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OAK PESTS A Guide to Major , Diseases, Pollution and Chemical Injury

United States Department of Agriculture

Forest Service State & Private Forestry Southeastern Area General Report SA-GR11 Southern Forest Experiment Station March 1980

OAK PESTS: A Guide to Major Insects, Diseases, Air Pollution and Chemical Injury By J. D. Solomon,* F. I. McCracken, * R. L. Anderson, t R. Lewis, Jr. * F. L. Oliveria, t T. H. Filer,* P. J. Barry, t

*Stationed at the Southern t Southeastern Area, State and Hardwoods Laboratory, maintained Private Forestry, USDA Forest Ser¬ at Stoneville, Miss., by the Southern vice, 1720 Peachtree Road, N.W., Forest Experiment Station, USDA Atlanta, Ga., 30367. Dr.’s Anderson Forest Service, in cooperation with and Barry are stationed at the the Mississippi Agricultural and Southeastern Area’s Field Office, Forestry Experiment Station, and the Asheville, N.C. Dr. Oliveria is at the Southern Hardwood Forest Research Southeastern Area’s Field Office, Group. Alexandria Forestry Center, Pineville, La. TABLE OF CONTENTS

Page INTRODUCTION .. . iv Oak branch borer . 26 INSECTS Oak-stem borer .. 26 DEFOLIATORS MISCELLANEOUS Elm spanworm ...... 2 INSECTS Fall cankerworm .. 3 Oak Phylloxerids . 28 Orangestriped oakworm ... 4 Oak aphids . 29 Variable oakleaf Oak lace bug .. 30 caterpillar ... 5 Periodical .. 31 Yellownecked caterpillar . 6 Lecanium scales .. 32 Forest tent caterpillar ... 7 Gouty oak gall . 33 Gypsy .... 8 Oak- gall . 34 Slug oak ..... 9 Acorn weevils . 35 Walkingstick .. . 10 MINOR MISCEL¬ Oak leafroller . . 11 Solitary oak leafminer ... 12 LANEOUS INSECTS Giant aphid . 36 Gregarious oak Pit scales...... 36 leafminer ... . 12 Kerrnes scales . 36 Oak skeletonizer .. 13 Obscure scale .. 36 MINOR DEFOLIATORS Spider mites .. 36 Spring cankerworm ...... _ . 14 White grubs .. 36 Linden looper ....___ . 14 DISEASES Pinkstriped oakworm _ . 14 Spiny oakworm .... 14 DECAY FUNGI Asiatic oak weevil .. 14 CANKER ROTS Oak leaftier ..... 14 Hispidus canker.. 40 Spiculosa canker . 41 INSECT BORERS Irpex canker . 42 Carpenterworm .. . 16 BUTT ROTS Oak clearwing borer .... 17 Hedgehog rot ..._ 43 oak borer ...... , 18 Polyporus fungus rot ... 43 White oak borer.. 19 Varnish fungus rot .. 44 Twolined borer ., 20 Sulfur fungus rot . 44 Oak timberworm ... 21 Oyster fungus rot _...... 44 Columbian timber ., 22 TOP ROTS Pin-hole borers.. 23 Stereum fungus rot . 46 Twig pruner ...., 24 Poria fungus rot. 46 Tilehorned prionus . , 25 ROTS Broadnecked root borer ...... , 25 Corticium root rot . 47 MINOR BORERS root rot . 48 Shoestring root rot . 49 Little carpenterworm ...__ . 26 Beech borer ..., 26 WILTS Spotworm borer . 26 Texas live oak decline .50 Flatheaded appletree borer ... 26 Oak wilt . 51

u CANKERS MINOR DISEASES Nectria canker.52 Leaf spot . 62 Botryodiplodia canker. 53 Powdery mildew . 62 canker . 54 Twig canker. 62 LEAF DISEASES Spot anthracnose. 62 Smooth patch . 62 Anthracnose .55 Iron-deficiency — chlorosis ... 62 Leaf blister :. 56 Actinopelte leaf spot . 57 Leaf rust (fusiform rust and Insects/ . 65 eastern gall rust) . 58 Fungi/ ...... 66 SEEDLING DISEASES CONTROLS . 66 Damping-off .59 ACKNOWLEDGEMENTS ... 67 INDEX .. 68 PHANEROGAMS Mistletoe.60 CHEMICAL DAMAGE, AIR POLLUTION, PESTICIDES, OTHER CHEMICALS Leaf necrosis — decline (Ozone, sulfur dioxide, fluoride, herbicide, ammonia) . 61 INTRODUCTION

