Page 57 - Grapevine July-August 2019

Around The Vineyard

A vineyard where part of the block was removed and
planted with new stock, while 1/3 of the infected block
remains sandwiched between a fallow portion

infection in a white fruited grape block such as presence of infection but likely will rely on the con-
Chardonnay or Sauvignon Blanc, ELISA may be the firmation of the presence of virus by testing vines.
only economical way of determining the leafroll dis-
ease status of specific vines as many samples must Effective disease control requires the availability
be tested in a yearly basis. of clean planting stock (i.e., certified disease-free
tested). However, to ensure that the vineyard
Leafroll Disease Management remains disease free, the grower must be aware
and Control Strategies of the presence of virus infection in neighboring
vineyards. It is important to devise procedures to
To manage leafroll disease, it is important to protect a healthy vineyard from potential disease
develop a map of virus infected vines. The map will introduction. The presence of insect vectors and
provide information of virus spread and determine ants should be routinely monitored and controlled.
the pattern of infection. A random distribution of Unfortunately, mealybugs are not always easy to
symptomatic vines would generally be associated observe in the vineyard, however the presence of
with planting infected vines. While symptomatic ants are usually associated with the presence of
vines aggregated or clustered in one area of the mealybugs. Special traps (including pheromone
vineyard block is an indication of virus spread. The traps) are available to monitor the presence of
initial assessment must be done using a testing lab mealybug infestation. The dispersal of mealybugs
to determine the presence of a virus species capa- by birds, wind, field equipment, and/or workers
ble of being transmitted. Once the vineyard man- are responsible for long distance spread of virus.
ager is familiar with symptoms, the mapping could Sanitary practices such as fallow periods, sanita-
be done by visual observation. It is much easier to tion of equipment, and sanitation of field worker’s
determine the characteristic leaf roll disease symp- clothing are recommended to avoid moving dis-
toms in red fruited varieties. In white varieties ease vectors from one vineyard block to another. I
it may be possible to train eyes to determine the always recommend to start work in the non-infect-
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