November 21, 2020


Tree abbrevs.
Blk =Q. kelloggii (California black oak) [R/B]
Blu =Q. douglasii (blue oak) [WH]
Colv =Quercus agrifolia (coast live oak) [R/B]
Cyn =Quercus chrysolepis (canyon live oak) [INT]
Eng =Q. engelmannii (Engelmann oak) [WH]
Huc =Q. vacciniifolia (huckleberry oak) [INT]
Inlv =Q. wislizeni (interior live oak): formerly included Shreve & parvula [R/B]
Lea =Q. durata (leather oak) [WH]
Nut =Q. dumosa (Nuttall's scrub oak) [WH]
Ore =Q. garryana (Oregon oak) [WH]
Pal =Q. palmeri (Palmer's oak) [INT]
Scr =Quercus berberidifolia (Calif scrub oak) [WH]
Mul =Q. cornelius-mulleri (Muller's oak--desert scrub) [WH]
Tuc =Q. john-tuckeri (Tucker's oak) [WH]
Val =Q. lobata (valley oak) [WH]

Live Oak Witches' Broom Fungus ( Cystotheca lanestris) This mildew causes whitening of affected parts of plant and/or witches’ broom. Colv Cyn Val & Tanbark

Irregular Spindle Gall Wasp (Andricus chrysolepidicola) Lumpy bark-colored acorn-like protuberances. Blu Val Scr Lea
Club Gall Wasp (Andricus coortus) Roundish gall at end of stem, but new stems may grow out of it. Ore Blu Scr

California Gall Wasp (Andricus quercuscalifornicus) All or nearly all white oaks
Beaked Twig Gall Wasp (Disholcaspis plumbella) Gall may not have a beak if found in the southern California desert on turbinella oak. Blu Scr Lea Turbinella
Honeydew Gall Wasp (Disholcaspis eldoradensis) Val Scr Lea Ore
Twig Gall Wasp (Disholcaspis mellifica) Like D. eldoradensis but bark is swollen and ruptured and galls line up in rows and are somewhat smaller. Scr Lea Ore
Round Honeydew Gall Wasp (Disholcaspis canescens) Blu Scr
Clasping Twig Gall Wasp (Disholcaspis prehensa) Scr Lea
Fuzzy Gall Wasp (Disholcaspis washingtonensis) Beige or gray; mealy-granular texture becoming wrinkled; slight stalk. Almost all white oaks
Round Gall Wasp (Cynips conspicuus) [syn. Besbicus conspicuus] Round and neckless—usually has short beige, rust, or brn hair. Blu [Val—per JG]
Dried Peach Gall Wasp (Disholcaspis simulata) Pointed or nippled; photos showing gall interior will help confirm ID. Scr Lea Blu Ore Eng
Bullet Gall Wasp (Disholcaspis mamillana) Ocher-colored gall with nipple. Blu Scr
Coral Gall Wasp (Disholcaspis corallina) Orangy. Ore [Blu—per JG]
Andricus opertus Stringy green/brown fibers coming from the bud or leaf midrib. Scr Lea Blu Val
Disholcaspis conalis Thornlike “witches’ hat gall. Ore

Thorn Gall Wasp (Cynips heldae) Spines laterally flattened and usually bent and twisted; rose-pink turning brown. Ore Val
Andricus wiltzae Rosette on terminal buds; see Russo 2006 p. 106. Val
Irregular Spindle Gall Wasp (Andricus chrysolepidicola) Ovoid gall w/ fine hairs. Blu Val Scr Lea
Leafy Oak Gall Wasp (Andricus quercusfoliatus) [syn. Andricus foliatus] Note that BugGuide page does not list any Western oaks for this gall. Val

Crystalline Gall Wasp (Andricus crystallinus) Blu Scr Lea Ore
Disc Gall Wasp (Andricus parmula) Most white oaks
Yellow Wig Gall Wasp (Andricus fullawayi) Most white oaks
Urchin Gall Wasp (Cynips quercusechinus) Either pink-with-white-tips or red-purple Blu Scr
Convoluted Gall Wasp (Andricus confertus) Leaf underside. Val
Saucer Gall Wasp (Andricus gigas) Edges may be either smooth or toothed. Alternate gen. produces cones on leaves and flowers. Blu Scr Eng
Striped Volcano Gall Wasp (Andricus atrimentus) Alternate generation produces a thin, round, green leaf gall. Blu
Clustered Gall Wasp (Andricus brunneus) Lavender, pink tan, brick etc w/ short cream-colored matted hairs; leaf underside. Most white oaks
Club Gall Wasp (Atrusca clavuloides) Sometimes bent over; parts of leaf turn brown. Val
Plate Gall Wasp (Andricus pattersonae) Leaf underside; plate 107 in Russo 2006. Most white oaks
Hair Stalk Gall Wasp (Dros pedicellatum) Leaf margin vein extension. Blu Val Scr Ore
Urn Gall Wasp (Phylloteras cupella) Leaf underside. See comments here Scr Lea Blu Eng & SW white oaks
Red Cone Gall Wasp (Andricus kingi) Alternate generation produces smallish tapering leaf-edge galls that turn black. Blu Val Ore
Spined Turban Gall Wasp (Cynips douglasii) Blu Val Scr
Cynips multipunctata Gray Midrib Gall Wasp. On leaf underside. Blu
Woollybear Gall Wasp (Atrusca trimaculosa) Roundish gall on leaf underside; Russo 2006 pl. 108. Most white oaks
Sunburst Gall Wasp (Andricus stellaris) Center usually dark red. Blu Ore
Ball-tipped Gall Wasp (Xanthoteras teres) Globe on a pedestal Lea Ore
Pear Gall Wasp (Andricus maculosus) Teardrop; leaf underside. Scr Lea
Hair Stalk Gall Wasp (Andricus pedicellatus) Blu Scr Val Ore
California Jumping Gall Wasp (Neuroterus saltatorius) Most white oaks
Andricus tubifaciens Clusters of bristly crystalline tubes; leaf underside. Ore
Andricus albicomus. Bristly 4mm galls on Ore [0 obs]
Andricus bakkeri This is the “Pinched leaf gall wasp,” Plate 127 of Russo 2006. See pg. 292 of Lyon 1984 Eng Nut Ore
Andricus stellulus Stalked cup. Nut Turbinella
Speckled Gall Wasp (Cynips mirabilis) [Syn: Besbicus mirabilis] Ore
Round Gall Wasp (Cynips conspicuus) Blu [also Val per JG]

Neuroterus fragilis Roundish swelling of petiole and/or midrib. Blu Scr Lea
Live Oak Erineum Mite (Aceria mackiei) Leaf blisters. Ore ?Lea
Eriophyes trichophila Blue oak erineum mite with fewer, larger blisters/bumps than Aceria mackiei; white/brown hairs. Blu [0 obs!]
Midrib Gall Wasp (Neuroterus washingtonensis) Leaf swellings 1 cm or more in size. [3 obs] Ore
Andricus opertus Stringy green/brown fibers coming from the leaf midrib. Scr Lea Blu Val
California Jumping Gall Wasp (Neuroterus saltatorius) Most white oaks

Andricus reticulatus. Small gall on petiole/leaf base. See pg. 290 of Lyon 1984 and Fig. 1B. Eng in SoCal & some SW species.

