Deadhead Common Diseases

In our “Taking Out The Top Five” article, Greenhouse Grower asked the technical experts from our industry’s leading chemical companies for tips on insect prevention, diagnosis and treatment.

This month, we’re using that same mold, but we’re now seeking out advice to tackle some of the most common diseases growers face worldwide. Keep in mind diseases do vary with climate, geography and crop. This top five list of common plant infections includes botrytis, powdery mildew, pythium, phytophthora and fusarium.

“If any growers are making a diagnosis for the first time, it is highly recommended that growers make clear notes and take pictures of the symptoms that were found,” advises Vijay Choppaktla, plant pathologist and director of research for BioSafe Systems. “Send infected plant samples or pictures to the nearest plant disease diagnostic laboratory for disease confirmation.” These services can be provided to growers at a minimal cost.

Botrytis

As a lover of humidity, botrytis is initially noticed as a general blight (a browning and collapse of tissue) on the leaves and flowering parts of a plant, says Nancy Rechcigl, a Syngenta field technical manager who specializes in ornamentals. “The telltale fuzzy spores are not produced until humidity reaches 85 percent or greater.”

Jeff Dobbs, director of technical service at OHP, Inc., also has some advice: “If conditions look favorable, be prepared to increase ventilation to keep flowers and leaves dry and space them out.”

Plants that have moisture (specifically condensation) on their foliage for more than four hours at a time are the ones most at risk of botrytis, which can be common with warm days and cool nights.

“Before you begin any concentrated removal of infected plants and plant parts from the growing area to prevent additional spread, be sure to first get a fungicide spray on first,” Rechcigl says. “When you dispose of the material, make sure the bag or container you put the waste in can be closed before you walk through the rest of the greenhouse. Using open dumpsters allow spores to dislodge and blow around freely.”

Also remember to use a fungicide application after any pruning has been done. And dead plant tissue also serves as an ideal host for botrytis reproduction.

“Growers that are proactive rather than reactive reduce disease pressure by applying fungicides starting the first week,” says John Schwartz, market manager for BioSafe Systems turf and ornamental division. “With this practice, growers actually eliminate mounting pressure every time they apply.”

BASF’s Steve Larson agrees. Larson is the national ornamentals account manager for BASF. He believes many growers are starting too late with preventative treatments.

“Prevention is much cheaper than curative,” he says. “Once you see symptoms, the disease is established and you may end up throwing away some plants.”

Powdery Mildew

Easily identifiable by the white powdery spore growth on the upper surface of the leaves, powdery mildew can sometimes be mistaken for downy mildew infection when the mildew happens to develop first on the underside of the leaves, says Syngenta’s Rechcigl.

Unlike botrytis, free moisture on plants does not favor powdery mildew, but actually limits its development. It does however enjoy a relative humidity of 70 percent or higher and cooler temperatures, 62 to 72 degrees. When the temperature reaches 85 degrees and above, you will see powdery mildew stop developing.

“High night humidity is congenial for establishment of powdery mildew,” says Choppaktla of BioSafe Systems.

By the time growers react to powdery mildew, there is already plant injury that cannot be reversed, says Schwartz of BioSafe Systems. “This also weakens the plants and leaves them susceptible to other diseases and insect injury.”

Emphasizing a “detective frame of mind,” any chance Schwartz has to “get a down and dirty view” of his plants with the Bausch & Lomb 10X magnifying lens his grandfather passed onto him is his best defense against a full blown epidemic.

Choppaktla agrees and recommends that scouting be done every three days to at least once a week.

Rechcigl says it’s good to start a preventative fungicide program on a 14-day schedule when environmental conditions are conducive to disease development. “If powdery mildew does break into your crop and you have an active infection, you’re going to want to reduce that interval down to seven days.”

Pythium

When it comes to pythium, don’t rely on visual observations only, Larson says. Send suspect samples to a qualified pathologist.

“Pythium is one of the most common causes of root rot or damping off, but it usually doesn’t leave many clues as to its identity,” says Dobbs of OHP, Inc.

Since pythium attacks a plant’s root system that results in a plant wilt, growers can mistakenly respond to this visual sign by additional irrigation. “Additional water is the last thing a pythium plant needs,” adds Larson.

Pythium symptoms can commonly misguide growers to believe they have another root disease on their hands like fusarium, phytophthora and rhizoctonia, and a broad spectrum formula fungicide will be necessary, Choppaktla says.

