Category Archives: Resistance

Carrot Weevil Control Update

Carrot weevil remains the most important insect pest to many Ontario carrot growers, and the amount of damage seems to be increasing in recent years. Carrot weevil females overwinter in the soil and plant debris and lay their eggs in cavities in the crown of the carrots. These eggs develop and hatch into larvae and begin to feed on the carrot root. Feeding damage from the carrot weevil larvae causes unmarketable tunneling near the crown of the carrot and can account for significant losses to commercial growers.

Continue reading Carrot Weevil Control Update

Understanding the Strobilurin Fungicides

Rutgers Plant and Pest AdvisoryIn order to understand and use fungicide resistance management strategies effectively, first learn how and why fungicide resistance may develop. This is the third in a series of articles by Dr. Andy Wyenandt, Rutgers Agricultural Research and Extension Center. Originally published in the Rutgers University Co-operative Extension Plant and Pest Advisory. Note that some fungicides mentioned here may not be registered in Canada. Always consult the label for your location before using any crop protectants.

Understanding the Strobilurin Fungicides (FRAC code 11)

The strobilurin, or QoI fungicides (FRAC code 11) are extremely useful in controlling a broad spectrum of common vegetable pathogens. You may know some of strobilurins as azoxystrobin (Quadris), trifloxystrobin (Flint), pyraclostrobin (Cabrio), or Pristine (pyraclostrobin + boscalid, 11 + 7). All strobilurin fungicides inhibit fungal respiration by binding to the cytochrome b complex III at the Q0 site in mitochondrial respiration. Continue reading Understanding the Strobilurin Fungicides

Growers Guide to the DMI or SBI Fungicides

Rutgers Plant and Pest AdvisoryIn order to understand and use fungicide resistance management strategies effectively, first learn how and why fungicide resistance may develop. This is the second in a series of articles by Dr. Andy Wyenandt, Rutgers Agricultural Research and Extension Center. Originally published in the Rutgers University Co-operative Extension Plant and Pest Advisory. Note that some fungicides mentioned here may not be registered in Canada. Always consult the label for your location before using any crop protectants.

Growers Guide to the DMI or SBI Fungicides (FRAC code 3)

The DMI (DeMethylation Inhibitors) or SBI (Sterol Biosynthesis Inhibiting) fungicides belong to FRAC code 3 which include the triazoles and imidazoles. Some of these fungicides are commonly known as Tilt (propiconazole), Rally (myclobutanil), Folicur (tebuconazole), and Procure (triflumizole). Continue reading Growers Guide to the DMI or SBI Fungicides

Growers Guide to Protectant Fungicides

Rutgers Plant and Pest AdvisoryIn order to understand and use fungicide resistance management strategies effectively, first learn how and why fungicide resistance may develop. This is the first in a series of articles by Dr. Andy Wyenandt, Rutgers Agricultural Research and Extension Center. Originally published in the Rutgers University Co-operative Extension Plant and Pest Advisory.

Growers Guide to Protectant Fungicides (FRAC codes M1 – M9)

Protectant (contact) fungicides typically offer broad spectrum control for many different pathogens. Protectant fungicides belong to FRAC groups which have a low chance for fungicide resistance to develop. These include:

  • the inorganics (copper, FRAC code M1) and sulfur (FRAC code M2),
  • the dithiocarbamates (mancozeb, FRAC code M3) and chloronitriles (chlorothalonil, FRAC code M5)

So, why wouldn’t fungi develop resistance to protectant fungicides?

Continue reading Growers Guide to Protectant Fungicides

Get the latest on herbicide resistant weeds in Ontario

Do you want to stay up-to-date on where herbicide resistant weeds have been identified in Ontario? Field Crop News can help with a searchable Master table of all herbicide resistant weed species in Ontario by County and Herbicide Group (confirmed by the University of Guelph). The post also features distribution maps (by county and herbicide group) of resistant weed species.

Here are a couple of examples of search results, the first simply typing in a county.

Herbicide Resistant Weeds - search by county Continue reading Get the latest on herbicide resistant weeds in Ontario

Management Strategies to Control Resistant Pigweed in Carrot Production

By: Kristen Obeid, OMAFRA Weed Management Program Lead – Horticulture and Clarence Swanton, University of Guelph

The Problem

Carrot growers in particular are struggling with resistant pigweed in Ontario fields, a problem that was studied extensively in 2011 and 2012. As far back as 1997, resistance to group 5 herbicides (prometryne) was noted. Then in 1998, resistance to group 2 (rimsulfuron) herbicides was noted. Resistance to group 7 (linuron) herbicides appeared in 1999. There are some weed populations with multiple resistance (i.e. resistance to both group 5 and group 7 herbicides or maybe even to three different herbicide groups).

Different pigweed species are showing resistance to herbicides, including:

  • Redroot pigweed (Amaranthus retroflexus, L.)
  • Green pigweed (Amaranthus powellii, S. Watson)
  • Smooth pigweed (Amaranthus hybridus, L.)
  • Common waterhemp (Amaranthus tuberculatus, syn, rudis)

Continue reading Management Strategies to Control Resistant Pigweed in Carrot Production

New Cucurbit Fungicides for 2014

Over the past few years there have been a number of new fungicide registrations for cucurbit crops in Canada. Each one has its own particular strengths; however it is important to find the right fit within the fungicide program.

Depending on the disease, the actual infection rates greatly between the different cucurbit crops.  For example, cucumbers are highly susceptible to downy mildew while pumpkins typically have a much greater level of tolerance to this disease. The more significant diseases for each cucurbit type are listed below (Table 1. Significant Cucurbit Diseases by Crop). When planning a preventative fungicide program, it is useful to keep these diseases in mind. Continue reading New Cucurbit Fungicides for 2014