The (Quercus spp.) are aware of, and use, cultural practices among our most valuable hardwood that maintain and promote tree vigor. resources, amounting to one-third of Match tree to the proper site. the hardwood sawtimber volume in Assure sufficient water, nutrients, the United States. Over half the an¬ space, and sunlight. Avoid accidental nual cut of oak is produced in injuries such as cuts, bruises, and the 13 Southern States. Oaks are best broken limbs. Use practices that known for their timber production favor natural controls such as birds and resulting fine furniture, beautiful and other predators, parasites, and flooring, and other products. Yet, insect pathogens. Practices such as aesthetics, watershed management, “pick-up and destroy” and “prune- recreation, and wildlife are goals now out and destroy” can help reduce given equal or greater priority by hibernating forms and inoculum many. The oaks are valued for shade reservoirs. When all else fails, and ornamental purposes — a single chemical controls may become tree sometimes adds thousands of necessary. dollars to real estate values. This booklet will help nur¬ Insects, diseases, and pollutants serymen, forest woodland managers, present a continuing threat to oaks. A control operators, and home- major portion of the acorn crop is owners to identify and control pest destroyed during some years — ham¬ problems on oaks. The major insect pering regeneration efforts. Seedling and disease pests of oaks in the South mortality and dieback add to this are emphasized. Descriptions and il¬ problem. Terminal and top injury ad¬ lustrations of the pests and their versely affect tree form. Repeated damage are provided to aid in iden¬ defoliations cause growth loss and tification. Brief notes are given on mortality. Borers and decay cause biology and control to aid in defect and degrade amounting to an predicting damage and making con¬ annual loss of millions of dollars. In¬ trol decisions. A list of chemical con¬ direct losses occur through disruption trols is provided. Chemical controls of sustained forestry practices, are subject to change as certain com¬ regulation of forest types, and altered pounds are banned and new materials wildlife habitat. Homeowners may approved. Thus, the chemical control incur the expense of chemical control section can be removed (tear sheet) and possibly the cost of tree removal and discarded when outdated. For if mortality occurs. Nuisances created further information on pesticides, by numerous insects decrease tourist contact your State Forester, county use and revenue. agent, or the nearest office of State It is far better to prevent attack and Private Forestry, USDA Forest by insects and disease than it is to Service. remedy them after they occur. Be

iv INSECTS

1 INSECT DEFOLIATORS ELM SPANWORM, Ennomos subsignarius (Hiibner)

Importance. — Elm spanworms Young larvae feed on the edge and attack red and white oaks, and other undersides of , causing a shot species especially Carya, (hickory, hole appearance. Later, they con¬ pecan and related trees) throughout sume the entire leaf except the main the East. This is a destructive forest veins, leaving a feathered appearance pest, particularly in the southern Ap¬ to the tree. palachians where widespread, severe Biology. -— Overwintering eggs outbreaks have occurred. Repeated hatch in early spring when the buds defoliation can cause growth loss, break, usually April in the South. The dieback, reduction in mast crops, and larvae feed for 4 to 6 weeks, and then mortality. pupate in net-like cocoons on the Identifying the Insect (figure la). host tree or understory. Six to 10 days — Larvae are slate grey to brownish- later, in late June to mid-July, the black with yellowish body rharkings emerge and deposit their eggs. (yellow or green at low population There is one generation per year. densities) and 1.6 to 2 inches (40 to 50 Control. — Insect parasites at¬ mm) long. The adults are snow-white tack the eggs of the elm spanworm. moths. The olive green eggs are laid Other natural enemies also are im¬ in masses on the underside of small portant in keeping infestations in branches (figure lb). check. Chemical controls are often Identifying the Injury (figure lc). needed to protect high-value trees.

Figure 1. — (a) Elm spanworm ; (b) elm spanworm egg mass on branch; (c) defoliation by elm spanworm.

