Tea Leaves Need Protection from Fungal Blisters

Funky Green Leaves

Blister Blight on Tea Leaves

Leaf diseases are very important in tea production since the plants are grown for their young leaves. The major foliar disease of tea in Asia is blister blight. Wind-borne spores germinate on the leaf in humid conditions and the leaf is penetrated. Further growth presses out and eventually a blister is formed on the leaf. Each blister can produce up to 20 million spores. Tea prepared from blistered leaves is weak, with poor color, aroma, brightness, and briskness. Before the use of fungicides, tea losses to blister blight were staggering with 30-50% losses. Preventive copper sprays have been the mainstay of tea production for the past 60 years. Blister blight is not a problem for organic tea growers since they are permitted the use of copper sprays.

Tea is one of the most popular beverages in the world owing to its taste, the stimulative effect, and also for its health benefits. Perennial habit of the tea plant, peculiar cultural conditions and warm humid climate of the tea growing areas are highly conducive for disease development… Among the leaf diseases, blister blight caused by Exobasidium vexans is the most important one. The disease is known to occur in almost all tea growing areas of Asia. E. vexans is an obligate parasite with no alternate host. Hence, its life cycle has to be completed on tea plant itself. The entire life cycle is completed in 11 days under conducive weather conditions or else it could extend up to 28 days… Comparisons between the crop harvested from tea fields protected by fungicide spray and those left unsprayed indicated a loss of 50% to blister blight disease in six months.”

Authors: Sowndhararajan, K., et al.
Affiliations: School of Life Sciences, India.
Title: Integrated control of blister blight disease in tea using the biocontrol agent Ochrobactrum anthropi strain BMO-111 with chemical fungicides.
Source: Journal of Applied Microbiology. 2013. 114:1491-1499.

Eat Your Lima Beans, They are Not Moldy

Lima Beans: the Good, the Bad, and the Edible.

Lima Beans: moldy (L); Fungicide Treated (R)

Lima bean has been an important crop grown for canning and freezing in the mid-Atlantic area of the United States since the nineteenth century. Lima bean grown for processing is planted on 6,500 hectares in Delaware, with production valued at $6.5 million. 13,000 hectares of lima bean are grown in the United States, with California being the largest producer of lima bean and Delaware being second. Lima bean is considered to be the cornerstone crop of the vegetable processing industry in Delaware, and Delaware remains one of the few states that produce the crop. Lima bean downy mildew was first reported in Connecticut in 1889, and the disease is in Delaware almost every growing season.

“Currently, P. phaseoli [lima bean downy mildew] is limited to the mid-Atlantic areas of Delaware, Maryland, and New Jersey and has never been reported to occur in California. This is likely to be due, at least in part, to California’s lower humidity compared with the eastern United States.

In 1958, P. phaseoli was responsible for an epidemic, with more than 907,185 kg of bean loss from 4,725 hectares in Delaware. In 2000, race E of P. phaseoli was responsible for an epidemic in Delaware during September and October, which resulted in an estimated production loss of 40%, equal to a farm value loss of $3,000,000.

Fungicide testing for control of downy mildew of lima beans began as early as 1897 when Bordeaux mixture was recommended for control.

Growers currently make preventative applications of copper fungicides either alone or in combination with insecticides for pod-feeding insects. When conditions for downy mildew are favorable and outbreaks occur, applications of Ridomil Gold/Copper (mefenoxam) or Phostrol are made curatively to unsprayed fields or those where copper fungicides have been applied preventatively.

Currently, several fungicides are labeled and effective for control of downy mildew if applied in a timely manner. Ridomil Gold/Copper (mefenoxam/copper), Phostrol (phosphorus acid salts), and copper fungicides are currently labeled on lima bean and are effective.”

Authors: Evans, T. A., et al.
Affiliations: Department of Plant and Soil Sciences, University of Delaware.
Title: Lima bean downy mildew: impact, etiology, and management strategies for Delaware and the mid-atlantic region, U.S.
Source: Plant Disease. 2007. 91[2]:128-135.

The Brazilian Soybean Miracle That Almost Didn’t Happen

Spraying For Soybean Rust

Spraying For Soybean Rust

Soybean production in Brazil grew rapidly since 1960 with area expanding from 400,000 hectares to 22 million hectares. Brazil is a major soybean producer-62 million tons per year. In 2001, soybean rust was first detected in Brazil and by 2003 the pathogen had spread to the entire country with yield losses up to 75% in individual fields. If fungicides are not used, Brazil would lose about 50% of its soybean production annually.

