Category Archives: Fungicides

What’s a Cucurbit? Downy Mildew Knows.

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Cucumber Downy Mildew

Cucumber Downy Mildew

Cucurbits are a plant family consisting of squashes, melons and gourds, including crops such as cantaloupes, cucumbers, pumpkins and watermelons. Most of the plants in the cucurbit family are annual climbing or trailing vines. Downy mildew of cucurbits is caused by a fungus which infects only cucurbit crops. Downy mildew symptoms are almost exclusively confined to the leaves. The tiny spores of the fungus fall on a leaf, germinate and force food absorbing organs into the leaf. These rootlike structures remove nutrients from the plant. Downy mildew can defoliate an entire watermelon field in 10 to 14 days.

“Clemson University plant pathologist Anthony Keinath urges South Carolina farmers to scout and spray after downy mildew infection was found June 18 on non-sprayed sentinel watermelon at Clemson’s Coastal Research and Education Center (REC) in Charleston. It is the earliest in the growing season that the watermelon strain of the disease has been found in South Carolina.The mildew also was found on cucumber, cantaloupe and several different varieties of squash over the past two weeks.

“The rainy, cloudy weather we’ve been having favors rapid outbreaks of downy mildew. Early detection is critical to controlling outbreaks,” said Keinath, professor of plant pathology in Clemson’s School of Agricultural, Forest, and Environmental Sciences (SAFES).

Keinath advises all South Carolina growers of cucurbits, a family of plants that includes various squashes, melons and gourds, to immediately apply preventative fungicides and walk their fields twice per week to scout for the mildew.”

Author: Clemson University
Affiliation: Clemson University
Title: South Carolina cucurbit growers advised to treat for downy mildew
Source: Southeast Farm Press. June 20th, 2013.

Organic Sugarbeets from Austria: Fungicide Use and Lots of Handweeding

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Organic Sugar

Organic Sugar

There is a retail market for organic sugar in the EU and until recently the demand was met with imports of organic sugar from Latin America. British Sugar began producing organic sugar in the UK in 2002 but abandoned the organic line because it was not commercially viable. Now, a small number of sugarbeet growers in Austria are growing organic sugarbeets. Without herbicides for weed control, these growers need an enormous amount of hand labor. For disease control, the organic growers spray copper fungicides.

“In the past organic sugar from sugar cane was imported to Europe. In 2008 AGRANA started to contract organic sugar beet… In 2008 organic sugar beet was grown by 105 farmers on 323 ha. Up to 2011 the organic beet area was increased to 913 ha and reached about 2% of the Austrian sugar beet acreage.

Weed control is a major issue in production of organic beet. Farmers are using harrows and inter row cultivators for mechanical weed control. In addition, an enormous input of hand labour is required, on average there is the need for 200 hours per hectare.

Control of Cercospora leaf spot and powdery mildew is carried out by spraying fungicides containing copper or sulfur. Normally two or three sprayings with copper products are required to control Cercospora. It is allowed to apply up to 2 kg Copper per hectare and year.”

Authors: Kempl, F., et al.
Affiliation: AGRANA Zucker GmbH.
Title: Organically grown beets? A growing segment in the Austrian sugar production.
Source: 73ed IIRB Congress. 2012. Proceedings of Papers:183-186.

Highest Sugarbeet Yields Ever in the UK Thanks to Fungicides

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Where Sugar Comes From

Where Sugar Comes From

The sugarbeet industry expanded dramatically in the UK in the 1920s to make Britain more self-sufficient in sugar production after severe shortages in World War 1 and after it lost most of its sugar-producing colonies. Until the introduction of new fungicides in the 1990s, UK sugarbeet growers relied on sulfur sprays for controlling diseases. The new fungicides provide better disease control and have a direct physiological effect on the plants which leads to higher yields. Refining the spray schedule with these new fungicides has resulted in the highest sugarbeet yields ever in the UK.

“In 2011, the UK sugar industry celebrated its highest ever national yield of 75.6 t/ha. A number of factors contributed to this excellent achievement, but a major contributor was the widespread and appropriate use of fungicide spray regimes across the vast majority of the sugar beet crop. These products control diseases including powdery mildew and rust, but also provide physiological benefits such as green leaf retention and early frost protection.”

