Grape Phylloxera, Entomology
- 1 Grape Phylloxera
- 2 There’s Still No Cure For Grape Phylloxera
- 3 What is Grape Phylloxera?
- 4 Grape Root Aphid Treatment – How To Recognize Phylloxera Symptoms
- 5 How to Recognize Phylloxera Symptoms
- 6 Grape Root Aphid Treatment
- 7 Phylloxera: the parasite that changed wine forever
- 8 Ministry of Agriculture, Food and Rural Affairs
- 9 Grape Phylloxera — Pest Management Program for Grape Series
ENTFACT-222: Grape Phylloxera | Download PDF
by Ric Bessin, Extension Specialist
University of Kentucky College of Agriculture
Grape phylloxera is native to eastern United States, but has been distributed to other grape regions of the U.S. and is also established in Europe where it is of great economic importance. The leaf galls caused by grape phylloxera are unsightly and do little damage, however, infestation of the roots can be difficult to control and can lead to severe root pruning and decline of vines. Severe infestations can cause defoliation and reduce shoot growth. Hosts include cultivated and wild grapes.
Figure 1. Phylloxera infested leaves often remain stunted in size.
The wingless forms of the insect are very small, yellow-brown, oval or pear-shaped, and aphid-like. The winged forms, which are less apt to be seen, are also aphid-like, except that wings are held flat over the back. Neither winged nor wingless forms have cornicles, tail pipe-like structures on the top of the abdomen, as aphids do. The presence of grape phylloxera is best recognized by characteristic galls it produces on the leaves or roots. Leaf galls are wart-like, about 1/4 inch in diameter, and are familiar to anyone growing grapes. Root galls are knot-like swellings on the rootlets, and may lead to decay of infested parts.
Root galls cause stunting and/or death of European varieties of grape vines. American varieties of grapes, European hybrids, or European grapes grafted onto American root stock are tolerant to the root gall form of the insect. Some varieties are resistant are to root galls, leaf galls or both.
The life cycle of grape phylloxera is complex due to the fact that generations with different life cycles may develop at the same time, at least in the eastern US. In spring, a female hatches from a fertilized egg that had been laid on the wood of a grape vine. She migrates to a leaf where she produces a gall and grows to maturity in about 15 days. She fills the gall with eggs and dies soon afterward. Nymphs that hatch from these eggs escape from the gall, and wander to new leaves where they in turn produce galls and eggs. There maybe 6 or 7 generations of this form during the summer.
In the fall, nymphs migrate to the roots where they hibernate through the winter. The following spring they become active again and produce the root galls on susceptible varieties of grapes. These wingless females may cycle indefinitely on the roots year after year. In late summer and fall, in the eastern U.S., some of the root inhabiting phylloxera lay eggs that develop into winged females. These females migrate from the roots to the stems where they lay eggs of two sizes, the smaller ones developing into males and the larger ones into females. Mating occurs and the female then lays a single fertilized egg that over winters on the grape stem. It is this egg that gives rise to leaf inhabiting generations.
It is important to note that phylloxera can cycle continuously as root inhabitants without leaf forms occurring, leaf inhabiting forms do not occur without the root form also present. Assume phylloxera is in all vineyards, regardless if the leaf form is observed.
On the west coast, there are grape phylloxera biotypes that can cause serious damage to hybrid rootstocks with any Vitis vinifera parentage. To date, these biotypes have not been reported in Kentucky.
European varieties of grapes should be grafted onto American or hybrid grape root stocks. The leaf form of phylloxera can cause damage to some varieties. For this reason, foliar sprays to control phylloxera during vary depending on the variety and level of infestation.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
There’s Still No Cure For Grape Phylloxera
What was the cause of the grape phylloxera destruction and how come there is still no cure?
What is Grape Phylloxera?
Phylloxera is a microscopic louse or aphid, that lives on and eats roots of grapes. It can infest a vineyard from the soles of vineyard worker’s boots or naturally spreading from vineyard-to-vineyard by proximity.
Families and businesses alike lost their vineyards to a microscopic aphid: Grape Phylloxera is a louse. credit
A lil’ history on the unstoppable plight
A scourge erupted in Europe that nearly destroyed every single wine grape in the world. In the late 1800’s, wineries all over Europe ripped up and burned their family’s ancient vineyards in a desperate attempt to stop the spread of disease.
By the 1900s Phylloxera had taken a beyond-imaginable toll: over 70% of the vines in France were dead –the livelihoods of thousands of families were ruined. All of a sudden, the world launched into an international wine deficit.
