In North America, swede midge was first noticed in Ontario and the eastern United States. It has affected canola production in Eastern Canada, in some cases leading to failed crops.

Swede midge (Contarinia nasturtii) is also a pest in vegetables because it attacks the growing points, preventing formation of heads in broccoli and cauliflower.

As an invasive species, swede midge could be a scary prospect for Saskatchewan farmers because of that province’s extensive canola acres. The Canadian Food Inspection Agency issued reports in 2007-08 of swede midge in Manitoba and Saskatchewan, which led to research in the Melfort and Tisdale areas of Saskatchewan.

However, when Meghan Vankosky, a field crop entomologist, and her colleagues from Agriculture and Agri-Food Canada conducted field research, they found an entirely different species of midge.

At last December’s Saskatchewan Agronomy Update conference, Vankosky said swede midge has been monitored in the Prairie provinces since 2006 through volunteer-based programs.

“Throughout all of those years we have not found any swede midge, but we do have something called canola flower midge, which is a newly identified species.”

First identified in 2016, Vankosky’s team conducted surveys across the Prairies and found evidence of canola flower midge in the south-central regions of all three provinces, although density was low.

Since 2017, three research programs have focused solely on canola flower midge, funded by the Canola Agronomic Research Program in Western Canada. The studies have focused on monitoring canola flower midge, its life cycle and impact research and development of a pheromone-based monitoring tool.

According to the Canola Council of Canada (CCC), canola flower midge and swede midge look very similar in appearance as they are from the same genus, Contarinia. Since the larvae and adult forms of both midge species are very small, it is recommended farmers look for the damage canola flower midge larvae cause to unopened canola flowers by feeding within them. The unopened canola flowers grow to form bottle-shaped galls rather than develop normally.

The potential threat to crops from canola flower midge (C. brassicola) is perhaps the biggest question in the minds of canola producers. Vankosky said damage risk to crops from canola flower midge is a challenge to estimate. So far, damage has been low, and, in most fields, yield loss is likely negligible, so the insect is not considered a domestic concern.

However, it is worth noting that some fields in the Melfort and Tisdale areas and some areas of Alberta, outliers in the research, have experienced extreme losses.

CANOLA FLOWER MIDGE LIFE CYCLE

An emergence cage study of canola flower midge showed eggs and larvae can be found from June 21 to Aug. 17, likely with multiple generations per growing season or prolonged emergence, with adults, eggs and larvae present simultaneously from June to September.

Midge eggs are laid in flower clusters where they hatch and develop into larvae in the enclosed flowers. Larvae feed in the unopened flowers, creating a gall and preventing pod formation. Mature larvae later drop to the soil to pupate. It’s possible that pupae can persist in the soil for more than one winter.

Flowers will stay on the plant for a long time but will dry out as the season progresses.

Midges have also been found in developing canola pods previously damaged by other insects.

“In the last two years, there were even reports of midge being found in developing canola pods, which was a surprise to us,” said Vankosky. “What we think is happening here is the canola flower midge is a secondary infestation, entering damaged areas from a different pest.”

Although canola flower midge has yet to be considered a significant pest, research led to the creation of a pheromone trap that can get accurate counts. Vankosky and her team want to optimize the trap for accuracy.

Vankosky said original research on swede midge showed negligible damage but now its threat to canola crops is great. Could this be the case with canola flower midge?

“We have seen this with a number of invasive species, so it is a possibility. But we think that canola flower midge may not be invasive and is actually native to Western Canada and it has just jumped to a non-native target in canola. There is not enough information to support this at this time, but it is our working idea.”

Canola flower midge is widespread across the Prairies and has low and variable parasitism rates.

CCC TIPS FOR BEST MANAGEMENT

The Canola Council of Canada offers the following scouting and management tips. More information can be found online in CCC’s Canola Encyclopedia under the topic of canola flower midge.

