Pests
While there are no "silver bullets" for combating wireworm, with ongoing research, Island farmers do have more options.

Dr. Christine Noronha, of Agriculture and Agri-Food Canada, has unveiled an effective wireworm trap. "The trap is a very simple light trap, called the NELT. It uses a solar powered light source to attract the adults of wireworms, click beetles. The beetles walk to the light and fall into a cup buried in the ground under the light,"  Noronha explained.

This is the first trap that catches female click beetles. Trapping the egg-laying females will gradually help reduce the wireworm population in the field. For the full story, click here
Published in Crop Protection
For the first time, evidence of the zebra chip pathogen has been found in potato fields in southern Alberta.

An infected potato psyllid insect carries the Lso (Candidatus Liberibacter solanacearum) pathogen that can cause zebra chip disease in potato crops.

Zebra chip has affected potato crops in the U.S., Mexico and New Zealand and caused millions of dollars in losses. Potatoes with zebra chip develop unsightly dark lines when fried, making affected potatoes unsellable.

The first detection of Lso came from sampling cards collected at one site south of Highway 3, near Lethbridge, Alta. For the full story, click here
Published in Diseases
A $25,000 Ignition Fund grant in 2016 helped Deep Roots Distillery owner Mike Beamish create a new line of buckwheat whiskey, which could have added benefit for area potato growers. 

"Buckwheat is beneficial to potato farmers especially as a rotation crop that aids in soil health and reduces certain pests – and as it happens, it makes a very fine whiskey," said Beamish, who is hosting the 2017 Ignition Fund award ceremony at Deep Roots Distillery. To read the full story, click here.
Published in News
The Japanese government has lifted an 11-year-old ban on importing fresh Idaho chipping potatoes, officials of the Idaho Potato Commission announced earlier in September.

Japan's Ministry of Agriculture, Forestry and Fisheries imposed a ban on importing all U.S. chipping potatoes in April 2006 in response to the discovery of a quarantined pest, the pale cyst nematode, in a small area of Eastern Idaho.

Trade was restored with other U.S. chipping potato states about a year later, but restrictions on Idaho were left in place.

This spring, IPC officials said Japanese chip makers experienced a shortage following a poor domestic harvest and had to stop selling some products. Japan will continue to exclude any Idaho chipping potatoes from Bonneville and Bingham counties, which encompass the PCN quarantine area. READ MORE
Published in News

Researchers are hoping Canadian potato growers will soon be able to use an innovative approach to control wireworms. This method uses just a few grams of insecticide per hectare applied to cereal seeds that are planted along with untreated seed potatoes. It provides very good wireworm control for the whole growing season, with a lower environmental risk than currently available insecticide options.

Published in Crop Protection

Just because black cutworms don’t overwinter in Canada doesn’t mean they aren’t a threat to potato crops. The insects spend their winters in the southern United States but travel north on low-level jet streams and, once they cross the border into Canada, they look for a tasty food source. Black cutworm moths prefer some of the weeds that grow in and around fields and, while potatoes are not their favourite food, they will adapt and can wreak havoc on an unmonitored field.

A researcher at the University of Minnesota says the cutworms’ new interest in potatoes could be the result of a change in potential host plants. If the moth’s desired weed is being well controlled in a field, it will eat what is available where the wind sets it down.

“Black cutworm moths are active flyers,” explains Ian MacRae, the extension entomologist at the university’s Crookston research station. “These insects can travel hundreds of miles in a short period of time aided by an extremely efficient bug highway [a jet stream].”

MacRae says if the wind and temperature are conducive and Canadian potato producers are able to get their crop planted in good conditions, there is a chance the moths will arrive about the same time as the plants are emerging. The possibility exists that early arrival could spawn a second generation of the insects later in the season. He says, once landed, reproduction occurs when the moths lay eggs. The emerging larvae will feed on the foliage, but once at the fourth or fifth larval stage they will begin actively eating near the base of the host plant, cutting it off.

“The first you might notice a cutworm problem will be plants that are cut at the base or wilting,” MacRae explains. “At night, the worms burrow into the soil and if the tubers are close to the surface, they will burrow into the tuber. They can do more damage to tubers in dry conditions because cracks in the soil will give the cutworms access to what is underneath.”

Damage to potato crops early in the season can be a greater problem because the young plants will not recover from being chewed off. There is a possibility that the seed piece might send up another shoot, but the crop will be set back. MacRae suggests early scouting will help identify the problem and allow time for control. There are effective insecticides for control of black cutworm and there are sources of natural mortality, such as predators or parasitic wasps. Birds may be less effective because of the location of the worms and their habit of eating at night.

“If you find yourself at a threshold of about 30 per cent of your plants cut, you may want to apply an insecticide,” MacRae says. “If defoliation is this high, it may be that natural mortality sources are not functioning well.”

