Category Archives: Fungicides

Fungicides Prevent Destruction of Pistachio Orchards in California

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Alternaria leaf blight

Alternaria leaf blight

Alternaria late blight infects both leaves and fruit, causing early defoliation, severe brown-black stains on the shells and mold contamination of the shells and kernels. Other damage from Alternaria includes poor flavor and possible mycotoxin contamination. Without fungicide applications, alternaria would reduce California pistachio production by 30-50%.

“Alternaria late blight (ALB), caused by Alternaria alternata, A. tenuissima, and A. arborescens, is now considered the most destructive disease of pistachio in California. The disease affects foliage and fruit and is an annual production concern for pistachio growers. On foliage, it can be recognized by the development of large necrotic lesions, and multiple, expanding lesions eventually consume the whole leaf. The lesions are black in the center due to the production of many spores and are surrounded by a chlorotic halo. Under optimal conditions for the disease, the fungus can defoliate a tree in late summer and autumn. On fruit, it is characterized by small necrotic lesions surrounded by a red halo. These are located on the hull of immature nuts. When the nuts develop, one or two lesions can penetrate and decay the hull, resulting in shell staining of the nut underneath. The staining of the shell and colonization of the kernel result in a reduction of the nut quality. Although cultural practices such as irrigation management and pruning to increase air movement and decrease air humidity in the orchard can help reduce ALB, the use of multiple fungicide applications is essential to achieve adequate disease control.”

Authors: Avenot, H. F., et al.
Affiliation: Department of Plant Pathology, UC-Davis.
Title: Sensitivities of Baseline Isolates and Boscalid-Resistant Mutants of Alternaria alternata from Pistachio to Fluopyram, Penthiopyrad, and Fluxapyroxad.
Source: Plant Disease. 2014. 98[2]:197-198.

Organic Coffee Farmers in Central America May Not Survive

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Coffee Fields

Coffee Fields

Organic coffee farms in Central America have typically been located at high altitudes where there has been less worry about fungal   disease. However, in recent years, fungal outbreaks have increasingly-occurred at these higher elevations and organic growers may not survive the huge yield losses due to their non-use of fungicides.

“Finca Santa Isabel, often held up as a shining example of success with organic agriculture in coffee, may not make it. The culprit? A fungus known as roya that often goes unnoticed until bright-orange pustules start appearing on the underside of leaves. This parasite interrupts the tree’s ability to nourish itself by redirecting nutrients to those colorful lesions. Eventually, the infected leaves shrivel up and fall off.

The Keller family owns Finca Santa Isabel, located in Santa Rosa, about an hour south-east of Guatemala City. It became the second estate to be Rainforest Alliance-certified in 1997, and the Kellers were named Sustainable Standard-Setter by the nonprofit in 2003. In a 2009 profile, the family was lauded for its successes with sustainable practices: caring for the land, being a profitable business, and having enough left over to help build needed infrastructure for their community. They grow Arabica at an elevation of 3,500 to 4,500 feet above sea level in a zone most growers thought roya could not thrive.

But the rusk outbreak is happening almost everywhere. By most accounts, large and low-lying estates accustomed to spraying to protect their trees will survive. …Growers in areas prone to the rust use fungicide prophylactically twice a year. Spraying, which typically occurs in July and September in Central America, is timed to happen just before and just after periods of heavier precipitation.

Farmers caught unprepared, like Keller, have to decide whether and how to fight this blight.

The fungus is causing huge shortfalls in coffee cherries at higher elevations and in shaded areas of Central America, in places where growers used to feel relatively immune. Keller was one of them and he relayed a stunning loss: “Last year, we had about a 70% drop in production and so did many other farms that work conventionally around us. The main reason is that nobody thought that it was going to be so bad.”

Guatemalan workers on coastal farms in lower altitudes that face the Pacific sprayed ahead of time. Farmers in these regions have also planted rust-resistant varieties as part of recovering from earlier outbreaks. Those growing coffee in hillier areas at higher altitudes did not. Nor do they use fungicides routinely.

“…The pathogen itself could be adapting to temperature variation or it could be a combination of the weather events with growers not using fungicides making disease more severe.”

Authors: J. Neill
Affiliation: STiR
Title: Central American Coffee Rust Crisis: No Easy Answers.
Source: STiR Tea and Coffee Industry International. Available at:  http://worldcoffeeresearch.org/files/2013/12/2013Jul-STiR-CoffeeRustCrisis.pdf

New Fungicides Improve Management of Vomitoxin

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Fusarium Head Blight

Fusarium Head Blight

Fusarium Head Blight (FHB), also known as scab, is a destructive disease of wheat and other small grains. In the spring, ascospores and/or conidia are released from crop residues and are spread by wind or splashing water. They land on wheat heads and during wet, warm weather they germinate and infect glumes, flower parts, or other parts of the head.

