Phylloxera caryaecaulis

Hosts: Carya glabra, ovata

[Phylloxera caryaemagna has previously been considered a synonym of this gall, and the two are very similar in appearance. Dr Hamilton notes in couplets 12 and 13 of her first key (page 115 of the pdf), that P caryaemagna is pubescent and spongy, while caryaecaulis has hard walls and a glabrous exterior.]

Globular and smooth, hard, pale yellowish-green with a hint of crimson, diameter 5.0–25.0 mm; occurs on petioles with an irregular opening or along mid-vein of leaves with a slit-like opening below.

Range: AR, SC

Phylloxera caryaecaulis (Fitch)

Galls are on young twigs, on petioles or at bases of leaflet main veins, sometimes in clusters; globular, diam. 5-25 mm, pale yellowish green tinted with red before opening, afterwards becoming leathery and black. Typically on Carya glabra in eastern USA. There is no host alternation.

Shimer (1869) described three other closely-related phylloxerid species producing somewhat different twig or petiole galls on other species of Carya, which may or may not be synonymous with P. caryaecaulis: P. spinosa, producing galls covered with fleshy spines on Carya sp, in Illinois; P. caryaemagna, producing velvety galls on petioles or at base of mid-rib on C. amara (= cordiformis) in Illinois and Missouri; and P. subelliptica, producing ellipsoid mottled green galls on side of twig of C. alba (= ovata) in Illinois (see also Pergande 1904).

Phylloxera caryaecaulis

Carya sp.
Petiole or twig galls
Globular or oval, often more or less conical, spiny or smooth, according to the tree on which they grow, and more or less confluent, diameter 5 to 25 mm.

Phylloxera caryaecaulis Fitch.

Pemphigus caryacaulis Fitch.
Dactylosphaera caryae-magnum Shimer.
Dactylosphaera spinosum Shimer.

Up to the present time these three forms of galls have been considered as quite distinct species on account of their dissimilarity, two of them being smooth and the other more or less profusely covered with fleshy spines. But a careful study of the architects of these forms forces the conclusion that they are identical, there being no tangible characters by which to separate them. The spiny form of gall always grows upon trees with pubescent leaves, such as Hicoria tomentosa, while the smooth forms are always found upon trees with smooth leaves, such as Hicoria glabra, amara and probably other species.

The typical form, growing upon the young and succulent limbs, petioles or the midrib of the leaflets of Hicoria glabra, occurs over the eastern half of the United States.

The size of the galls varies from 5-25 mm in diameter. Those growing singly often attain immense proportions, but when numerous or crowded they are reduced in size and often confluent, so as to form an elongated mass. Before maturity of the inhabitants the gall is closed, but as soon as any of the inmates have acquired wings, it cracks transversely into 3-6 or more broad and more or less irregular bracts so as to allow the mature migrants to escape, and to leave room and food for the younger individuals. The color is pale yellowish-green, more or less tinted with red or crimson. The walls of the galls are rather thick and succulent when young, becoming more tough and leathery when older and hard, brown or black when empty and dry.