Phytophthora: Not Just a Bean Disease

Mention the word “Phytophthora” and many readers will think of damping off in soybean fields. They think of massive seedling death due to fungal infection. However, this disease is not only a scourge in grain production. Phytophthora can present a serious threat in peppers, tomatoes, and eggplants. In our area, it is well known for sometimes causing devastating losses in pumpkins.

The water-loving fungus responsible for causing this disease is not the same species that plagues soybean fields, but it is related. Beans are attacked by Phytophthora sojae, while pumpkins are attacked by Phytophthora capsici. The names may be different, but the lifecycles of both fungi are similar. Phytophthora fungi can infect plants throughout the growing season killing seedling plants, causing crown collapse in more mature plants, forming leaf and/or stem lesions, and infecting fruit both pre- and post-harvest.

Phytophthora capsici persists in the soil and/or within debris as thick walled spores, termed oospores, that tend to be very hardy. Oospores are the “offspring” of “mating” by strands of fungal hair (mycelia). Given warm, wet conditions – oospores produce “bag-like” structures called sporangia (singular “sporangium”). Eventually, zoospores (swimming spores that actually have “tails” – correctly named “flagella”) are produced. Given time and wet conditions, these swimming spores come into contact with and eventually enter the plant. Additional sporangia are produced from this infection, and those sporangia release additional zoospores. The fungus itself may be observed as a white mold growing on plant tissue.

Symptoms of infection vary. Small dark lesions may develop in proximity and a few inches above the soil line as plants are eventually killed by the “damping off” version of this disease. Crown rot may eventually produce dark brown lesions that girdle the stem, killing everything above. Leaf symptoms may eventually cause foliage to brown. Fruit can become covered with white, moldy lesions. Lesions often start on the portion of the fruit in contact with the soil, but they can also appear in proximity to the fruit stem. Yield losses may approach 100 percent in some cases.

Phytophthora management in beans and Phytophthora management in pumpkins have some similarities. However, there is one significant difference between management in pumpkins and management in beans.

In beans, the use of resistant varieties is widespread. Soybean growers are familiar with resistant traits such as Rps1k, Rps1c, and Rps1a, and they often use these traits in the field. Unfortunately, resistance has not proven to be an option in pumpkin production. Instead, pumpkin growers rely upon a host of cultural and chemical management techniques.

On the cultural side, growers are encouraged to rotate pumpkin production from field to field to reduce the chances of encountering Phytophthora blight. They are also encouraged to stay away from fields that were previously in other Phytophthora host crops (peppers, tomatoes, etc.).

Growers also try to encourage a less-favorable environment for the disease by planting the crop where water does not tend to stand. In a similar fashion, growers are also encouraged to maintain good drainage. Both practices eliminate water from the Phytophthora-equation making it difficult for zoopsores to reach healthy plant tissue. Minimizing the spread of this disease is also important. The University of Illinois discourages growers from working fields when wet, encourages growers to clean equipment – when possible – before moving from field to field, and emphasizes that diseased fruit/plant material should be removed from the field as soon as possible.

Growers are encouraged to harvest ripe fruit as soon as possible to reduce any potential exposure to the fungus and/or time for the disease to develop post-infection. Chemical recommendations typically revolve around the use of mefenoxam (an RNA inhibiting seed treatment) and mixtures of dimethomorph (a post-emergence, sterol-inhibiting fungicide) and copper compounds. The former provides a few weeks of protection following emergence.