Ideal conditions for pythium include poor water aeration, water logged media and cool temperatures. Allow plants to dry down between irrigations. It’s important to also monitor the level of soluble salts in the growing media. “High soluble salt in the growing media can injure roots and make them susceptible to infection,” says Rechcigl. “If you’re using a lot of liquid fertilizer on a constant basis, it’s important to check that routinely and leach when necessary, because salts can build up in the media and cause root burn.”

Lastly, water sanitation can play a role in the introduction of pythium, especially for those growers using recycled water sources (e.g., ponds). The filtration/sanitation system may need to be improved or if one is not in place, one should be considered.

Pythium and phytophthora belong to the same class of fungi-like organisms called Oomycetes. They thrive in familiar conditions and produce symptoms that are very similar to each other, says Choppaktla. This commonality reinforces the importance of lab diagnosis in order to accurately treat the disease. There are also test kits available for growers to make accurate, on-site identification, says Dobbs.

Fusarium

A disease common in chrysanthemums and cyclamen, fusarium can overwinter in the soil, festering in the waste of infected plants, says Dobbs. Once it has established itself, it can be extremely difficult to completely remove fusarium from the soil.

“Know your crop,” stresses Larson. If the crop has shown a receptiveness to this disease in the past, start early and consider a preventative “sprench” (spray/drench) program that gets down to the crown of the plant.

Unfortunately, once the symptoms of a vascular disease like fusarium appear, it may be too late for the plant. It can cause root, crown and stem rot by growing into the vascular system and blocking movement of water and nutrients into the upper canopy.

When further investigating the symptoms, cut into the stem, says Rechcigl. “You’ll notice a reddish-brown streaking in the vascular tissue that’s very indicative of a fusarium infection.”

Leave a Reply

Latest Stories
HV-100 Robots (Harvest Automation)

May 3, 2016

Harvest Automation Makes Strong Commitment To Greenhous…

The company recently announced it is selling off its robotic warehouse automation business to focus more on providing robotic materials handling to the greenhouse, vegetable, and fruit markets.

Read More

May 3, 2016

Migrant Farm Workers Moving Around Less Than In The Pas…

The number of farm workers who migrate and work on multiple farms during the growing season dropped from 55% in 1998 to 20% in 2009.

Read More
Wave Petunias Team

May 3, 2016

Hot Pink Wave-Rave Van Making Its Way To The Big Apple …

Imagine driving down the road, minding your own business, when you’re passed by two smiling, waving, happy women driving a hot-pink van that’s adorned with petunia and pansy flowers. That’s not something you see every day, but motorists in the Midwest and Northeast may catch a glimpse of the Wave-Rave van this week as Ball Horticultural Co.’s Claire Watson, Product Marketing Manager, and Katie Rotella, Marketing Communications Manager, make their way to a media tour and plant giveaway in New York City. Watson and Rotella visited Cleveland’s WOIO Channel 19 news on Tuesday morning to tell consumers about Wave Petunias and Wave Pansies, and remind them to visit their local garden centers to purchase gifts for Mother’s Day this weekend. Check out this clip on Periscope. After the morning news, the ladies stopped by to visit the Greenhouse Grower staff at Meister Media Worldwide in Willoughby, OH. Next stop: Chelsea Garden Center in Brooklyn, NY, where […]

Read More
National Garden Bureau CAST 2016 Bloggers

May 3, 2016

5 Things Gardens Bloggers And Writers Learned At Califo…

For the second year in a row, the National Garden Bureau hosted five popular garden bloggers and writers on a trip to California Spring Trials. Here’s what each of them had to say about their experience.

Read More

May 3, 2016

SNA’s Summer Tradeshow Is Revamped As SEGreen

SNA is hosting a new summer show, SE Green, in Athens, GA. It mixes a conference for Southeast-based landscapers, growers, and retailers, with exhibitors.

Read More

May 2, 2016

A Fire At A New Hampshire Garden Center Challenges Spri…

Petal Pushers Farm in Laconia, NH, suffered a two-alarm fire two weeks prior to Mother's Day Weekend. It is already back up and running, but is scrambling to replace its losses.