In one scenario, three small precious plots of Pinot Noir owned by Bollinger in Champagne magically resisted the louse. The resulting 3000 bottles of wine called “Vieille Vignes Françaises” (French Old Vines) became the most sought-after bottles of Champagne.
A Bounty for the Cure
Devastated by the wrath, the Minister of Agriculture and Commerce in France offered 20,000 Francs –$1 million today– to anyone who could find a cure.
Where did Phylloxera come from?
Sorry to say, it came from the United States! This is where things start to get interesting:
The sad tail of Count Agoston Haraszthy
Phylloxera may have spread through the unintended actions of “Count” Agoston Haraszthy, the man who started Sonoma’s oldest winery, Buena Vista Winery, in 1857.
In 1861, Haraszthy traveled to Europe tromping through the vineyards in France, Germany and Switzerland to collect samples. He brought back cuttings of 350 different types of grapes and started an experimental vineyard in Sonoma.
Sadly, the vines turned brown and died –the first infestation of Phylloxera in the U.S.. After much defeat, Agoston Haraszthy filed for bankruptcy and eventually left the U.S., never to return.
Scientists of the day made a great effort to understand the little louse.
The genus Phylloxera is characterized by having three-jointed antennae, the third or terminal much the longest, and by carrying its wings overlapping flat on the back instead of roof-fashion. It belongs to the whole-winged bugs (Homoptera), and osculates between two great families of that sub-order, the plant-lice (Aphididae) on the one hand and the bark-lice
CHAS. V. RILEY, M. A., Ph. D. “The Grape Phylloxera” Popular Science, May 1874
The Reward Was Never Paid!
Over 450 articles poured out about the subject of Phylloxera between the years of 1868 – 1871. Studies were conducted with test plantings, poison, flooding, soil types, grape breeding alternatives, and much more.
Then, an independent group of researchers including a Frenchman, Jules Émile Planchon, and an American, Charles Valentine Riley, discovered a solution! Grafting vitis vinifera (the European grapevine) onto American root stock stopped the root-eating louse.
While the original researchers never sought the reward, which had grown to nearly $5 million of today’s money, a viticulturist in Bordeaux called Leo Laliman did. Laliman had taken the experimental techniques and turned them into a commercial practice in Bordeaux. The government turned him down, saying that he’d merely used preventive measures and didn’t develop a cure.
European Wine Grapes with American Roots
Today rootstock is still used for much of the wine world and phylloxera is still a danger.
The danger is no less in the U.S. In the 1990’s a mutation of Phylloxera called “Biotype B,” was found thriving in AXr1, which was a common rootstock. About two thirds of the vineyards in Napa during the 90’s were replanted. Phylloxera has also devastated many ungrafted vineyards in Oregon, whose owners had hoped that the louse wouldn’t infest the virgin soils.
Phylloxera Resistant Vineyards
There have been several cases where vineyards have remained untouched by grape phylloxera. While many of these locations are a mystery, a high proportion of the phylloxera-resistant vineyards have sandy soils in areas with high winds.
In Australia, Queensland was infected in the 1870s. The Australian governement responded to protect their precious vineyards with the Vine Protection Act of 1874, which ceased the common practice of transporting vines, machinery and equipment throughout the states. Today, Tasmania and Western Australia have still never been infested.
Grape Root Aphid Treatment – How To Recognize Phylloxera Symptoms
When new to growing grapes, it may be very concerning to look at your dense grapevines one spring day and see what appears to be warts all over the grape leaves. This is a legitimate concern, as wart-like galls on grape leaves are a tell-tale sign of grape root aphids. What are grape root aphids? Continue reading for that answer, as well as grape root aphid treatment options.
How to Recognize Phylloxera Symptoms
Grape root aphids are not actually aphids. They are simply small insects that look like aphids and cause great destruction to their host plant – grapes. Grapevine aphids are scientifically known as grape Phylloxera or Daktulosphaira vitifoliae. They are small insects, which over winter as nymphs on grape roots beneath the soil.
In spring, when soil temperatures stay consistently around 60 degrees F. (16 C.), the insects become active, feeding on grape roots, maturing into adults and then breeding. The female crawls up to the foliage where she creates galls to lay eggs in.
These wart-like galls may be the only visible phylloxera symptoms. When the eggs hatch, young grape root aphids make their way back down to the roots, or move onto the roots of other grapevines where the cycle continues. Occasionally, winged types of phylloxera are seen.
