Phylloxeridae

Phylloxera

Carya tomentosa

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North American Phylloxerinae affecting hicoria (Carya) and other trees

Phylloxera perniciosa

Phylloxera perniciosa Pergande, n. sp. 

[Key]
Galls more or less globular or irregular, terminating in a tooth-like nipple.
Growing on tender twigs, petioles, or ribs of leaves, often confluent. Smooth. Diameter 2-8 mm.

This is one of our most destructive species, occurring in the District of Columbia, Maryland, Virginia and Pennsylvania, where it takes the place of Ph. carycecaulis and Ph. magna, having the same habit and there proving as disastrous to the foliage of Hicoria tomentosa as those prove in the North and Northwest to the other species of Hicoria. It attacks, as do those species, the tender twigs and petioles and the different parts of the leaves at times in such immense numbers as to completely deform and cause them to dry up and drop to the ground, literally, at times, defoliating the tree. My attention was first called to this particular species in May, 1883, when, passing through a strip of woods bordering the Potomac River in Virginia, I observed that the air was swarming with the migratory form. The insects were settling not only on the leaves of the different species of Hicoria, but on all other kinds of trees and shrubs and even on weeds, on all of which they were actively engaged in depositing their eggs; but they all originated from a tall slender tree of Hicoria tomentosa, every leaf, petiole and young twig of which was affected by the galls. 

[Pergande provides a detailed timeline of oviposition and development]

By the 28th of April most of the young stem-mothers had settled either on the young petiole or mid-rib, on the cross-rib, or on the more fleshy parts of the young leaves, where small depressions or cavities had been formed. 

By May 8th it was noticed that the galls had been formed on almost all parts of the leaves or on the petioles or on the more tender twigs. The more perfect specimens were growing singly, resembling a blunt tooth or thorn, those on the leaves projecting about evenly on both sides though ordinarily more prominently on the under side. The stem-mother had already by this time acquired full growth and began depositing numerous eggs, covering almost the whole inner surface of the gall, the eggs placed on end and side by side reminding one in miniature of the regular crystallizations in the cavities of some geode. By the 18th of May the galls contained, besides the eggs, both larvae and pupae in different stages of development. By the 25th the winged insects had formed and were leaving the galls in large numbers and settling, as at the same time the previous year, on all kinds of vegetation in the neighborhood of the tree on which they had developed. 

To sum up the life-history of this species, the winter or impregnated eggs are deposited early in June in all sorts of sheltered positions, especially on the upper portions of the tree; they hatch early in April of the following year, remaining dormant some ten months. The stem-mother attains maturity and begins ovipositing in about twenty days after hatching, while the winged migratory females (sexuparae) mature and begin to leave their galls in about twenty days after the first eggs are laid. The first sexual individuals appear about ten days subsequently and some ten days further elapse before the true female, after pairing, begins to consign her single egg to its winter quarters. 

Phylloxera perniciosa

Carya

Leaf folds and ridges
Globular or irregular, terminating in a toothlike nipple and occurring on tender twigs, petioles or ribs of leaves, often confluent, smooth, diameter 2 to 8 mm. 

Petiole or twig galls
Globular or irregular, terminating in a toothlike nipple and occurring on tender twigs, petioles or ribs of leaves, often confluent, smooth, diameter 2 to 8 mm. 

Key to American Insect Galls

Phylloxera perniciosa Pergande    

Galls on young twigs, leaf petioles and along midribs of leaflets of Carya tomentosa are elliptical, with a blunt tooth-like or thorn-like projection.  In Maryland, Virginia, D.C. and Pennsylvania; large gall populations in Virginia caused defoliation of trees (Pergande 1904).  Also reported from C. illinoensis in Louisiana and Mississippi (Carpenter et al. 1979), although the identity of these populations with Pergande's species needs confirmation.  Living all year around on Carya, with three generations per year; fundatrices, alate sexuparae and sexuales.  Alate sexuparae emerging from galls in May-early June laid eggs indiscriminately on trees and surrounding vegetation.  Sexuales laid overwintering eggs in June, mostly high in trees on twigs that had been previously galled.  The eggs were preyed upon through the summer by various natural enemies. including mites of six different genera.  Surviving eggs hatched the following April (Pergande 1904).

Aphids on the world's plants

Phylloxera perniciosa

Thorny, yellowish-white, and smooth; diameter 2.0–8.0 mm; occurs on petioles, stems, or along midvein of leaves with the underside usually more convex. Opening is elongate and thorn-like.

Species Diversity of Hickory-feeding Phylloxerans (Hemiptera: Phylloxeridae) in the U.S.

The fact that this gall can occur on flowers is tentatively inferred from the fact that it is apparently profligate it its oviposition, and based on observations like [this one](https://www.inaturalist.org/observations/46837266), which are not confirmed to be induced by P perniciosa. 

Gallformers ID Notes