by Dave Jefferson, Horticulture Specialist with Syngenta Canada

Note: This article was first submitted to Norfolk Farms in March 2023. Adjusted and more details added October 2024.



Vegetable growers in Ontario have become quite familiar with a new pathogen foe: Phytophthora capsici.

Spotting the early signs of Phytophthora can be tricky, and managing it can be even tougher as it moves through water and soil from one field to the next. Luckily, using a multi-pronged approach can help to lower the risk of spread.

My number one tip is to spend time on careful scouting for early disease detection.

Scouting tips

A quick drive-by won’t be enough when you’re field scouting this season.The most common symptoms of Phytophthora crown rot are wilted or stunted plants. Because of this, Phytophthora is often misdiagnosed as Fusarium, or as a drowned-out area.

When it comes to fruit rot, it’s common for foliage to appear healthy while the fruit is symptomatic. Look for water-soaked spots where soil has splashed onto the fruit. In advanced cases, white spores resembling powdered sugar can be found on the fruit.

Best management practices

There are several ways to mitigate the risk of Phytophthora in your vegetable crop. These preventative cultural practices go further than relying on crop protection technology.

Choose a well-drained site, or in fields with known Phytophthora, avoid planting the low areas to reduce the likelihood of infection.

Use raised beds and ensure your planter isn’t leaving a depression at the base of the plant to minimize pooling water.

A third solution is to grow varieties tolerant or less prone to Phytophthora, partnered with a longer crop rotation including crops that are not susceptible to this particular strain of Phytophthora.

Even before planting, consider putting a fungicide plan in place with the help of your local agronomist, retail sales rep, or Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) specialist. Certain crops are more prone to Phytophthora at the crown, while others are more prone to fruit rot. When using a fungicide, I recommend targeting where you need protection – in the root zone or on the fruit.

As Phytophthora can spread quickly and easily to multiple vegetable crops, ensure you clean your equipment, including boots, when travelling between infected and non-infected fields to avoid contamination.

What is a tool to help pepper growers battle Phytophthora? 

Orondis^® Gold DC is available to help growers manage tough water mould diseases. Orondis Gold DC is a preventative fungicide with two active ingredients: oxathiapiprolin (OXTP, Group 49) and metalaxyl (Group 4). This combination has been available on the market since 2016, but to get the most out of this tool, understanding the "what", "when", and "how", will allow wise use of this tool for the long term.



Orondis Gold DC fungicide harnesses the novel mode of action of oxathiapiprolin (Group 49), combined with metalaxyl-M, to protect from root rot in several crops, including peppers. Preventative use is key to successful management of Phytophthora capsici, so use Orondis Gold at 0.81L/ac early in the season, targeting the soil zone, as early as at planting.

How does Orondis Gold DC work? 

Physical and chemical properties 

• When applied as a drench, soil spray, or through irrigation, the two active ingredients, oxathiapiprolin and metalaxyl-M, move into the roots within two weeks. 

Source: Internal Syngenta research (Jealotts Hill, UK, 2016). Images taken 7 days after treatment and daily watering. 
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• Oxathiapiprolin has low water solubility – this means Orondis Gold sticks and stays in the application zone, providing long-lasting protection against root rot. This also means it’s important to put the product where you need it to be through application placement or supplemental irrigation.
• Metalaxyl-M redistributes across the surface and percolates down to the root zone, complementing the movement of oxathiapiprolin and providing optimal coverage of the root zone. 

Biological mode of action 

• Orondis Gold is most active against the early stages of pathogen life cycles and will stop spore germination and inhibit mycelial growth in the roots.  
• Orondis Gold is effective against Phytophthora root rot and manages populations that are insensitive to metalaxyl-M. 
• The oxathiapiprolin component of Orondis Gold disrupts the flow of lipids between cells and membranes, causing them to drown in their own fat. 
• The oxathiapiprolin component has limited or no activity against Pythium spp. 

 

How has Orondis Gold performed in peppers? 

Oxathiapiprolin and metalaxyl, the active ingredients in Orondis Gold DC, applied once at transplanting showed healthier root growth in peppers than the untreated check. This occurred even in a Phytophthora-infested field without extensive crown and root rot symptoms because of dry conditions. 

The champion of Phytopthora root protection 


Source: Low pressure field-scale research authorization in Norfolk County, Ontario, in 2022 using Orondis Gold at transplanting. Oxathiapiprolin and metalaxyl were applied as Orondis® Gold. Orondis® Gold DC contains the same active ingredients and is applied at the same g ai per hectare as Orondis Gold. Photo taken five weeks after transplant. N = 1. Performance evaluations are based on internal trials, field observations and/or public information. Data from multiple locations and years should be consulted whenever possible. Individual results may vary depending on local growing, soil and weather conditions. Always read and follow label directions. Trademarks are property of their respective owners.

What if wet conditions persist?

Consider alternating soil applications of Orondis Gold DC with a soil application of Revus® fungicide.

Plan for success

Although these tips are helpful starting points, disease control strategies are never one size fits all. Reach out to your crop advisor, trusted retail partner or your Syngenta rep (like Dave in Ontario) to help create a plan that will set you up for success this season.

With the unpredictable weather patterns, the frequency of water mould these diseases seems to be increasing and in the case of Phytophtora capsici, often once you have it, it is hard to get rid of.  

Performance evaluations are based on internal trials, field observations and/or public information. Data from multiple locations and years should be consulted whenever possible. Individual results may vary depending on local growing, soil, and weather conditions. 

Always read and follow label directions. Orondis^®, Ridomil Gold^® , Revus^® and the Syngenta logo are trademarks of a Syngenta Group Company.