Meanwhile, male and young phylloxera feed on the roots of grapevines, causing young root shoots to swell and turn yellow. Older roots that are fed on by grape root aphids will turn mushy and die. These two grape root aphid problems occur from a secondary fungal infection that the phylloxera inject as they feed.
When these grape root aphid problems get out of hand, affected vines will grow stunted and produce little to no fruit. Phylloxera grape root aphids specifically infect roots in clay soil. They are not a pest in sandy soils.
Grape Root Aphid Treatment
When treating grape root aphids, chemical controls are oftentimes ineffective against because the insecticides cannot penetrate heavy clay soils or leaf galls. A foliar insecticide can be used in spring, weekly or biweekly, to kill the insects as they move from roots to leaves. However, the best offense is a good defense.
When purchasing grapevines, select only grafted phylloxera resistant varieties. Grapevine aphids can also be transported from plant to plant on shoes, clothing, tools and equipment. Therefore, it is best to only care for one plant at a time and then properly sanitize everything before working with another plant.
Phylloxera: the parasite that changed wine forever
How the discovery of a tiny parasite, less than one millimetre long, changed the worldwide wine industry forever
In June 1863 Prof JO Westwood, a leading entomologist and biologist at Oxford University, took delivery of a vine leaf taken from a greenhouse in Hammersmith. It was covered with a small insect and its eggs. Westwood identified it as an aphid, Phylloxera Vastatrix. He was not aware of its importance, but he was the first in Europe to discover the existence of this tiny parasite that was to change the world of wine forever. At around the same time an unknown disease destroyed several vineyards in the Rhône valley.
Large numbers of plants, including vines, were transported from America to Europe throughout the 19th century. A large greenhouse planted with exotic plants from around the world was an essential part of the wealthy fashionable household. Little thought was given to what diseases these might carry with them. This was to have calamitous consequences for European vine growers. First Oidium, a fungal disease, arrived in Europe in 1847, attacking vines and severely affecting the entire economies of wine-producing regions, followed later by downy mildew in 1878 and then black rot in 1888. But Phylloxera proved the most deadly of all.
The aphid is less than one millimetre long, barely perceptible to the human eye. It attacks the roots of a vine (the only plant affected) feeding on the sap of the roots. It spreads from one vine to another through cracks in the soil, but can also be carried for long distances by wind, farm machinery or on human feet. Affected plants become stunted and eventually die.
The disease quickly spread outwards to include first the Languedoc, then other parts of France. By the end of the century, most of Europe and north Africa had been affected. It is estimated that almost half of all vineyards in France were affected. Many wine regions went into decline, never to recover. Others lost valuable plant material, and changed to more productive lower quality grape varieties. It is hard to imagine how devastating it was for farming communities who were entirely reliant on sales of wine for survival.
At first, many refused to accept that this small parasite could be culpable, believing it to be a symptom rather than a cause. It took a French government inquiry in 1869 to determine that it was indeed responsible. The hunt for a cure took longer than it should, partly due to professional jealousies between French and American researchers. Possible cures included flooding vineyards with water (effective, and still practised in Argentina, but rarely practical) spraying with carbon disulphite (highly flammable and dangerous). Finally, in the 1880s, researchers discovered the only way to prevent infection was to graft resistant American rootstocks onto European scions. Today virtually every vine you see in a vineyard has been treated this way prior to planting.
A few areas managed to stay free of Phylloxera; the aphid cannot survive in very sandy soils, so the great plains of Hungary, Colares in Portugal were immune from attack. Chile, surrounded by the Andes and Pacific Ocean has remained free of Phylloxera and many other plant diseases.
In order to plant a vine, a grower need only stick cuttings directly into the ground. South Australia, by observing strict controls and quarantine has so far remained free. For a time, it seemed as if the dangers posed by Phylloxera had passed. However, several supposedly isolated regions such as Oregon and New Zealand, have discovered to their cost that nowhere is immune. The most expensive recent outbreak occurred in California in the 1980s.
Growers, advised by Davis University, planted many vineyards in California with the AxR1 rootstock, despite warnings from European viticulturists that it did not have sufficient resistance to Phylloxera. The error was to cost dearly; 50,000 acres of vines were destroyed. It is estimated to have cost the industry up to $6 billion to uproot valuable mature vines and replant with vines grafted on to sturdier rootstocks.
