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Radicicola

Latin name (root phylloxera) for the phylloxera occurring underground at the roots of the vine; see there.

This most dangerous of all vine pests (bot. Dactylosphaera vitifolii) is an insect of the order Plant Aphids (Homoptera), suborder Aphidina and family Phylloxeridae. The phylloxera exclusively attacks the grapevine, sucking on the leaves and/or roots and releasing its saliva into the sap pathways, causing galls (growths) that then serve as oviposition and food. Different species are suspected based on different behavioral patterns toward the vine. The German biologist Dr. Carl Börner (1880-1953) distinguished between a less dangerous long-nosed phylloxera and a more harmful short-nosed phylloxera. From the initial infestation, it usually takes a maximum of three years for the vine to die and be completely destroyed due to secondary effects such as nutrient deficiency and root rot. The French scientist Jules Émile Planchon (1823-1888) aptly named the phylloxera vastatrix (devastating louse) when he identified it in France in 1868.

Life cycle

The life cycle is highly dependent on the species of grapevine attacked, namely European gra pevine or American grapevine. It takes place either in the form of a complete cycle or a continuous cycle between vine (aboveground) and root (underground) or only on leaves (only aboveground) or only roots (only underground) and thus a shortened cycle. There are parthenogenetic (virgin production from unfertilized eggs) and sexual generations. According to the place of infestation, a distinction is therefore made between the yellow-green 1.5 mm long leaf aphid (Gallicola = leaf gall aphid) and the yellow-brown 1.35 mm long root aphid (Radicicola = root louse). The latter is much more dangerous, as it damages the leading tissue, which leads to water and nutrient deficiency. Infestation of the leaves, on the other hand, is usually not life-threatening. Among the grapevine species there are those which form both leaf and root galls, the root galls but no leaf galls, as well as the leaf galls but no root galls. The group of completely resistant grapevine species forms neither leaf nor root galls.

Blattreblaus - Blattgallen und Mutterlaus mit Eigelege

In Europe, mostly only the reproduction by the root galls takes place, while the full cycle takes place only in America. Only in the above-ground cycle do offspring with new genetic material develop, as only here are there males and females. In root lice, there are only females, which reproduce parthenogenetically and lay 600 eggs. Young hatched ones do not infest the roots immediately, but overwinter deep in the soil. In spring, the roots are punctured with the proboscis (at half body length) and saliva is introduced into the tissue. As an almost panicky defensive reaction of the vine, nodular thickened growths form. The aphids then feed on these soft structures, sucking them up. The pest can therefore only live by forming galls, because the hard roots themselves could not be gnawed directly.

Reblaus - Wurzelrebläuse mit Eianlage

In Central Europe, there are four to six generations of phylloxera per year. The young aphids of the last generation (Hiemalen) form the overwintering form. Towards the end of midsummer, nymphs develop, which are larvae with wing attachments. These leave the soil and develop into winged vine lice (sexuparae) after their last moult. Due to their ability to fly, they can quickly spread to other vineyards even over long distances. They lay small male and large female eggs on the perennial bark of the vine, from which the soothless sexuals hatch. These cannot ingest food and have the sole function of copulation during their life, which lasts only about eight days.

Rebläuse in verschiedenen Stadien und weibliche Reblausfliege

The mated females lay a single fertilized olive-green winter egg in a bark crack. From this egg, the May gall aphids hatch in spring, forming leaf galls only on American grapevine species (Vitis vinifera is resistant on the leaves) and laying up to 1,200 eggs. Two types of larvae hatch from these after eight to ten days. One of them forms leaf galls again, especially on younger leaves. They reproduce parthenogenetically with six to eight generations per year. The others are leaf-born root aphids and seek out the vine roots in the soil. There they complete the underground development cycle or start it anew. An overwintered phylloxera with 1,000 eggs yields about 25 trillion offspring by autumn. The tremendously complex cycle or life cycle of leaf and root aphids is shown in the diagram:

Reblaus - Lebenszyklus (Geisenheim)

Nodosities and Tuberosities

A distinction is made between two root types and thus different effects due to infestation. In the case of minor infestations, the young, unwoody root tips are pricked first. The resulting root galls are called nodosities. They occur not only in European but also in most American grapevine species, but are relatively harmless and do not lead to destruction. However, in more severe infestations, the older, woody roots are also pricked and tuberosities are formed as a result. These are much more dangerous because they can penetrate much deeper into the vascular system of the roots. Certain American grapevine species are...

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