Manitoba Weekly Vegetable Report

Introduction

The persistent cold weather, and rain events the last week have not been welcomed in our scouting area. Many fields remain moist, and harvesting operations have been delayed in many crops. Cole crops were expected to be completed this week and the next, an estimate that was overly optimistic as harvest could continue until the end of September.

Most onion crops have been pulled (as in removed from the ground) but still remain in the field to dry prior to placement in storage. The rain over the past week, has posed some real problems, and concerns regarding post-harvest problems could become a reality. There has also been sizing issues with some later planted onions, which have not reached the desired size in order to reach the most desirable price.

Pumpkins and cucumbers are being harvested, size is quite variable.

Some carrot harvesting has taken place, but about 80% remains in the field,

Sunny, warm (20°C) and dry weather would be appreciated for the next two to three weeks.

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Carrots

Carrot growth continues and is approaching near harvestable size.

Forked carrots appear to remain at the typical 10-15% level in sampled carrots, observed from previous weeks. It is becoming apparent that aster yellows is at a significantly lower level than last year.

There are still carrots that are showing symptoms, but the incidence level is quite low. (Random sampling of carrots would put this at "trace" levels--too low to accurately assess). This is obviously good news.

The pictures below show fields near Delta, Manitoba. The picture on the left shows a field from 2007 in which the level of disease was estimated at about 60%. The picture on the right is a carrot field from this year, in almost the same location. The picture from 2007 was taken in early September, the 2008 picture was taken on September 10. These pictures very clearly illustrate what a difference a year can make with respect to aster yellows. Last year was the highest population we have seen in nearly ten years of scouting. This year is the lowest in those same ten years. The difference? A lack of movement into the Province of aster leafhoppers during their regular migration. It would seem the storms through the American Midwest in spring did us a tremendous favor in blowing the usual aster leafhopper migration off course. We don't expect the same thing to happen next year.

No other diseases or insect issues to report on carrots at this time.


Aster Yellows symptoms from Delta, MB, mid-September 2007	Aster Yellows symptoms from Delta, MB, September, 10, 2008

AYI is calculated by taking the number of leafhoppers and multiplying this by the infectivity level below. The migrating aster leafhopper population infectivity in Wisconsin is 4%. This is slightly higher than the normal 0-2%.

Crop	AYI
Carrots
Resistant (eg. Six Pak II)	100
Intermediate	70-75
Susceptible (eg. Spartan Bonus)	40-45
Celery, Romaine	30-35
Head Lettuce	20-25

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Cole Crops

Cauliflower with some early symptoms of Alternaria leaf spot and Black rot were observed in the outer most leaves. Black Rot in particular can cause significant problems in the field, but levels do not appear to be of economic concern, with harvest underway. Alternaria can cause rotting in storage, primarily in cabbage (due largely to the fact that most of the cauliflower foliage is removed-and cauliflower generally aren't stored anyway, this is not a great problem on cauliflower.

Flea beetles continue to be present in fields though they seem to only be damaging cabbage at this time. They will soon go into the ground to spend the winter, but until they do they are causing significant damage to wrapper leaves at this time in some fields.

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Sweet Corn

Appears Sweet corn is still being harvested, crop appears to be in good shape.

Rust, holcus spot, northern corn leaf blight and northern corn leaf spot, raised concerns throughout the season, but in the end the crop has done well, and damage from these pathogens, was minimal in the fields scouted.

A number of concerns regarding the disease gray leaf spot, were brought to our attention. To reiterate, we have not seen this disease in Manitoba. It is on the labels of fungicides registered for use in sweet corn grown in Manitoba, and in the parts of North America where it is found (largely the east coast and midwestern states) it can be a serious problem. Thus far we are fortunate not to have this pathogen in Manitoba, or more accurately we have yet to see symptoms of gray leaf spot in Manitoba.

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Cucurbits

Cucurbits are being harvested, and while sizing may not have been ideal, a crop is being harvested.

Since angular leaf spot was detected in July, no other cucurbit diseases have appeared in our scouting fields.

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Onions

Many onions have been harvested, many remain in the field, either actively growing, or drying.

Disease wise, there are significant concerns related to Neck rot (Botrytis allii) and also Pink root (Phoma terrestris). Both are serious diseases of onions.

Pink root can cause reductions in bulb size, when roots are significantly damaged, and ultimately yield and economic return are impacted. The fungus can also survive in soil for 6 years or more so rotations would be necessary when planting susceptible cultivars.

The recent wet weather is raising concerns in Portage fields that this could be a very bad neck rot year. The fungus grows into the bulb, via the green portions of the leaves, and can cause a softening and subsequent decay of the bulbs. As this disease shows up in storage, and is an internal rot, seemingly healthy onions can be stored and shipped. As a result, this can lead to rejections of shipments, economic losses, and challenges as to where to even dispose of the onions.

Pink root symptoms (left and right), compared to healthy (middle).

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Others

95% of Red Beets are harvested, the season is now complete.

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Prepared by: Brent Elliott Entomologist Ph. 204-745-5669 Philip Northover Pathologist
Ph. 204-745-5694 Manitoba Agriculture, Food and Rural Initiatives, Crops Knowledge Centre, Carman