In addition to lowering grain yield and quality, F. graminearum produces mycotoxins, primarily the trichothecenes deoxynivalenol (DON), nivalenol (NIV) and T-2 toxin. …These mycotoxins are harmful to humans and livestock. In North America, DON, also known as vomitoxin, is the most common and economically important mycotoxin found In Fusarium-infected wheat. …Grain with high concentrations of DON often is discounted or rejected at the elevator, which exacerbates the losses incurred by the farmer.

“In the U.S., a less than desirable number of current commercial wheat cultivars have moderate resistance to FHB and this resistance can be overwhelmed in years with high disease intensity. Fungicides are often applied to control FHB when favorable conditions for disease development are forecast.

Over the last two decades, there has been considerable improvement in the effectiveness of fungicides in controlling FHB and DON. This improvement is attributable in part to improved fungicide chemistries and greater knowledge gained through research on fungicide application rates, timing, and technology.

The best approach to managing FHB is to integrate available management strategies. Research has shown that integrating cultivar resistance with fungicide application can be effective management strategy for FHB.

Availability of moderately resistant cultivars and new fungicide chemistries coupled with improved fungicide application technology has led to greater farmer adoption of an integrated strategy in the management of FHB and DON.”

Authors: Wegulo, S. N., et al.
Affiliation: Department of Plant Pathology, University of Nebraska-Lincoln.
Title: Integration of fungicide application and cultivar resistance to manage fusarium head blight in wheat.
Source: InTech. Fungicides – Showcases of Integrated Plant Disease Management from Around the World. Available at: http://www.intechopen.com/books/fungicides-showcases-of-integrated-plant-disease-management-from-around-the-world

Fungicides Prevent Significant Yield Losses in Argentinian Wheat Fields

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Wheat Rust is a Common Problem in Argentina

Wheat Rust is a Common Problem in Argentina

Argentina is one of the countries with the largest wheat-growing area in the world with more than 5 million hectares spread all over the country.

The grain production region has experienced severe tillage changes in the past twenty years, mostly due to the increased interest in maintaining soils covered with plant residues.

No tillage can reduce costs by decreasing fuel consumption required to produce a crop. However, in the wheat/soybean system under no tillage, as in wheat following wheat, the inoculum of fungi may survive until the next wheat season. Therefore, the use of fungicides is essential to decrease the severity of diseases.

Fungicides are usually applied on foliage to control diseases but they are also used for seed treatments to prevent seed decay. Leaf rust, septoria leaf blotch, and tan spot are the most important diseases in terms of potential yield reduction in Argentina.

“Planting resistant cultivars is one of the least expensive and most effective management strategies to prevent diseases. However, cultivars with an adequate genetic resistance level to necrotroph foliar diseases are scarce, and usually resistance to leaf rust is complete, conditioned by one or a few genes and has a low level of durability in Argentina. Therefore, chemical protection together with cultural practices is a common method of control. In addition, fungicides are also important because Argentinian wheat region combine high yield potential cultivars with high infection pressure, both deriving from adequate temperature and moisture levels, large application of N fertilizers and rotations dominated by cereals, which promote progression of some foliar diseases.

The results of experiments carried out in Argentina indicate that sowing wheat following wheat in no tillage is possible without significant yield losses if effective disease management practices including moderately resistant cultivars, N fertilization and fungicides are applied.”

Authors: Simon, M. R., et al.
Affiliation: National University of La Plata, Argentina.
Title: Recent Advances on Integrated Foliar Disease Management with Special Emphasis in Argentina Wheat Production.
Source: InTech. Fungicides – Showcases of Integrated Plant Disease Management from Around the World. Available at: http://www.intechopen.com/books/fungicides-showcases-of-integrated-plant-disease-management-from-around-the-world

Numerous Fungicide Options a Boon for California Peach Growers

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Brown Rot on Peaches

Brown Rot on Peaches

The University of California’s IPM Guidelines list 37 fungicide products available for controlling diseases in peach orchards. Major flower, foliar and fruit diseases of peach include peach leaf curl, shot hole, brown rot, powdery mildew and rust. The key is to select the best fungicide product with the broadest spectrum of activity against these pathogens and time the application at a critical stage.