Gouty Stem Gall Wasp (Callirhytis quercussuttoni) Integral stem galls that are so abrupt they can look pasted on based on. All red/black oaks
Ruptured Twig Gall Wasp (Callirhytis perdens) Gradual; lengthwise fissures along stem. All red/black oaks

Live Oak Apple Gall Wasp (Amphibolips quercuspomiformis) Spiky round galls; but Garth Harwood notes “I see a good deal of variability in this gall, from finely spiny to billiard-ball smooth (especially while developing, when they can be bright red. ) ...Two other clues ... are the central dot at the distal end ... and the faint 'longitudinal' lines radiating down from that spot along the sides.” All red/black oaks

Kernel Flower Gall Wasp (Callirhytis serricornis) Colv Inlv
Callirhytis congregata All red/black oaks; Colv espec.
Mottled Acorn Gall Wasp (Callirhytis carmelensis) All red/black oaks
Callirhytis eldoradensis

Live Oak Bud Gall Wasp (Callirhytis quercusagrifoliae) All red/black oaks

Pumpkin Gall Wasp (Dryocosmus minusculus) All red/black oaks
Two-horned Gall Wasp (Dryocosmus dubiosus)
Live Oak Apple Gall Wasp (Amphibolips quercuspomiformis) Green-red upcurved gall on leaf underside. All red/black oaks

Live Oak Erineum Mite (Aceria mackiei) Inlv Colv

Ball Gall Wasp (Callirhytis perfoveata) All red/black oaks
Gouty Stem Gall Wasp (Callirhytis quercussuttoni) This alternate generation galls produces blisters on leaf veins. All red/black oaks
Live Oak Bud Gall Wasp (Callirhytis quercusagrifoliae) This alternate generation galls produces blisters on leaves, petioles, buds. All red/black oaks

Live Oak Petiole Gall Wasp (Melikaiella flora) [syn. Callirhytis flora] Colv Inlv ?Blk
Gouty Stem Gall Wasp (Callirhytis quercussuttoni) This alternate generation galls produces blisters on petioles and leaf veins. All red/black oaks

Tapered Stem Gall Wasp (Protobalandricus spectabilis) Russo 2006 describes this as “abruptly swollen”; larval chambers are much better separated by plant tissue than with Dryocosmus asymmetricus.
Kidney Stem Gall Wasp (Andricus reniformis) Variable. Check all JG photos. Cyn Huc Pal

Split Twig Gall Wasp (Dryocosmus asymmetricus)
Andricus frondeum not in Russo 2006 Cyn&? [24 obs]
Neuroterus chrysolepis. This gall is described on pg. 290 of Lyon 1984 As a blisterlike swelling on “young stems” of canyon live oak. Drawing is Fig. 1A on pg. 291. Cyn

Beaked Spindle Gall Wasp (Heteroecus pacificus)
Heteroecus melanoderma
Mushroom Gall Wasp (Heteroecus sanctaeclarae)
Potato Gall Wasp (Andricus truckeensis)
Andricus frondeum not in Russo 2006 Cyn&?
Heteroecus malus “[G]alls ... tend to occur in grape-like clusters and have a fine white pubescence when fresh. Underneath ... the galls are green or green with red. Older galls are tan. The galls are monothalamous (single larva). Host is Quercus chrysolepis (canyon live oak)” JG . not in Russo 2006 Cyn&?
Golden Oak Apple Gall Wasp (Andricus vacciniifoliae)
Hairy Gall Wasp (Andricus lasius)

Torpedo Gall Wasp (Andricus projectus) Red with yellow tip when frest; bud scales at base; on leaf axil or catkin. Cyn

Bowl Gall Wasp (Acraspis patelloides) Cup or hat on midrib; leaf underside. Cyn
Muffin Gall Wasp (Disholcaspis chrysolepidis) Dome-like crust is darkish and rough; sides smooth. All intermediate oaks
Little Urn Gall Wasp (Andricus rotundula) Row or double row of extremely small galls along midrib on leaf underside. Cyn Pal
Little Oak Apple Gall Wasp (Andricus coquilletti) Huc
Hairy Gall Wasp (Andricus lasius) Round and fluffy; dark beige or goldish; leaf underside. Cyn
Woolly Gall Wasp (Heteroecus dasydactyli) Cyn
Acraspis insolens See
Beaked Spindle Gall Wasp (Heteroecus pacificus) ) Alternate generation produces thornlike cone that is tough to pull off leaf underside, normally red to purple.

Round Leaf Gall Wasp (Heteroecus flavens)
Intermediate Oak Disc Wasp (Acraspis guadaloupensis) 6mm; leaf underside. Cyn
Live Oak Erineum Mite (Aceria mackiei). Cyn Huc
Contarinia Leaf tightly rolled to underside. Cyn Huc
Fold Gall Midge (Dasineura silvestrii) Cyn Huc

Wool-bearing Gall Wasp (Andricus quercuslanigera) Southern live oak in CA

Posted on November 21, 2020 11:21 by nancyasquith nancyasquith | 0 comments | Leave a comment

September 26, 2020

New Russo Field Guide being issued in March!

Princeton Field Guides will be issuing Plant Galls of the Western United States, a guide to "536 species of plant galls found west of the Rockies" including 120 species new to science and expanded coverage of desert galls and SW oak galls. $29.95


Posted on September 26, 2020 17:12 by nancyasquith nancyasquith | 3 comments | Leave a comment

August 26, 2020

CALIFORNIA GALLS, A Host Plant List with Links

This list of close to 200 plant galls includes all those non-oak California gall inducers that had at least 8 observations in iNaturalist's Galls of California project in August 2020 except for galls caused by fungi, mistletoes, or bacteria. You'll find some oak, fungus, mistletoe, and bacteria galls listed, but the coverage is spotty. Root galls are also omitted. For oak gall ID, I recommend perusing Joyce Gross's excellent photo-guide.

A few incompletely described species that have been identified to the genus level are included here too, but California has a lot of galls that remain undescribed. The list also emphasizes species that Ron Russo's impressive, 2006 "Field Guide to Plant Galls of California and Other Western States" either does not include or mentions only briefly. [9/26 update: An expanded Russo guide is only months away.]

Alphabetizing this list by plants' scientific names seemed like the the only good way to keep related plant species together. However, you can search the list by a host plant's common name. Just enter [cntrl]F and type the common name. [BTW, for some species for which we had few or no observations as of late August 2020, the entry ends with the # of California iNat obs[ervations] of the gall--roughly as of then--and where they occurred--e.g., SFBA, meaning SF Bay Area.]