Today four wines with a connection to Phylloxera; a wine from disease-free Chile; the Barossa Valley in South Australia has been planted with vines for 150 years and remains free of Phylloxera. Geoff Schrapel of Bethany has old vineyards almost completely planted with ungrafted vines, including most of those used for his delicious Semillon. In Spain, the first disease-free vines to appear were grafted on to to the productive but very neutral Palomino variety. It took 80 years for Ribeiro in Galicia to rediscover its native grapes. And lastly, a Côtes du Rhône, from the first region to suffer from this deadly disease.
Ministry of Agriculture, Food and Rural Affairs
Grape Phylloxera — Pest Management Program for Grape Series
|Written by:||Todd Leuty — Agroforestry Specialist/OMAFRA; Kevin Ker — formerly Crop Technology Branch/OMAFRA|
Table of Contents
Grape phylloxera, Daktulosphaira vitifoliae (Fitch) is an insect pest which attacks many grape species both wild and cultivated. During feeding, phylloxera secrete a chemical which causes plant tissue to grow near the feeding site, resulting in the characteristic galls. Phylloxera is an indirect pest of grapes, damaging vines by feeding on plant sap from roots, leaves and tendrils, but not causing actual fruit injury. It is often described as an «aphid-like», sucking insect or a «vine louse».
Figure 1. Phylloxera leaf galls on De Chaunac grapes.
Above-ground feeding by phylloxera occurs mainly on the foliage (Figure 1), but it can also occur on stems and tendrils if population densities are high. French hybrids and a few North American cultivars are very susceptible to leaf gall formation. Light to moderate levels of leaf gall formation can occur on Vitis vinifera. While plant sap in the leaves provides nourishment for the insect, the affected areas of the leaf are induced to provide protection as well. Leaf galls are hollow, pea-sized swellings of plant tissue, usually red or green in color, that form on the undersurface of the leaf, a result of the growth inducing chemical secreted by the phylloxera insect. Unlike root feeding, leaf feeding occurs from inside the leaf gall. The hollow, thick-walled leaf gall is both a perfect incubation chamber for eggs and a barrier to the harsh external environment of insecticides, as well as dessication, predators, and diseases.
On cultivars susceptible to root infestation, mainly ungrafted V. vinifera, phylloxera infestations may be lethal to the vine. Infested roots swell to form root galls while the phylloxera continue to feed on the outer surface of the swollen area. Large galls on older roots are often attacked by root rot diseases, which usually results first in decline, and then death of the vine, three or four years following a phylloxera infestation. In major grape growing regions, phylloxera-tolerant American rootstocks are used to cultivate V. vinifera. In Ontario vineyards, the grape phylloxera inhabits most root systems, but has no lethal effects due to low winter temperatures which prevent excessive buildup of the phylloxera population. The root form in Ontario is currently classified as a minor pest.
Grape phylloxera adult females, both root and leaf feeding forms, are wingless and oval, 0.7 mm to 1.0 mm long and about 0.5 mm wide. On the leaves, young adults are bright yellow to orange becoming brown with age. On roots, they are pale green, light brown or orange. Newly deposited eggs are oval, bright yellow, approximately 0.4 mm long and 0.2 mm wide. Just prior to hatching. the eggs turn dark yellow with 2 visible red eye spots at one end. Emerging nymphs are similar in size to the egg. The nymphs progress through 4 developmental stages before reaching the adult stage. The winged adult female, emerging from the soil in late summer and early fall, is orange with a grey-black head and thorax with two pairs of lightly veined wings.
A. Root Cycle
On roots, phylloxera overwinter as first instar nymphs (Figure 2). In the spring, as soil temperature rises. nymphs begin feeding on root sap and mature to adults in 15 to 20 days. The spring and summer feeding adults, which are strictly females, reproduce without male fertilization. One female can produce 100 to 150 eggs over a period of approximately 45 days. New nymphs move to other root areas, begin feeding and cause gall formation. When mature, they will start producing the next generation of eggs. Five to nine overlapping generations can occur during a growing season. In September and October, newly hatched first instar nymphs begin hibernation for the winter.
Figure 2. Instar nymphs.
B. Leaf Cycle
The phylloxera leaf feeding cycle begins later in the growing season. In late July through to October, some of the nymphs on the roots develop wings and emerge from the soil when mature (Figure 2). Winged adult females lay eggs on the upper vine. The eggs hatch to give wingless male and female phylloxera. Mating occurs and one egg per mated female is deposited under the bark of the grapevine. This egg is the overwintering stage of the leaf infesting cycle of phylloxera.
