Fungicides: How Controls Impact Efficacy

Fungicides: How Controls Impact Efficacy

Chemical control of plant disease remains a popular and often over-used mainstay of our industry. Even the best fungicides and bactericides work better when cultural control methods are used, as well. In fact, if you try to put the entire weight of disease control on the fungicides you apply after a disease appears, you will be out of business quite soon. You cannot afford to waste your money on fungicides if the deck is stacked against them working. Using an integrated disease management program is the only way to make sure you get the most out of your fungicides and bactericides.

There are many factors in cultural control of plant diseases, but a few stand out in their effect on fungicide efficacy. Some factors, like new pots and sanitation, may be important in reducing disease but have relatively low impact on the ability of a fungicide to control the disease. Other methods, like using the right amount of water or keeping the leaves dry, can make all the difference in the world on whether or not a fungicide (or bactericide) has a chance to work.

If the conditions are too much in favor of a disease, the disease will not go away even when very effective fungicides are used. Anything that stresses the plant or promotes the pathogen makes the disease worse and, therefore, the fungicide must work harder. There is no such thing as a fungicide that can overcome a disease under all growing conditions.

Recommendations

Use only new or thoroughly cleaned pots, flats and other containers. If you must re-use containers, wash and disinfest them using products containing quaternary ammonium, chlorine, peroxides or other disinfestants. I performed some simple tests in cooperation with a nursery operation to determine the actual need for cleaning if a quaternary ammonium soak was used on recycled plug flats. The best control was a thorough washing followed by a five-minute soak in a quaternary ammonium at labeled rates.

Even higher rates used much longer were not as effective as when flats were washed before treating. Other research has shown steaming flats can be very effective if the plastic will withstand it. This has been especially effective in reducing contamination of flats with the black root rot pathogen, Thielaviopsis basicola.

Use new potting media whenever possible. Do not add native soil to any potting medium without steaming or treating with a product like methyl bromide. Consider how potting medium gets into a compost or dump pile. The plants fail to grow and are not salable (signaling the possibility of a disease), or they are simply overage.

Even if plants are all overage, the quality of the potting medium when it has already been through a growing cycle is reduced, and it now contains roots and at least lower stems of the crop. Further, there usually are pesticides and fertilizers that remain active. All of these things make the “new” crop a challenge to produce because the consistency from one crop to another is gone.

How can you determine the rate of fertilizer to add when you do not know what is already in the potting medium? If you reuse contaminated potting media, you are stacking the deck against your crop and even the best fungicides do not work if the disease pressure is too high.

Don’t Dip Cuttings

Avoid dipping cuttings. This is an excellent way to spread bacterial and fungal pathogens, including Xanthomonas, Erwinia, Fusarium and Cylindrocladium. Even when effective fungicides or bactericides are used, the spores will spread throughout the entire batch of dipped cuttings. If you suspect a pathogen, a post-sticking sprench will be the most effective way to apply a fungicide.

In other cases, spraying the stock plants the day before cuttings are made can be an effective way to reduce losses from pathogens like Cylindrocladium. I have been involved in several situations where a Fusarium or Cylindrocladium cutting rot was controlled simply by stopping the pre-stick fungicide drench.

If you recycle water, consider a water treatment. This water has the same concerns as reused potting media. Fertilizer, pathogens and pesticides may wreak havoc in your propagation and throughout production of the crop. The most common pathogens spread this way are the water-molds: Pythium and Phytophthora.

Additionally, do not water crops from overhead. Wet leaves are ideal targets for many plant pathogens. Splashing rain water or overhead irrigation spreads spores for bacteria and many fungi.

Keep in mind that rescue treatments with fungicides do not work when disease pressure is too high.

Table 1. Relative impact of cultural controls on disease and fungicide efficacy. 

Cultural Control Strategy Effect On Disease Effect On Fungicide Efficacy
Sanitation Low to medium Low
Disinfesting tools and equipment Low to medium Low
New pots, flats Medium (soil-borne mainly) Low to medium (can be high if a resistant strain is carried over)
New potting media Very high, easiest way to have root and crown disease Very high
Clean seeds, plugs, cuttings and liners Very high, easiest way to have root and crown disease Medium
Dipping cuttings Very high, best way I know to spread disease to all cuttings at once High (adding effective fungicides to a dip is often ineffective due to extreme disease pressure)
Remove diseased plants Medium, stops spread Medium
Keep leaves dry Very high, can control many foliage diseases with dry leaves alone High, disease pressure is low when leaves are dry
Use the right amount of water Very high High, over-watering shortens longevity of fungicid