• Scout for this newly discovered insect in canola fields from early bud stage through harvest.
• Look for bottle-shaped galls formed from unopened flowers, as well as unusual plant structures, plant discolouration and distorted growing points. Carefully examine inside the galls or malformed pods for larvae.
• The flying adult midges don’t cause any direct damage, but they lay their eggs in developing canola flower buds so that the hatching larvae can feed on developing flowers.
• No economic threshold exists yet for this insect, but based on the limited available data, it isn’t currently believed to cause economic damage.

The post Canola flower midge damage less severe than swede midge appeared first on Grainews.

Yearly scouting is needed to assess what pests exist in fields, as populations don’t always remain constant. For example, in 2016 there were higher counts of cutworm but lower incidence of Bertha armyworm. Diamondback moth arrive via winds from our Southern neighbours, and thus are very unpredictable. Flea beetles are usually present but damage depends on the effect growing conditions have on their development as well as ability of the canola crop to outgrow feeding damage.

Identifying pests can also help prevent future problems. Recently, a team of researchers from Saskatchewan, Alberta and Ontario identified a species of midge that is slightly different from the Swede midge. The Swede midge has caused major issues for canola growers in Northern Ontario, however the economic impact to Prairie canola growers, as well as the insect biology, is still being assessed. The new midge species is different physically and in DNA makeup, according to the research scientists at Agriculture Canada. However, the economic impact of this new species is not yet known.

Establishing a canola crop with good, uniform plant counts goes a long way towards minimizing pest impact. Well-fertilized crops allow for more rapid and even development and maturity. Proper rotations can also help to reduce impact.

For more information on insect identification, the Canola Council of Canada website (canolacouncil.org) has excellent information on pests and scouting

Doug Fehr is with DuPont Crop Protection Canada.

The post Midge scouting in canola appeared first on Grainews.

Researchers with Agriculture and Agri-Food Canada, the University of Guelph and the Canadian Food Inspection Agency have reported a new species of midge damaging canola crops in those areas.

The species “has yet to be named and scientifically described,” the scientists reported Monday on Alberta’s provincial Insect Pest Monitoring Network website.

The only confirmed symptom of damage so far from the anonymous midge is in the form of “bottle”-shaped galled flowers caused by larval feeding inside flowers, which then won’t produce pods or seeds, the researchers said.

Midge damage in Saskatchewan last summer “appeared to be low” in most fields, the researchers said, but the new midge’s full economic impact isn’t yet known. Swede midge in recent years were believed to be damaging Saskatchewan crops around Nipawin and Carrot River.

In Alberta, meanwhile, midge and suspected midge damage were detected last year from the Saskatchewan border around Lloydminister, westward to around Stettler and Smoky Lake.

Work is now underway to formally describe and name the new species, which the researchers said appears similar to Contarinia nasturtii, better known to growers in Eastern Canada as swede midge.

In Ontario, swede midge has been a known plant pest in brassica crops, such as cruciferous vegetables and canola, since 2000. It’s now “widely distributed” in both Ontario and Quebec and has also been seen in Nova Scotia and at least five U.S. states.

Crop scouts for years have noted differences between the Ontario pest and the Saskatchewan midge, researchers said, noting the type and amount of damage caused, the adult midge size and the number of generations per year.

Biologist and chemical ecologist Dr. Boyd Mori of AAFC’s Saskatoon Research and Development Centre also noted “extremely low” capture rates of adult swede midge in pheromone traps despite the “apparently high” rates of adult swede midge emergence.

With that in mind, Mori then collected adult midges and sent them to Guelph for study, where Dr. Rebecca Hallett and James Heal “immediately” noticed differences between the Saskatchewan and Ontario midge.

The Saskatchewan midge, the researchers said, “were more robust, had hairier wings and had slight differences in the antennae and genitalia” compared to the Ontario midge, they observed. Dr. Bradley Sinclair, CFIA’s midge expert in Ottawa, confirmed those differences and others.