Authors: Stevens, M., and E. Burks.
Affiliation: Rothamsted Research-Broom’s Barn
Title: Fungicide strategies for maximizing yield potential: lessons from 2011.
Source: British Sugar Beet Review. Summer, 2012. 80[2]:10-13.

Fungicides Cover for Failure of Crop Breeding for Rust Control in Dry Beans

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Bean Rust

Bean Rust

Bean rust usually is observed first as discrete pustules which are filled with cinnamon-brown spores, which leave a dusty brown streak when rubbed. The last bean rust epidemic in North Dakota in the 1990s caused in excess of $10 million in crop losses. Following the introduction of rust-resistant dry bean varieties produced through crop breeding, rust was not a problem until 2008 when a new race appeared which could overcome the resistance. Since the new race was first detected, rust has re-appeared every year. However, the disease has caused little damage due to frequent fungicide applications for white mold (most of the fungicides applied for white mold have some efficacy against rust).

“Between 1996 and 2008, bean varieties with resistance to rust made the threat of a bean rust epidemic in North Dakota very low. However, in 2008 a new race of the pathogen was identified in North Dakota. The new race has the ability to cause disease on the only commonly used effective resistance gene in common varieties. In 2010, the new race spread throughout North Dakota and into northwestern Minnesota. With the spread of the new race, the region is at risk again for the multimillion dollar yield losses caused by bean rust decades ago.

A fungicide application can be a very effective tool for rust management… In rust trials conducted between 2009 and 2011, all fungicides tested reduced rust severity… Because of this, a secondary benefit to a fungicide for white mold (which occurs at early bloom, R1-R2) is that the application may offer some measure of rust protection.

A fungicide application is most effective soon after the disease is found, making scouting for the disease critical.”

Authors: Markell, S., Olson, L., and Acevedo, M.
Affiliations: NDSU Department of Plant Pathology
Title: Dry edible bean rust
Source: Plant Disease Management. NDSU Extension Service. January 2012. Available at: http://www.ag.ndsu.edu/pubs/plantsci/pests/pp1601.pdf

Fungicides Enhance the Economic Viability of Southeast Asian Refugee Farmers in California

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Local Food

Roadside Stand

Most of the 95 strawberry farm stands in and around the Sacramento region are owned and operated by Mien and Hmong refugees from Laos, a small country in Southeast Asia that neighbors Vietnam. When the U.S. left Southeast Asia in 1975, hundreds of thousands of Hmong and Mien fled to the U.S. Most of the refugees were farmers in Laos and turned to farming in the U.S. Most growers lease small plots of land and grow strawberries for sale. A group of University of California researchers received a USDA grant to work with these refugee farmers. It became apparent that fungicide use is a critical element in improving the economic viability of the refugee farmers.

“Sacramento County Southeast Asian strawberry growers are very limited-resource growers who sell almost strictly at their roadside stands. UC Cooperative Extension has been working with these growers for 14 years and holding an annual meeting every March. This year’s meeting was held on March 24, 2010, and was supported by the California Strawberry Commission… A total of 52 growers attended the meeting, including several from nearby counties. In 2009-10, we received funding from the USDA to work with Sacramento County growers on food safety education, pest and nutrient management education, variety trials and market expansion.

Two of the most challenging and consistent pest problems facing Southeast Asian strawberry growers are spider mites and fruit rot… Fungicides are rarely used, and botrytis fruit rot caused by pre-Mother’s Day 2009 rains decimated all growers’ crops just before the busiest time of year. A leading grower did spray fungicide and estimated that he saved 50% of his crop.

Four treatments were compared to evaluate their effectiveness in reducing fruit rot, as well as their effects on yield.

The amount of rot per plant in the tunnel and fungicide treatments was significantly less than that of the untreated control.”

Author: Ingels, C.
Affiliation: UC Cooperative Extension
Title: Spider mite and botrytis rot trials
Source: California Strawberry Commission Annual Production Research Report. 2009-2010 Research Projects. Pgs. 99-103

Eastern Filbert Blight Would Kill All the Western Hazelnut Trees Without Fungicide Sprays

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EFB Killing Hazelnut Tree

EFB Killing Hazelnut Tree

Hazelnuts have been commercially produced in Oregon since the early 1900s when they were called “filberts.” In 1981, Oregon “filbert” growers began referring to their crop as “hazelnuts” to be consistent with the rest of the world. Oregon’s hazelnut orchards, concentrated in the Willamette Valley, account for 99% of US production and 5% of world production. Eastern filbert blight is a destructive disease of hazelnut trees that is only present in North America. The disease is known as eastern filbert blight because a shrub harbors the disease in the eastern US. In the 1920s, growers tried to start a hazelnut industry in New York. Filbert blight destroyed the trees. In 1974, the disease was found for the first time in Oregon and has spread throughout the Valley. Without fungicide sprays, the blight would kill the hazelnut trees.