Ensure proper identification of the larvae as black cutworms so the correct product can be chosen for control. Combining regular field scouting with pheromone or light traps to catch the male moths is an effective way to identify the insects.

“When scouting, look for stalks at an odd angle or wilting,” MacRae suggests. “Look in the evening when the cutworms come out to feed, and look as much as a half metre away from the plant because they are good walkers. Black cutworms are aptly named because they are a dark caterpillar with a waxy appearance. They will often curl into a C if disturbed. They hang out during the day under clods of soil or in cracks.”

MacRae says climate change may be the reason black cutworms are being seen farther north. He doesn’t believe they will begin to overwinter in Ontario or the Prairies, but a warmer climate means they develop faster and may overwinter in more northern states, making the migration north earlier and causing greater problems.

“Black cutworms have certainly become a problem in Ontario in the last few years,” MacRae says. “They can be a significant pest issue.”

MacRae adds there are some cultural practices that may minimize the impact of black cutworms when they arrive. Planting late can put new, young plants directly on a collision course with the moths and their offspring, so plant early, if possible. He says controlling weeds will reduce the areas where the moths might lay eggs. Growers in the United States use pre-plant tillage to turn over the soil to destroy potential habitat.

To date, there is no accurate monitoring system in place for potato crops, according to MacRae, but the cutworms also like corn and the corn growers in some states, such as Iowa, have a black cutworm monitoring network. “The moths seem to appear in Ontario about three weeks after they are seen in the United States,” he says. Ontario growers could tap into the monitoring networks south of the border and use that information as an early warning system, he suggests.

Black cutworms could be considered a stealthy yield robber because by the time you begin to notice a problem, it could be a challenge to execute effective control. The best defence is early and frequent field scouting and adopting cultural practices that could minimize the attractiveness of the crop. MacRae believes Canadian potato growers will see black cutworm more often in the coming years, so preparation for and understanding of the pest is a wise approach. 

 

Published in Crop Protection

There are other, more sophisticated methods of testing for the presence of late blight spores in growers’ fields, but that’s precisely the reason Eugenia Banks selected a very simple test for her 2016 project.

Published in Crop Protection

Nov. 28, 2016, Prince Edward Island – Health Canada's proposal to phase out a pesticide over three years will have a significant impact on Island farmers looking to control the Colorado potato beetle, says the P.E.I. Potato Board. | READ MORE

Published in Pest Control

Sept. 29, 2016, Ontario – The potato IPM training module, an educational tool with information for the common insect pests, diseases, viruses and disorders of potatoes in Ontario, is now available online. | READ MORE

Published in Diseases

Sept. 8, 2016 - According to Manitoba Agriculture, aphid counts in weeks 9 increased slightly in most locations. However, one western field had no aphid trapped. While another field in the same region continued to have massive numbers; with significantly higher potato aphids compared to last week. Most of the seed fields are being desiccated, so this will be the last week of aphid report.
 
One more potato psyllid adult was confirmed on Aug. 24 in a card from Northfolk-Treherne Rural Municipality.For more information and detailed report please visit: www.mbpotatoes.ca

Published in Diseases

August 26, 2016 -  According to Dr. Vikram Bisht, of Manitoba Agriculture, aphid counts in weeks 8 in all but one sample were low. There was one Green Peach Aphid (GPA) trapped in southern seed growing area, but not anywhere else. Potato aphids were trapped in southern and central areas. One field showed a sudden influx of aphids, probably from nearby crops being harvested or desiccated. There were low counts of Aster leafhoppers were trapped in all seed areas.

Some of the seed fields are being desiccated, so Bisht reports there will be one more week of aphid monitoring. The results from suction and pan traps in seed fields for the 6th and 7th week of sampling can be seen in a chart (please click here):

In 2016 season, as in 2015, as part of the Canadian Hort Council, Growing Forward 2, Canadian Potato Psyllid and Zebra Chip Monitoring Network project, yellow sticky cards are being sent to Dan Johnson, Univ of Lethbridge. One potato psyllid adult was confirmed today (August 22) in a card (in field July 12-18) from Northfolk-Treherne Rural Municipality. This is the first find for 2016 in a province outside Alberta.

North Dakota has also reported occurrence of potato psyllids in their fields. "We have confirmed that psyllids are present potato fields in western ND. Psyllids are the vector of zebra chip disease and can do damage without the Lso bacterium (Gary Secor, NDSU)".

Published in Diseases

Disease update
The number of new finds of late blight seems to have slowed down, even though the disease continues to be a concern. All of the isolates tested so far, were determined to be US23. Late blight was found in market-garden plots of potato and tomato in Oakville area, in Central Manitoba. 

There were scattered rains and strong winds on Aug. 4 and 7, which may have spread the disease. 

It is extremely important to continue to scout for late blight, especially in low lying, irrigation pivot center, wheel tracks of irrigation systems (guns/pivots), tree-line protected areas and under hydro-power lines (areas where applicators may have difficulty covering). Full fungicide coverage of foliage in high risk areas should be maintained. It is also critical at this time to monitor potato and tomato plants in home gardens. 