2 FALL CANKERWORM, Alsophila pometaria (Harris)

Importance. — The fall the leaves. Larger larvae consume all cankerworm is one of the most com¬ except the midrib and major veins. mon and injurious species of loopers Feeding is complete in 5 to 6 weeks. in eastern forests. Repeated defolia¬ Biology. — Overwintering eggs tion causes growth loss, reduction in hatch in late April or early May. The mast, can eventually kill trees and larvae feed on young leaves at branch causes a nuisance in high-use areas. tips. Mature larvae enter the soil to Identifying the Insect (figure 2a). pupate. Adults emerge, mate, and — Larva color varies with population deposit eggs in November and density from light green with yellow December. There is one generation stripes, to green with a dark dorsal per year. stripe, to black with whitish lines. Control. — The eggs and larvae The mature larva is .8 to 1-inch (19 to of the fall cankerworm are attacked 25 mm) long. The adult female is by insect parasites. Other natural wingless and ash gray; males have enemies also help control this pest. wings. Eggs are laid in masses of Sticky bands placed on trunks of more than 100 on small twigs (figure high-value trees can snare the 2b). wingless females before they lay their Identifying the Injury (figure 2c). eggs. Chemical controls may be — Early signs are small holes in needed. leaves or complete skeletonization of

Figure 2. — (a) Fall cankerworm larva; (b) fall cankerworm female moth and egg mass on branch; (c) oak stand defoliated by fall cankerworm.

3 ORANGESTRIPED OAKWORM, Anisota senatoria (J. E. Smith)

Importance. — This defoliator consume all but the main veins. Older occurs over much of the East. It larvae are less gregarious and can be defoliates trees in parks, found crawling on lawns and sides of campgrounds, picnic areas, and along houses. city streets. However, forest stands of Biology. — Adults appear in June red and white oaks on upland sites and July, and deposit clusters of suffer most when outbreaks occur. several hundred eggs on the under¬ Identifying the Insect (figure 3a). side of leaves. The eggs hatch within a — The larva is black with eight few days and the caterpillars feed narrow yellow stripes; it is about 2 in¬ during July to September for 5 to 6 ches (50 mm) long. There is a pair of weeks. In the fall, mature larvae long, curved “horns” on the second pupate in the soil, where they thoracic segment. The adult moth is overwinter. There is generally one yellowish-red; forewings are orange- generation per year. and each has an oblique band Control. — Natural enemies and white spot. generally prevent widespread defolia¬ Identifying the Injury (figure 3b). tion, but chemical control may be — Young larvae feed in groups, needed for high-value trees. skeletonizing the leaf. Later, they

Figure 3. — (a) Orangestriped oak worm larva; (b) tree defoliated by orangestriped oak worm.

4 VARIABLE OAKLEAF CATERPILLAR, Heterocampa manteo (Doubleday)

Importance. — This defoliator is with three dark wavy lines across the common throughout eastern North forewings. America. It feeds on all species of Identifying the Injury (figure 4b). oaks, but prefers the white oaks. — Young larvae skeletonize the leaf Some infestations have covered while older larvae devour the entire millions of acres — retarding growth leaf except the leaf stalks and main and tree vigor. Outbreaks usually veins. There are two periods of subside after 2 to 3 years, before defoliation — one in June to July and serious tree mortality occurs. another in August to October. Identifying the Insect (figure 4a). Biology. — There are two genera¬ — Caterpillar color is variable, but is tions in the South and one generation generally yellowish green with a in the North. In the South, the larvae narrow white stripe down the center feed from early May until late June, of the back, bordered dorsally with and pupate in the soil. Second- reddish-brown, and one or two generation larvae feed from mid- yellowish stripes on the sides. Mature August until late September, then larvae may reach 1.5 inches (37 mm) move to the ground to spin cocoons long. The adult moth is ashy grey and overwinter as prepupae. Larvae of the single generation in the North are present during June to mid- August. Control. — Insect parasites and predators eat the eggs and larvae of this pest. Winter mortality also helps keep most infestations in check. Chemical control is occasionally needed to protect high-value trees.

Figure 4.—(a) variable oakleaf caterpillar larva; (b) defoliation by variable oakleaf caterpillar in residential area.

5 YELLOWNECKED CATERPILLAR, ministra (Drury)

Importance. —- This caterpillar is Identifying the Injury. — Newly a defoliator of oaks and a few other hatched larvae skeletonize the leaf; hardwoods throughout the United older larvae devour all except the leaf States. Infestations have been most stalk. Individual trees, or even stands, common in the Appalachian and may be defoliated during summer Ozark Mountains and foothills. and early fall. Damage is more severe to shade and Biology. — Moths appear during ornamental trees than to forest June and July and deposit white eggs stands. in masses of 50 to 100 on the under¬ Identifying the Insect (figure 5). sides of the leaves. Larvae feed in — The larva is yellowish and black groups, maturing in August and Sep¬ striped, and moderately covered with tember. Mature larvae drop to the fine, white hairs. The head is jet soil and pupate at depths of 2 to 4 in¬ black; the segment behind the head is ches (5 to 10 cm) where they spend bright orange-yellow — hence its the winter. There is one generation name, yellownecked caterpillar. Full per year. grown larvae are about 2 inches (50 Control. — Natural enemies mm) long. When disturbed, the lar¬ generally keep infestations in check. vae lift their head and tail in a dis¬ Chemical controls are occasionally tinctive “U” shape. needed.

