Part II. Pictorial Guide to Common Pest of Aspen. The following photographs represent the common pest of aspen. This is not a complete list, there are many others agents.
This guide is meant to be used as a quick pictorial reference to assist you with pest identification. For complete descriptions, habits and life cycles of these pests consult online sources such as the Canadian Forest Service’s “Insect and Diseases of Canada’s Forests” http://imfc.cfl.scf.rncan.gc.ca/accueil-home- eng.html
Each pest is presented with its Agent Type, Name and Level. Some pest agents are classified with more than one Agent Type. Diplodia gall, for example, may be found on branches (Type 32) and or on stems (Type33). For a description of Agent Types and appropriate Levels, see Appendix 1.
*Unless indicated otherwise, all photos by M. Michaelian*
2
FOLIAGE INSECTS (Types 1 - 9)
Forest tent caterpillar -Malacosoma disstria Type Name Level 1 MALDIS 5-95
M. disstria larva on leaf.
3
M. disstria defoliation and larvae on stem.
4 Bruce spanworm - Operophtera bruceata Type Name Level 1 OPEBRU 5-95
O. bruceata larvae on leaf.
5
O. bruceata adult male (female wingless).
6
Large aspen tortix -Choristoneura conflictana
C. conflictana mature larva (15-25mm 7
Typical rolled leaf of C. conflictana
8
C. conflictana moderate defoliation.
9
Aspen twoleaf tier -Enargia decolor
E. decolor mature larvae (25-33mm). Larvae construct a shelter by binding two leaves together. Pupation occurs in on the ground in the soil.
10
E. decolor adult moth. Adults emerge late July to late August. Eggs are laid in August on the soil.
11
E. decolor defoliation. Although defoliation may be severe, infestations rarely last more than a few years.
12 Poplar leafminer -Phyllocnistis populiella Type Name Level 3 PHYPOP 5-95
P. populiella defoliation. Serpentine mines can occur on both the upper and lower surfaces of the leaf. 13
Silver appearance of aspen infested with P. populiella. Although little damage is done to the trees, infestations can be very large covering hundreds of square kilometres.
14 Aspen leaf beetle -Chrysomela crotchi Type Name Level 4 CHRCRO 5-95
C. crotchi larvae skeletonising a leaf.
15
Gall mites - Eriophyes spp. Type Name Level 7 ERISPP 5-95
Mite galls plus some unknown defoliation. 16 FOLIAGE DISEASES (Types 10 to 19)
Leaf and twig blight -Venturia macularis Type Name Level 10 VENMAC 5-95
Shepherd's crook on aspen. 17
V. macularis on aspen. Damage can be severe when wet weather conditions prevail.
18 Ink spot -Ciborinia whetzellii Type Name Level 11 CIBWHE 5-95
C. whetzellii ink spots on aspen. Eventually, the dark spots will disintegrate leaving the leaves riddled with holes.
19
Leaf rust -Melampsora medusae Type Name Level 13 MELMED 5-95
Leaves with rust fruiting bodies of M. medusae. Alternate hosts are conifers such as tamarack and pine. Damage is usually slight.
20 WOODY TISSUE INSECTS (Types 20 - 29)
Poplar budgall mite -Aceria parapopuli Type Name Level 21,22 ACEPAR 99
A. parapopuli stem gall. Use Type=22. 21
A. parapopuli branch gall. Use Type=21. The mite is a small wormlike organism invisible to the naked eye. They feed on sap within the gall. 22
A. parapopuli branch gall close-up \ 23
Carpenterworm -Acossus spp. Type Name Level 25 ACOSPP 1-10
Acossus empty pupal case. Emergence hole usually at base and is large enough to stick a pencil in it.
24
Acossus populi adult (wingspan ~50mm). Acossus spp. is not common but is memorable because of their large size of the exit holes.
Bronze poplar borer -Agrilus liragus 25
Type Name Level 25 AGRLIR 1-10
Typical ‘D’ shaped exit hole of A. liragus. This is a very common pest of aspen especially when trees are stressed. The Level of this pest is scored as the number of exit holes to a maximum of 10. 26
A: Arrows indicate ‘D’ shaped exit holes. Flat side of the ‘D’ usually on top. B: Small white fruiting bodies of Cytospora canker often associated with Agrilus damage. 27
A. liragus larva in gallery. Larvae are long (to 40mm), slender and fragile. Galleries are tight, such as this one, when tree defences are strong.