The DSVs (late blight risk values) accumulated over seven days at various weather stations suggest mostly moderate risk in most of the province. There is forecast for a few rain days in many potato growing areas, in the coming week. 

Due to wet and warm conditions there are reports of stem rot/blackleg. Hail damage and European Corn Borer (ECB) injury appears to have contributed to some of the stem rotting. Early blight in general appears to be very minor.

Pest update
The aphid counts remained low in the third week (July 5-11) and the fourth week (July 12-18) especially in the southern seed production area. Potato aphids, but not Green Peach aphids (GPAs), were found in these weeks. There were no aster leafhoppers (ALH) and potato leafhoppers (PLH) noted in the traps. 

In the fifth week (July 19-25), the aphid counts have increased significantly over the previous week. Green peach aphids were trapped from the Portage area only. The potato aphids were trapped in all the three seed production areas. Potato aphids are fairly efficient PVY transmitters, but not as efficient as GPAs. The “other aphids” in the traps are poor transmitters, but make up with higher numbers. 

With other crops in the region maturing and near harvest, the aphids will find the green potato crop very attractive. It may be helpful to the seed growers to consider tank mixing insecticide with the aphid-oils application, especially if the crop planted had some level of PVY in the seed itself. 

The results from suction and pan traps in seed fields for the third, fourth and fifth week can be found here.

Currently, there is no report of any serious Colorado potato beetle (CPB) feeding in commercial potatoes. 

European Corn Borer:
Delta trap monitoring for the ECB moths using pheromone lures continue to show some adult moth activity – in Carberry, Brookdale in Rural Municipality of North Cypress-Langford, Treherne (RM of Victoria), Shilo (RM Cornwallis), Glenboro (RM of Glenboro-South Cypress) and Carman (RM of Dufferin) area. 

After a peak activity in mid-July, the number of trapping has reduced. After the appearance of very young larvae (Figure 1) was the trigger for insecticide application in fields close to last year’s serious infestations. Some ECB injury and larvae were noticed in the Carberry area. 

Insecticide application could be considered when significant larval counts appear, and especially in areas where the stem infestation was high in 2015. Please consult the 2016 Manitoba Guide to Field Crop Protection for the choice of insecticides.

 

Published in Diseases

April 28, 2016, Charlottetown – Christine Noronha, an entomologist with Agriculture and Agri-Food Canada’s Charlottetown Research and Development Centre, has designed an environmentally green trap that could be a major breakthrough in the control of wireworms, an increasingly destructive agricultural pest on Prince Edward Island and across Canada.

In this exslusive webinar hosted by Potatoes in Canada magazine, Christine will share details about the Noronha Elaterid Light Trap (NELT). Don't miss the opportunity to ask questions and learn more from Christine Noronha. 

Date: May 12, 2016

Time: 2 p.m. ADT (1 p.m. EDT)

Cost: $20

Register today!

Published in Crop Protection

March 14, 2016, Prince Edward Island – Agriculture and Agri-Food Canada entomologist Dr. Christine Noronha has designed a simple and environmentally green trap using hardware store items that could be a major breakthrough in the control of wireworms, an increasingly destructive agricultural pest on PEI and across Canada. 

The Noronha Elaterid Light Trap, or “NELT”, is made with three pieces - a small solar-powered spotlight, a plastic white cup and a piece of screening. The light is set close to the ground to attract the source of the wireworms, the female click beetles that emerge from the ground in May and June. Each of these beetles can lay between 100 and 200 eggs that produce the larvae known as wireworms. In a six-week test with 10 traps, more than 3,000 females were captured in the plastic cups, preventing the birth of up to 600,000 wireworms. The screening prevents beneficial predator insects from being caught in the trap.

Agriculture and Agri-Food Canada’s Office of Intellectual Property is trademarking the trap name and design and work is underway to find a manufacturer who might be interested in mass-producing the trap.

The NELT is the latest in a series of wireworm control measures being developed by a team that includes Agriculture and Agri-Food Canada, the PEI Potato Board, the PEI Department of Agriculture and Fisheries, the Pest Management Regulatory Agency, Cavendish Farms, the PEI Horticultural Association, growers and consulting agronomists.  Wireworms live in the soil and drill their way through tuber and root crops like potatoes and carrots. The PEI Potato Board estimated wireworm damage to the province’s potato crop alone at $6 million in 2014.

To learn more about the NELT, be sure to sign up for an exclusive webinar with Christine Noronha, hosted by Potatoes in Canada magazine, on May 12. 

Published in Technology

 

New hope is on the horizon for potato growers engaged in the ongoing battle against Colorado potato beetle (CPB). Researchers are currently field-testing one of the most effective controls ever developed for the potato’s chief insect villain, and it is entirely chemical-free.

