What is Phytophthora: Prevention and Treatment for Your Soil and Crops

Phytophthora outbreaks can lead to huge economic losses in many agricultural crops, especially vine crops. It is a major concern that growers are spending large sums of money trying to solve. Let’s take a look at ways we can stop the spread of phytophthora and help prevent it all together. 

What is Phytophthora?

Phytophthora is a very destructive pathogen that spreads rapidly in specific conditions, generally faster than many soil-borne diseases, since phytophthora moves through water. Phytophthora is not technically a soil borne disease, being an oomycete (also known as a water mold).

How Does Phytophthora Impact Your Crops?

Phytophthora can infect young plants with what is commonly known as damping-off. As plants mature, they become susceptible to what is called crown rot or root rot. As fruit matures, they become susceptible to fruit rots. 

Whether the pathogen is attacking the roots, stems, or leaves, the disease generally spreads very quickly, starting at the interface of the soil and the plant with plants dying within several days. The fruit is usually affected as well, sometimes decaying in storage just after harvest, and then spreading to other fruit in the bin.

Conditions for Phytophthora Development

Since phytophthora spreads through water, soils with serious compaction or poor drainage are ideal settings for rapid spread of the pathogen. This is why plants in the lower parts of fields are generally the first affected, then the disease spreads from there. 

Once present in the field, the pathogen can exist for several years by living on infected plant material in the soil, then spreading or splashing through moisture and/or spore release into the atmosphere. 

How to Prevent Phytophthora

Crop rotation and cover crop integration is key to preventing phytophthora. Avoid growing vine crops after peppers, tomatoes, or strawberries. The possible exception to this rule of thumb is when you either have fields with strong biological activity, or use a cover crop blend with mustard seed designed to “fumigate” the soil in between the two crops. This blend should include oats and mustard as a minimum, and the crop should be left to grow until the mustard has been blooming for about 5-7 days, at which point it should be terminated and worked into the soil if possible. We recommend ReCoverIt FUMIGANT which offer a blend of brown mustard, buckwheat, spring oats, spring peas, nematode control radish, and African cabbage. This provides a fumigation effect which reduces phytophthora infection on the next crop. 

Subsoiling should be considered in fields that have serious compaction. Tiling is beneficial in fields with poor drainage. A biological inoculant and soil primer should also be considered in the fall before the crop, since this has the triple-action effect of loosening the soil (improving drainage), breaking down plant residues quicker (reducing infected plant material), and helping to outcompete the phytophthora by building a robust microbial community that overpowers the pathogen. The biological primer can also be added to transplant solutions and drip irrigation as desired. 

How to Treat Phytophthora In-Season

There are times when, despite your best efforts upfront, the phytophthora gets a foothold in your crop during the season. What do you do in this case? 

When this happens, it is important to closely scrutinize watering practices. Generally speaking, it is better for your crop to be on the drier side, since phytophthora spreads through water. We would rather see the plant have some water stress than die from the phytophthora. 

The use of potent microbial inoculants, such as BioQuest Foundation on the soil and BioQuest CropShield as a foliar, can help to outcompete the phytophthora pathogen and prevent it from becoming a serious problem. 

Nutrient balance is also important. Crops with adequate levels of trace minerals and other nutrients are much more resistant to disease than crops with inadequate nutrition. 

There are some chemical controls that can be used as well, although many of them are not considered organic and therefore cannot be used in organic production. 

Find a Trusted Agricultural Consultant

Phytophthora is a fast-spreading disease that can infect crops and create significant financial hardships due to crop loss. If you are experiencing phytophthora in your soil, or are having trouble growing a healthy crop, contact one of our experienced regenerative agriculture consultants to help get your soil and plant health under control.