“More than 50 different fungicidal products are currently labeled for managing soybean rust in Brazil, and many of these have been evaluated annually since 2003/2004 in a nationwide network of standardized, uniform field trials (UFTs) coordinated by Embrapa Soja, a research unit of the Brazilian Agricultural Research Corporation.

We present a meta-analytical synthesis of the results of 71 uniform fungicide trials containing 930 entries (specific fungicidal treatments) conducted in Brazil from 2003/2004 to 2006/2007. …on average, fungicide treatments… increased yield by 43.9%.

The results of this analysis showed that fungicidal control of soybean rust in Brazil is highly effective… (indicating a relative disease reduction of between 90 and 100% in response to treatment). …these comparisons show that, despite favorable environmental conditions for soybean rust epidemics in Brazil, the disease can be managed very effectively with modern fungicides.”

Authors: Scherm, H, et al.
Affiliation: Department of Plant Pathology, University of Georgia.
Title: Quantitative review of fungicide efficacy trials for managing soybean rust in Brazil.
Source: Crop Protection. 2009. 28:774-782.

Strawberry Fields Forever? Thanks to Fungicides

Strawberry Yields: UK

Strawberry Yields: UK

Strawberry cultivation in the UK reached 13000 hectares by 1924. While the area today is just one-third of the 1924 area, strawberry production has more than doubled due to yield per hectare increasing 5-6 fold. A major factor in increased strawberry yields in the UK has been the increased use and variety of fungicides used.

“The second productivist practice was the increased use of plant protection products from the 1960s. In 1965, up to 11% of the strawberry crops were not sprayed with pesticides; this figure had decreased to less than 2% by 2006. The spray area for fungicides also increased, from 6058 ha in 1965 to 45,960 ha in 2006. This is higher than the area of land cultivated for strawberries since it takes into account multiple sprays per season. The increased use of pesticides during this phase contributed to increasing yields, by decreasing disease pressure. This also had an impact on reducing yearly variations in yield, as pesticides enabled growers to reduce the impact of weather on their crop by reducing disease incidence.”

Authors: Calleja, E. J., et al.
Affiliation: University of Warwick, UK.
Title: Agricultural change and the rise of the British strawberry industry, 1920-2009.
Source: Journal of Rural Studies. 2012. 28:603-611.

A Longer Strawberry Season in Canada Would Require More Fungicide Sprays

Anthracnose fruit rot

Anthracnose fruit rot

Ripening strawberries are very susceptible to anthracnose. The pathogen spreads rapidly through fruiting fields during rainy, warm harvest seasons and can quickly destroy a crop. Light-brown water-soaked spots form on ripening fruit and rapidly develop into firm round lesions followed by the eruption of pink spore masses in a slimy sticky matrix which are dispersed by splashing or wind-driven rain.

“In Canada, strawberry is cultivated mainly in Quebec, Ontario, British Columbia and the Atlantic provinces. Ontario ranks as the second highest strawberry producer (30%) in the country, with a farm-gate value of Cdn$ 20.8 million. Most of the fruit produced in Canada are from June-bearing cultivars, with a season that usually spans 5-6 weeks in June and July. In the off-season, large quantities of strawberries are imported, which were five times higher in 2011 than in 2003. The Canadian strawberry industry has given high priority to cultivation of day-neutral strawberry to become more competitive with the import market and increase the availability of fresh Canadian-grown strawberries to 4-5 months.

Anthracnose fruit rot (AFR), caused by Colletotrichum acutatum Simmonds, is one of the major diseases affecting yield in Ontario and other provinces. Pre- and post-harvest fruit rots caused by the fungus reduce marketable yields and the marketability of fruit, respectively. Long wet periods and warm temperatures (20-25 °C) during flowering and fruit development are favourable conditions for development of anthracnose fruit rot.

With the increase in production of day-neutral cultivars in Canada, attention should be given to the differences in cultivation practices from June-bearing cultivars. Since day-neutral strawberry have a longer cycle of fruit production, the risk of diseases and pests is also higher and thus different management strategies are required.