RNA interference (RNAi) is a biological process whereby RNA (ribonucleic acid) molecules activate a protective response against parasite nucleotide sequences by inhibiting their gene expression. In other words, it is the method by which organisms – including pests such as CPB – defend themselves against threats and regulate their own genes. But the same process that is used by a beetle to protect itself can be used to destroy it when it consumes the long double-stranded RNA (dsRNA) in genetically modified plants.

Since 2009, researchers at the Max Planck Institute in Potsdam and Jena, Germany, have been developing genetically modified potato plants to enable their chloroplasts to accumulate dsRNA targeted against essential CPB genes. After feeding on a potato’s leaves – and ingesting the dsRNA – the beetles in the study showed 100 per cent mortality within five days.

Why chloroplasts, rather than plant cell nuclei? In past breeding projects, expression of dsRNA in potato plants’ nuclei has proven inefficient because natural RNAi pathways in nuclei prevented the plant from producing enough long dsRNA. But long dsRNA are free to accumulate in chloroplasts – which have no RNAi mechanism – and the plants are fully protected against CPB.

According to Jiang Zhang, a professor with the College of Life Science at Hubei University in China, and the lead on the project, the technology shows great promise for the future of pest management, but there are no immediate plans for commercialization until all regulatory hurdles have been overcome.

“We encourage more scientists and industry involvement in this field for a better future,” Zhang says. “There is still a long way to go to make it really useful in daily life and be accepted by customers.”

RNAi-based biocontrol
RNAi for control of CPB has also gained significant momentum in private research and development. Monsanto and Syngenta have both devoted major investments toward the technology.

In early 2015, Monsanto’s BioDirect technology platform targeted at CPB advanced to Phase 2 – early product development – of the company’s research and development pipeline. The product will have to complete advanced product development and pre-launch before broad commercialization early in the next decade.

While the principle is the same, Monsanto’s product works differently than Max Planck’s modified potato plant: it is sprayed onto the plant’s foliage. Rather than expressing dsRNA in its leaves, dsRNA is applied exogenously to the plant.

“The Colorado potato beetle consumes the leaves of the potato plant where we can focus the BioDirect application, versus needing a plant to produce the dsRNA targeting the pest below-ground where sprays cannot reach,” explains Greg Heck, weed control team lead for Monsanto’s chemistry technology area.

Heck says there are thousands of dsRNA naturally present in host plants that serve a variety of functions, and beetles consume and incorporate dsRNA all the time. “When targeting them for pest control, we seek to supply one additional dsRNA that will turn down a specific gene critical to their ability to feed and grow on the plant.

“Field research conducted on our BioDirect treatment for Colorado potato beetles has already demonstrated some early positive results. This includes reduced Colorado potato beetle larva infestation and plant defoliation in multiple geographies.”

Syngenta’s most advanced RNA-based biocontrol targets CPB in potato – and is also applied via a spray. The company has tested the product in multiple geographies over several years with positive results, says Luc Maertens, Syngenta’s RNAi platform lead based in Belgium. The company hopes to commercialize the product early in the next decade pending continued development and regulatory reviews.

Maertens says the company’s biocontrol is highly selective and starts to work before CPB can cause too much damage.

“The biocontrol is not systemic [in the plant], nor does it work through contact,” he says. “It does not change or have any effect on the DNA of the pest, nor does it involve genetic modification of the plant.”

No technology can work forever, however. Insect resistance to RNAi is a potential risk – one companies and researchers alike are keen to avoid so the technology has maximum benefit and longevity.

Maertens says that as resistance emerges to existing technologies, and the pest spectrum shifts along with climate change and other factors, growers’ needs will change. “Those challenges cannot be answered by only one technology,” he says. “It is imperative to gain insights into probable resistance mechanisms to RNAi triggers in insects, to monitor possible resistance in the field, and to support the use of the technology with appropriate stewardship requirements.”

Of the two methods of RNAi application (genetic modification and spray-on), Zhang believes the former might be better for growers. “Applying dsRNA exogenously is much less cost-effective than expressing dsRNA in the plant itself,” he says. “Spraying may also cause other potential problems in the environment.”

RNAi is not meant to be a silver bullet and should be used as part of a multifaceted pest control strategy. Regardless of the method of application, RNAi may soon be working in a field near you.

 

 

 

Published in Pest Control

February 12, 2016, Calgary, Alta – Potato growers across Canada have the option of applying Delegate insecticide by air for control of Colorado potato beetle and European corn borer.

“If a seed treatment was not used, or is not offering sufficient control of insects, plan to use Delegate insecticide in your crop,” says Mark Alberts, product manager at Dow AgroSciences. “Delegate is a non-neonic product which provides rapid foliar control of target pests. This aerial application registration is an opportunity for applicators and growers to integrate an excellent new control measure with a unique mode of action into their programs.”

