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Potato Pests Outlook 2017

Insect, disease outlook varied across the country.

By all accounts, the potato industry in Canada is a healthy one, and things are certainly looking up for 2017.

But to get there, potato growers know they must deal with the inevitable snags that can arise during the growing season. Namely: potato pests, such as insects and diseases.

Spud Smart reached out to some experts in the field in late June to determine what risks growers may face.

Prince Edward Island

Sebastian Ibarra, agri-environmental specialist with the Department of Agriculture and Fisheries says the main potato pest in P.E.I. in 2016 was wireworms (the larvae of click beetles), with the main problems caused by the larvae of Agriotes sputatorAgriotes lineatusAgritoes obscurus and potentially Hypnoidus abbreviates.

“It is likely that these pests will cause trouble again,” says Ibarra. “The reasons for this are one, there are multiple species of wireworm in P.E.I. causing trouble – some invasive, some endemic; two, the wireworms have long life cycles and it is difficult to monitor their presence before tuber damage is done – up to four years underground; and three, they have a generalist feeding behaviour capable of surviving in the rotation years by feeding in other crops such as grains.”

Ibarra adds that growers should also be on the lookout for Colorado potato beetle, aphids (buckthorn, cereal, foxglove, green peach and potato), European corn borer, tarnished plant bug and flea beetles.

New Brunswick

Khalil I. Al-Mughrabi, a pathologist with the Potato Development Centre, Department of Agriculture, Aquaculture and Fisheries, says the main potato insect pests in New Brunswick last year were Colorado potato beetle and aphids.

“European corn borer can be an issue in the northern part of New Brunswick, [while] wireworms were found in isolated fields in the potato belt region,” he says. “These will be the same insect pests that are expected to be a challenge this year and which the growers should be on the outlook for in 2017.”

Al-Mughrabi adds it is hard to eradicate insect pests and, therefore, management is the only option. “That is why they are expected to be a problem each year in potato fields.”

When it comes to diseases, Al-Mughrabi says late blight, early blight, pink rot and early dying (caused by both Verticillium, which is a fungus, and nematodes such as root lesion nematode) are diseases of potential impact on potato production in New Brunswick and elsewhere. Other diseases include Fusarium dry rot, silver scurf, bacterial soft rot and scab.

“Potato virus Y (PVY) can be an issue in potatoes but it is well managed in New Brunswick by managing and controlling the aphid vectors using insecticides and mineral oils,” he notes. “Growers plant virus-free (or low virus) seed potatoes which give them a clean start.”

PVY levels in potatoes produced in New Brunswick are extremely low due to the enforcement of the Mandatory PVY Laboratory Post Harvest Testing Program (a provincial program enforced under the Potato Disease Eradication Act) and setting the PVY level for seed potatoes destined for planting in New Brunswick to a maximum of four per cent (any seed with more than four per cent PVY is not permitted for planting in the province).

“We feel that volunteer potatoes might become an issue this growing season as we did not have a good snow over last winter which would have resulted in protecting the un-harvested seed potatoes from winter kill,” says Al-Mughrabi. “These may regrow and act as volunteers which should be managed during the growing season in order prevent them from becoming potential sources of inoculum.

Quebec

As of mid-June, Quebec potato growers in some areas have seen some seed rot mainly because of bad weather, but it was limited to few areas, according to Clément Lalancette, Directeur general with Les Producteurs de pommes de terre du Québec.

“However, the insect activity is increasing, especially with Colorado potato beetle,” he notes.

Other insects to watch out for include all the usual suspects, including flea beetles and leafhoppers, with the latter showing more activity in fields without insecticide applied at seeding.

Ontario

In Ontario, the main “pest” problem in 2016 was weeds. According to the Ontario Potato Board, weeds such as lamb’s quarters and pigweeds were very bad, mainly due to herbicide tolerance.

“The problem is expected to continue this year because herbicide tolerance is a genetic problem and not related to weather conditions,” notes Kevin Brubacher, general manager of the Ontario Potato Board.

For 2017, the very wet spring weather set the stage for diseases that thrive in those conditions, such as blackleg, aerial stem rot, while mould, grey mould “and, worst of all, late blight.

“Early blight and brown spot are endemic – they develop each year – and growers are well prepared to reduce their incidence in 2017,” says Brubacher.

The Ontario Potato IPM program, supported by the Ontario Potato Board, will provide resources to monitor the potato psyllid, the insect that transmits zebra chip. Zebra chip has not been found in Canada yet. (See sidebar.)

Manitoba

The main insect pest in Manitoba in 2016 was Colorado potato beetle (CPB) and, according to Tracy Shinners-Carnelley, director of research and quality enhancement with Peak of the Market, CPB will be a pest again this year with more farms seeing a reduction in performance with neonicotinoids.

“I don’t expect there will be complete failures, but the typical response is to see a reduction in the duration of control,” she says. “As a result, growers may be faced with making decisions on the need for foliar insecticides if the soil/seed-applied neonics ‘break down’ early. The other observation is that it is becoming more common to see all stages of CPB in the field at relatively the same time. This creates challenges for making decisions on foliar insecticide application timing.”

Vikram Bisht, plant pathologist with Manitoba Agriculture, says potato psyllids appear to be spreading north from the U.S. and could cause extensive economic damage. However, so far, none of the potato psyllids trapped were infective with bacteria.

“If non-infective with bacteria, low number of potato psyllids will not cause economic harm; however, larger numbers could cause feeding damage,” says Bisht. “Their populations will be monitored again in 2017, and if trapped they will be tested for presence of zebra chip bacteria.”

Shinners-Carnelley says growers should continue to monitor for insects like aphids, potato leafhopper and variegated cutworm. And both she and Bisht say European corn borer (ECB) has been causing problems in a limited number of fields.

On the disease side, Bisht says late blight was quite extensive in the province last year, staring in mid-July. Late blight disease is extremely dependent on favourable weather conditions (high humidity i.e. many rain days) and warm (but not hot) conditions. The affected tubers get culled out and often put in huge piles; these piles often allow plants to emerge and create the risk of late blight disease spreading under favourable conditions, such as strong winds with rain.

If the weather conditions are warm to hot this season, Verticillium wilt, an endemic problem in many potatoes, could become severe. Good irrigation management can reduce the losses from this disease, notes Bisht.

Alberta

In Alberta, no major potato insect problems were reported in 2016. According to Terence Hochstein, executive director with the Potato Growers of Alberta, they keep close tables on the aphid and potato psyllid monitoring programs for updates.

As for diseases, Hochstein says growers will be very vigilant on late blight in 2017.

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