“Eastern filbert blight (EFB) is caused by the fungus Anisogramma anomala…it causes severe perennial cankers, branch die-back, and eventual death of nearly all cultivars of the commercially important European hazelnut, C. avellana. …The pathogen was inadvertently introduced into southwestern Washington in the 1960s and devastated commercial hazelnut orchards because control measures were lacking at the time. It is now widespread across the Willamette Valley of Oregon, where 99% of the U.S. hazelnut crop is produced. Diligent scouting for cankers, extensive pruning, and copious fungicide applications are necessary to continue production in the presence of the fungus.”

Authors: Molnar, T. J., et al.
Affiliation: Department of Plant Biology and Pathology, Rutgers University.
Title: A real-time PCR assay for early detection of eastern filbert blight.
Source: Plant Disease. June 2013. 97[6]:813-818.

Powdery Mildew of Grapes Must be Controlled for Wine Quality

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Powdery Mildew On Grapes

Powdery Mildew On Grapes

Powdery mildew exists wherever grapes are grown for wine. The fungus that causes grape powdery mildew is an obligate parasite, which means it must grow on grape tissue and will not parasitize any other species of plants. The fungus penetrates only the epidermal cells sending tubular suckers into them to absorb nutrients. The mass of fungal growth on grape skin give the impression that the grapes are sprinkled with flour. This impression is enhanced by the smell of moldy flour released by the diseased grapes. Fungicide sprays effectively control the incidence of powdery mildew of grapes from 99% to < 1% which is very important for the quality of wine.

“Analysis of wines made from powdery mildew-affected grapes has revealed that even slight infection leads to compositional changes, an oily mouthfeel and undesirable fungal/earthy flavours when compared with wines made from disease-free grapes.

The strongest link to the effect of powdery mildew was elevated ratings of ‘oily’ and ‘viscosity’ attributes in wines made from grapes with as little as 1-5% powdery mildew compared to wines made from disease free grapes.

…wines made from diseased grapes were rated as having more pronounced fungal, earthy and cooked tomato aroma attributes than wines made from uninfected grapes.

Juice from the most severely diseased grapes had a dusty and mushroom aroma and acid taste compared to the others.

When subjected to the heat test, wines made from grapes with severe powdery mildew showed greatest haziness, so there is the potential for spoilage of wine during storage due to haze.”

Authors: CRCV Update
Title: Powdery mildew impacting on wine quality
Source: Wine Industry Journal. 2004. 19[6]:71-75.

Fungicide Recommendations Are Being Made for Increasing African Groundnut Production

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Fungicide Experiment: Ghana (top=untreated bottom=treated)

Fungicide Experiment: Ghana (top=untreated bottom=treated)

Peanuts (or groundnuts) are widely used as a food by Africans as they are a major source of protein. The productivity of peanut in Africa is very low which is particularly attributed to foliar diseases. Disease severities are so high in Africa that at harvest 80% of the leaves on peanut plants are defoliated. Research has shown that application of fungicides can successfully control diseases of peanuts in Africa and lead to substantial increases in yield.

“Lower productivity of peanut in West Africa is attributed to biotic factors (mainly foliar diseases)…

Farmers usually attribute leaf defoliation to maturing of the crop, and yield loss from foliar diseases is not recognized. Fungicide use is not a common practice in developing countries of this region partly because of lack of resources and lack of awareness of the extent of economic and yield benefits from application of fungicide.

Data on yield benefits under on-farm studies should be quantified to bring awareness to agricultural communities, and to improve access to capital resources to demonstrate that fungicide application can be economically viable with greater returns.

The objectives of our research were to quantify yield losses due to disease and to demonstrate the influence of fungicides and SSP fertilizer application on severity of leaf spot, dry matter production and pod yield of peanut crops grown in on-station and on-farm conditions in Northern Ghana, which is representative of the important peanut producing regions of West Africa.