Figure 5. — Yellownecked caterpillar larvae.

6 FOREST TENT CATERPILLAR, Malacosoma disstria (Hubner)

Importance. — Outbreaks occur Egg masses of 100 to 350 eggs encircle periodically on oaks and other the twigs and are covered with frothy, hardwoods over wide areas of the dark brown cement. eastern half of North America. Identifying the Injury (figure 6b). Growth loss and dieback occur, but — The first noticeable signs of attack trees are seldom killed unless they are sparse crowns and falling frass. sustain 3 or more successive years of Caterpillars often cluster on the lower defoliation. trunks of infested trees. Trees or even Identifying the Insect (figure 6a). stands may be completely defoliated — Caterpillars have pale bluish lines during spring. along the sides of a brownish body; a Biology. — Eggs hatch in early row of keyhole-shaped white spots spring. Caterpillars feed for 4 to 6 down the middle of the black back; weeks on the opening buds, foliage, sparsely covered with whitish hairs; and flowers. Despite its name, this and reach 2 inches (50 mm) at species does not form tents. Pupation maturity. Adult moths are buff- occurs in yellowish cocoons and lasts brown with darker, oblique bands. 10 to 14 days. Moths emerge from late May to July and deposit their eggs, which overwinter. There is one generation per year. Control. — Natural controls in¬ clude insect parasites of the pest’s eggs, larvae, and pupae. Predators, virus and fungus diseases as well as high and low temperatures also kill forest tent caterpillars. Several chemicals and a microbial are registered for control.

Figure 6. — (a) Forest tent caterpillar larvae; (b) defoliation by forest tent caterpillar.

7 GYPSY MOTH, Lymantria dispar (Linnaeus)

Importance. - The gypsy moth, Identifying the Injury (figure 7b). which came from , has long — Young larvae chew small holes in been considered one of the most im¬ leaves. Older larvae feed on leaf portant pests of red and white oaks in edges, consuming entire leaves except the Northeast. It has spread for the larger veins and the midrib. southward to and appears to The entire tree may be defoliated. be moving in on southern Biology. — Larvae emerge in hardwoods. It causes widespread May from overwintering eggs and defoliation resulting in reduced feed until mid-June or early July. growth, loss of vigor, mortality, and Pupation occurs in sheltered places reduces aesthetic, recreational and and lasts 2 weeks. Adults emerge in wildlife values. July and August. Females deposit Identifying the Insect (figure 7a). masses of 100 to 800 eggs covered — Larvae are brownish gray with with buff-colored hairs on trunks and tufts of hair on each segment and a other sites. double row of five pairs of blue spots, Control. — Natural controls in¬ followed by six pairs of red spots, on cluding introduced insect parasites the dorsum. Larvae are about 1.6 to and predators, virus disease, and ad¬ 2.4 inches (40 to 60 mm) long. Adult verse weather conditions help control females are whitish and males are the gypsy moth. Chemical and dark brown. microbial insecticides have been used extensively.

Figure 7 .—(a) Gypsy moth larva; (b) defoliation by gypsy moth.

8 SLUG OAK SAWFLY, quercuscoccineae (Dyar)

Importance. — This pest is with a fine network of veins. Defolia¬ usually endemic on the oaks; tion starts in the upper crown in early however, during 1974-1976, it was summer and progresses downward. epidemic in Kentucky, Virginia and By late summer, heavily infested trees Tennessee. Repeated defoliations may be completely defoliated. retard growth, vigor, and mast crops, Biology. — Larvae in cocoons and kill some trees. survive the winter. Larvae pupate in Identifying the Insect (figure 8a). the spring. Adults and larvae are pre¬ — Larvae are slug-like, yellowish- sent throughout the summer. Eggs green and shiny with a black head are deposited in single rows of slits on and thoracic legs, and .5 inch (12 the lower leaf surface along main mm) long. Larvae feed in groups. The veins. There are two to three genera¬ adult is a typical sawfly, about .25 tions per year. inch (6-8 mm) long, and light brown. Control. — Microbial diseases Identifying the Injury (figure 8b). and other natural enemies generally — Leaves may be skeletonized. Lar¬ keep the slug oak sawfly in check. In¬ vae consume the epidermis, making secticides may be needed on high- the leaf transparent. The leaf is left value trees.