The active ingredient in Delegate is Spinetoram, a member of the spinosyn class of chemistry (Group 5) and controls a broad spectrum of pests by both contact and ingestion. It provides knockdown and residual activity in many fruit, vegetable and field crops, including potatoes. According to the company, Delegate affects the insect nervous system. It does not interact with the known binding sites of other classes of insecticide. Because of Delegate’s mode of action, it is an excellent rotational product that can be used in an IPM system.

Further information on Delegate is available at DowAgro.ca.

Published in News

Nov. 10, 2015 – It is never too early to find out about the new crop-protection products, reminds Eugenia Banks, potato specialist at OMAFRA, in her latest potato update.

These new products were recently registered and should be available for the 2016 season. Here is a list of pesticides, some with new active ingredients:

Trade name Application method Disease or insect
Aprovia
(Syngenta) Group 7
In-furrow *Suppression of Rhizoctonia stem canker, stolon canker and black scurf
Sercadis 
(BASF) Group 7
Foliar and aerial Control of early blight and white mould.
Use of a non-ionic surfactant is recommended
Sercadis 
(BASF) Group 7
In-furrow

Control of Rhizoctonia canker

Voliam Express
(Syngenta)
Group 3A and 28
Foliar

Control of black curworm, variegated cutworm, armyworm, potato psyllid
Active ingredients: pyrethroid + diamide

Agri-mek SC
(Syngenta) Group 6
Foliar

Control of potato psyllid and spider mites (not a pest in Ontario)

Control is at least 85 per cent control
*Suppression is 65 to 85 per cent control
"May provide some control" is less than 65 per cent control.

There are also label changes to some registered products. For instance, the label of Rampart (phosphite) has been expanded to a foliar application for suppression of late blight and pink rot. In general, any product that suppresses late blight should be tank mixed with a compatible control product. A better approach would be to tank mix two compatible control products. If the weather is favorable for late blight, this disease can explode and devastate potato fields very quickly.

There are new registrations for potato psyllids. This tiny insect is the vector of the bacterium that causes zebra chip. This past season, I placed several yellow sticky cards in three Alliston fields to monitor for potato psyllids, but no potato psyllids were caught on the cards. In the past, this insect has been reported in British Columbia, Alberta, Saskatchewan and Quebec. Psyllids were found in Ontario a few years ago, but only in a greenhouse, not in the field. It is always good to have registered products available for the control of potential pests. There will be more updates to come as new products are registered. 

Published in Pest Control

The root-knot nematode is a parasitic roundworm that can infect about 2,000 plants and is one of the three most damaging parasitic nematodes to agricultural crops worldwide. Photo by UNH.

Sept. 14, 2015, Durham, NH – Roundworms that feed on plants cause approximately $100 billion in annual global crop damage. But a new way of disrupting the motility and reproduction of these plant parasitic nematodes discovered by a University of New Hampshire (UNH) scientist may one day provide farmers with a new way to safely manage these agricultural pests.

Published in Research

Severe Colorado potato beetle larval damage to potatoes. Photo by Vikram Bisht, MAFRD.

Colorado potato beetle (CPB) has been a challenging pest for potato growers for more than a century, and today it continues to be the most damaging insect defoliator of potatoes across Canada and the U.S. If uncontrolled, growers suffer yield losses and potential crop failure in potato crops and other field vegetable crops such as tomatoes and eggplant. Growers continue to rely on insecticides for control, however CPB is very adept and successful at developing resistance, creating additional challenges for researchers, industry and growers.

 With increasing potato farm size and repeated use of effective insecticides, there has been high selection pressure on CPB to survive. Insecticide resistance develops largely from the overuse and repeated application of chemicals with similar modes of action that increase the selection of the resistant individuals in the population. “Colorado potato beetles resistant to DDT were first reported in 1955, and have since developed resistance to over 51 different insecticides, including imidacloprid and eight other neonicotinoids in the U.S.,” Ian Scott, research scientist with Agriculture and Agri-Food Canada (AAFC) in London, Ont., says. “Colorado potato beetle resistance in Canada has developed more slowly, with the first findings of resistance in 2003, to imidacloprid (Admire), the first neonicotinoid registered in Canada, and increasing reports of problems and crop failures in Ontario and Quebec by 2007.”

 In 2008, Scott and colleagues initiated a four-year project to survey CPB neonicotinoid resistance in Canadian potato fields. Growers and agronomists from across Canada sent live samples to AAFC every summer. “We partnered with different chemical companies on the project and, depending on which products were surveyed in a particular year, we conducted bioassays in the lab,” Scott says. “We were able to screen quite a few populations of Colorado potato beetle through the bioassays. We were trying to confirm what growers and extension people were seeing related to resistance concerns with registered neonicotinoid uses. Also, some companies were planning to introduce new products of the same class or different groups and wanted to see if there was any potential cross-resistance with the older products.”