Applications of fungicide were effective in controlling leaf spot and improved peanut pod yield on average by 48% in the three tested village sites under on-farm conditions and by about 40% under on-station conditions at two sites.

…farmers have an interest in adopting new technologies if they are certain of economic benefits. In view of the tremendous yield advantage, fungicide recommendations are being made to peanut farmers in this region.”

Authors: Naab, J. B., et al.
Affiliation: Savanna Agricultural Research Institute
Title: Response of peanut to fungicide and phosphorus in on-station and on-farm tests in Ghana
Source: Peanut Science. 2009. 36:157-164.

A floating Fungus Would Destroy Much of the World’s Rice Crop Without Fungicide Sprays

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Rice Field With Sheath Blight

Rice Field With Sheath Blight

Sheath blight is a disease of rice plants which is caused by a fungus that lives in the soil. When rice fields are flooded, the fungus floats to the top of the water and contacts rice plants; the fungus grows out and moves into the rice leaf. The fungus spreads across the water to adjacent plants. The fungus grows across touching plant parts. The flow of water and nutrients in the rice plant is interrupted and the leaf dies, reducing rice yield. Development of resistant cultivars has been slow, because resistance is linked to undesirable traits such as tall plant stature, late maturity, and poor milling quality. Research has shown that a single application of a fungicide provides almost season-long control of sheath blight.

“Sheath blight of rice, caused by the fungus Rhizoctonia solani, is an economically important rice disease that is occurring throughout the rice-producing areas in the world, including the southern United States. Significant losses in grain quality and yield may occur in severely infected rice fields. Despite its economic importance, there are no completely resistant rice cultivars against this fungal rice disease and control methods for sheath blight are limited to heavy usage of fungicides.”

Authors: Shrestha, B. K., et al.
Affiliation: Louisiana State University Agricultural Center, Baton Rouge
Title: Suppression of sheath blight development in rice and sclerotia germination of Rhizoctonia solani by rice-associated strains of Bacillus spp.
Source: Phytopathology. 2013. 103(Supplement 1)(5):S1.9

Downy mildew of Basil is here to Stay

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Downy Mildew Close-up

Downy Mildew Close-up

Downy Mildew Spore Growth on Basil Leaves

Downy Mildew Spore Growth on Basil Leaves

Downy mildew of basil is a new destructive disease that appears to be here to stay. In the first years of its appearance in the U.S., complete crop losses occurred for some growers because basil leaves with any mildew are unmarketable. Applying fungicides frequently and starting before first symptoms are considered necessary to control basil downy mildew effectively.

“Sweet basil (Ocimum basilicum L., Fam. Lamaiaceae) is the most commercially important annual culinary herb crop grown in the United States. Sweet basil is grown for culinary use for both fresh and dry consumption and as a source of essential oil and oleoresin for manufacturing perfumes, food flavors, and aromatherapy products.

Basil downy mildew… is a new disease of basil in the United States. …In the United States, the pathogen was first discovered in Florida in the fall of 2007. Since that time, basil downy mildew has been found throughout the eastern United States and in regions of commercial basil production in the Midwest and California.

Once basil plants become infected and develop symptoms, they are no longer marketable as a fresh product. …Currently, there is no known resistance or tolerance to basil downy mildew leaving 100% of the sweet basil acreage in the eastern United States vulnerable to the pathogen. Without adequate chemical control options and genetic resistance, basil downy mildew has the potential to destroy basil production in the eastern United States and in all other areas where basil is being produced.

Selection criteria such as foliar morphology, plant architecture as well as the presence of secondary metabolites and other factors that provide a less favorable microenvironment to the pathogen need to be examined as potential avenues for developing downy mildew-resistant sweet basil cultivars. Until this can be achieved, basil growers will have to rely on multiple applications of the few commercial fungicides currently registered to produce a marketable crop. Additionally, for organic basil growers, control of basil downy mildew will be even more challenging because there are fewer approved products labeled for organic use.”

Authors: Wyenandt, C. A., et al.
Affiliation: Department of Plant Biology and Pathology, Rutgers University
Title: Susceptibility of basil cultivars and breeding lines to downy mildew (Peronospora belbahrii)
Source: HortScience. 2010. 45(9):1416-1419.