Those differences, and DNA sequencing, have led to the conclusion that the Saskatchewan pest is a separate midge species, the researchers said. — AGCanada.com Network

The post Anonymous midge appears in Prairie canola appeared first on Grainews.

The adult is a very small, delicate, light- brown/grey fly, smaller than the orange wheat blossom midge fly. Also unlike orange wheat blossom midge, swede midge is active during the day. Male swede midge will live about a day, whereas females will live up to three days, using their long ovipositor to insert eggs into rapidly growing areas of the host plant — in between bud leaves, in very young flower buds and similar places. The female lays about 100 eggs in clumps of two to 50.

The eggs hatch in about three days and larvae start feeding cryptically within whatever structure they are located. Feeding can last up to three weeks, depending on temperature. Swede midge larvae are described at gregarious, meaning they live in close proximity without competition during feeding. The larvae have no external chewing mouth parts and feed by regurgitating salivary fluids on the plant to liquefy the tissue, then slurp it up.

• More the from Grainews website: Swede midge: a potential ‘perfect storm’

The plant responds to this feeding activity by developing malformed and misshapen structures. Complete cessation of growth can occur if the growing tip is destroyed. Typical symptoms include twisted plant structures, premature bolting, swollen or closed buds and fused/bottle-shaped flowers. Depending on when the adults emerge and the eggs are laid, there may be no flowers at all formed and/or deformed racimes. “For example, in 2012 infestation in Saskatchewan occurred in mid-to late June,” says Dr. Julie Soroka, Agriculture and Agri-Food Canada entomologist. “The canola was in early flower at that point and the flowers showed damage as a result of the larval feeding.” In 2013, however, swede midge emergence was earlier and early canola growth was deformed and in some cases no flowers were formed at all.

Swede midge larvae are capable of jumping, which they will do if disturbed while feeding or when they are ready to pupate in the soil. There are several generations of swede midge per season, with a generation occurring every 21 to 44 days in the summer. When days get shorter in the fall, larvae enter the soil and diapause in a cocoon over the winter similar to wheat midge. Pupation occurs when temperatures warm in the spring, and adults emerge when the soil reaches adequate moisture levels.

This article appeared in the May 20 issue of Grainews.

The post Swede midge life cycle appeared first on Grainews.

Such is the potential situation with an up-to-now unknown and non-native pest of cruciferous plants — swede midge. “This pest displays a wide host range in the Cruciferae family which includes canola, mustards and the cruciferous weeds,” says Dr. Julie Soroka, Agriculture and Agri-Food Canada entomologist. “Additionally, the adults are short lived so chemical control of that life stage, if there were any, is difficult. The larvae feed cryptically so they cannot be killed with any contact insecticide and they have multiple generations in a single season, up to three on the Prairies. Top that off with non-synchronous emergence and overwintering capability for up to two years and, yes, this pest has all it takes to become a real economic problem for canola growers.”

How swede midge got here

“We’re not exactly sure how swede midge arrived in Canada,” says Soroka. “More than likely it was on live cruciferous plant material as it is not seed-borne.” It was in 1996 that misshapen broccoli, cabbage and cauliflower were noticed in Ontario, the problem bad enough that the heads were unmarketable. In some cases, yield loss was up to 80 per cent. Initially it was thought to be some sort of nutrient deficiency and it wasn’t until four years later swede midge was identified as the culprit.

“After swede midge was identified, the Canada Food Inspection Agency immediately implemented quarantines preventing host transportation from infected to uninfected areas,” explains Soroka. “Additionally, they set out traps across the country in an effort to monitor spread. It was positively identified by CFIA in Saskatchewan in 2007 and in Manitoba in 2008.”

