse with a huge load of bacteria,” Hausbeck said.
Growers had more welcome news from Phil Richards, a director with the Ontario Processing Vegetable Growers, which negotiates prices with Ontario’s processors.
This year growers delivering to the Conagra Foods at Dresden and Sun-Brite Foods near Leamington will receive a 6.5 percent increase for all categories of production: whole pack, juice and paste.
The same increases are likely to apply to smaller processors, but Highbury Canco, which took over the old H.J. Heinz Company plant at Leamington, has yet to settle.
Richards said Highbury Canco is pushing for a fourth category, which would include a $12 a ton discount for tomatoes grown for paste destined for resale.
The idea may help compete in the export market, he added.
Ontario tomato growers also received significant price increases last year, which were as much as $120 per ton depending on the category.
Ontario growers typically produce 40 to 50 tons per acre, which is comparable to those in California, the state that dominates the North American tomato industry.
Contracted tonnage is also likely to be up by 40,000 to 50,000 tons ,which translates into another 1,000 acres, Richards said.
Acreage was down last year be-cause of Heinz’s announcement that it would end its Leamington operation. Highbury Canco scaled down production at the site.
