Tag Archives: grapes

New Insecticides Greatly Improve Grape Insect Management

Posted on by
Reply

62

The grape berry moth is an annual problem on about 50% of the grape acres around the Great Lakes in New York, Ohio, Pennsylvania and Michigan. Females glue their eggs on the berries and larvae hatch out and feed in the berries. Insecticides have been used for 100 years to control the grape berry moth and reduce the infestation from 24-30% to less than 1%. Until recently, broad-spectrum insecticides with long residuals were used to manage grape berry moth. However, new insecticides have been registered and they provide tremendous opportunities to selectively manage insect pests in grape vineyards.

“The past 10 years has seen a dramatic change in the spectrum of insecticides available for grape producers, with new modes of action and pest spectra allowing an unparalleled opportunity for growers to target specific pests for control while also minimizing the risk to non-target organisms.

There is now increased potential for realizing integrated control, since many of the most effective new insecticides have been evaluated and shown to have relatively low impact on natural enemies. For example, registration of the insect growth regulator insecticides methoxyfenozide and diflubenzuron for use in vineyards and the recent availability of the diamide insecticdes rynaxapyr and flubendiamide allow more selective and long-lasting control of lepidopteran pests without high levels of natural enemy mortality.

Acaricides have also changed from broad-spectrum to more selective chemistries. The vineyard manager now has an array of different acaricide modes of action available, many of which can selectively kill pest mites without injuring predatory species. Some of these are also systemic, thereby providing a route of exposure that further protects predators from direct contact with the acaricide.”

Authors: Isaacs, R., et al.
Affiliation: Department of Entomology, Michigan State University
Title: Vineyard IPM in a changing world: adapting to new pests, tactics, and challenges.
Source: Anthropod Management in Vineyards: Pests, Approaches, and Future Directions. 2012. Springer. Pgs. 475-480.

Fungicides Protect South African Grapes from Rot

Posted on by
Reply
Bunch Rot

Bunch Rot

South Africa ranks eleventh in the world for grape production. Wine is South Africa’s biggest agricultural export, earning R2.2 billion in foreign exchange annually. South African farmers also produce about 1.8 million tons of table and dry grapes annually. The industry is primarily export oriented with up to 90% of the total production being exported with a value of R1.5 billion per year. The majority of South African grapes are available in northern hemisphere countries during their winter and spring seasons. Fungicide spray programs are commonly applied in South African vineyards to control Botrytis bunch rot.

“Botrytis cinerea Pers: Fr. is a common, destructive pathogen causing grey mould. …In South Africa, this is an economically important disease on grapevines. …In table grape production, the most serious damage is the loss of fruit quality due to pre-harvest or post-harvest berry rots. …In wine grape production, the fungus causes a serious decrease in quality of juice and wine. Wines produced from B. cinerea infected berries have off-flavours and are sensitive to oxidation and bacterial contamination, making them unsuitable for ageing.

Chemical control is the main way to reduce grey mould on crops. Producers in South Africa invest heavily in chemical products and routine spray applications each year.”

Authors: van Zyl, S. A., et al.
Affiliation: Department of Plant Pathology, University of Stellenbosch, South Africa.
Title: The use of adjuvants to improve spray deposition and Botrytis cinerea control on Chardonnay grapevine leaves.
Source: Crop Protection. 2010. 29:58-67.

Powdery Mildew of Grapes Must be Controlled for Wine Quality

Posted on by
Reply
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.

It Never Rains in Southern California, But When It Does, Fungicides are Essential

Posted on by
Reply
Gray Mold

Gray Mold

Most of the table grape production in the U.S. is located in the San Joaquin Valley. Rainfall at harvest is uncommon. However, when it does rain, gray mold can reach epidemic proportions if fungicides are not used. Gray mold is caused by a fungus that is activated by rainfall. The fungus produces a short tube with a suction cup and a peg that forces its way through the grape cuticle. Inside the grape, the fungus grows and exudes enzymes that degrade the fruit. Cracks form in the grapes and spores are produced that spread gray mold to other grape clusters. Even a single infected fruit within a table grape package can cause severe losses.

“Timing of fungicide applications to control gray mold is primarily driven in vineyard environments by the occurrence of rainfall. Rainfall at harvest, an uncommon event in the San Joaquin Valley of California, causes abundant production of inoculum and epiphytotics of the disease in vineyards, and fungicide applications are critically needed when this rare event occurs. This area, where most of the table grape production in the United States is located, is typically rainless throughout these periods and B. cinerea seldom causes significant vineyard bunch rot, but it routinely causes substantial postharvest decay if measures to control it are not taken.”

Authors: J.L. Smilanick, et al.
Affiliation: USDA ARS
Title: Control of postharvest gray mold of table grapes in the san Joaquin valley of California by fungicides applied during the growing season
Source: Plant Disease. 94[2]:250-257. 2010.

Chile #1 Exporter of Table Grapes Thanks to Fungicides

Posted on by
Reply

Chile leads the world in the export of table grapes. A major challenge for Chile is the distance from the fields to the export markets. The long distance makes necessary having grapes of extremely high quality that can endure the trip and have a long shelf life. Botrytis is a disease that severely affects stored table grapes because it can infect the grapes in the field and then continue to grow in the berries’ storage, producing nests of gray-white fungus. Botrytis is common in Chilean vineyards, so the development of mold is prevented by the use of fungicides.

“Gray mold caused by Botrytis cinerea is a common disease that causes important economical losses in grape production in Chile. Under cool and humid conditions, several fungicide treatments between bloom and harvest, in addition to cultural control measures, are essential to control gray mold of grapevines. … Gray mold requires several fungicide treatments to achieve satisfactory control in Chile.”

Authors: B.A. Latorre and R. Torres
Affiliation: Pontificia Universidad Católica de Chile, Santiago, Chile
Title: Prevalence of isolates of Botrytis cinerea resistant to multiple fungicides in Chilean vineyards.
Publication: Crop Protection. 2012. 40:49-52.