Leave a Reply

More From Crop Inputs...
Fred C. Gloeckner Foundation logo

September 1, 2015

Gloeckner Foundation Elects New Directors And Board Member

The Fred C. Gloeckner Foundation, Inc. held its annual meeting on May 30, 2015, electing a new president, vice president and one new board member. Newly elected officers, directors and board members are: Former vice president of the foundation, Dr. Richard Craig was elected president and chair of the research committee. Craig, a professor emeritus of plant breeding and the J. Franklin Styer Professor Emeritus of horticultural botany at Pennsylvania State University, is considered a pioneer breeder in the industry. In 1990, he was inducted into the Floriculture Hall of Fame, the industry’s highest honor. Craig has spent 45 years in genetics and breeding research, and has made countless contributions to horticultural science. Dr. Paul Allen Hammer, professor emeritus of floriculture at Purdue University, was elected vice president. Hammer has served on the Gloeckner Foundation board since 2001. His expertise in greenhouse production and management, experimental design and analysis and plant […]

Read More
Bill Lewis grower manager at Delray Plants

August 31, 2015

Delray Plants Takes Preventative Approach To Pest Control With Biological Controls

The 300-acre nursery in Venus, Fla., has made biologicals its first line of control when dealing with pests.

Read More
Fred C. Gloeckner Foundation logo

August 31, 2015

Gloeckner Foundation Awards 15 Research Grants

The Fred C. Gloeckner Foundation recently awarded 15 grants totaling $149,776. Fred C. Gloeckner had a keen interest and firm resolve to facilitate innovation and improve practices in floriculture. It was this vision that inspired him to start The Fred C. Gloeckner Foundation, Inc. 55 years ago. Since the foundation’s inception, more than 66 institutions have been awarded grants for this purpose, and the foundation’s support of floriculture research has totaled $6,525,642. The following grants were recently awarded: $14,000 – Kansas State University, to study the effect of the entomopathogenic fungus, Beauveria bassiana and the rove beetle, Dalotia coriaria, in suppressing populations of the western flower thrips, Frankliniella occidentalis $12,264 – North Carolina State University, for expanding leaf tissue nutritional standards in bedding plants $12,000 – University of Florida, to illuminate Lilium floral fragrance $11,842 – Stephen F. Austin State University, for its herbaceous perennial species trial garden $10,000 – Iowa […]

Read More
Latest Stories
Bill Lewis grower manager at Delray Plants

August 31, 2015

Delray Plants Takes Preventative Approach To Pest Contr…

The 300-acre nursery in Venus, Fla., has made biologicals its first line of control when dealing with pests.

Read More
Bob’s Market and Greenhouses’ Ron Morris pours Stockosorb into the hopper for distribution on the conveyor line

August 13, 2015

Soil System Improves Growing And Sales

My father started our company 45 years ago growing bedding plants, mainly early season production and finished plants for our West Virginia market. It was in the early 1980s that we started growing earlier spring production and shipping materials to southern markets, and by the late 1980s, we also produced pansies for fall. We started using hydrogels when they first came on the market in the early 1990s and found that they really helped with our production by keeping plants healthier for these new markets. Over the years, we’ve grown to be a large young plant producer and have a sizable business growing finished plants in cell packs, 4 1/2-inch pots, 6-inch pots, gallon containers, hanging baskets, multiple sizes of large containers and large baskets for municipal use. Creating The Ideal Soil Mix With our old system, it took several workers to mix pre-made soil with slow-release fertilizers in cement […]

Read More
Fertilizer Rates Feature Image

August 12, 2015

Selecting Fertilizer Rates For Several Spring Bedding P…

Fertilizing bedding plants can be difficult due to the differing needs of the large variety of plants that we grow. Many operations do not grow enough of any one crop to cater the fertilizer specifically for each crop. Therefore, grouping crops with similar fertilizer requirements and having two to three fertilizer strengths available is a practical way to ensure plants are getting the fertilizer they need. With many new plant varieties on the market, we wanted to conduct a trial at Cornell University to determine best fertilizer rates for several common bedding plant crops. 22 Bedding Plants Studied To Establish Fertilizer Rates Plugs and rooted liners of 22 crops (Table 1) were transplanted into 4-inch (500 mL volume) round pots with a commercial peat/perlite based substrate. The plants were grown in a glass greenhouse at Cornell University during the spring season at a spacing of one plant per square foot. Heating set […]

Read More
Feature image The Aphid Guard Aphid Banker Plant, coming soon to the market, supports beneficial insect populations.

June 21, 2015

The Latest In Crop Protection

Protecting your plants from the latest threats is no easy task, but new product lines promise to safely and effectively eliminate a wide range of pests and diseases, without harming your employees or the environment.