Abies sp--Fir: Fir Broom Rust (Melampsorella caryophyllacearum) See USDA info sheet and PNW Handbook entry. Causes witches' brooms, sometimes large, with yellow needles that drop off in the fall. [9 obs]

Acer negundo--Boxelder : Box elder pouch gall mite (Aceria negundi) pouch galls on leaves [2 obs SFBA]

Adenostoma fasciculatum--Chamise: Eriophyes adenostomae [Synonym: Phytoptus adenostomae] Mite-induced leaf "pouch" gall that looks like a conglomeration of puckered beads attached to the slender leaf [8 obs SFBA]

Aesculus californica—California buckeye: Taphrina aesculi leaf blister; witches’ broom [3 obs SFBA]

--Alder Leaf Gall Mite (Eriophyes laevis) Small, often colorful hemispheric-to-round galls on top of leaf; same but hemispheric-to-flat on underside [19 obs]
-- Alder Leaf Gall Mite (Acalitus brevitarsus) Leaf blister gall [1 unconfirmed obs in N’ern CA; Russo has found this on red and Sitka alder but half of the 35 iNat sightings of this gall in the U.S. are in Alaska]
--Leaf Fold Gall (Dasineura sp.) Undescribed leaf gall induced by midge [Note that feeding by the Woolly Alder Aphid (Prociphilus tessellatus) can also cause leaf folds in alders; look for white wool as evidence of aphids]
-- Western American Alder Tongue Gall (Taphrina occidentalis) [82 obs Big Sur and north to border]
--Catkin Gall (Dasineura) Another undescribed midge gall

Aloe sp & other Asphodelaceae: Aloe gall mite (Aceria aloinis) photos These tiny mites can produce large formations on the plants. [5 obs SoCal]

--Contarinia partheniicola Per Gagne 1975, "forms whitish, woolly cupulate [cup-shaped] galls" on Ambrosia spp. & Mariola that are 5-8mm x 4-5mm. They occur singly or in small groups on axillary buds, leaves, staminate florets, and the rachis and have been collected from five species of Ambrosia in SoCal [1 unconfirmed obs]
--Asphondylia ambrosiae According to Gagne 1975, this midge "forms fuzzy, globose bud galls on Ambrosia spp." [1 obs Riverside Cy.]

Ambrosia psilostachya—Western ragweed: Ragweed Gall Mite (Aceria boycei) Leaf blister [50 obs all LA-SDiego]

--Blaesodiplosis Undescribed species of this midge genus induce a variety of leaf galls on serviceberries. See BugGuide for one example.
--Taphrina amelanchieri Causes witches' brooms
--Gymnosporangium inconspicuum See photo at bottom of page. "Horns" of whitish to yellow-orange rust stick out of fruit. Uncommon in California; common in some SW states. [0 obs]
--Russo reports finding an undescribed aphid that induces leaf-roll galls on serviceberry.

Amsinckia sp--Fiddleneck:
-- Schizomyia macrofila See midge-induced flower bud gall [8 obs but some may be Anguina--see next entry]
-- Fiddleneck Gall Nematode (Anguina amsinckia) large gall replaces flower head preferential galling of the lowermost flowers (Fl-F6) within a given inflorescence. See and

Arbutus menziesii--Pacific madrone: Cowberry Redleaf (Exobasidium vaccinii) Marianne Elliott writes that "Blister blight (Exobasidium vaccinii) forms pinkish blisterlike galls that" can distort and twist the leaves of A. menziesii and can make the fruit "turn red and swell." [pg. 58] The tree is also host to a variety of other pathogenic fungi.

Arctostaphylos—Manzanita: Cowberry Redleaf (Exobasidium vaccinii)

Arctostaphylos—Manzanita: Manzanita Leafgall Aphid (Tamalia coweni) Pod-shaped leaf gall at leaf edge about twice as long as it is wide. This aphid also causes roundish flower galls and sometimes midrib galls, but this occurs only with A. patula and perhaps some other species. For help distinguishing Tamalia galls from the surprisingly similar Cowberry Redleaf fungal galls, see this UC-IPM webpage. See also note below. In addition, it is not clear whether Tamalia milleri, a new species that Kanturski & Wieczorek 2015 describe from museum specimens, introduces galls on its host, A. columbiana (hairy manzanita).

Arctostaphylos pringlei--Pringle's manzanita: Tamalia dicksoni Galls are very similar to Tamalia coweni galls, so galls on this plant should probably be attributed to Tamalia spp. Although this UC-IPM webpage states that T. dicksoni galls other species of manzanita as well, Aphids on the World's Plants, based, I believe, on a more recent article, lists it as not being known to gall more than this one species. San Bernardino Mountains.

Artemisia californica—California sagebrush:
-- Sagebrush Woolly Stem Gall Midge (Rhopalomyia floccosa) Look for white "cotton balls" along the stem.
-- California Sagebrush Gall Mite (Aceria paracalifornica)

Artemisia douglasiana--California mugwort: Aceria abalis Bumps on leaves; white erineum pockets on underside [1 obs--San Diego]

Artemisia tridentata--Great Basin sagebrush:This one species hosts at least 28 different midge-induced galls, plus a few other types of galls. Some additional info [in a 7-species chart and a footnote] on p. 4 of Nevada NPS.
-- Sponge Gall Midge (Rhopalomyia pomum)
-- Woolly Bud Gall Midge (Rhopalomyia medusirrasa) Info & photos at
--Sagebrush Plum Gall Midge (Rhopalomyia calvipomum)
--Eutreta diana Stem gall; can occur on Artemisia filifolia and other species in the genus

Atriplex canescens & A. confertifolia--Fourwing Saltbush & Shadscale: Tumor Stem Gall Midge (Asphondylia atriplicis) Relatively large, fleshy integral stem gall. A 2004 Marchosky/Craig study described the gall as a "fleshy, rounded stem-gall near the apical meristem," varying from "small spherical galls to large, slightly irregular, ellipsoid galls" with diameters at the study sites ranging between 4 and 10 mm.

Atriplex canescens--Fourwing Saltbush:
--Asphondylia atriplicicola
--Asphondylia caudicis
--Asphondylia neomexicana According to BugGuide, these are "detachable dense woolly, white, spherical bud galls ... about 1 cm in diameter."

Atriplex polycarpa, A. spinifera, & A. confertifolia—Saltbush & Shadscale: Saltbush Woolly Stem Gall Midge (Asphondylia floccosa) Excellent description at

Baccharis pilularis--Coyote brush:
-- Baccharis Leaf Blister Mite (Aceria baccharipha) Leaf blister gall
--Coyote Brush Bud Gall Midge (Rhopalomyia californica) Bud gall Also galls B. halimifolia & B. neglecta
-- Coyote Brush Rust (Puccinia evadens) Integral stem gall--orange rust visible through cracks in stem at certain times of year
--Coyote Brush Stem Gall Moth (Gnorimoschema baccharisella) Integral stem gall [common]
-- Rhopalomyia baccharis Curvaceous integral stem gall with elongated diamond-shaped exit holes.

