Surprise! Your Strawberries are Moldy

Grey mold on strawberries

Gray mold on strawberries

Consumers sometimes buy picture-perfect strawberries only to find them covered in mold after a few days. The cause: the gray mold fungus which infects the berries in the field but which remains symptomless until the fruit ripens. The fungus produces a velvety gray growth on the surface of the berry. Gray mold spreads in shipping containers when the fungus grows from a rotting berry to an adjacent healthy fruit. 100% of US strawberry acres are estimated to be infected with the gray mold fungus. Widespread infections are prevented with fungicide treatments.

“Gray mold is one of the most economically important diseases of cultivated strawberry (Fragaria × ananassa), and a significant threat to the United States’ $2.4 billion strawberry crop… Crop losses resulting from gray mold disease are especially severe under moist weather conditions, and occur not only during the crop growing season but also after harvest and during storage and transit.

The control of gray mold in commercial strawberry fields is largely dependent on the application of fungicides during bloom and fruit maturation.”

Authors: Grabke, A., et al.
Affiliation: Clemson University.
Title: Fenhexamid resistance in Botrytis cinerea from strawberry fields in the Carolinas is associated with four target gene mutations.
Source: Plant Disease. 2013. 97[2]:271-276.

Michigan Tart Cherry Orchards Rely On Fungicide Protection Every Year

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.

$17 Billion in Sales of Ornamental Plants in the US-Growers Have to Use Insecticides to Satisfy Consumers

Azalea Leafminer

Azalea Leafminer

Ornamental plants are big business in the US-$17 billion in retail sales. Ornamental plants provide visual beauty and reduce the stagnation that occurs in everyday work environments. Ornamentals may have a profound effect on observers or occupants. Several studies have shown that ornamentals have a positive impact on an individual’s well-being and emotional stability and may improve productivity. When purchasing an ornamental plant, consumers demand that they be free of insects and insect damage.

“The intensive nature of production and aesthetic quality requirements of producing ornamental plants supports the necessity of using pesticides to manage arthropod pests. The use of pesticides is vitally important to the ornamental industry in order economically to prevent the multitude of arthropod pests from damaging plants and at the same time produce quality plant material that may be purchased by consumers/homeowners. Furthermore, the use of pesticides allows ornamental producers successfully to compete in national and international markets.

…a single arthropod pest can significantly damage or vector a disease, rendering a crop unmarketable. As such, ornamental producers cannot wait for arthropod pest populations to build up to a critical level, and so, in actuality, pesticides serve as an ‘insurance policy’ to manage or regulate the diversity of arthropod pests so that they do not damage ornamental crops.

The aesthetic value and the consumer demand for high-quality ornamental crops necessitates the application of pesticides in order to protect crops from the myriad of arthropod pests encountered in ornamental production systems.”

Authors: Bethke, J. A., and Cloyd, R. A.
Affiliations: University of California, and Kansas State University.
Title: Pesticide use in ornamental production: what are the benefits?
Source: Pest Management Science. 2009. 65:345-350.

Downy mildew of Basil is here to Stay

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.

Onion Plants Die Without Insecticide Treatments

Onion Maggot Damage

Onion Maggot Damage

100,000-300,000 onion maggots overwinter on every acre of onions in northern states. The average number of eggs laid by a single female in the spring is about 50. The emerging maggots seek out the roots and bulbs of onions and tunnel into the bulb. Maggots feed for two to three weeks. Damaged plants are usually so severely injured that they wilt, dry out and soon disappear.

“Management of onion maggot Delia antiqua is an integral component of onion production in the northern United States and Canada. There are three generations of D. antiqua per year in the northern United States and infestations of first-generation D. antiqua typically cause the most serious damage because maggot feeding kills seedlings. If onion seedlings are not protected with an insecticide applied during planting, D. antiqua can reduce plant stands by one-half to near 100%.”

Authors: B. Nault, J.Z. Zhao, R. Straub, J. Nyrop and M.L. Hessney.
Affiliation:  Department of Entomology, NYSAES, Cornell University.
Title: Onion Maggot (Diptera: Anthomyiidae) Resistance to Chlorpyrifos in New York Onion Fields.
Publication: Journal of Economic Entomology. 2006. 99(4):1375-1380.