Read More
Bee On Flower

June 18, 2015

Pest Management And Marketing Strategies For Bee-Friend…

Michigan State University Extension shares pest management practices to produce plants that are safe for pollinators and marketing strategies for clearing up confusion about bee-friendly plants.

Read More
NSOrganicPlantFood3-1-1_featured

June 13, 2015

UMASS Fertilizer Trials Recommend Nature’s Source Organ…

In a recent online fact-sheet at its Extension website, the UMass Amherst Center for Agriculture, Food and the Environment lists Nature’s Source Organic Plant Food 3-1-1 as “the best liquid organic fertilizer,” according to Dr. Douglas Cox, Stockbridge School of Agriculture. It is called-out by the Extension after a number of years of studying the use of organic fertilizers for growing commercial greenhouse crops. The trials evaluated traditional water soluble and granular slow-release chemical fertilizers. Dr. Cox recommends Nature’s Source Organic Plant Food 3-1-1 as a liquid fertilizer that is readily available, cost effective, OMRI-listed and with good label directions for greenhouses. He also mentions the ease-of-use in how it mixes well with water and can pass fertilizer injectors. “Nature’s Source is currently the best liquid organic fertilizer,” Cox wrote in his article “Organic Fertilizers – Thoughts on Using Liquid Organic Fertilizers for Greenhouse Plants,” “I have seen no foliar chlorosis yet with this fertilizer. Nature’s source is widely available and a great […]

Read More

June 10, 2015

BASF’s Sultan Miticide Receives California Regist…

BASF Sultan miticide recently received registration in California, giving ornamental growers a new rapid, targeted mode of action for mite control. Sultan miticide, with active ingredient cyflumetofen, offers ornamental growers targeted knockdown of all life stages of tetranychid mites, with long residual control. It has practically no toxicity to beneficial insects, including predatory mites and pollinators. Sultan miticide offers a new mode of action to combat cross-resistance with other commercial miticides, and is compatible with integrated pest management programs (IPM). “The long-awaited California registration of Sultan miticide is exciting news. Greenhouse, nursery and landscape professionals in the state now have a new class of chemistry that gives them fast control over all life stages of plant-damaging mite populations,” says Joe Lara, senior product manager for BASF. “Sultan miticide now provides California growers with a much needed new first choice for miticide resistance management programs that won’t disrupt populations of beneficial […]

Read More
Bee on a Sedum

May 27, 2015

Industry Associations State Their Support Of National P…

AmericanHort, Society of American Florists, American Floral Endowment and Horticultural Research Institute joined together to embrace key aspects of the federal government’s recently announced National Strategy for the Protection of Honey Bees and Other Pollinators. The long-awaited strategy has three major goals: reducing honey bee colony losses, increasing Monarch butterfly populations, and restoring or enhancing millions of acres of land as pollinator habitat through public and private action. According to the statement, the associations are studying the details, but they agree that the overall approach appears balanced and mostly sensible. The rest of the statement reads as follows: “The national strategy’s overarching goals dovetail well with the focus of the ongoing Horticulture Industry Bee and Pollinator Stewardship Program. Under that initiative, we have directly funded several priority research projects, and collaborated on additional research funded by others, to provide critical scientifically sound guidance for professional horticulturists. We are developing a grower […]

Read More
Bee On Flower

May 20, 2015

White House Task Force Releases Pollinator Health Strat…

An interagency Pollinator Health Task Force commissioned by President Obama released its “Strategy to Promote the Health of Honey Bees and Other Pollinators” on May 19. The strategy, released in accordance with the Presidential Memorandum issued last June, is accompanied by a Pollinator Research Action Plan, which outlines needs and priority actions to better understand pollinator losses and improve pollinator health. The recommended actions will be supported by a coordination of existing federal research efforts and accompanied by a request to Congress for additional resources to respond to losses in pollinator populations. Pages 47 through 52 specifically address pesticides and pollinators. The report calls out plant production, native plants, mosquito control and all urban uses in its Pollinator Action Plan. RISE (Responsible Industry for a Sound Environment) says it supports the goals of improving pollinator health and habitat contained in the White House Pollinator Task Force’s release of its National […]

