Staff Writer
PRESQUE ISLE – Officials with the Maine Potato Board and the University of Maine Cooperative Extension recently presented a proposed potato late blight management strategy to their counterparts in New Brunswick at a meeting of the International Maine Maritime Potato Action Team, or IMMPACT. Potato late blight is caused by a fungus that overwinters in infected tubers, cull piles, and in infected volunteer plants. The 2008 epidemic cost growers in both Maine and New Brunswick millions of dollars in additional management costs and crop losses.
“This disease appears to be a recurrent problem which is largely preventable,” said Jim Dwyer, crops specialist with the University of Maine Cooperative Extension. “The potato industries of Maine and New Brunswick need to implement a comprehensive late blight disease management program which can prevent late blight in the future from becoming a major economic issue of the magnitude experienced in 2008.”
The plan is divided into two sections – imperative and critical program components. Imperative components include:
• Late blight seed testing. All potatoes planted in Maine and New Brunswick will be screened for potato late blight. The 400 tuber late blight testing protocol currently utilized by Maine will detect lot infections at approximately the 1 percent incidence level. This will prevent highly contaminated lots from being planted. This protocol should be instituted by both Maine and New Brunswick. It is hoped that potato processors will support this concept by including late blight testing within contracts in Maine and New Brunswick.
• Shipping point inspection of seed lots. All potato seed lots for export will be inspected at the point of shipment by the Maine Department of Agriculture in Maine or by the Canadian Food Inspection Agency in New Brunswick.
“Point of shipment inspection will be a recommended practice for local sales,” said Dwyer. “This will insure that potato seed lots being shipped are within acceptable tolerances.”
• Potato seed treatment. All potato seed lots prior to being planted in Maine and New Brunswick will be treated with a mancozeb-based potato seed treatment. Mancozeb has been shown to significantly reduce the incidence of potato late blight in plants in which the seed had been treated with mancozeb.
• Plant only certified seed. Only certified seed will be planted for any type of potato production in Maine and New Brunswick. Seed not having been certified by the appropriate certifying agency in Maine or New Brunswick will not be planted.
• Cull piles. All cull piles will be controlled by June 10 and rechecked on a regular basis. Cull piles pose a significant threat to the potato industries in Maine and New Brunswick.
• Sprayer calibration. All sprayers will be calibrated and regular maintenance performed prior to the pest control season.
Critical program components in the draft proposal include:
• Seed handling. If possible, growers should consider not precutting seed. Precutting seed under some conditions has led to spread of late blight within the seed lot. Growers may also want to consider using cymoxanil as part of their seed treatment strategy. Growers should only purchase late blight tested seed.
• Initiate fungicide applications via severity values.
• Build a good hill. Building a good hill helps to prevent late blight spores from washing onto tubers.
• Maintaining fungicide protective coverage on new growth.
• Regular field observations.
• Train employees for late blight detection.
• Additional or alternated chemical strategies. Some disease management situations may be enhanced by the addition or selection of a specialized chemistry. Some fungicide materials may enhance the grower’s ability to manage potato late blight depending upon matching the situation to the chemistry.
• Finding potato late blight. If potato late blight is found on your farm, report it so that other growers in the region can protect their crop and make any needed changes to their disease control strategy. Keeping late blight a secret is unfair and hurts everyone in the industry in both Maine and New Brunswick.
• Management of early season late blight.
• Management of mid season late blight finds.
• Management of late season late blight infections.
• Vine killing.
Dwyer said when the proposal was pitched to New Brunswick officials, they “agreed with everything.”
“Late blight is largely preventable,” he said, “especially if we work together.”
Donald Flannery, executive director of the Maine Potato Board, said he was surprised but encouraged with how quickly New Brunswick officials agreed to the proposed plan.
“It’s real simple,” he said, “we can’t let it slide anymore … growers have to report late blight. There’s no excuses, no shame. We’ve just got to do it.”
Another IMMPACT meeting will be held later this month to fine-tune the proposal.