Figure 8. — (a) Slug oak sawfly larvae; (b) feeding injury by slug oak sawfly.

9 WALKINGSTICK, Diapheromera femorata (Say)

Importance. — The walkingstick about 2.5 to 3 inches (62-76 mm) attacks oaks and other species long. Body color varies. throughout the East. Branches are Identifying the Injury (figure 9b). killed or die back in heavily — The entire leaf blade, except the defoliated stands. Continued defolia¬ base of stout veins, is consumed. tion for several years can kill the During heavy outbreaks, large stands trees. The insects create a nuisance in are often completely denuded. Trees high-use areas such as parks and may be defoliated twice during the recreation areas. same season. Identifying the Insect (figure 9a). Biology. — Overwintering occurs — Nymphs and adults are slender in the egg stage, in leaf litter. Eggs and have long thin legs and antennae. hatch in May and June. Nymphs While motionless, they closely resem¬ reach adulthood during summer and ble twigs of their host. Adults are fall. Females deposit up to 150 eggs which are dropped randomly to the forest floor. There is one generation per year in the South; 2 years are re¬ quired farther North. Control. — Natural controls are often effective. Chemical control is occasionally needed in high-use areas.

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Figure 9.—(a) Walkingstick adult; (b) forest stand defoliated by walkingsticks.

10 OAK LEAFROLLER, semiferanus (Walker)

Importance. — This insect leaves together, forming an enclosure sometimes defoliates many red and for protection and rest, when not white oaks throughout the East. feeding. Extensive stands of trees may Defoliation has been most severe be completely defoliated, including along ridge tops where white and the understory. chestnut oak frequently occur. Forest Biology. — Overwintering eggs areas are often defoliated for several hatch in April and the young larvae consecutive years, killing many trees. begin rolling the leaves and feeding. Identifying the Insect (figure 10). Feeding is complete by mid-June and — Larvae are various shades of green pupation occurs in cocoons within about 1.2 inch (29 mm) long, and the rolled leaf or in bark crevices. have black heads. At rest, the wings Moths emerge in late June or early of the adult appear bell-shaped and July and deposit eggs in masses on are creamy brown and gray with a the trunk and branches. darker cross band. Control. — Natural enemies are Identifying the Injury. — The lar¬ usually effective. Chemical controls vae either fold or roll individual may be needed to protect high-value trees.

Figure 10. — Oak leaf roller larvae.

11 SOLITARY OAK LEAFMINER, Cameraria hamadryadella (Clemens) GREGARIOUS OAK LEAFMINER, Cameraria Cincinnatiella (Chambers)

Importance. — These leafminers mines just below the upper leaf sur¬ occur over much of the East. They at¬ face; a single leaf may contain several tack various oaks, but prefer the contiguous mines (figure 11). Larvae white oak group. Heavy infestations of the gregarious oak leafminer feed cause browning and premature drop¬ together, forming large mines. ping of foliage — sometimes over Biology. — The winter is spent in large areas. the larval stage in leaves on the Identifying the Insect. — Adults ground. Adult moths emerge during and larvae of both species are similar. the spring and females lay eggs on the Young larvae are flat and taper leaves. There are two to several toward the rear, and are about .25 generations per year. inch (6 mm) long at maturity. Adults Control. — Rake fallen leaves are pale and silvery with bronze promptly and burn them to destroy patches on the wings. pupae in cocoons. Natural enemies Identifying the Injury. — Larvae are helpful. Chemical control is oc¬ of the solitary oak leafminer feed casionally needed. singly, forming irregular, blotch-like

Figure 11. — Leafmines caused by the solitary oak leafminer.

12 OAK SKELETONIZER, Bucculatrix ainsliella (Murteldt)

Importance. — This insect is skeletonized appearance (figure 12b). common on the oaks, particularly the As heavily infested trees are red oaks, in the East. Trees that defoliated, the skeletonized leaves sustain repeated attacks are drop off and cover the ground. weakened and suffer crown Biology. — Winter is spent in the and die-back. Ornamental trees ap¬ pupal stage in white cocoons, about especially vulnerable. .1 inch (3 mm) long and ridged Identifying the Insect (figure 12a). longitudinally on leaves and trunks. — Larvae are slender, yellowish- Adults emerge during the spring and green, and .2 inch (5 mm) long. They deposit eggs on the undersides of often spin down on silken threads fully grown leaves. The youngest when disturbed. Adults are small, (first-instar) larvae enter the leaves to blackish and marked with paler feed, forming tiny mines. Older lar¬ areas. vae feed externally. There are two or Identifying the Injury. — Cater¬ more generations per year. pillars eat the fleshy green part of the Control. — Rake fallen leaves lower surface, entirely or in part, promptly and burn them to destroy which gives the leaves a brownish, cocoons. Insecticides may be necessary on high-value trees.