Baccharis sarothroides, B. pilularis, B. salicina—Desert broom and probably Coyote Brush & Willow Baccharis:
--Desert Broom Gallfly (Aciurina thoracica) Integral stem gall 5-17mm long induced by a tephritid fly. See Headrick/Goeden 1993 (gall photos on pg. 75). Article indicates that B. pilularis & B. salicina also serve as hosts, but doesn't discuss whether galls occur. 3 obs of the fly--not the gall--in the SF Bay Area

Baccharis sarothroides—Desert broom:
--Gnorimoschema powelli Spindle-shaped integral stem gall 8x13mm-12x17mm. See also Zobodat site. [1 obs SoCal]
--Rhopalomyia Page 43 of Russo's 2010/2011 Fremontia article shows an undescribed red-purple bud gall ID'd as Rhopalomyia sp.
--Neolasioptera lathami See BugGuide. Soft globular galls near the ends of branches

Baccharis viminea & B. glutinosa--Mule fat and Seep willow: Mule Fat Blister Mite (Aceria baccharices) Irregular bumps on leaves

Buxus --Boxes/Boxwood:
-- Box sucker (Psylla buxi) See Ore. State U. site. Psyllid-induced gall in which leaves cup together [common in Sunnyvale & elsewhere]
--Boxwood Leafminer (Monarthropalpus flavus) BTW: Charley Eiseman considers this a gall midge, not a leafminer despite the name, so resist adding it to either leafminer project. Leaf gall [common in Sunnyvale & elsewhere]

Calocedrus--Incense-Cedars: Pacific Coast Pear Rust (Gymnosporangium libocedri) For more info see PNW handbook webpage, USDA page, and Mycoweb page Causes both witches' brooms and orange jelly-like deposits on branches.

Calystegia--False bindweeds: Neolasioptera convolvuli See BugGuide. Integral stem gall [for a leaf gall mite, Aceria malherbae, that is used for biocontrol of Convolvulus arvensis see Bugwood fact sheet].

Camassia--Camas: Dasineura camassiae More info here Flower bud gall [known only from Pacific NW 0 obs]

Carya--Hickories, including Pecan This genus is not that common in California (although pecan trees are naturalized in some areas). In parts of N. America where it is common it hosts a variety of gall inducers, especially midges. If you do find a hackberry with galls, take a look at this iNat guide to Hickory Midge Galls. If you are still in doubt, ID the gall as "Gall midges," note the host species, and add "@megachile" in a comment, since he made the guide.

Ceanothus sp.--Ceanothus: Ceanothus Bud Gall Midge (Asphondylia ceanothi) In the 2017 world catalog of cecidomyiidae, the host for this is listed as "Ceanothus sp.; C. cuneatus," although Russo's guide and Gagne's 1989 guide limit the host to Ceanothus velutinus. Round, compact "leafy" bud gall

Celtis--Hackberries This genus is not that common in California, but in parts of N. America where it is common it hosts a variety of gall inducers, especially midges and psyllids. We do have 2 observations of the hackberry nipplegall psyllid in California, for example. Best advice if you find a hackberry with galls is to ID the gall as "Gall midges" and note the host species. (You can add "@megachile" if you want, since he is familiar with these galls and is very comfortable with being "@'d.")

Cercocarpus betuloides--Birchleaf mountain-mahogany: Cacopsylla insignita ***This is a tentative ID. We will need sharply detailed photos of an adult psyllid collected from the galled plant to confirm species. Leaf gall

Cercocarpus parvifolius & possibly C. betuloides--Mountain-mahogany: Dasineura cercocarpi Hairy bud gall; 8-10mm., very tomentose, containing several larvae [Use of this ID for witches brooms is very speculative.] See Felt 1913 p 3/7, p 215

Chamaenerion angustifolium--Fireweed: Mompha sp. This moth causes soft stem galls that often have leaves growing from them. See for more info.

Chloracantha spinosa--Spiny chloracantha/Spiny aster: Anthonomus ligatus Weevil induces galls [most weevils in galls are inquilines] not sure where gall occurs on plant

Chrysolepis chrysophylla & C. sempervirens--Golden chinquapin and Bush chinquapin: Dryocosmus castanopsidis Round, red gall on catkin/flower

Chrysolepis chrysophylla--Golden chinquapin: Dryocosmus rileypokei This is a wasp that researchers found galling chinquapin NUTS in Plumas County--see [no obs] FYI, The golden chinquapin leaf gall appearing as plate 198 in Russo is now identified as Dryocosmus sp.

Chrysothamnus viscidiflorus--Yellow rabbitbrush: 5 tephritid fruit flies plus one or more each of moths and midges form bud galls on this host per Goeden/Teerink 1996b.
--Medusa Gall Tephritid (Aciurina ferruginea) Goeden/Teerink 1996 redescribed this gall as "subspheroidal and covered by many thin, threadlike leaves." Adjacent galls can combine to form compound galls. See photo F on p. 432 of article. NOTE: Smooth, non-leafy galls on same host are presumably induced by A. michaeli, as described in this article.
--Aciurina idahoensis Goeden/Teerink 1996b described this gall as a stunted axillary branch (or sometimes branch apex) shaped like a pine cone, and elongating from subspheroidal to ovoid as it matures. Gall bears basally expanded, linearly tapered, apically pointed, smooth-margined leaves, which are shortened and more dense toward the gall apex. Mature galls were ~8-20mm long & 6-12mm wide. Photos on p. 692 of article.
--Rhopalomyia Russo's 2010/2011 Fremontia article mentions his finding "cotton-like terminal flower gall" on this plant and also on rubber rabbitbrush that was identified as a new species of Rhopalomyia [photo on p. 43 of article top left]

Convolvulus: See Calystegia

Cornus florida—Flowering dogwood (non-native): Resseliella clavula Known as the dogwood clubtail midge. Swollen twig; wilted or deformed leaves may also occur. See [no obs]

Corylus avellana—Common hazel: Big bud mite (Phytoptus avellanae) See [0 obs] [Note that bud galls on native Corylus cornuta are caused by an undescribed midge]

Corymbia citriodora--Lemon-Scented Gum: Eucalyptus Gall-forming Wasp (Epichrysocharis burwelli) Chalcidoid wasp forms small reddish or brownish blister galls on both sides of leaf [1 obs UCLA]

Cotoneaster--Cotoneaster: Plum Bud Gall Mite--see Prunus

Cupressus--Cypress: Chamaediplosis nootkatensis Per Russo's updates to his guide--this is "Contarinia sp. A" shown as Plate 41. [13 obs] "Contarinia sp. B" [plate 42] is now Chamaediplosis sp.

Cupressus sargentii, etc.--Sargent's Cypress and Pygmy Cypress: Cypress Gall Midge (Walshomyia cupressi)

Cytisus scoparius--Scottish Broom: Broom gall mite (Aceria genistae) Bud galls of varying size and shape (often diameters of 5 to 30 mm). See Xue et al. article [15 obs N/NW Cal. & SFBA]

Delairea odorata—Cape-ivy: Cape Ivy Gall Fly (Parafreutreta regalis) Spherical gall, about ½" diameter; started in nodes or growing tips, looks like internal stem gall in [cropped] photos; released for biocontrol; More info on p3 and cover. [2 obs SF &SFBA]

Dichelostemma capitatum--Blue Dicks: Lasioptera Perhaps. Stem gall similar to stem galls on related Triteleia laxa

Diplacus aurantiacus--Orange Bush Monkeyflower : Neolasioptera diplaci Stem gall. [1 obs SFBA]

Dryopteris arguta--Coastal Woodfern: Fern Leaf Curl Fungus (Taphrina californica) Light yellow-green jelly-like blobs on both sides of leaflets; found May-July

Encelia californica, E. farinosa--[California] Brittlebush: Asphondylia enceliae Felt describes the gall as a "greenish or dark gray, conical, globose, thick-walled gall sometimes confluent and distorting the stem" and also as "a conical, thick-walled, lateral bud gall" 6mm long x 3mm diam., "sometimes twisting the stem." Noticeably hairier than rest of plant. See also Millie's comment

