Phylloxera

Phylloxera
Dactylosphaera vitifolii 1 meyers 1888 v13 p621.png
Scientific classification
Kingdom:
Phylum:
Class:
Order:
Suborder:
Sternorrhyncha (was Homoptera)
Superfamily:
Family:
Genus:
Daktulosphaira

Shimer, 1866[1]
Species:
vitifoliae
Binomial name
Daktulosphaira vitifoliae
(Fitch 1855)

Grape phylloxera (Daktulosphaira vitifoliae (Fitch 1855); family Phylloxeridae, within the order Hemiptera, bugs); originally described in France as Phylloxera vastatrix; equated to the previously described Daktulosphaira vitifoliae, Phylloxera vitifoliae; commonly just called phylloxera (ə/; from Ancient Greek: φύλλον, leaf, and ξηρός, dry) is a pest of commercial grapevines worldwide, originally native to eastern North America.

These almost microscopic, pale yellow sap-sucking insects, related to aphids, feed on the roots and leaves of grapevines (depending on the phylloxera genetic strain). On Vitis vinifera, the resulting deformations on roots ("nodosities" and "tuberosities") and secondary fungal infections can girdle roots, gradually cutting off the flow of nutrients and water to the vine.[2] Nymphs also form protective galls on the undersides of grapevine leaves of some Vitis species and overwinter under the bark or on the vine roots; these leaf galls are typically only found on the leaves of American vines.

American vine species (such as Vitis labrusca) have evolved to have several natural defenses against phylloxera. The roots of the American vines exude a sticky sap that repels the nymph form when it tries to feed from the vine by clogging its mouth. If the nymph is successful in creating a feeding wound on the root, American vines respond by forming a protective layer of tissue to cover the wound and protect it from secondary bacterial or fungal infections.[2]

Currently there is no cure for phylloxera and unlike other grape diseases such as powdery or downy mildew, there is no chemical control or response. The only successful means of controlling phylloxera has been the grafting of phylloxera-resistant American rootstock (usually hybrid varieties created from the Vitis berlandieri, Vitis riparia and Vitis rupestris species) to more susceptible European vinifera vines.[2]

Biology

Phylloxera nymphs feeding on the roots

The phylloxera aphid has a complex life-cycle of up to 18 stages, that can be divided into four principal forms: sexual form, leaf form, root form, and winged form.

The sexual form begins with male and female eggs laid on the underside of young grape leaves. The male and female at this stage lack a digestive system, and once hatched, they mate and then die. Before the female dies, she lays one winter egg in the bark of the vine's trunk. This egg develops into the leaf form. This nymph, the fundatrix (stem mother), climbs onto a leaf and lays eggs parthenogenetically in a leaf gall that she creates by injecting saliva into the leaf. The nymphs that hatch from these eggs may move to other leaves, or move to the roots where they begin new infections in the root form. In this form they perforate the root to find nourishment, infecting the root with a poisonous secretion that stops it from healing. This poison eventually kills the vine. This nymph reproduces by laying eggs for up to seven more generations (which also can reproduce parthenogenetically) each summer. These offspring spread to other roots of the vine, or to the roots of other vines through cracks in the soil. The generation of nymphs that hatch in the autumn hibernate in the roots and emerge next spring when the sap begins to rise. In humid areas, the nymphs develop into the winged form, else they perform the same role without wings. These nymphs start the cycle again by either staying on the vine to lay male and female eggs on the bottom side of young grape leaves, or flying to an uninfected vine to do the same.[3]

Phylloxera eggs inside a leaf gall

Many attempts have been made to interrupt this life cycle to eradicate phylloxera, but the aphid has proven to be extremely adaptable, as no one stage of the life cycle is solely dependent upon another for the propagation of the species.

Other Languages
Afrikaans: Filloksera
Alemannisch: Reblaus
العربية: فيلوكسرا
català: Fil·loxera
Deutsch: Reblaus
Ελληνικά: Φυλλοξήρα
Esperanto: Filoksero
euskara: Mahats-zorri
فارسی: شته مو
français: Phylloxéra
galego: Filoxera
ქართული: ფილოქსერა
Кыргызча: Филлоксера
Lëtzebuergesch: Rieflaus
magyar: Filoxéra
Nederlands: Druifluis
norsk: Vinlus
português: Filoxera
română: Filoxeră
slovenščina: Trtna uš
srpskohrvatski / српскохрватски: Filoksera
suomi: Viinikirva
svenska: Vinlus
Türkçe: Asma biti
中文: 根瘤蚜