28
Loose A. liragus galleries indicating poor tree defences. 29
Numerous Agrilus galleries on newly dead tree. If the galleries are extensive enough they will girdle and kill the tree.
30
A. liragus adult (7 to 12mm). Adults are slightly flattened, blackish with a green metallic reflection sometimes present. Adults emerge from June to late August, feed on aspen foliage and the females lay eggs in bark crevices a week later. You will more often see exit holes than you will see the adult.
31
Dicerca species Type Name Level 25 DICSPP 1-10
Discoloration and woodpecker holes are indications of Dicerca. 32
Another photo of discoloration and wood- pecker holes indicating the presence of Dicerca.
33
A: Indistinct gallery of Dicerca. Arrows indicate where woodpeckers have bored to catch Dicerca larvae. The damage from this pest sometimes mimics that of Hypoxylon canker. Complicating matters, it is often the vector for Hypoxylon so you might see both Dicerca and Hypoxylon on the same tree.
34
Dicerca larva and gallery under the bark. Note, the gallery is less distinct than that of Agrilus. These galleries are found all along the stem and often found high in the stem. This pest can be common in many of our CIPHA stands.
35
Dicerca pupa in gallery with dead bark stripped away.
36
Dicerca adult. A: indistinct gallery typical of Dicerca. There are up to 17 species of Dicerca found in Canada. Identifying specimens to the species level requires microscopic examination.
37
Dicerca adult (15 to 20 mm). These beetles are often seen on the bark of aspen trees. Females can often be seen ovipositing in bark crevices.
38 Poplar borer -Saperda calcarata Type Name Level 25,45 SAPCAL 1-10
Typical sap flow and large bore shavings of S. calcarata. Large amounts of sap flow are almost always associated with new Saperda attacks. Saperda most often attacks exposed trees on stand edges or gaps and in low density stands. Galleries are most often found on the south and southwest sides of the tree.
39
Sap flow and stem wounds typical of S. calcarata. There are few, if any, other pests that will cause this amount of sap flow. S. calcarata galleries can be found anywhere along the stem from base to upper crown.
40
Large bore shavings are indications of S. calcarata.
41
Large bore shavings on understory are indications of Saperda. 42
Sunken bark is another indicator of Saperda. Sometimes the gallery will cause a localized lack of radial growth, therefore, a few years later the bark appears sunken.
43
Typical elongated exit hole and large bore shavings of S. calcarata. 44
Arrows indicate egg slits cut by adult females. Unlike Agrilus and Dicerca, Saperda do not lay their eggs in bark crevices. Egg slits will most often be found on the south and southwest side of the tree. 45
Large bore shavings and galleries of S. calcarata. The stem, weakened by Saperda and associated decay fungi indicated by discoloured heart wood, has snapped. The Agent Type in this case would be 45 for Broken Stem. 46
Old healed S. calcarata stem wounds. Mortality due to Saperda is much less than that due to Agrilus or Dicerca.
47
S. calcarata larva deep in the heartwood. Note the discoloured heart wood indicating the possible presence of a decay fungus that would have been carried by the larva.
48
S. calcarata adult (20 to 30mm) in gallery. This beetle has a 3 to 4 year life cycle. The adults emerge from mid-June to mid- August. Much like Agrilus, you will more often see the other signs of Saperda such as bore holes, savings and sap flow than you will see the adult itself.
49
Poplar ambrosia beetle -Trypodendron retusum Type Name Level 25,45 TRYRET 1-10
Fine boring dust from multiple T. retusum bore holes. 50
Typical small and round bore hole of Ambrosia beetle. The beetle attacks only stressed trees. These holes, most often found below 3m, are almost a sure indicator that the tree will be dead within a few years.
51
Ambrosia adults (4-5 mm) are very small. The adults emerge in late summer and fall and overwinter in forest litter. This insect carries a symbiotic ambrosia fungus that probably accelerates tree decay.