Leave a Reply

Fungicides Stories
FungicidesSudden Death Syndrome, Brown Stem Rot Reported In Indiana Soybeans
September 3, 2014
Farmers and retailers should be watching for symptoms of these two diseases over the next few weeks as they are best managed through preventative methods. Read More
FungicidesResearchers Target Soybean Disease With Genetic Resistance Study
August 6, 2014
University of Illinois researchers will share new information on controlling sudden death syndrome through genetic resistance at this year's Agronomy Day. Read More
Soybean field
FungicidesValent Launches New Seed Protection Fungicide For Soybeans
July 16, 2014
The INTEGO SUITE System contains the first new, novel seed protection fungicide chemistry registered in 30 years by the EPA for protection against Pythium and Phytophthora. Read More
FungicidesNew Players May Make Pest Headlines In Corn, Soybean
April 1, 2014
The usual insects and diseases took a bit of a break in 2013, but other culprits surfaced — and could return. Read More
Top 100 Articles
CropLife 100Pinnacle Expands Sanders Brand In The South
February 27, 2015
Pinnacle has acquired Hopkins Seed and Chemical in Qulin, MO, which expands the company's Sanders brand to nine Southern states. Read More
CropLife 100Pinnacle Launches New Providence Agriculture Location In Indiana
February 27, 2015
Pinnacle Agriculture Holdings — ranked No. 6 on the CropLife 100 — has established a new retail location in New Castle, IN, which will operate as part of Pinnacle's Providence Agriculture brand. Read More
CropLife 100Cooperative CHS Returns $518 Million To Owners
February 23, 2015
The 2015 cash return to owners is based on CHS net income of $1.1 billion, the company's second highest on record. Read More
corn field
CropLife 100The Andersons’ Humic DG Now Available In Canada
February 13, 2015
The Andersons, Inc. Turf & Specialty Group has announced its Humic DG product is now available to customers in the Canadian turf, agriculture and horticulture markets. Read More
Farmer on tablet
CropLife 100Southern States Co-op: An Inside Look At Our Aerial Imagery Program
February 8, 2015
Now is as good a time as any to explore the basics of what a retail aerial imagery program looks like today. Read More
CropLife 100Wilbur-Ellis Inks Satellite Imagery Agreement
February 3, 2015
Wilbur-Ellis Company has reached an agreement with Planet Labs to bring satellite imagery to the AgVerdict software platform. Read More
Latest News
CropLife 100Pinnacle Expands Sanders Brand In The South
February 27, 2015
Pinnacle has acquired Hopkins Seed and Chemical in Qulin, MO, which expands the company's Sanders brand to nine Southern states. Read More
CropLife 100Pinnacle Launches New Providence Agriculture Location I…
February 27, 2015
Pinnacle Agriculture Holdings — ranked No. 6 on the CropLife 100 — has established a new retail location in New Castle, IN, which will operate as part of Pinnacle's Providence Agriculture brand. Read More
Management2,4-D Celebrates 70 Years; GROWMARK Uses Super Bowl Ad …
February 27, 2015
Jim Gray, executive director of the 2,4-D Research Task Force, lays out planned activities to mark the chemistry’s 70th anniversary. Read More
HerbicidesUniversity Of Arkansas Flag The Technology Program Adds…
February 27, 2015
Started in 2010, the Flag the Technology program provides a visual reference for applicators to distinguish between fields planted with different herbicide-tolerant trait technologies. Read More
Luckey Farmers, Inc.’s Berkey Farm Center
Industry NewsLuckey Farmers’ Berkey Branch Certified In 4R Nut…
February 26, 2015
The 4R Nutrient Stewardship Certification Program has announced Luckey Farmers Inc.’s Berkey Farm Center in northwest Ohio has been added to its growing list of nutrient service providers to achieve certified status. Read More
Crop InputsWinField Unveiling NutriVision Technology, Ascend Dry F…
February 24, 2015
New for 2015 are NutriVision Technology, a unique tool for monitoring in-season plant nutrient availability, and Ascend WSG plant growth regulator, a new dry formulation of Ascend plant growth regulator. Read More
FertilizerNew Formulation Of NutriSphere-N Protects High Volume U…
February 24, 2015
Verdesian Life Sciences is launching NutriSphere-N HVTM, a new polymer formulation of the proven NutriSphere-N Nitrogen Fertilizer Manager that protects high-volume applications of UAN. Read More
EquipmentIowa Ag Secretary Northey Names Hagie Water Quality Lea…
February 24, 2015
Iowa Secretary of Agriculture Bill Northey has named Hagie Mfg. as a recipient of the Secretary’s Water Quality Initiative (WQI) Leader Award. Read More
FungicidesEvito Fungicide Gives Canadian Wheat Growers New Diseas…
February 24, 2015
EVITO fungicide from Arysta LifeScience North America gives Canadian wheat and barley growers a new option for disease control. Read More
Eric SfiligojThe Commodity Classic Turns 20
February 23, 2015
Two decades in, this annual gathering of all things agriculture has become a must-see event. Read More
CropLife 100Cooperative CHS Returns $518 Million To Owners
February 23, 2015
The 2015 cash return to owners is based on CHS net income of $1.1 billion, the company's second highest on record. Read More
ManagementCropLife Retail Week: On The Road Edition
February 20, 2015
Editors Paul Schrimpf and Eric Sfiligoj discuss their recent trips to the National Farm Machinery Show in Louisville and the Read More
Crop InputsLand O’Lakes Acquires FLM+ Assets
February 19, 2015
FLM+ will become a wholly owned subsidiary of Land O'Lakes, Inc., and the company will retain its employee base after closing of the deal, which is scheduled for the second quarter of the year. Read More
Seed/BiotechUnited Suppliers, Stine Seed Form Marketing Alliance
February 19, 2015
The new alliance will greatly expand sales opportunities for Stine Seed with the United Supplier Seed Link Owners. Read More
Crop InputsVilsack To Deliver Commodity Classic Keynote Address
February 19, 2015
The secretary will deliver a keynote address to several thousand farmers and ag allies during the event's General Session, to be held Friday, February 27, in Phoenix, AZ. Read More
Crop InputsSoybean Storage Tips
February 19, 2015
On-farm storage of soybeans requires some special considerations compared to corn. Read More
Monsanto Sign
Crop InputsBioAg Alliance Delivers Promising Field Trial Results
February 19, 2015
In its first full year of field trials, the BioAg Alliance reported that the top 10 microbial strains tested in corn and soybeans showed very promising results. Read More
National Farm Machinery Show overview
EquipmentNational Farm Machinery Show Attendance Up By 16K
February 18, 2015
The 2015 event saw the second highest attendance total of all time as 310,589 attendees that included exhibitors and agribusiness professionals traveled to the Kentucky Exposition Center to participate in the nation’s largest indoor ag trade show. Read More