Encelia farinosa--Brittlebush: Rhopalomyia Midge induces a hairy gall on leaves and sometimes petioles or flowers that is taller than it is wide

Ephedra--Mormon Tea: A BugGuide webpage discusses the difference between the two integral stem galls:
--Mormon Tea Stem Gall Midge (Lasioptera ephedrae) Integral stem gall
--Ephedra Stem Gall Midge (Lasioptera ephedricola) Another integral stem gall on several species of ephedra

Epilobium canum—California fuchsia (zauschneria): California Fuchsia Gall Midge (Contarinia zauschneriae) BugGuide page Bud gall with bud leaves rolled and curled—turns red

Ericameria linearifolia--Narrowleaf goldenbush: Gnorimoschema coquillettella Tip gall B&W photos p. 45

Ericameria nauseosa--Rubber rabbitbrush: Russo lists 8+ species that induce galls on rubber rabbitbrush. These include:
--Gnorimoschema octomaculella [Synonym: G. octomaculella] Budlike gall composed of terminal leaves. [9 gall obs Sierras and mtns nr LA]
--Rhopalomyia utahensis Felt describes the galls as "Ovoid, hypertrophied leaf buds ... green or somewhat purplish," 10-11mm long with a 7-8mm diam., usually covered externally with "short, recurved, aborted leaflets" covered usually with a thick gray pubescence. Two or three are often confluent.
--Aciurina bigeloviae Cottony white bud galls induced by a fruit fly
--Aciurina trixa Roundish galls attached to the stem. See photo
--Medusa Gall Tephritid (Aciurina ferruginea) See Chrysothamnus viscidiflorus above for more info.

Erigeron spp.--Fleabanes and Horseweeds; plus some “daisies”: Asteromyia modesta More info here Leaf gall--concentric circles on leaf or raised irregular areas; green, purplish, or brown [found on gumplant in San Mateo Cy]

Erodium spp.--Stork's-bills: Synchytrium papillatum (Stork’s bill chytrid) Articles about this fungus refer to the enlarged epidermal cells filled with colored fluid as one-cell “galls” fungus looks like purple-red fish eggs [SoCal&few SFBA]

Eucalyptus--Eucalyptus: Eucalyptus Gall Wasp (Ophelimus maskelli) Reddish bumps on leaves

Eucalyptus--Eucalyptus (particularly blue gum): Eucalyptus Redgall Wasp (Leptocybe invasa) Yellow-green or red swellings along petiole/midvein galls leaf midrib, petiole, and stem. More info here [SoCal]

Eucalyptus globulus--Tasmanian blue gum: Blue gum gall wasp (Selitrichodes globulus) Galls twigs. Photos here

Eucalyptus--Eucalyptus: Red Gum Lerp Psyllid (Glycaspis brimblecombei) More info here. White sugarloaf structures on leaves.* Eucalyptus camaldulensis, River redgum, is especially susceptible.

Ficus benjamina--Weeping fig: Weeping Fig Thrips (Gynaikothrips uzeli) Non-native insect on non-native plant. Leaf-roll and leaf-fold galls

Ficus microcarpa--Chinese banyan (aka Laurel fig): Ficus Gall Wasp (Josephiella microcarpae) Leaf blister gall. Info and/or photos here. [SoCal]

Ficus microcarpa, F. retusa--Cuban laurel etc.: Cuban Laurel Thrips (Gynaikothrips ficorum) Can cause rolling, pitting, and discoloration of leaf. See USDA Pest Thrips Field Guide Ficus microcarpa is preferred, but F. retusa, viburnum, and citrus are also hosts.

Frangula californica & F. rubra--Coffeeberry and Sierra coffeeberry: Midrib Gall Moth (Sorhagenia nimbosa) leaf folding in half lengthwise

Frangula californica--Coffeeberry: Dasineura sp. See page 58 of Pepperwood Preserve Vascular Flora, "The flowers are galled by an undescribed gnat of the genus Dasineura that causes the flowers to inflate in a way that mimics the green fruits."*** And see photo. Flower gall

Fuchsia spp.--Fuchsia [not California “fuchsia”]: Fuchsia gall mite (Aculops fuchsiae) More info here. Thickens and distorts leaves and shoots

Garrya sp.—Silk tassel: Asphondylia garryae Catkin and bud galls

Gleditsia triacanthos—Honeylocust: Gleditsia Gall Midge (Dasineura gleditchiae) More info here. Leaflet tip swelling [SFBA]

Glechoma hederacea--Ground-Ivy: Glechoma Gall Wasp (Liposthenes glechomae) Non-native wasp galling non-native plant in Eastern U.S. and Eurasia--possible for California, where plant also occurs. According to Taylor, galls usually occur on leaf or petiole, but stem, flower, and apical galls are possible. Smaller galls are round, green (turning reddish) and hairy and typically 6-10mm in diameter. Compound galls are more variable in shape and can be 18mm long. See also BugGuide. [0 CA obs]

Grindelia sp.--Gumplants:
--Asteromyia modesta More info here. Leaf gall (circles on leaf or raised irregular area on leaf; green, purplish, or brown) [SFBA-- 1 obs]
--Asteromyia grindeliae Described by Felt as a "greenish or [sic] oval, blister leaf gall" 3-4mm diameter and found by him on Grindelia hirsutula and G. robusta.

Grindelia hirsutula—Hairy gumweed:
--Gnorimoschema grindeliae Soft stem (node) gall turns white with purple-brown by May—BW photos here. on p45. [3 obs SF East Bay]
--Rhopalomyia grindeliae: Monothalamous (single-chambered) gall on flowerhead; only 5mm long unless they agglomerate [0 obs]
--Cecidomyiidae: Undescribed multi-chambered leafy bud gall shown in plate 234 of Russo that can grow to 8x the size of R. grindeliae

Gutierrezia sp.—Matchweeds and snakeweeds:
--Matchweed Stem Gout (Asteromyia gutierreziae) Felt describes the galls as "irregular, dull black thickenings" 6-8mm long that double the flower stems' thickness to 0.5mm. [2 obs SoCal + 1 NMex]
--Epiblema rudei J. Powell article in Fremontia; see photo bot.rt. pg 9. Woody stem gall [0 gall obs]

Hedera helix—English ivy: Phytoptus hedericola Info and/or photos here on pg 9. Galls in buds and at petiole bases cause deformation and stunting [no obs. May not be a true gall]

Helianthus annus--Common Sunflower: Bucculatrix longula Moth that reportedly causes a stem gall [0 obs]

Heteromeles arbutifolia--Toyon: Toyon Gall Thrips (Liothrips ilex) Leaf blistering, curling, and distortion. Info and/or photos here and here.

Holodiscus discolor--Ocean spray:
--Dasineura sp. Swollen leaf vein fold
--Colomerus holodisci Erineum mite causing erineum galls on leaves [possibly colorful]. Only iNat obs in BC but holotype was in Calif.

