Technical Report


Grape Phylloxera Biology and Management in Oregon Public Deposited

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  • Grape phylloxera (Daktulosphaira vitifoliae), a root-feeding aphid-like insect, is the most important pest of European winegrape vineyards worldwide. They cannot be controlled on infested vines which eventually die. There are currently no satisfactory chemical or biological control methods for this pest; its management throughout the world has been by planting resistant rootstocks and through techniques that seek to limit the rate of spread. Although it has been in California since the mid- I 800s, phylloxera was discovered for the first time in a commercial vineyard in Oregon in 1990 and in Washington in the late 1980s. Seven vineyards are now known to be infested. With over 95 percent of Oregon's 6,000 acres of grapes being own-rooted, susceptible vines, the potential for serious economic loss to the industry is great. Infested vineyards will have to be replanted on grafted vines (resistant rootstock) at a cost of over $1 1,000 per acre for re-planting and years out of production. Rate of spread of this insect within a vineyard is estimated to be 2 times to 4 times in Oregon -- thus at the very least, a 1/8 acre infestation will be I acre in size in 3 years. Phylloxera can be spread from one vineyard to another on infested soil or plant material. The life cycle of this insect varies with location. Our findings indicate the presence of sexual, winged forms in the Pacific Northwest. The relevance of this discovery to viticulture here is unknown but may be important to insect population variability and movement (greatly increase rate of spread). Because distribution of phylloxera in the Pacific Northwest is currently limited, characteristics of its current distribution and movement are necessary to limit movement in the future. Although replanting vineyards on phylloxera resistant rootstock is the long term, preferred and inevitable mechanism for control of the pest, there is a large number of resistant rootstocks to choose from, but none of which have yet been characterized as suitable for production systems in Oregon. Existing phylloxera infestations must be managed to decrease the rate of spread, within and among vineyards. Delaying the need for the industry to replant on resistant rootstock is essential, as growers will have to make educated decisions on what stocks are best for Oregon. Our industry does not want to be faced with having to replant 80 percent of existing vineyards because of inappropriate initial rootstock recommendations, a situation now in effect in California's Napa and Sonoma counties. Research on phylloxera biology, rate of spread, and its association with other pests in Oregon is needed to better manage this insect. We need sufficient time to conduct concurrent research on rootstocks resistant to variations of phylloxera, resistance to other pests such as nematodes and fungal pathogens, and suitability for our viticultural region. Studies on other traits of rootstocks, to provide consistent productivity and quality perfection for Oregon conditions has the potential to make Oregon's change to rootstocks a positive development and an enhancement of long-term competitiveness. Additional information on phylloxera biology, rate of spread, methods to decrease the rate of spread, and rootstocks for Oregon vineyards is available in the Oregon Winegrape Growers' Guide (1992). The objectives of our research were to determine when phylloxera hibernants (over-wintering populations) become active in the spring and how populations change throughout the season. This would not only determine the number of generations a year, but also when spread can begin in the spring. Also, it's important to be able to estimate the rate of spread as accurately as possible so that growers may predict replanting date and the industry can forecast spread within the Oregon. We also wanted to determine whether we have a winged form of phylloxera in Oregon, because this could greatly affect the rate of spread of this pest. Determining the low temperature tolerance of phylloxera found in Oregon is necessary to better estimate number of generations per year and the potential amount of population die- back in cold winters. Finally, we planned to determine the resistance of rootstocks to biotype(s) of phylloxera found in Oregon.
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