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Photo by Brian Perchtel, Bugwood.org
Verticillium wilt
Healthy strawberry plant (left) and strawberry plant infected with verticillium wilt (right)
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Photo by S. T. Koike
Fusarium Wilt
An example of strawberry plants with Fusarium wilt that will eventually die.
Armed with a list of 13 crown and root diseases in strawberries, Siva Sabaratnam of the Ministry of Agriculture took the stage at the 2016 Pacific Agriculture Show in Abbotsford to discuss options for management of some of the most likely suspects to damage the berry crop. The information for growers was plentiful, but as is often the case, the old methods of scouting, knowing what’s in the field and following solid management practices are the best course of action.
“I’ve been seeing lots of issues in strawberries,” Sabaratnam said. “There are not enough tools out there to manage all of them.”
Two of the biggest concerns Sabaratnam has seen recently are black root rot and Fusarium Wilt.
Although similar in appearance and behavior to Verticillium Wilt, Fusarium Wilt is a different problem. Verticillium Wilt is generally associated with longer dry weather periods, so is more frequently seen in the interior of B.C. than in the Lower Mainland. Unfortunately, the 2015 berry season was an unusual one with just the kind of weather Verticillium Wilt enjoys. It led to stressed plants that were much more susceptible.
“Verticillium Wilt is not common in the Fraser Valley, but last year there were several cases,” Sabaratnam noted. “It can kill plants very, very quickly.”
Early symptom of both types of wilt are when the older leaves turn brown and die while the inner leaves are stunted. The entire plant will die soon after this phase is complete.
Unfortunately, there are no solutions for issues like Fusarium and Verticillium Wilt. Sabaratnam said it comes down to overall management practices to prevent certain challenges from cropping up in the first place.
“Soil diseases are really challenging,” he said.
He noted it’s very important for a grower to know what is happening in their field regardless of the issue.
“Confirmation of a pathogen by a reliable source is very important for selecting the right management tool,” he said.
This step is of the greatest importance when there is a possible solution such as in the case of black root rot caused primarily by Rhizoctonia fragariae; red stele root rot which can be identified by cutting across the root to see the discolouration; and crown rot which is caused by a number of organisms. Knowing what the issue is allows for the right treatment when one exists.
In order to set plants up for the best possible health, start with the soil before planting, advised Sabaratnam. He noted that pH is very important and recommended well-draining soil with a pH of 5.5 to 6.5. If the soil is infected he suggested a three-year crop rotation using mustard, cole crops or grains and to seek out disease-free cultivars in resistant or tolerant strawberry varieties.
“Also a root dip or furrow application of fungicide or a biological control at planting,” he added.
Earliglow is the only variety Sabaratnam noted as resistant to black root due to its wide range of causes.
Post planting management involves scouting for early detection and confirmation of disease, followed by fungicide application.
When the field is patchy with some plants struggling and others not, Sabaratnam feels that this is a case of nematode or drainage issues rather than root rot or other root diseases.
Fumigation and soil treatments were also mentioned including the potential of bio-fumigants from brassicas.
“Only three fumigants can really have an impact on soil pathogens, nematodes and weed seeds,” Sabaratnam said. “Basamid, Telone C-17 and Vapam.”
Sabaratnam also pointed to solarization, stating, “It is one of the good practices that is possible to do with other chemical applications.”
He recommended a .6 mm thick transparent polyethylene from mid-July to mid-September so soil temperatures reach 33 to 48 degrees Celsius.
Switiching to a different crop is often the best option for growers according to Sabaratnam.
While it is possible to control and stop some strawberry challenges, there is no stopping other issues. Prevention and management remain the key ingredients to a healthy field. ■