Hypochaeris spp.--Cat's-Ears: Catsear Gall Wasp (Phanacis hypochoeridis) Integral stem gall

Isocoma acradenia--Alkali Goldenbush: Procecidochares blanci Tephritid bud gall with up to 20 rows of scale-like leaves. See photo F in Goeden & Norrbom 2001 [0 obs]

Isocoma menziesii--Coastal goldenbush: Gnorimoschema crypticum Info and/or photos here. “[F]leshy stem gall . . . galls . . . are soft, variable in form, and ephemeral, similar to [G. grindeliae].” [no obs]

Juglans californica & J. hindsii--Southern California walnut and Northern Calif. Black Walnut:
-- California Black Walnut Pouch Gall Mite (Aceria brachytarsa) leaflet gall consisting of bumpy sometimes reddish pouches raised about the upper leaflet surface on short stalks
--Black Walnut Petiole Gall Mite (Aceria caulis) petiole gall of thick pinkish, purplish, or brown erineum
-- Aceria neobeevori More info here. Catkin gall [1 obs nr Ventura]

Juglans regia--Persian Walnut: Walnut Blister-Mite (Aceria erinea) Leaf blisters

Juniperus californicus & J. occidentalis—California juniper and Western Juniper: Juniper Urn Gall Midge (Walshomyia juniperina) Joyce Gross's photos.

Juniperus californicus & possibly others—California Juniper: Walshomyia sp. Joyce Gross's photos.

Larrea tridentata--Creosote Bush: 15 described species of Asphondylia and an undescribed Contarinia species induce galls on Creosote bush in the desert SW. Helpful online resources include: a 1990 Gagne & Waring article with tiny drawings of all 15; photos by Joyce Gross here and here; and an iNat Creosote gall project.
--Creosote Gall Midge (Asphondylia auripila) Round bud gall composed of densely packed narrow [?]bracts.
--Leafy Bud Gall Midge (Asphondylia foliosa)
-- Creosote Antler Gall Midge( Asphondylia digitata)
--Creosote Cone Gall Midge (Asphondylia rosetta)
--Asphondylia pila This is Russo's "Leaf Club Gall Midge" in plate 218. Per Russo's updates to his guide, the name has been changed from A. pilosa to A. pila.
--Creosote Resin Gall Midge (Asphondylia resinosa)
--Creosote Bush Flower Gall Midge (Asphondylia florea)
--Asphondylia apicata
--Creosote Bush Club Gall Midge (Asphondylia clavata)
--Asphondylia discalis
--Asphondylia fabalis See Tim O'Connor's comments to this observation for his description of the gall.
--Asphondylia barbata See Tim O'Connor's comments to this observation for his description of the gall.

Lavatera assurgentiflora--Island Mallow: Island mallow psyllid (Bactericera lavaterae) See Leaf blister

Lepidospartum squamatum--California broomsage:
--Scalebroom Bud Mite (Eriophyes lepidosparti) Bud gall [1 obs. Kern Cy.]
--Scrobipalpopsis sp.; Moth stem gall mentioned on p. 54 of Russo's guide

Lonicera hispidula—Pink honeysuckle: Lonicerae russoi [NEW SPECIES—was Rhopalomyia sp. B--Russo plate 238] More info here and photo Green, leafy rosette bud gall

Lonicera subspicata--Southern Honeysuckle: Lonicerae lonicera Midge-induced bud gall (formerly Honeysuckle Gall Midge (Rhopalomyia lonicera)) [Russo's guide also illustrates an undescribed bud gall for this species.]

Lupinus arboreus--Coastal bush lupine and possibly other species
--Dasineura lupini Large hairy, irregular bud gall
--Neolasioptera lupini Stem swelling

Lupinus arboreus, varicolor, albifrons, albicaulis & chamissonis—Coastal bush lupine et al.: Lupine Leaf Gall Midge (Dasineura lupinorum) See Gagne 1993 Leaflet gall that develops while leaflet is still folded and elongating; leaflet remains folded above larva/e--galls that turn reddish are likely to have dead larvae.

Lycium cooperi--Peach-Thorn:
--Gnorimoschema sp. Stem gall shown in Plate 182 of Russo (2006) is induced by a moth in this genus
--Contarinia sp. Described as "cabbage-like bud galls" in Russo's 2010/2011 Fremontia article. See photo at bottom left of pg. 43 of article.

Myoporum sp.--Ngaio: Ngaio Thrips (Klambothrips myopori) More info here Look for severe leaf distortion

Notholithocarpus densiflorus--Tanoak:
--Live Oak Witches' Broom Fungus (Cystotheca lanestris) A powdery mildew that causes witches' brooms and/or whitening on new branches of tanoak, as well as several oaks
--Tanoak Gall Wasp ( Andricus notholithocarpi) Nicholls et al. 2018 Forms small conical/pip pale green galls on catkins, buds, and leaf edges. The leaf edge galls induce folds. In addition, a 4th type of gall causes swelling and some bending of leaf midrib. [found in Humboldt and possibly San Mateo cys]
--Tanoak often displays a thick growth of yellowish erineum not too different from the Aceria mackiei gall. Although A. mackiei cannot be completely ruled out, most believe this is an undescribed Eriophid mite gall.

Opuntia--Prickly pears: Asphondylia betheli See BugGuide page. Swollen fruit gall, sometimes with cylindrical exuvia poking sideways out of it. [0 Calif. obs]

--Douglas Fir Adelgid (Adelges cooleyi) This aphid relative, also known as the Cooley spruce adelgid, galls the tips of spruce branches. See Forest Pests brochure pp. 53-5 and Influential points website for info and photos.
--Spruce Witch's Broom Rust (Chrysomyxa arctostaphyli) See Forest Service webpage. Witches' broom. Infected leaves turn yellow, produce spores, and drop off. [3 obs]

--Western Gall Rust (Cronartium harknessii) Integral stem gall, but fungus can sometimes also produce grapefruit-sized galls on trunks
--Podapion gallicola Spindle-shaped stem gall; adult weevil chews a niche in the bark of a one-year-old twig. See ForestPests webpage. Only iNat sighting of weevil occurred in Ontario, but BugGuide confirms it ranges into California. [0 obs]

Populus sp.--Poplars, Cottonwoods, and Aspens:
--Poplar Twiggall Fly (Euhexomyza schineri) See Montana field notes and page 83 of USDA aspen guide Integral stem gall on twigs of various Populus species
--Prodiplosis morrisi Description and photo at Forest Pests brochure. Before the leaves curl up, the galls appear as beads along the leaf edges.
--Phyllocolpa sawflies roll or fold the edges of Salaceae leaves, including Populus species, sometimes forming galls or pseudogalls.

