Ministry of Agriculture
Grape Insect and Mite Pests
Grape Phylloxera
(Daktulosphaira vitifoliae (Fitch)
- Identification
- Life Cycle and Damage
- Monitoring and Spray Thresholds
- Biological Control
- Cultural Control
- Chemical Control
Prepared by D. Thomas Lowery, Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland.
Grape phylloxera (Homoptera: Phylloxeridae), native to eastern North America, are a type of aphid found on the roots of grapes or in galls formed on the leaves of wild grapes or hybrid varieties. European vinifera varieties are particularly susceptible to this pest, and the accidental introduction of phylloxera to California, Europe, and elsewhere initially devastated these industries. Management of phylloxera with insecticides was not successful and the wine grape industry was only rescued with the development of resistant rootstocks derived from American Vitis species or hybrids between these and susceptible V. vinifera. Phylloxera were first identified in the Penticton area in 1961; infestations currently are scattered and at relatively low levels in British Columbia vineyards, mostly due to the use of resistant rootstocks and the failure of this pest to thrive on sandy soils.
As early as 1914 it was recognized that grape phylloxera consisted of several distinct biotypes or races. Biotypes differ in their ability to form galls on the leaves of certain cultivars, in the degree of feeding damage caused to roots, and their propensity to form sexual or winged forms. One study demonstrated that rootstocks with unsatisfactory levels of resistance to phylloxera in Europe and South Africa were suitable for California, Australia and New Zealand. Loss of resistance can also occur over time as new biotypes of phylloxera arise.
Identification
Adults are very small, usually wingless, and less than 1mm long and half as wide. Colour varies from pale green, yellowish-green or light brown on vigorous roots, to brown or orange-brown on declining roots; as adults age they become a darker brown or even purplish-brown. Winged sexual forms are rare in British Columbia and the northwestern U.S. and they do not appear able to reproduce sexually on vinifera grapes. Leaf galls are formed on French-American hybrids, Concord juice grapes and some rootstocks. The relatively small galls on the undersides of leaves are green and roughly circular. These should not be confused with the white or brown fuzzy galls of variable sizes and shapes formed on the undersides of leaves by erineum (leaf blister) mite.
 |
 |
| Grape phylloxera adults and eggs on grape roots. Photo courtesty Agriculture and Agri-Food Canada |
Grape phylloxera - winged adult |
 |
 |
| Phylloxera-induced galls on grape roots. Photo courtesty Agriculture and Agri-Food Canada |
Phylloxera galls on leaf of grape hybrid |
Life Cycle and Damage
Phylloxera overwinter on roots as small, dark hibernating nymphs that complete development in spring to become females that reproduce without having mated. Two or three generations are produced each year. When populations are large or the vines are declining, some newly hatched nymphs leave the roots through cracks in the soil and migrate to the roots of nearby vines. These small crawlers have been known to climb vine trunks and be blown on the wind for some distance. In late summer a portion of the nymphs develop into winged females (alates) that leave the soil and fly to other vines where they lay eggs in the crevices in the bark that hatch into males and females. After mating females produce a single larger overwintering egg. In spring the eggs hatch into females that feed on developing leaves and produce galls on susceptible varieties. Nymphs produced in the galls can infest other leaves or migrate down to the roots. Most grapes grown in British Columbia are not susceptible to leaf galls and the life cycle here largely consists of asexual forms confined to the roots of grapes. For this reason, infestations spread at a relatively slow rate.
Feeding of phylloxera on the roots of grapevines results in severe water and nutrient stress and eventual death of the vines. Roots become stunted and galled and die prematurely from the injection of harmful saliva and invasion of fungal pathogens. Depending on vine vigour and the size of the infestation, vines can slowly become stressed and chlorotic, or they can decline rapidly.
Monitoring and Spray Thresholds
Vines that fail to thrive and become chlorotic and unproductive should be inspected for the presence of phylloxera. Galls on leaves are an obvious indication of phylloxera on hybrid varieties, but damage confined to roots of vinifera wine grapes can be confused with damage from nematodes or root diseases. Carefully expose the roots and search for the typical swellings and dying roots. A hand lens or dissecting microscope will help verify the presence of phylloxera.
Insecticide treatments were previously not effective and there are no spray thresholds for phylloxera on roots. Hybrid cultivars that develop leaf galls are better able to tolerate or resist feeding damage to roots, but elimination of the leaf gall forms soon after they are detected might help reduce the extent of the infestation.
Biological Control
Biological control of phylloxera has not been studied in detail. A number of generalist predators are known to feed on phylloxera in leaf galls. In Ontario, larvae of two species of predaceous flies were commonly associated with leaf galls. Predaceous soil-dwelling carabid beetles undoubtedly feed on phylloxera infesting roots, and because they do not produce honeydew, ants are likely to feed on phylloxera rather than protect and ‘milk’ them. Although natural enemies are unable to effectively control populations of phylloxera, diseases and predators will help keep populations low and reduce the rate of spread.
Cultural Control
When establishing a new vineyard, purchase plants from reputable suppliers and ensure that planting material is healthy and free of phylloxera.
Note that grape plants or plant parts for propagation moving from phylloxera-infested areas of Canada into British Columbia, must be accompanied by a Movement Certificate issued by the Canadian Food Inspection Agency (CFIA), and must be treated with a CFIA approved treatment prior to movement. If you wish to source grapevine material from outside of B.C., please contact your local CFIA office to get details on the requirements.
To ensure that phylloxera are not moved from infested to clean areas on farm machinery, disinfest all equipment. Less frequent cultivation that penetrates the root zone is thought to be helpful.
Resistant rootstocks provide an effective means of combating phylloxera. Almost all resistant rootstocks were developed from crosses between several species of wild grapes native to eastern and southern North America (V. riparia, V. rupestris, V. berlandieri and others). Some of the more common grape rootstocks with good phylloxera resistance include SO4, 5BB, 5C, 420A, and 161-49C. Rootstocks vary in characteristics such as vigour and it is often difficult to select an appropriate rootstock for a particular vineyard. Soil types, resistance to nematodes, vine spacing and several other factors need to be considered in addition to phylloxera resistance. Prior to planting it is advisable to read appropriate publications and consult with vineyard managers or consultants.
Vigorous vines resist phylloxera damage better than stressed vines. Provision of additional water and nutrients can help delay the rate of decline. Infested vines should not be heavily cropped and extra care is required to prevent additional stresses from insects and diseases.
Some varieties are more vigorous and are better able to resist damage. Phylloxera infestations are more damaging and spread more rapidly on heavier soils that are prone to cracking, while vines planted in sandy soils can be nearly immune to attack.
Chemical Control
Movento™ (spirotetramat), a systemic insecticide effective against plant-feeding insects with sucking mouthparts, was recently registered for the control of grape phylloxera and mealybug. Sprays should be applied in a minimum spray volume of 500 L/ha as per the label instructions.
September 2010