Since the day-neutral cultivars can be grown for a long season (4-5 months), numerous sprays (8-10) of fungicides are required to control diseases.”

Authors: Burlakoti, R. R., et al.
Affiliation: Weather Innovations Consulting LP.
Title: Evaluation of epidemics and weather-based fungicide application programmes in controlling anthracnose fruit rot of day-neutral strawberry in outdoor field and protected cultivation systems.
Source: Canadian Journal of Plant Pathology. 2014. 36[1]:64-72.

Fungicides Keep Lettuce from Turning Slimy


Lettuce Drop

The fungus causing lettuce drop causes a rot that usually begins on the stem near the soil surface and a water-soaked area appears; it can spread downward until roots decay and can spread upward.  The pathogen rapidly ascends the stalk, killing the leaves in succession until it reaches the heart of the lettuce plant. Layers of collapsed leaves lie flat on the soil surface after infection. Inner leaves are invaded completely by the fungus, which reduces the head to a wet, slimy mass. The entire plant may collapse in less than two days.

“Lettuce drop is one of the most destructive diseases of lettuce and has been reported in all lettuce-growing regions of the world. In the USA, the disease regularly occurs in the two primary lettuce-producing states of Arizona and California. Yield losses vary from 1% to nearly 75% depending on conditions, but under ideal disease conditions an entire field may be lost. The disease is caused by two closely related soilborne fungi, Sclerotinia sclerotiorum (Lib.) de Bary and S. minor Jagger.

Sclerotia of S. sclerotiorum can survive up to seven years and their longevity is affected by location of sclerotia within the soil profile, duration of burial and soil temperature and moisture.

Commercially acceptable cultivars with adequate levels of resistance are not currently available. Thus, current management strategies for lettuce drop rely primarily on fungicides such as iprodione and boscalid.”

Authors: Chitrampalam, P., and B. M. Pryor.
Affiliation: Department of Plant Sciences, University of Arizona, Tucson
Title: Population density and spatial pattern of sclerotia of Sclerotinia sclerotiorum in desert lettuce production fields.
Source: Canadian Journal of Plant Pathology. 2013. 35[4]:494-502 Available: http://www.tandfonline.com/doi/abs/10.1080/07060661.2013.841758#.U35Ck_ldV1Y

Australia’s Most Delicious Bush Nut Protected with Fungicides


Husk Spot on Macadamia Nuts

Australia is the home of the macadamia nut. Australia accounts for about one-third of world production. Husk spot caused by Pseudocercospora macadamiae is a serious disease affecting macadamia in Australia. Husk spot has not been reported from any other macadamia producing nation. The spores adhere to the husk, germinate and penetrate the host through openings (stomata). A major part of the economic impact is caused by premature fruit abscission from the tree when the kernels are still immature and of low oil content, making them unsuitable for processing and consumption.

“Husk spot, caused by Pseudocercospora macadamiae is a major fungal disease of macadamia in Australia, costing over $10 million in lost productivity if the disease is not adequately controlled. P. macadamiae infects macadamia husks on which it continually produces inoculum, the infection causes premature abscission of diseased fruit, thus, resulting in extensive yield losses and reduced kernel quality. Application of fungicide is currently the only effective method of controlling husk spot.”

Author: Akinsanmi. O. A., et al.
Affiliation: Tree Pathology Centre, The University of Queensland.
Title: An integrated approach to husk spot management in macadamia.
Source: Plant Health Management: An Integrated Approach. APPS 2009. Pg. 22.

Some Like It Hot: Horseradish Needs Protection to Prevent Discoloration


Horseradish: (A) Normal; (C) Internal Discoloration

Horseradish is a root plant from the mustard family. The root is harvested in the spring and fall and is sold to processors who grate the root, releasing the oils that distinguish horseradish from all other flavors. The oil creates a hot and spicy flavor. Consumers expect horseradish to be a light color. Internal discoloration of horseradish roots is the main production problem. Internal discoloration of the root begins with dark brown to black discoloration of the vascular system and gradually spreads to the core and cortex areas in the root. Internally discolored horseradish roots are useless for industrial purposes such as preparing horseradish sauce. Research has shown that fungicides can prevent the discoloration.