While CFIA identified swede midge in 2007 in Saskatchewan, it was another very observant agronomist, Neil Abrahamson, who was with Agricore United and now Viterra, who noticed strange larvae in a field he was scouting pre-swathing. “I was checking for seed set and opened a pod completely at random and found larvae,” he says. “When I opened the pod, the larvae jumped. I had never seen anything like that before, so I gathered some up and sent them to Dr. Soroka in Saskatoon for identification.” Soroka was able to determine that the larvae were in the Cecidomyiid family of flies, which also includes wheat midge, but they couldn’t pinpoint it any closer than that. “The only known Cecidomyiid that would live in canola earlier than the pod stage was swede midge, but it hadn’t been identified in the West at that point,” says Soroka. “It was then that we started monitoring for swede midge in earnest.”

• From the Manitoba Co-operator: Swede midge threat looms over Manitoba canola crops

By 2008, swede midge had been found in the Maritimes and New York state. CFIA discontinued the quarantine requirements and monitoring. “The horse had left the proverbial barn, by this time,” says Soroka. “However, the damage caused by swede midge was never severe enough or widespread enough to warrant a great deal of research and monitoring on the Prairies, and indeed, I stopped my own sampling in 2011.” As it turned out, 2012 was the first year there was noticeable damage in Saskatchewan and by 2013 it was clear swede midge was going to be an issue of some significance that farmers were not prepared for. “By 2013, the damage swede midge was causing was very easy to see and it was likely at economic levels in some fields,” says Soroka. “More concerning to me was to see how far it had spread from the epicentre — over 200 km.”

Swede midge damage

While the swede midge itself is very difficult to spot, either as an adult fly or a larva, the damage telegraphs itself very clearly. Depending on when the eggs are laid during the plant life cycle, the damage varies.

The adult flies lay eggs into the growing points of the plant where there are high levels of nitrogen and other nutrients. If the eggs are laid shortly after seedling emergence, the plant might even cease growing if the growing tip is destroyed by larvae. Twisted growth and premature bolting are also symptomatic. If the eggs are laid later, fused flowers shaped like bottles and swollen or closed buds are very common. “The most easily recognizable symptom is the fused flowers,” says Soroka. “We saw a lot of that in 2013 in the infected areas.”

In the earlier years of study of this pest, it was thought that earlier-seeded crops were less likely to suffer damage; however, the level of damage depends on the emergence of the fly from its pupa in the soil, where it overwinters. If emergence is early, whether the crop was seeded early or later is immaterial, swede midge can infest the crop.

There are registered insecticidal controls for swede midge, but control with insecticide is difficult. “This is the problem,” says Soroka. “Multiple generations per season with overlapping development stages in the life cycle in the crop coupled with these larvae that live and eat cryptically, or hidden away, in large groups make it almost impossible to target with an insecticide.” Because the adults fly during the day, even if there were an insecticide available, pollinators would be impacted negatively.

“The best way to combat swede midge is by rotating out of a cruciferous crop for at least two seasons,” says Soroka. “However, cruciferous weeds and volunteers should be well controlled.” Rotation won’t stop the spread of swede midge entirely. The adult fly is a weak flier and is easily blown downwind. Population build-up can be gradual but is generally more noticeable at the edges of fields abutting canola fields and where they can accumulate in windbreaks.

Swede midge do not tolerate drought very well. However, multiple rain events in the spring will favour their emergence. “It may well be that our more typically drier climate will inhibit swede midge,” says Soroka. “In fact, it’s very likely the buildup of swede midge in north east Saskatchewan is a result of the wetter years it has experienced recently.

Controlling swede midge in the future

Long term, a great deal of research has to be done. Soroka and her team, as well as others, will be looking at integrated management strategies combining cultural and chemical controls.

Further understanding of the insect’s preferences for host plants is required, as it appears to tolerate some cruciferous weeds, but favours plants like canola and mustard.

For the long term, the possibility of breeding resistance into canola and mustard needs more exploration. Recognizing it took 25 years for breeders to finally deliver wheat midge resistance, this is not anything that will happen overnight or even in the next decade.

In the meantime, this perfect storm pest is going to continue to be a serious threat to canola and other cruciferous crops in North America.

The post Swede Midge: a potential ‘perfect storm’ appeared first on Grainews.