52
Ambrosia gallery in snapped tree. The female bores a hole a few centimetres into the tree (A), then bores along a tree ring (B) and lays eggs. Larvae then bore laterally (C). Tree has snapped due to weakening by associated decay fungi.
53
Unknown carpenter ant species Type Name Level 26 ANTSPP 99
Typical oval bore hole of carpenter ants. These holes are usually seen in the lower stem bole. 54
Another oval bore hole of unknown carpenter ant species probably of the genus Camponotus. Carpenter ants do not eat the wood, instead they make nests in damp wood. For this reason, they are often found in cracks and scars at the tree base.
55
Damage caused by carpenter ants.
56 Dipteran cambium miner -Phytobia cambii Type Name Level 28 PHYCAM 99
Heavy example of Phytobia cambii. Female lays eggs just below cambium. Larvae then radiate outward from the egg laying point. The cambium miner is quite common. We record only heavy examples like this one.
57
WOODY TISSUE DISEASES (Types 30 - 39)
Cytospora canker -Cytospora chrysosperma Type Name Level 30,31 CYTCHR 5-95
Typical bark discolouration of early Cytospora canker. Bark is also slightly sunken. 58
Typical bark discolouration of early Cytospora canker. This is a very common pest and is often introduced to the tree by one of the boring insect. Orange horizontal line is painted DBH mark.
59
Pimple like pycnidial fruiting bodies seen in later stage Cytospora. This canker will expand year by year eventually girdling the tree and causing its death. The Agent Level for this pest, like all cankers, is assessed as the percent of stem girdled. If you see more than one patch of Cytospora, assess the one which girdles the most.
60
Pimple like pycnidia seen in later stage Cytospora. The orange is the painted tree number.
61
Orange spore tendrils occasionally seen with Cytospora canker. Under moist conditions spores ooze out of the pycnidia.
62
Orange spore tendrils occasionally seen with Cytospora canker.
63
Ceratocystis canker -Ceratocystis fimbriata Type Name Level 31 CERFIM 5-95
Perennial target canker of C. fimbriata. This is a less common canker especially compared to Cytospora.
64
Perennial target canker of C. fimbriata. Typically, the canker is elliptical in shape and is sunken with concentric ridges.
65
Sometimes Ceratocystis canker can have this appearance. The canker seldom girdles or kills trees but they can enlarge for 30 to 40 years. 66
Another example of a target type canker that is most likely Ceratocystis. Boring insects are the primary mode of infection.
67
Ceratocystis canker on many trees in stand. 68 Cryptosphaeria canker -Cryptosphaeria lignyota Type Name Level 31 CRYLIG 5-95
Long narrow canker typical of C. lignyota. This is another not so common canker.
69
Close-up of Cryptosphaeria canker. Dead bark is stringy, canker is sooty-like with white flecks. Cytospora canker is often associated with this canker.
70 Sooty-bark canker -Encoelia pruinosa Type Name Level 31 CRYLIG 5-95
Typical “Barber Pole” markings of the sooty-bark canker.
71
Fruiting bodies (apothecia) of E. pruinosa. Sooty-bark canker can girdle mature trees in just a few years. Although this canker is common in some areas it is rarely found in our CIPHA stands possibly because it is uncommon in younger stands (<60 yrs).
72 Hypoxylon canker -Entoleuca mammata Type Name Level 31 ENTMAM 5-95
Early stage Hypoxylon canker. Note the yellow to orange slightly sunken areas of bark. 73
Typical mid-stage Hypoxylon canker. Hypoxylon is wind-borne but we’ve found that it has a high association with wood borers which may serve as the vector.
74
Late stage Hypoxylon canker. Note the diffuse gallery (A) typical of the woodborer Dicerca spp. 75
Bark cracked in a checkered manner typical of E. mammata. Arrows indicate hyphal pegs (perithecia).
76
Checked bark and hyphal pegs (arrows). Hypoxylon canker will often kill tree within 3 to 8 years.