Populus fremonti, P. tremuloides, angustifolia, trichocarpa—Fremont cottonwood, Trembling aspen, Narrowleaf cottonwood, Black cottonwood: Poplar Petiole Gall Aphid (Pemphigus populitransversus) Swelling of petiole (leaf "stem") with sideways slit

Populus fremonti, P. tremuloides, P. trichocarpa--Fremont cottonwood, Trembling aspen, Black cottonwood: Aceria parapopuli Galls on buds/catkins [16 obs all E of Sierra crest]

Populus fremonti, P. angustifolia, P. trichocarpa—Fremont cottonwood, Narrowleaf cottonwood, Black cottonwood: Pemphigus populivenae Leaf fold galls but also, according to Russo, pouchlike galls on midrib or along leaf edges

Prunus--Plums, cherries, and allies [stone-fruit; also almonds, cotoneaster]: Almond and Plum Bud Gall Mite (Acalitus phloeocoptes) first found in Morgan Hill, CA 2/2019 and at UCSC 1/2020 Enlarged bud scales (diameter ~ 1.5mm) surround buds [0 obs]

Prunus—Peach, Nectarine, and other stone fruits: Peach Leaf Curl (Taphrina deformans)

Prunus subcordata--Pacific plum: Pocket plum (Taphrina pruni or T. pruni-subcordatae) See T. pruni causes fruit-pockets on various Prunus species, including Pacific/Sierra plum; T. pruni-subcordatae, which may be a distinct species, causes witches' brooms on Pacific/Sierra plum. The latter is mentioned in Russo's Table 7. See NatureNiche for a description of finding the plum pockets on Modoc Forest Rd. in Shasta County [0 obs]

Prunus andersonii—Desert peach: Eriophyes (?) prunandersonii pg 7-8 baggy erineum deformation on leaves [no obs]

Prunus virginiana and other prunus--Chokecherry and other prunus: Plum Finger Gall Mite (Eriophyes emarginatae) Narrow finger-like pouches on upper leaf surface [17 obs]

Pyrus communis, P. malus—Pear and Apple: Pear Leaf Blister Mite (Eriophyes pyri) See and Leaf blisters may be shallow and reddish or brownish [1 obs Santa Cruz]

Quercus sp.--Oaks:
--Stegophylla Stegophylla essigi, a woolly aphid, known only from the West Coast, creates leaf fold galls on "many California oaks, including blue, valley, Oregon white, coast live, interior live, California black, and scrub oak." The leaf margins--at least those on Coast live oak--become reddish. See USDA California oak guide However, Merav believes that several aphids make leaf roll/fold galls on California oaks. So it's probably best to ID to genus level. To further complicate matters, Joyce Gross has commented that she has found Cecidomyiidae larvae in Quercus agrifolia leaf folds. Leaf fold gall
--Live Oak Witches' Broom Fungus (Cystotheca lanestris) A powdery mildew that causes witches' brooms and/or whitening on new branches of Coast live, Canyon live, and Valley Oaks, in addition to tanoak.

Quercus chrysolepis--Canyon live oak: Heteroecus malus Joyce Gross's photos. Non-integral stem gall (usually found in clusters)

Quercus douglasii—Blue oak: Aceria trichophila Leaf pouch gall [1-2 obs]

Quercus dumosa, Q. garryana, Q. engelmanni (oak): Andricus bakkeri [="Pinched Leaf Gall Wasp." in Russo’s guide] See page 292 and Leaf gall [11 obs]

Quercus cornelius-mulleri--Muller's oak: Russo's "Brown eye gall wasp" [plate 132] that galls the underside of Muller's oak leaves along the midrib has been identified as as species of Dryocosmus

Quercus palmeri--Palmer’s oak:
--Heteroecus fragilis More info here. Stem gall—spongy
--Lyon’s gall wasp (Heteroecus lyoni) detailed drawings in a 1924 article More info here. Photo on pg. 45 of Russo's Fremontia article. Leaf gall shaped like planter/urn [0 obs]
--Loxaulus boharti Dailey/Sprenger 1983. says the wasp induces an integral stem gall: 0.5mm holes in 2 mm circles and slight bark swelling**** [holotype from CCosta Cy.; paratypes Riv. Cy.]
--Andricus burnetti More info here. Photo on pg. 45 of Russo's Fremontia article. Bud or petiole gall

Quercus suber—Cork oak: Plagiotrochus suberi/amenti [non native gall on non native cork oak] tiny photos of gall p2 [0 obs.]

Quercus vacciniifolia--Huckleberry oak: Dasineura sp. Russo has determined that the "Purse gall midge" in Plate 151 is a species of Dasineura

Rhododendron—Azalea specifically: Cowberry Redleaf (Exobasidium vaccinii) See Strangely shaped leaf galls and witches brooms

Rhus integrifolia; R. trilobata--Lemonade berry & Rhus trilobata: Asphondylia integrifoliae
This midge causes "swollen, aborted flower buds"

--Ribesia sp. See Leaf gall induced by midge; forms round purplish blisters on leaves
--Potato Aphid (Macrosiphum euphorbiae) Leaf rolls that can go all the way to the midrib. Look for pale green.
--Rhopaolmyia Undescribed flower-like bud gall; Russo 2006 plate 231

Robinia pseudoacacia --Black locust: Locust Gall Midge (Obolodiplosis robiniae) See photos Leaf roll gall [2 Calif. obs--L.A.]

Rosa —Roses:
-- Mossy Rose Gall Wasp (Diplolepis rosae) See Miles Zhang's comments. Bud gall consisting of a roundish cluster of bracts; the gall is essentially multi-chambered, has branched hairs, and appears to be far more common in California than D. bassetti.
-- Spiny Rose [Stem] Gall Wasp (Diplolepis bicolor) Round galls with long reddish spikes attached to stems
Spiny Leaf Gall Wasp (Diplolepis polita) Round galls with long reddish spikes attached to leaves
-- Rose Stem Gall Wasp (Diplolepis nodulosa) Modest integral stem gall that swells from 3-4mm diameter to up to 20mm diameter when influenced by the inquiline Periclistus pirata and becomes shiny and somewhat round.
--Diplolepis rosaefolii Leaf blister gall [probably a synonym of Diplolepis lens]

Rubus--Blackberry: Redberry mite (Acalitus essigi) fruit discoloration gall. Keifer: “Infested berries show swollen, brilliant red or pink and greenish drupelets among unaffected purple or maroon drupelets. Some berries have entirely red drupelets. Affected berries remain red or green and do not ripen normally.” pg 126 [0 obs]

Rubus parviflorus—Thimbleberry: Diastrophus kincaidii See Wangberg 1975. Lumpy, irregular integral stem gall

Salix—Willow: [To ID common Calif. willows see this key.]
--Willow Bead Gall Mite (Aculus tetanothrix)
--Willow Apple Gall Sawfly (Pontania californica) Leaf gall--one of many bright red roundish sawfly galls on willow. Look for tiny "tubercules" interrupting the smooth surface.
--Willow Bean Gall Sawfly (Pontania proxima) Bean shaped, bright red leaf gall
--Aculops aenigma Believed to cause catkin and bud galls [3 obs E of Sierras & SF East Bay]
--Willow Pinecone Gall Midge (Rabdophaga strobiloides) Pine cone shaped apical bud gall
--Willow Rosette Gall Midge (Rabdophaga salicisbrassicoides) There are several willow rosette galls on willow, and the taxonomy appears to be very confused.**
--Willow Beaked-gall Midge (Rabdophaga rigidae) See BugGuide 1 & 2& Joyce Gross's photos.
-- Potato Gall Midge (Rabdophaga salicisbatatus) large [up to 2cmx4cm] integral stem gall
--Euura sp. Willow sawfly galls that are truly on the petiole rather than at the leaf base are the work of Euura sawflies, according to S.K. Monckton, an iNat curator who studies sawfly systematics. For the present, leaf base galls can be attributed to Pontania sp. [FYI, the petiole is the stalk that attaches the leaf blade to a twig]
--Phyllocolpa sawflies roll or fold the edges of willow leaves, sometimes forming galls or pseudogalls. See BugGuide webpage.