 The results of the four-year survey confirmed previous studies showing that many CPB populations have become less sensitive to imidacloprid and that cross-resistance with the second-generation neonicotinoids thiamethoxam and clothianidin is a growing concern. Scott adds the survey also demonstrated cross-resistance is on the rise.

“Using comparisons of Colorado potato beetle mortality generated from lab bioassays with Admire, Actara and Titan, a strong positive correlation indicated there is potential for cross-resistance between these three neonics,” Scott notes. “However, cross-reaction correlation was weaker between neonic Admire (Group 4A) and diamide insecticide Coragen (chlorantraniliprole, Group 28), indicating the cross-resistance between these classes is less likely to develop.”

 According to Vikram Bisht, plant pathologist with Manitoba Agriculture, Food and Rural Development, the Atlantic provinces, and Quebec and Ontario have had a greater problem with CPB resistance to Group 4 insecticides. “However, Manitoba has seen some population shifts to resistance,” he notes. “Alberta currently does not have serious issues and so far even older chemistries appear to still be effective there. Resistance to the newer insecticides is highly likely if the products are continuously used without proper insecticide resistance management practices being applied. It is important to rotate chemistries to prevent multiplication of insecticide resistant populations.”

 Vikram adds CPB populations collected from treated fields in Manitoba in 2012 and 2013 and tested by Scott were also found to be imidacloprid resistant (with less than 30 per cent mortality) or showed reduced sensitivity to clothianidin or thiamethoxam (with 30 to 70 per cent mortality). Repeated use of similar mode-of-action insecticides may often lead to development of cross-resistance against newer insecticides, even though they had not been previously applied. Therefore, resistance against clothianidin and thiamethoxam has a greater chance of appearing in imidacloprid-resistant CPB populations.

“Generally, every commercial grower treats seed potato for Colorado potato beetle and in most cases control is quite effective,” Bisht says. “In areas where resistance is developing and in situations where growers also need to use a foliar application for in-crop control, they must make sure to use a different chemistry in-crop than was used for seed treatment. There are at least five different seed treatment or in-furrow chemistries and a few other chemistries for in-crop, so growers do have options available. Growers should make rotating insecticide chemistries a priority whether or not they have resistance concerns, as it is good practice to ensure long-term use of the good tools available.”

 Bisht adds crop rotations of two years or longer are needed to be effective. However, fields must not be adjacent to last year’s crop. “Short distances from previous potato crops reduces the advantage of crop rotation, since the overwintering Colorado potato beetle adults from last year’s field can easily crawl to adjacent fields. Also, Colorado potato beetles can fly short distances during warm days and can easily move 100 to 200 metres.”

New research and management options
“We are working on other projects focused on understanding the mechanisms responsible for resistance of Colorado potato beetle through molecular and biochemical analyses,” Scott says. “We have maintained a number of Colorado potato beetle colonies in the lab for use in various projects; for example, screening alternative biopesticide products and the use of natural plant compounds as insecticide synergists.”

 One recent project studied the potential use of dillapiol, the main constituent in Indian dill (Anethum sowa), as a synergist to help improve insecticide activity and longevity, and control of resistant pest populations. Synergists have a long history of use, one of the most frequently used ones being piperonyl butoxide (PBO) in combination with the natural insecticide pyrethrum. PBO is a very effective synergist but has related toxicological concerns.

“Our laboratory trials testing of pyrethrum alone versus pyrethrum combined with dillapiol indicated that the synergist increased the activity of pyrethrum against insecticide-susceptible and -resistant Colorado potato beetle,” Scott explains. “In field trials, both the PBO and dillapiol synergized pyrethrum had 10 times the efficacy of pyrethrum alone. We continue to work on dillapiol and other natural plant-derived synergists that may offer compounds with improved health and environmental safety and potential for organic certification.”

 Research continues on other strategies to help growers manage the challenges of CPB. “There continues to be a focus on the development of new varieties with Colorado potato beetle resistance, however transgenic varieties have not yet been accepted by the market,” Bisht says. “Plant breeders are also using conventional breeding to introduce natural resistance genes from wild species, and hopefully in the future varieties will become available.

“There are other cultural practices that can be options for organic or smaller growers, but so far most are not practical for larger commercial growers. There is a new biological insecticide available – Novodor (Bacillus thuringiensis subsp. tenebrionis, strain NB-176) – but it is not currently used by commercial potato growers. Plastic-lined trenches on field edges could be effective for small farms, which trap Colorado potato beetle and prevent movement into the field.”

 Considerable efforts continue to be focused on addressing resistance. Scott and Bisht remind growers everyone must do their part to be vigilant in monitoring and scouting for CPB resistance, follow proper insecticide resistant management practices and alternate classes of insecticides available.

“The survival of beetles after an insecticide application could be due to a variety of factors, including improper coverage, failure to apply the full rate of insecticide, or precipitation soon after application and existence of actual insensitivity (tolerance/resistance) to the insecticide,” Scott says. “It is very important for growers and industry to practice good stewardship and maintain the use of these products as long as possible. It takes a considerable [amount of] resources, time and funds to develop new chemistries, so protecting the tools we have as long as possible is a best practice.”

