2.4.3.e Phylloxera

Native to the Eastern United States, Phylloxera is a sucking insect related to aphids. It was first reported in France in 1863. In the 19th century, Phylloxera had a dramatic economic and social impact on French and European viticulture, which was devastated and had to be completely rebuilt. Today, Phylloxera has colonized almost every wine region in the world.

"The history of agriculture does not present us, at any time and for any other cultivated plant, a crisis as serious as that experienced by the vines of the old continent when they were invaded by Phylloxera." Gustave Foex, 1900.

What damage does phylloxera cause to leaves?

Phylloxera does not cause significant damage by feeding on sap, it is the reaction of the vine's tissues to the aphid's secretions that is the cause of major problems. By proliferation and thickening of the tissues, phylloxera causes the formation of galls on the underside of the leaf which contain thickened bristles, the insect and its eggs.

Phylloxera galls (Source: Vigne Vin Occitanie)

As the larvae emerge from these galls, they may form new galls. American varieties, especially V. riparia and V. berlandieri, are particularly reactive and sensitive to leaf symptoms. These symptoms can explode with these varieties in July when the phylloxera galls eventually invade the entire leaf blade. These galls, by compromising photosynthetic potential, cause a decrease in sugar accumulation in the berries, with little significance in hybrid rootstocks and varieties.

On the other hand, the galls can be detrimental to the constitution of reserves in the wood, which can affect rootstock quality from mother vines in the event of a heavy attack. There is no registered insecticide that is phylloxera specific, but most of the products used against the flavescence dorée leafhopper vector (compulsory treatments in nurseries and mother vines) have an effect on the aphid, which in most cases enables damage to be reduced to a low level. For V. vinifera, the reaction is much weaker and the galls, rarely observable, remain very small, contain less oviposition and present slower development.

What damage does phylloxera cause to roots?

In V. vinifera, Phylloxera symptoms appear as nodosities and tuberosities. The increased root sensitivity of the species is the main cause of the rapid eradication of the European vineyards, which were then cultivated without any grafting, at the end of the 19th century. Nodosities are the consequence of Phylloxera wounds on the tip of the growing rootlets. At the puncture site, growth stops while the surrounding tissues proliferate. The structure formed takes on a hook or bird's beak shape, and the rootlets can no longer perform their absorption function. Tuberosities form on large roots (> 50 mm diameter).

Phylloxera on roots (Source: Vigne Vin Occitanie)

If the number of insects is high, the generative base can be affected and cause bumps and irregularities on the root surface. Phylloxera, by developing under the periderm, can leave the door open to microorganisms responsible for rot, which can quickly cause the vine to die. American varieties react differently. Some are not attacked but most of them are tolerant and allow Phylloxera to develop without causing the vine to die. Hybrid varieties have intermediate sensitivity.

What is the biology of phylloxera?

Phylloxera has a complex life cycle. There are two types of non-winged parthenogenetic females that develop from unfertilized female gametes:

Gallicolous Phylloxera which develops on foliage. Each female lays about 600 eggs from which larvae emerge, which after 4 moults, transform into adults, starting a new cycle that can be repeated over several generations. While the first generations remain gallicolous, some larvae from subsequent generations can migrate towards the roots and have radicicolous descendants. These larvae are then said to be "root-feeding neogallicolae".
The root-feeding Phylloxera develops on the roots. Females lay between 40 and 100 eggs, resulting in larvae, adults and new generations that can continue indefinitely. Some first-stage larvae may hibernate and resume activity in the spring. In the summer, some females undergo an additional moult and transform into pupae, which in turn produce winged Phylloxera. The Phylloxera eggs laid on the aerial parts of the vine produce males and females. The latter only live a few days, the time it takes to mate and produce a winter egg. From this egg, a founding female hatches, causing the first galls on the foliage the following spring. There is considerable diversity in the species and the observed biotypes are characterized by different levels of aggressiveness.

Are there any preventive measures?

Growing methods: by growing vines in sandy soils. This type of culture is still used on the Mediterranean coast.
By the use of direct-producer hybrids or rootstocks from American species that are Phylloxera tolerant. The hybrids, which represented nearly 30% of French vineyards during the first part of the 20th century, have been replaced due to the mediocre quality of their wines by V. vinifera grafted onto resistant rootstocks. The hybrids represent the first example of a successful genetic fight against a crop pest.

Due to the widespread use of grafting, whose development has also made it possible to have a range of rootstocks adapted to cultivation in many soil and climatic conditions, Phylloxera is no longer a major problem in our vineyards. However, the recent phylloxera crisis that occurred in California in the early 1990s, mainly caused by the massive use of rootstock insufficiently resistant to the parasite (Aramon-rupestris Ganzin no. 1), as well as the sometimes significant presence of the gallicolous form in V. vinifera in certain vineyards, serves as a reminder that we must remain vigilant.

Extracts from Vigne Vin Occitanie.

Contribute Print

Contribute