Read More
r3bv2 disease

May 20, 2015

SAF And AmericanHort Ask Government To Take Ralstonia O…

The Society of American Florists (SAF) and AmericanHort want Ralstonia solanacearum, Race 3, Biovar 2 (R3Bv2) taken off a list of animal and plant diseases that the federal government has determined could be misused as terrorist weapons. SAF and AmericanHort submitted formal comments together on the horticulture industry’s science-backed position on the matter. According to Lin Schmale, SAF’s senior director of government relations, extensive research has proven R3Bv2 does not belong on the government’s list of animal and plant diseases that can be misused as terrorist weapons. Every two years, USDA’s Animal and Plant Health Inspection Service (APHIS) requests a public review of the Select Agent list, asking for comments on whether plant or animal diseases should be taken off the current list or added to it. In the floral industry, R3Bv2 can have a devastating impact on geranium (pelargonium) crops, Schmale says, and both the potato and tomato industries also could be adversely affected by introduction […]

Read More
Two-spotted spider mites, adults and eggs

May 18, 2015

Beware Of Spider Mites In Bougainvillea And Mandevilla …

Greenhouse growers need to scout for spider mites on bougainvillea and mandevilla and use appropriate treatments that minimize pesticide resistance.

Read More
CrownBees_Blue-Orchard-Bee-Female_Artz

May 14, 2015

Pollinator Health 2015: What’s Next For Horticult…

The news on pollinators and neonicotinoids continues to fluctuate between good and bad. Research and outreach efforts backed by the Bee and Pollinator Stewardship Initiative help move the industry in a positive direction.

Read More
empress-intrinsic-brand-fungicide

May 13, 2015

BASF’s Empress Intrinsic Fungicide Is Approved Fo…

BASF’s Empress Intrinsic brand fungicide received supplemental labeling, providing California growers with an effective drench fungicide for disease control and plant health. The supplemental labeling is for use on herbaceous and woody plants in greenhouse, nursery container and field production in California. Empress Intrinsic fungicide provides protection against the four major root and crown disease pathogens: fusarium, phytophthora, pythium and rhizoctonia. Research shows Intrinsic fungicides control the broadest range of ornamental diseases while improving plant resilience to quality and reducing stresses that commonly occur during commercial production, handling and transportation. “More and more growers across the country are discovering the benefits of Empress Intrinisic brand fungicide treatments at propagation for rooted plugs, cuttings and seedlings, and in drench applications on transplants during the production cycle to protect against the major root diseases,“ says Joe Lara, senior product manager for BASF ornamentals. “A BASF fungicide program utilizing Pageant Intrinsic and Empress Intrinsic […]

Read More
Green Mum Basket

April 21, 2015

Growers Face Dilemma In Managing Plant Growth

Whether you’re applying plant growth regulators, manually pinching plants or using automated trimming, the most important thing is to find the right balance.

Read More

April 20, 2015

Three Michigan State University On-Demand Webinars Offe…

The first rule of effective insect and disease control for vegetables is to take action to prevent problems before they occur. But in order to do that, you need to have an effective pest and disease management strategy in place that incorporates best practices to ensure a successful outcome. Michigan State University offers three pest and disease management on-demand webinars that will get you started and keep you on the right track.

Read More

April 15, 2015

BASF’s Pageant Intrinsic Fungicide Registration A…

The state of California has approved the supplemental label registration of Pageant Intrinsic brand fungicide for disease control in the commercial production of greenhouse-grown tomatoes and tomato transplants for the home consumer market.

Read More
Egg card used for insect control in Parkway Garden’s retail area.

April 13, 2015

Biocontrols Use Requires Commitment

For some companies, a switch to biocontrols is an easy decision to make. Parkway Gardens of Ontario, Canada, began using biocontrols nine years ago after Erik Jacobsen, the company’s owner, wanted to expose Parkway, its customers and the environment to fewer pesticide products. “Many pesticides were increasingly ineffective, and in Canada, new product registration moves with glacial slowness,” Jacobsen says. “The labor cost of applying pesticides is much greater than using biocontrols.” In addition, it was also an opportunity to market the company’s eco-friendliness to a younger demographic, he says. In a Q & A with Greenhouse Grower, Jacobsen explains what biocontrols and methods have proved effective for Parkway Gardens Greenhouse Grower: In what types of greenhouse structures are you using biocontrols? Erik Jacobsen: Our greenhouses are all poly covered. About half the range is a Westbrook 14-foot at peak gutter-connected block, and the remaining half a mix of quonset-style […]

Read More

April 11, 2015

Lowe’s Announces Commitment To Phase Out Neonicotinoids…

Home improvement retailer Lowe’s companies announced April 9 that it has committed to eliminate neonicotinoid pesticides from its stores in a gradual phase-out over the next 48 months. In response, horticulture industry associations issued a statement that Lowe’s position is surprising, considering the most recent and positive reports on the state of honeybee health and recent peer reviewed research, and that this is an issue for which sound science must take priority.

Read More