 

Burn, beetle, burn
In February 1994, Potatoes in Canada magazine, a sister publication to Top Crop Manager magazine, published a story with an eye-catching headline: “Burn, beetle, burn.”

The story explains that in the summer of 1992, field trials began on an eight-row flamer designed to control Colorado potato beetles (CPB) that had recently demonstrated resistance to traditional chemical treatments. The flamer tests were initiated by ICG Propane, in co-operation with the Ontario Ministry of Agriculture, the University of Guelph, and growers in Alliston and Leamington, Ont.

The trials showed that flaming had several mechanisms for limiting beetle damage. The most obvious was that it could kill the beetle adults outright. But the trials also shows there were three secondary controls: First, flaming caused sufficient damage to the CPB so that it died in the near term; second, if eggs and antennae were damaged, the beetles became disoriented and, thus, unable to feed or mate; and third, the heat from the flaming resulted in a high mortality for the eggs already laid.

The trials showed that using the propane flamer in the spring for overwintering adults gave control of 70 to 80 per cent of the adult beetles and also killed nearly 50 per cent of the eggs. Late season control, the time of top killing, gave 95 to 100 per cent control of adult CPB. In addition, the 1994 story stated growers were “astonished at the level of weed control that came as a result of the flaming activity.”

Even more interesting was the low level of plant damage from the flaming. The story states that in almost all locations of the study, slight plant injury similar to that observed when plants are hit by a late frost did occur. However, the growing tip of the plant was not affected, and most injury was unnoticeable after about a week. “Potato yields taken at four of the test sites showed no difference in yield between flamed and unflamed areas.”

At the end of the day, physical methods to control Colorado potato beetle and other pests are seeing resurgence, as the very real threat of insecticide resistance increases.

 

Published in Pest Control

A new study at the Harrington Research Farm in P.E.I. is examining how to make buckwheat crops an even more effective and practical option for potato growers looking to control wireworm. Photo by AAFC.

Growing two years of buckwheat in a potato rotation is effective at managing wireworms, one of the toughest pest problems for potato growers. But how does buckwheat actually affect wireworms, and can we make buckwheat rotation even more effective and practical for growers? A rotational study is underway on Prince Edward Island to answer these questions.

The P.E.I. study is part of a major project to investigate different strategies for dealing with wireworms, led by Christine Noronha, a research scientist with Agriculture and Agri-Food Canada (AAFC). The project, funded by AAFC, involves AAFC scientists across the country because wireworms cause serious problems in many regions and many crops.

Wireworms are the soil-dwelling larvae of click beetles. Canada has about 30 wireworm species of economic importance. In most species, the beetles lay eggs in the soil in the spring. A few weeks later, the larvae hatch. The larval stage lasts about four or five years, depending on the species. Then the larvae pupate and the adults emerge from the soil in spring.

In potatoes, wireworms tunnel into the tubers, reducing marketable yield. The tunnels can also be entry points for potato pathogens.

Noronha has been conducting wireworm research in P.E.I. for over a decade. Her rotational studies show growing either brown mustard or buckwheat as a cover crop for two years before growing potatoes can reduce tuber damage by about 80 per cent or more. Brown mustard is known to release chemicals into the soil that control wireworms, but the reasons for buckwheat’s effect on wireworms are not yet known.

AAFC research scientist Aaron Mills is leading the new P.E.I. buckwheat agronomy study. It is taking place at the Harrington Research Farm and runs from 2014 to 2016.

“Christine Noronha has done an excellent job at figuring out how to control wireworm with buckwheat; it’s now another tool in the toolbox for controlling wireworm. A big part of this new buckwheat study is to find out how and why buckwheat affects wireworms,” Mills explains.

“We also want to establish local protocols for how to deal with buckwheat in the rotation, so growers wouldn’t be as intimidated by the potential for buckwheat to become a weed problem, and to establish some protocols for managing buckwheat as a grain as well.”

Better understanding of how buckwheat impacts wireworms could potentially lead to advances that enhance wireworm control. For instance, one possibility is that buckwheat is releasing compounds into the soil that kill or suppress wireworms directly or perhaps affect other components of the soil ecosystem in ways that make conditions less favourable for wireworms. If such compounds are released when buckwheat foliage decomposes in the soil, then the most effective wireworm control strategy might be to disk the plant into the soil as a green manure. Or it may be best managed as a mulch, in which case flail mowing as a green manure may be best. If the compounds are released by the roots, then perhaps it might be better to let the buckwheat crop grow for a longer period before terminating it. If buckwheat produces compounds that deter other insect pests or pathogens, in addition to wireworms, then it could provide even greater benefits in the crop rotation. In the longer term, perhaps buckwheat lines could be selected that have higher levels of those compounds, or perhaps a bio-insecticide could be developed using the compounds.