“Illinois produces approximately half of the total commercial horseradish in the United States. Over the past years, horseradish growers have experienced internal discoloration in horseradish roots, causing up to 100% yield losses.  …Fungicide fludioxonil (Maxim 4FS or Maxim Potato WP) and biofungicides Trichoderma virens (G-41/ABM 127 or SoilGard 12 G) and Bacillus subtilis (Serenade MAX), applied to pathogen-free sets, protected horseradish roots against the soil-borne pathogens for approximately 12 weeks. …Application of either the fungicide or one of the biofungicides to the tissue culture-generated sets protects roots in the field through July. The remaining period of the growing season is not long enough for infection and discoloration of the roots.”

Author: Babadoost, M.
Affiliation: Department of Crop Sciences, University of Illinois, Urbana.
Title: Set treatment for controlling internal discoloration of horseradish root.
Source: Phytopathology. 2006. 96[6](Supplement):S7

Europe Needs to Plan for Increased Need for Fungicides Due to Climate Change


The climate is changing in Europe with increasing temperatures predicted. Higher temperatures create improved conditions for the growth of fungi and infection of crops. More infection events will create the need for more fungicide use. Will European policymakers be ready?

“Here, we estimated the evolution of potential infection events of fungal pathogens of wheat, rice, and grape in Europe. …Our results show an overall increase in the number of infection events, with differences among the pathogens, and showing complex geographical patterns. For wheat, Puccinia recondite, or brown rust, is forecasted to increase +20-100% its pressure on the crop. Puccinia striiformis, or yellow rust, will increase 5-20% in the cold areas. Rice pathogens Pyricularia oryzae, or blast disease, and Bipolaris oryzae, or brown spot, will be favored all European rice districts, with the most critical situation in Northern Italy (+100%). For grape, Plasmopara viticola, or downy mildew, will increase +5-20% throughout Europe. …Our findings represents the first attempt to provide extensive estimates on disease pressure on crops under climate change, providing information on possible future challenges European farmers will face in the coming years.

On the whole, moving from the 2030 to the 2050 time frame, an increase in the number of potential infection events is expected. …Policy makers can use the outcomes of this study to be aware of possible future challenges to face when planning regional or local policies in terms of disease pressure and consequently of chemical control.”

Authors: Bregaglio, S., et al.
Affiliation: University of Milan.
Title: Fungal infections of rice, wheat, and grape in Europe in 2030-2050.
Source: Agron. Sustain. Dev. 2013. 33:767-776.




Give Peas a Chance

Pea Powdery Mildew

Pea Powdery Mildew

Pea powdery mildew caused by the obligate biotrophic fungus Erysiphe pisi DC is an air-borne disease of worldwide distribution, being particularly important in climates with warm dry days and cool nights. The disease can cause 25-50% yield losses, reducing total yield biomass, number of pods per plant, number of seeds per pod, plant height and number of nodes. The disease can also hasten crop maturity, rapidly raising tenderometer values beyond optimal green pea harvesting levels. Severe pod infectation leads to seed discolouration and downgrading of seed quality. It can also damage quality of processing pea giving tainted and bitter characteristics. Conidas and fungal debris from heavily infected crops can cause breathing and allergy problems for machinery operators.

“Crop rotation is of limited usefulness in managing powdery mildew. Powdery mildew epidemics sweep large areas with ease, and the separation of crops in time and space can delay epidemics but not prevent them.

Fungicide must be applied when the number of plants infected is still low and infection level on each plant is minimal (<5% infection).

Generally, only one application is required, unless infection comes in very early and/or conditions conducive to infection persist. In this case, follow-up applications may be required.

Extensive research throughout the agrochemical industry expanded options for powdery mildew control in the 1980s through introduction of several triazoles (sterol demethylation inhibitors) and two additional members of the morpholine group, fenpropimorph and fenpropidin. These have proven very effective in controlling pea powdery mildew.

More control options are recently available with the broad-spectrum fungicides strobirulins and anilinopyrimidines and the powdery mildew specifics spiroxamine and quinoxyfen. New mixtures are continuously being tested and approved for powdery mildew control in pea, such as the formulation mixture of the strobirulin pyraclostrobin plus the carboxamide boscalid.”  

Authors: Fondevilla, S., and D. Rubiales.
Affiliation: University of Cordoba, Spain.
Title: Powdery mildew control in pea. A review.
Source: Agron. Sustain. Dev. 2012. 32:401-409.