“Fungicides are the most effective and safe way for managing diseases of cling peach. Fortunately, there are numerous choices because multiple fungicides with different modes of action (MOA) are registered for each disease. This may appear to make a decision more difficult, but having multiple active ingredients available allows for competitive pricing, development of highly effective management programs that target problematic diseases at individual orchard sites, and resistance management. …In recent years, many active ingredients have become available as generic products under different trade names. This has further increased the complexity but also allows for reducing fungicide costs to the grower.”

Author: Adaskaveg, J. E.
Affiliation: UC Riverside
Title: Effective and Economical Management of Flower, Foliar, and Fruit Diseases of Cling Peach
Source: Orchard Notes. January 2014. Pgs. 2-4.

Apple Rots Reappear Because of Fungicide Cancellations

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Core rot

Core rot

 

Many storage rots of apples are actually initiated in the orchard. There are often no pre-harvest symptoms. Core rot is a wet rot that spreads into the flesh of the apple. Core rot can be controlled with spring fungicide sprays in the orchard. However, core rot has reappeared in some Australian apples in storage due to cancellation of some key fungicides.

“In the last couple of months I have attended to a couple incidences of core rot in apples that have arrived in their destination market. This is not a pretty sight and costs the packer/marketers both in financial and brand terms, not to mention degradation of Australia’s reputation as a supplier of quality fruit.

This situation has probably arisen due to low levels of core rots being encountered in the last 15 or so years. This has meant that this problem has slipped from our memories and we have forgotten that in the 1980s core rot could be present in up to 20 per cent of our fruit. This level of infection cannot be tolerated in today’s marketing environment. Its re-appearance is probably due to the de-registration of both Benlate and Rovral for spraying onto the apple flowers, a treatment in common use in the 1990s and 2000s for the control of core rots.”

Author: Brown, G.
Affiliation: Technical Editor.
Title: Getting to the core of the problem: Core rots.
Source: Australian Fruitgrower. September 2012. Pgs. 12-15.

Michigan Tart Cherry Orchards Rely On Fungicide Protection Every Year

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Cherry Leaf Spot Infection

Cherry Leaf Spot Infection

Michigan is the leading producer of tart cherries in the United States, with annual yields of 90.9-127.3 million kg, which represents approximately 75% of the total US production.

Leaf spot is the most important fungal disease of cherry trees in Michigan. The appearance of numerous spots on the leaf is usually followed by rapid yellowing and dropping. In experiments, it has been demonstrated that poor control of leaf spot can result in 72% of the tree branches dying during the winter months.

“Cherry leaf spot (CLS) is the most damaging pathogen of tart (sour) cherry trees. All commercial tart cherry cultivars grown in the Great Lakes region of the United States are susceptible to CLS, including the widely grown cultivar Montmorency, which accounts for more than 90% of the tart cherry acreage in Michigan. Left unmanaged, CLS infection causes significant defoliation by mid-summer, resulting in fruit that is unevenly ripened, soft, poorly colored and low in soluble solids. Early defoliation also delays acclimation of fruit buds and wood to cold temperatures in the fall, increases tree mortality during severe winters and reduces fruit bud survival and fruit set the following year.

The almost complete reliance of the tart cherry industry on the cultivar Montmorency has driven a strict dependence on fungicides for disease management. Typically, 6-8 fungicide applications per year are required, beginning at petal fall and continuing through to late summer after harvest.”

Author: Proffer, T. J., et al.
Affiliation: Michigan State University
Title: Evaluation of dodine, fluopyram and penthiopyrad for the management of leaf spot and powdery mildew of tart cherry, and fungicide sensitivity screening of Michigan populations of Blumeriella jaapii.
Source: Pest Management Science. 2013. 69:747-754.

Toxins Appear in Apple Juice Due to Fungicide Cancellations

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Contaminated Apple

Apple Contaminated by Penicillium expansum

Patulin is a mycotoxin that is produced by certain species of molds that may grow on a variety of foods. Patulin does not appear to pose a safety concern with the exception of apple juice; patulin present in apple juice survives the pasteurization process.

The US FDA conducted a review of the toxicological studies on patulin and this found that patulin is toxic upon repeated administration of oral doses around 1.5 mg/kg body weight (bw), which caused premature death in rats.

“In March this year, a consignment of Australian apple juice was tested in Japan and found to have unacceptably high levels of the toxin patulin in it.

The initial critical control point for reducing the risk of patulin contamination of apples is the control of P. expansum in the orchard.