A key aspect of successfully including buckwheat in a crop rotation is to ensure volunteer buckwheat doesn’t become a weed issue. “Traditionally buckwheat has been grown as a weed control measure, and some growers are concerned about growing it because it can become a weed itself if you let it grow too long and go to seed,” Mills says. He explains buckwheat grows very well in P.E.I.; the seedlings emerge and grow quickly, enabling the crop to outcompete weeds. As well, some research indicates buckwheat releases chemicals into the soil that inhibit the growth of certain plant species. Those characteristics make buckwheat great at fighting weeds, but can also make volunteer buckwheat a problem for the next crop.

Although letting buckwheat go to seed is a weed risk, growing buckwheat for grain would be an important opportunity for growers to obtain some income from growing two years of buckwheat for wireworm control.

“Right now I would say the majority of growers on the Island are growing buckwheat for wireworm control, but I think people are interested in growing it as a crop for grain as well,” Mills notes. “I think the main export market for buckwheat is for use in noodles in the Asian market, although it has been grown in places like New Brunswick to make flour for buckwheat pancakes. And there may be opportunities in the health food industry; for example, buckwheat oil is reported to have some bioactive benefits.” Buckwheat also attracts pollinators and is used for honey production.

Wireworms, organic matter, microbes and more
Mills’ study is comparing five different three-year potato rotations. Three of the rotations involve two years of buckwheat and are comparing three strategies for terminating buckwheat: disking, flailing, and desiccating and then harvesting it for grain.

“For termination through disking, we wait until the lower seeds start to drop off and then we use a set of disks to incorporate the aboveground crop material into the soil. For termination through flailing, we wait for the lower seeds to start to drop, and then go in with a flail mower and completely flail off the top of the aboveground biomass, leaving the residue on the top of the soil surface, almost as a smothering effect. And to manage buckwheat for grain, we desiccate the crop and then take it off with a combine,” Mills says.

He adds, “We wait for the lower seeds to start to drop off when flailing or disking because we’ve found that buckwheat turns to jelly when you flail or disk it – the remaining residue breaks down fairly quickly. So rather than ending up with bare soil going into the winter, we wait for the lower seeds to start to drop off to make sure there will be a little bit of cover going into the winter.”

For the three buckwheat treatments, Mills’ research team is measuring factors like buckwheat biomass and seed yield, as appropriate.

The other two rotations in the study are traditional three-year potato rotations used in P.E.I.: barley underseeded with clover and then potatoes; and barley underseeded with a grass and then potatoes. These traditional rotations have benefits for soil conservation, but they favour the spread of wireworms because the beetles prefer to lay their eggs in grassy areas.

The researchers will be gathering data on such factors as potato yields and the levels of wireworm damage in the tubers for the five rotations.

As well, they will examine effects of the different rotations on water quality, soil organic matter content and soil nutrient levels, so nutrient management specialist Judith Nyiraneza and water quality specialist Yefang Jiang are involved in the study.

“Although any green cover on the soil helps to reduce erosion, the study will be examining whether or not buckwheat is particularly good at preventing erosion or building up soil organic matter,” Mills says. “I think the jury is still out on whether buckwheat is a soil builder or not.”

Buckwheat’s effect on soil nutrients also needs to be clarified. Some previous research has suggested buckwheat may make nutrients like phosphorus more available to the next crop, while other sources suggest buckwheat may reduce levels of certain nutrients.

To better understand how buckwheat controls wireworms, Christian Gallant, a graduate student from Dalhousie University, is looking at the soil organism communities in the plots, especially the nematode communities, and also the fungal and bacterial communities. He will be examining how species diversity and populations change through the course of the growing season and with the different crops.

Mills explains the value of examining nematode communities: “Most people focus on the plant parasitic nematodes. Those nematodes feed on plant roots, and the damage from their feeding also opens up spots for pathogens like Verticillium to enter the plant’s root system. But there is a whole other side of the nematode community. They all have specific jobs to do; there are bacterial feeders, fungal feeders and predators that feed on other nematodes and even mites. By studying the overall nematode community, we can get a snapshot of how things are happening biologically in the soil.”

In addition, researchers will be testing the soil for buckwheat compounds that could be affecting soil organisms. “We’re trying to figure out if buckwheat is actually releasing chemicals into the soil that are affecting the soil pest populations, or if buckwheat is just a non-host for some of these pests,” Mills says.

With one field season completed so far, Mills is looking ahead to the results from 2015 and 2016. “By the end of 2015, we’ll have a really good idea of how the different buckwheat treatments affect soil organisms, nutrients and organic matter, [and water quality]. And by the end of the study’s third year, we’ll have an excellent idea of how everything affects potato production.”

In the meantime, growers are welcome to visit the Harrington Research Farm to see the plots and learn more about the study.

 

 

 

Published in Pest Control
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