77
Close-up of E. mammata hyphal peg. These hyphal pegs are distinctive of Hypoxylon. 78
Late stage Hypoxylon canker showing hyphal pegs (arrows). Typical Dicerca galleries (A) often associated with the canker. Complicating matters, Hypoxylon canker may be over reported because Dicerca damage can often look like Hypoxylon damage. 79
Rough bark -Rhytidiella baranyayi Type Name Level 31 RHYBAR 5-95
Rough bark caused by Rhytidiella. This is a hard organism to identify because some aspen clones naturally present with rough bark. Therefore, we only classify extreme examples such as this tree. 80 Diplodia galls -Diplodia tumefaciens Type Name Level 32,33 DIPTUM 99
Start of Diplodia. It is relatively rare in our CIPHA network
81
Older Diplodia galls. Damage from D. tumefaciens is minimal. It does not cause mortality. 82
Diplodia on branch. When found on branches use Agent Type of 32 (Branch gall).
83
Older Diplodia. When found on the stem use Agent Type of 33 (Stem gall).
84 White rot -Peniophora polygonia Type Name Level 34 PENPOL 99
Fruiting bodies are almost always found underneath dead branch stubs and usually within the bottom 3m of the stem. 85
Peniophora fruiting bodies can sometimes be very small and can be confused with lichens also found under the branch however Peniophora fruiting bodies are pink to reddish with white edges. 86 False tinder conk -Phellinus tremulae Type Name Level 34 PHETRE 1-10
Smaller Phellinus conks. These conks may be found all the way up the stem. Like Peniphora, spores are wind borne and infect dead branch stubs and wounds.
87
Typical P. tremulae conks. Like Peniophora, damage is confined to heartwood rot. Trees can live for decades with these organisms.
88 Armillaria root disease -Armillaria spp. Type Name Level 35 ARMSPP 99
White mycelia found by digging under the bark of roots. Armillaria is often spread by rhizomorphs (root like fungal hyphae) from a disease center of dead infected trees or stumps. Therefore, Armillaria should be suspected when you come across a circular patch of dead tree. Confirmation requires digging at the roots to find the white mycelia (remember destructive sampling is only allowed on dead trees).
89
White mycelia under the bark of roots. The reported incidence of Armillaria in CIPHA is very dependent on the amount of time you spend digging for it. 90
Extensive mycelial fan found the stem. Armillaria is very common and can often kill trees on its own. All newly dead trees should be checked for Armillaria.
91
OTHER DAMAGE AGENTS (Types 40 - 49)
Frost crack Type Name Level 43 FROST 5-95,99
Recent frost cracks. Frost cracks are common.
92 Frost damaged foliage Type Name Level 41 FROST 5-95
Frost damaged foliage. Edges often turn black. Succulent new leaves may die and eventually drop. Frost damage may be confused with leaf-roller damage.
93
Frost damaged foliage. Damage may appear to be clonal because some clones leaf out earlier than others and therefore are more likely to be damaged by frost.
94 Mechanical scars Type Name Level 43 MECHSCAR 5-95,99
Recent mechanical damage caused by a falling tree. Look for bark discolouration, stem cracks, and broken branches on the same side. 95
Old partially healed mechanical scar. Old scars will appear with a heal callus.
96
Old mechanical scar. Sometimes it may be hard to distinguish mechanical scars from canker. Look for typical fruiting bodies associated with cankers.
97
Moose -Alces alces Type Name Level 43 ALCALC 5-95,99
Fresh moose scar. Bark removed with lower incisors leaving vertical grooves. 98
Older moose scars. Distinguishing between ungulates can be difficult. Deer usually browse below 1.5m and moose below 2.3m. Both can also damage stems by antler rubbing. 99
Black bear -Ursus americanus Type Name Level 43 URSAME 5-95,99
Typical black bear scars. 100
Typical black bear scars. The trees most often marked by bears are those with tree paint or tree tags. 101
Woodpecker species -Picoides spp. Type Name Level 43 PICSPP 5-95,99
Woodpecker damage. Woodpecker probably extracting ants.
102
Woodpecker holes due to feeding on wood borer larvae.
103
Possible woodpecker nest. Note Phellinus conks.
104 Yellow-bellied Sapsucker -Sphyrapicus varius Type Name Level 43 SPHVAR 5-95,99
Typical sapsucker damage.
105
Red Squirrel -Tamiascurus hudsonicus Type Name Level 43 TAMHUD 5-95,99
Squirrel nest at base of tree. 106
Subterranean damage caused by squirrel.
107