Salix laevigata, amygdaloides, hookeriana, matsudana, & nigra--Willow: Western Red Willow [Gall] Mite (Aculus laevigatae) Beadlike leaf galls with lower surface openings

Salix lasiolepis--Arroyo Willow: Arroyo Willow Stem Sawfly (Euura lasiolepis) stem gall

Salix exigua--Narrowleaf Willow: Willow Stem Sawfly (Euura exiguae)

Salix gooddingii--Goodding's willow: Aculus vallis mite bead gall on leaf; per comment by megachile, presumably based on unpublished Amrine catalog

Salvia mellifera & S. apiana--Black sage and White sage:
-- White Sage Leaf Gall Midge (Rhopalomyia audibertiae) Tubular galls, 8mm x 12 mm, on leaf or petiole, with a shallow protrusion on the opposite side of the leaf from each tube and an opening/depression at the end of each tube.
--Rhopalomyia salviae produces smaller [2mm x 5 mm] tubular galls on leaf or, more commonly, stem that are straight-sided and are ordinarily at right angles to the stem.

Sambucus cerulea & S. canadensis—Elderberry: Elderberry Gall Midge (Schizomyia umbellicola) Florets expand to form vase-like galls

Schinus molle--Peruvian peppertree: Peppertree psyllid (Calophya schini) [U.S. psyllid had been mis-identified as Calophya rubra] Pit galls on leaves [also on petioles, twiglets, and flower buds]

Senegalia greggii--Catclaw acacia: Tanaostigmodes howardii Krombein's 1979 Hymenoptera catalog says this wasp "produces small, spherical bud galls on Acacia [Senegalia] greggi, Mimosa biuncifera, Prosopis sp." Russo 2006 attributes an integral stem gall to this wasp [Plate 186], and his "errata" webpage adds that the gall in Plate 17, which looks like a group of spiny pinecones, is also attributable to T. howardii. [Note that BugGuide shows an unidentified gall very similar to the Plate 17 gall with the caption "Gall midges emerging..."]

Solidago sp.--Goldenrods: Asteromyia modesta More info here. Leaf gall (concentric circles on leaf or raised irregular area on leaf; green, purplish, or brown)

Symphoricarpos albus & S. mollis-- Common snowberry and Creeping snowberry:
--Snowberry sawfly (Blennogeneris spissipes) Lumpy, whitish bud gall
--Phyllocoptes triacis Slender leaf roll gall induced by a mite
--Dasineura sp. Slightly thicker leaf roll gall caused by a midge Gall was originally mis-attributed to Reseliella californica; ID remained Dasineura sp. as of 5/2020
--Chiosperma turgidum elongate bud gall 5mmx8-10mm [Wash. holotype—may not be in Calif. Use only if Blennogeneris spissipes doesn’t fit]

Symphyotrichum chilensis—Pacific aster: Gnorimoschema subterraneum BW photos in Powell & Povolny article on p45. Large, nearly spherical to watermelon-shaped stem galls (17-27mm long, 12-16mm diameter) soft, becoming woody; most 12-15 cm or more above ground level some 2-5cm above roots [0 obs. reported from SFBA]

Syzygium--Brush Cherry and Lilly Pilly: Syzygium Leaf Psyllid (Trioza adventicia) [formerly misidentified as T. eugeniae] Leaf pit galls

Tetradymia axillaris, T. glabrata, & T. stenolepis--Horsebrushes and cottonthorns: Scrobipalpopsis tetradymiella Integral stem gall covered in white woolly fibers—[1 obs SoCal]

Toxicodendron diversilobum--Pacific Poison Oak: Poison Ivy Leaf Mite (Aculops rhois) [Synonym: Aculops toxicophagus]

Trichostema--Bluecurls: Stagmatophora enchrysa Moth stem gall; no details [no obs yet]

Trifolium--Clover: Clover Leaf Midge (Dasineura trifolii) Photos and info at Bladmineerders website European gall that has been found in N. America since 19th century. BugGuide has sightings from New England, status in Western US unknown. Leaf fold gall [0 obs]

Triteleia laxa--Ithuriel's spear: Lasioptera Integral stem gall

Vaccinium--Blueberries, cranberries, and allies: Cowberry Redleaf (Exobasidium vaccinii) [Note that Exobasidium maculosum, which has made headlines, galls Vaccinium species in the SW U.S--not in California.]

Vaccinium ovatum--Evergreen huckleberry: Huckleberry Broom Rust Fungus (Pucciniastrum goeppertianum) Photos and info, see PNW handbook. Affects various Vaccinium species and fir, but causes swollen (often leafless) stems and witches' brooms on V. ovatum.

Viola--Violet: Prodiplosis violicola Midge-induced leaf roll gall affecting several species of violets, native and not. See Oregon IPM webpage. Rolls one or both leaf edges up. [1 obs in San Jose 10/2020]

Vitis sp.—Grapes:
--Grape Erineum Mite (Colomerus vitis) Red or green leaf blisters with white-to-fuchsia erineum pockets on underside
--Grape Phylloxera (Daktulosphaira vitifoliae) Induces what Aphids on the World's Plants describes as "hairy, scabrous galls" on leaf underside with openings on the upper leaf surface. Also galls roots. Susceptibility, presence and number of leaf and/or root galls, and other factors depend on which species of Vitis is involved and climate. Galls are much more common in NE and N. Central states of the US than they are further south, but the leaf galls do occur in California to some extent on native and hybrid grapes.

Wyethia—Mule ears: Anguina balsamophila This nematode induces leaf blisters

  • Not a true gall. A true gall is a growth of the plant itself in response to a stimulus from another organism. Many of the mistletoes and rusts in the Galls of California also are not true galls, although at least some mistletoe and rust species can sometimes cause galling.

** More on willow rosette galls:
--An Alaska study of willow rosette galls had some interesting findings.
--Ron Russo's guide to California galls mentions only Rhabdophaga strobiloides (which is pine-cone-shaped), R. salicisbrassicoides [also recorded in Iowa and Mich], and an undescribed cone-shaped rosette-like Rhabdophaga bud gall that occurs on arroyo willow and related species.
--R. rosaria species complex is not confirmed for North America. per yet we have nearly 100 iNat obs in the U.S. [] and Canada.
--Rhabdophaga saliciscoryloides is discussed in Charley Eiseman’s book [Eiseman, Charley and Noah Charney. 2010. Tracks & Sign of Insects and Other Invertebrates]. That species' holotype came from Illinois.
--For Raymond Gagne's couplet and some info, see
--A 2/2020 article looking at R. rosaria and some R. brassicoides in Eurasia and Alaska proposes subdividing them into many species based on clades. []

*** Dasineura sp. ID based on Raymond Gagne's ID of samples author Greg de Nevers sent to him.
**** In their 2000 article at, Melika and Abrahamson apparently erroneously describe Loxaulus boharti galls as "yellow, pubescent aborted axillary bud or leaf petiole galls." The same paragraph "Biology," also states a different emergence time than Dailey/Sprenger for the only generation known, but does end with the attribution "(Dailey and Sprenger 1983)."

Posted on August 26, 2020 03:22 by nancyasquith nancyasquith | 13 comments | Leave a comment