The overwintering egg under the bark hatches early in the spring as grape buds break dormancy and begin to open. The wingless female nymph crawls to a new shoot up to the growing point. From the upper surface of a young, unexpanded leaf, the nymph begins feeding on plant fluids by inserting its stylet into the leaf cell tissue. As the leaf expands, the leaf gall develops around the phylloxera, forming a hollow, pea-sized growth on the undersurface of the leaf in which feeding continues. If the nymph begins feeding on a mature leaf, incomplete gall formation results. This first generation of female adults causes the first appearance of leaf galls about mid-May.
Figure 3. Phylloxera gall on lower leaf surface cut open to reveal adult female and eggs
Figure 4. Phylloxera nymphs emerging from a gall through the exit hole on the upper leaf surface
Figure 5a. Grape shoot tip attacked by phylloxera nymphs. New leaf galls are becoming visible on lower leaf surface.
Figure 5b. Phylloxera nymphs on upper leaf surface beginning to feed and form galls on a young unexpanded leaf.
When the female reaches maturity, 10 to 15 days after feeding initiation, and when gall formation is complete, eggs are deposited inside the gall. Up to 200 to 300 eggs may be deposited by a female over a period of 30 to 40 days (Figure 3). As eggs hatch, the new nymphs immediately emerge from the gall through a small exit hole on the upper leaf surface (Figure 4). The nymphs crawl from the leaf gall to the stem. Many of the nymphs move upwards along the shoot, again, to feed on unexpanded leaves at the shoot growing point and begin forming new galls of their own (Figures 5a, 5b). Other nymphs crawl or are windblown to other shoots on the vine and form galls there. This new formation of leaf galls represents injury caused by the second generation of phylloxera in which third-generation eggs are deposited. The lifecycle is repeated as the shoot grows and the season progresses. Therefore, early generations of leaf phylloxera can generally be distinguished by the location of galls along the shoot with the youngest generation being nearest to the growing point. Five to seven generations can occur over a season, which begin to overlap by the third generation, making it difficult to distinguish between generations by mid-summer. As many as 200 phylloxera galls can be found on a leaf during heavy infestations. In the fall, some hatching nymphs migrate, are windblown or fall to the ground and crawl down to the root system to hibernate through the winter.
Grape phylloxera causes indirect damage to susceptible grapevines. With foliar infestations, heavily galled leaves are malformed and rolled, causing a decrease in leaf surface area (Figure 6). Leaf gall tissue may contain up to 90% less chlorophyll than healthy leaf tissue, suggesting a reduction of photosynthesis. The loss of carbohydrates, due to severe infestations, could result in reduced fruit sugar levels at harvest. The vine may also be unable to adequately store carbohydrates as food reserves, which would otherwise promote winter hardiness and supply energy for new growth the following spring. Severe infestations of phylloxera galls on the foliage will also cause defoliation and retard shoot growth.
Figure 6. Healthy grape shot (left), compared to shoot with severely leaves (right).
|High||Moderate to Low|
*Phylloxera are able to cause variable levels of gall formation on some V. vinifera.
Monitoring and Control of Leaf Phylloxera
Monitoring the leaf feeding cycle of grape phylloxera depends on timely visual observations. Leaf galls caused by first-generation phylloxera generally appear about mid-May, usually as one or two galls on the first to third new expanding leaves. Samples of these galls should be opened and checked with a hand lens, or better, dissected under a low-power microscope to determine when second-generation eggs begin to hatch. Two to three days after egg hatch begins is an ideal time to apply chemical control, as the new nymphs emerge from galls and crawl to the young, unexpanded leaves. The crawling and early gall development phase is the stage that phylloxera are most vulnerable to an insecticide because once new gall formation is complete, chemical control becomes difficult due to the protection offered by the leaf gall structure. Systemic insecticides may control the feeding females inside the galls; however, deposited eggs are often unaffected. Similarly, leaf galls caused by second-generation phylloxera can be sampled to determine when egg hatch begins and subsequent nymph crawling for spray timing.
Early-season chemical control may be more effective than mid- to late-season control in problem vineyards. A split-age structure in the phylloxera population develops by the beginning of the third generation, making spray timing more difficult as the season progresses. Research indicates that grapevines are able to withstand light to moderate amounts of leaf gall formation without having adverse effects on fruit quality or vine health. Therefore, chemical control is only recommended in vineyard blocks that have a history of serious leaf phylloxera problems.
Common predators, including lacewing nymphs (Figure 7) and a predatory fly larvae (Figure 8) will help to reduce phylloxera populations.
Figure 7. Lacewing nymphs are common predators of grape phylloxera.
Figure 8. Predatory fly larvae feeding on phylloxera adult and eggs inside a leaf gall.