Read More

May 2, 2016

Surprise Customers With Over-The-Top Service This Mothe…

The day before Thanksgiving a few years ago, I reluctantly pulled into Central Market’s parking lot. Central Market is a popular, high-end Texas grocery store chain, the luxury brand for the middle-of-the-road HEB stores. As expected, the parking lot was packed. There wasn’t a space in the main part of the sizable lot, so I had to park some distance away. It wasn’t a promising start to what I fully expected to be an irritating afternoon. But I was making butternut squash soup and providing wine for the holiday dinner the next day, and so I couldn’t procrastinate any longer. I was doomed to endure the busiest shopping day of the year for grocery stores. I grabbed a mini double-decker cart, resigned to cranky crowds and jostling for space in the produce aisles. I walked in and paused to figure out where I could find the butternut squash. Almost instantly, an […]

Read More
Small Aphid Colony on Calibrachoa

May 2, 2016

How To Stop Aphids In The Greenhouse

When untreated, aphids damage ornamental crops and act as vectors for disease. Integrated Pest Management combined with vigilant scouting can help you stay ahead of the problem.

Read More
Priva FS Reader

May 2, 2016

What’s New In Greenhouse Environmental Controls

Growers today are looking for systems that save energy, are easy to use, and can be accessed remotely. New products from leading manufacturers are designed to tap into these needs.

Read More
PMA Floral Anaheim

May 1, 2016

Produce Marketing Association Plans Floral Supply Chain…

The PMA Fresh Connections: Floral events will unveil new market research and trends, while offering insights into the changing landscape of floral retailing.

Read More
Farwest Show Floor

April 30, 2016

Registration Is Open For Farwest 2016 In Portland, OR

This year’s show takes place Aug. 25-27 and features educational sessions, nursery and retail tours, and an expansive trade show floor.

Read More
Chick Charms

April 29, 2016

Kelly Norris: Why The Plant Collector Market Is Set To …

In his latest column for Greenhouse Grower magazine, Kelly Norris says there are more plant collectors out there than we think, which opens the way for the gift plant market to explode.

Read More
Natureworks Monarch life cycle caterpillar FEATURE

April 29, 2016

Do Customers Really Care How Plants Are Grown?

The consumer uprising against neonicotinoids has roiled the industry over the past couple of years. In June 2013, someone applied pesticide to a tree in full bloom, using the product in an off-label manner. That misapplication killed tens of thousands of bees, capturing the attention of activists. A short three years later, that activism has led to policy changes for big chains like The Home Depot and Lowe’s. Several cities and towns across the country have banned the sale of neonicotinoids, as has the state of Maryland. All of this made me curious. How was all the publicity affecting consumer attitudes at local garden stores? Traditionally, customers have shown little interest in how flowering plants are grown, other than they like the idea that they are from a local source. They have been much more particular about food plants than they have ornamentals. So I sent questions out to a […]

Read More
Pennisetum Fireworks

April 28, 2016

Why Ornamental Grasses Are Great For People In Condos A…

Allan Armitage says breeders need to do a better job of making growers, brokers, and garden centers aware of better ornamental grass cultivars for the increasingly shrinking garden space.

Read More

April 28, 2016

Holistic, Integrated Approach To Pest Control Rooted In…

Greenhouse growers have been practicing integrated pest management for decades, but it’s becoming increasingly more important with the continued scrutiny of conventional pest control by a number of “regulators” — government, retail, and consumers. I just returned from Meister Media Worldwide’s Biocontrols USA 2016 Conference, in Monterey, CA, at the beginning of March this year, which served 450 attendees and 50 exhibiting supplier companies. It’s clear from the presentations and the growing attendance at this specialized event — now only in its second year — that use of biocontrols in IPM will continue to be adopted widely, as more growers get past their personal hurdles of doubt and intimidation, and embrace a new way to approach pest and disease control. Many growers think of using biocontrols as an all-or-nothing approach, but ultimately, IPM is about balance. Growers will need to continue to focus on IPM, integrating chemistry with biology, because […]

Read More
Drip irrigated citrus liner

April 27, 2016

Unclog Drip Emitters In Your Greenhouse

This is the first article in a series of case studies designed to help growers reduce, remediate, and recycle irrigation water as part of a multi-state research grant (CleanWateR3.org).

Read More

April 27, 2016

Use Your Data To Make Smarter Marketing Decisions

Learn which marketing metrics are important to your business, measure successes, and learn where changes are needed.

Read More
Andropogon gerardii Blackhawks (Intrinsic Perennial Gardens)

April 27, 2016

Know Your Market When Choosing Ornamental Grasses

Growers have no shortage of choices in the ornamental grass market. Narrowing down the selection comes down to finding the right plant for the right purpose.

Read More
[gravityform id="35" title="false" description="false"]