Pest description and crop damage Phylloxera are small, aphid-like insects that feed on roots of grapevines causing stunted growth, reduced vigor, and vine death of own-rooted Vitis vinifera grape varieties. Depending on the vineyard location and climate, death can occur within as few as 3 to 10 years. Mortality of vines is quicker in drier climates where vines experience more nutrient and water stress. Vineyard decline has been a slower process in Oregon as compared to other warmer, more arid regions, particularly because vines are under limited soil moisture or nutrient stress. Phylloxera can be found in most grape-growing regions of Oregon with the exception of the Milton-Freewater area of eastern Oregon. Some regions of Washington and the Walla Walla Valley region of Oregon are free of phylloxera at this time. Preventing the entry of phylloxera is critical for vineyards known to be phylloxera-free. Sampling of declining vineyards is encouraged to determine presence of phylloxera in areas thought to be phylloxera-free, particularly to avoid further spread.
Biology and life history The wingless females are oval in shape; egg layers are pear-shaped. They vary from 0.03 to 0.04 inch long. Adults vary in color according to food supply: on fresh, vigorous roots they are yellow, yellowish green, olive green, or light brown; on weakened roots, they are brown or orange.
Sampling and thresholds Sampling for phylloxera should be conducted during late summer and early fall when populations are at their highest. Dig 12 to 18 inches below the soil surface about 12 inches away from the vine trunk. Sample both soil and roots. Use a stereoscope to view the roots and search for root swellings (nodosites and tuberosites), adults and eggs. If you do not have a stereoscope or dissecting microscope available with adequate magnification, contact your local Extension agent or crop consultant for assistance in identifying the insect. Only one phylloxera is needed to start an infestation within the vineyard, as populations can increase and spread over time and attack grapevine roots.
Prevention is the key to phylloxera management. However, because of the widespread nature of this pest, it is advised that vineyards be planted with vines grafted to phylloxera-resistant rootstock. Once an own-rooted Vitis vinifera vineyard is infested, there is no reversing the damage. Vines can be maintained for longer periods of time by reducing vine stress through managing nutrition and irrigation.
Management-chemical control: HOME USE
Insecticides effective at controlling root populations are not registered for home use. See cultural control information for management option.
Management-chemical control: COMMERCIAL USE
There are commercially available chemicals labeled for phylloxera control. However, applications have limited efficacy in reducing phylloxera populations or reversing the damage already done to infested vines. Soil applications of insecticides labeled for use on phylloxera are ineffective in reaching all roots that may be hosting phylloxera populations. Also some chemical controls are for foliar forms of phylloxera, but these are often not observed in Vitis vinifera vineyards in the PNW.
- fenpropathrin (Danitol 2.4 EC) at 0.2 to 0.4 lb ai/a. Foliar application for foliar-feeding phylloxera. PHI 21 days. Group 3 insecticide. Do not apply more than 2 times per season (max 0.8 lb ai/a per year). Restricted use pesticide.
- spirotetramat (Movento) at 0.10 to 0.13 lb ai/a. Apply with a high-quality adjuvant. Ensure there is adequate foliage to enable absorption into tissues. PHI 7 days. Allow 30 days between applications. Do not exceed 0.2 lb ai/a per season. Group 23 insecticide acts as a systemic to control phylloxera adults and larvae.
- thiamethoxam + chlorantraniliprole (Voliam Flexi) at 0.11 lb ai/a. PHI 14 days. Do not apply more than 2 applications per season (not to exceed 0.109 lb ai/a of thiamethoxam or 0.2 lb ai/a of chlorantraniliprole per season). Allow 14 days between applications. Groups 4A and 28 insecticides.
For more information:
Grape Phylloxera: Biology and Management in the Pacific Northwest. https://catalog.extension.oregonstate.edu/ec1463.