In recent times P. expansum has been well controlled in the orchard and in postharvest by applications and drenches of Benomyl and its related fungicide carbendazim. Unfortunately these products have been removed from the market due to pesticide safety concerns such that the risk of high levels of mycotoxins on the fruit has increased.”

Author: Brown, G.
Affiliation: Technical Editor.
Title: Are your fruit safe for juice? Patulin – the toxic substance found in juice fruit.
Source: Australian Fruitgrower. June 2012.

Fungicides Protect Sunflowers From Rust

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Sunflower Rust

Sunflower Rust

North Dakota, South Dakota, and Minnesota account for two-thirds of U.S. acreage of commercial sunflowers. 1.8 million acres of sunflowers produce an annual crop of nearly 2.8 billion pounds valued at $700 million. This valuable crop was recently threatened by a plant pathogen.

“Since 2008, sunflower rust has been a huge issue across the Northern Plains, increasing every year in severity and incidence.

The good news is that research trials conducted at North Dakota State University locations over the past two years demonstrate fungicides do work and in most cases, only one application of fungicide applied at the right time gives effective control .

“About three years ago, rust became an increasingly big issue,” said Sam Markell, NDSU plant pathologist, at the National Sunflower Association’s annual summer seminar in Bismarck. “When it comes really early, it causes a lot of yield loss.”

And that is precisely what began happening.

Previous to 2007, rust was typically found in late July and early August when it is less likely to cause an epidemic. But an NDSU Extension agent found rust in the aecia stage (which indicated the rust pathogen had completed its sexual cycle) three years ago in mid-June, which was very rare, Markell said.

“This may have been a result of favorable environment or it could be that a resistant sunflower was no longer resistant,” he said.

For example, when the NDSU scientist found rust in the aecia stage, he had the field aerially sprayed twice with fungicide except for one untreated test strip. In the treated field, the yield was 1,400 pounds, but in the untreated strip, the yield was 200 pounds, Markell said.”

Author: Roesler, S.
Affiliation: Farm & Ranch Guide.
Title: Type of fungicide on sunflowers not as vital as timing.
Source: Farm and Ranch Guide. July 16, 2010.

Soggy Weather in the Southeast Leads to doubling of Fungicide sprays on Pecan Trees

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Top: Fungicide Treated Bottom: Scab Infected

Top: Fungicide Treated
Bottom: Scab Infected

Pecan scab is the most significant disease affecting pecan trees in the US. The scab fungus survives the winter in masses of cells in twigs. During the spring, spores are abundantly produced and infection occurs during periods when rains are frequent. In the absence of spray programs, pecan nut losses approaching 100% can occur. 2013 was a very wet year in the Southeast where most pecans are grown.

“The last time Tom Stevenson remembers pecan disease being as bad as this year was in 1994, when a tropical storm stalled over south Georgia and dumped record rainfall in 24 hours – deadly flooding followed it.

Though not deadly, record soggy weather dominated the Southeast in many areas this summer. It left pecan orchards vulnerable for a big attack from the crop’s No. 1 enemy. The fungal disease scab scars husks, cuts yield and hurts quality.

“We’ve had some wet years before, but not like it has been this summer where it has rained all summer long,” said Stevenson, a south Georgia-based pecan orchard manager.

This year, he said, to try and stay ahead of the disease, his orchards got 16 or 17 fungicide sprays, or twice as much as in a normal year, costing $600 per acre this year for fungicide applications. Again, that cost is double what it is typically.

Scab claimed about 20 percent of the crop in 2003.

But unlike 2003, though, growers have more products and better practices to fight scab, even in bad years, Wells said. And, most importantly, growers have a bigger incentive to fight the disease to max out yields. “A lot of it now is nuts are worth more and growers are more willing to spend money on them,” he said.

The U.S. pecan industry has hit a boom in recent years with exports to China now vying for near half of the U.S. production each year. Where once prices fell into a production-driven boom or bust cycle, steady high prices, or $2 to $2.50 per pound, have put orchard management on the front burner for established growers and those looking to expand in it.

Pecan growers have good chemistries to fight scab with several modes of action, including strobilurin, triazole, triphenyltin hydroxide, organotin. Plus, an old tried-and-true chemistry called dodine is once again working on scab in Georgia, where growers stopped using it many years ago because it had lost some effect on the disease. But it seems to be working again, especially in combination with the other chemistries.”

Author: Brad Haire
Affiliation: Southeast Farm Press
Title: Pecan disease worst in recent memory
Source: Southeast Farm Press. September 5, 2013. Available at: http://southeastfarmpress.com/orchard-crops/pecan-disease-worst-recent-memory