Figure 12. — (a) Larvae and cocoons of oak skeletonizer on undersurface of leaf; {b) leaf skeletonized by oak skeletonizer.

13 MINOR DEFOLIATORS Insect Injury Control* Spring cankerworm, Many hosts, heavy on live oak in 1

Paleacrita vernata (Peck); Texas; skeletonizes leaves at branch 2 the larva (figure 13) is a typical tips; may devour all but midribs and 11 looper, yellowish-brown to greenish- large veins; outbreaks can occur on 12 black with two yellowish stripes, shade trees and forested areas; about 1.2 inch (30 mm) long; the reduces tree vigor and growth. female moth is wingless, gray with black dorsal line; one generation per year.

Linden looper, Many hosts, heavy on white oaks 1

Erannis tiliaria (Harris); in South; partial feeding on 2 the larva (figure 14) is a looper-type, individual leaves (ragging) is typical, 11 yellow with brown head and 10 wavy complete defoliation occurs during black lines on dorsum, 1.5 inches (37 outbreaks; outbreaks less common in mm) long; female moth is wingless, South than in North; reduces tree yellowish-gray with two rows of vigor and growth. black spots; one generation per year.

Pinkstriped oak worm, Red and white oaks; leaves eaten 1

Anisota virginiensis (Drury); except leaf stalks and midribs; 11 the larva (figure 15) is greenish- stripped branches and trees common, brown with four pink stripes, a pair entire stands less common; of long, curved “horns” is on the defoliation in summer and fall; less second thoracic segment, 2 inches common than orangestriped (50 mm) long; the adult is a oakworm, except in bottomland brownish-red moth, white spot on forests; causes growth loss and crown forewings; two generations per year. decline.

Spiny oakworm, Red and white oaks; larvae feed on 1

Anisota stigma (Fabricius); leaves, July to September, consuming 11 the larva (figure 16) is tawny and all but leaf stalk and main veins; pinkish with white specks, 2 inches partial defoliation common; heavy (50 mm) long, two long curved widespread defoliation uncommon. “horns” are on the second thoracic segment, and short spines on all other segments; one or two generations per year.

Asiatic oak weevil, Wide host range, including red and 1

Cyrtepistomus castaneus (Roelofs); white oaks; adults emerge in spring 11 adults (figure 17) are greenish-brown and feed on leaves by chewing in to black weevils, .25 inch (6 mm) from the margins toward the midribs long, with short snouts; one and devour all but the larger veins; generation per year. during fall they create nuisances by invading houses in large numbers.

Oak leaftier, Foliage of red oak group; young 1

Croesia semipurpurana (Kearfott); larvae feed on buds in early spring; 11 the larva (figure 18) is dirty white to older larvae fold or tie together light green, .5 inch (12 mm) long, sections of leaves with webbing and pale head, brownish thoracic legs; feed inside the folds until late May; adults are yellow with brown severe outbreaks have occurred in markings; one generation per year. upland oaks, killing some trees, with decline of others. *See CONTROLS, page 66.

U Figures 13-18.—(13) Springcankerwormlarvaeondefoliated branch;(14)lindenlooperlarva; UMri (15) pinkstripedoakworm larvae;(16)spinyoakworm larva:(17)asiaticoakweevil and feedinginjury; (18)oakleaftierlarva. 15 INSECT BORERS CARPENTERWORM, robiniae (Peck)

Importance. — Carpenterworms mm) in diameter under the bark, and are serious borers throughout the galleries .5 inch (12 mm) in diameter United States. Wormholes cause and 5 to 8 inches (12 to 22 cm) long in degrade estimated at 15 percent of the the are typical. Galleries are value of rough sawn lumber and un¬ open or only loosely plugged with sightly scars on ornamental trees. frass. Holes in lumber are dark Identifying the Insect (figure 19a). stained. — Newly hatched larvae are .25 inch Biology. — Adult moths appear (6 mm) long and reddish pink. Larvae in April to June and deposit 400 to gradually become greenish white and 800 eggs in bark crevices. Eggs hatch are 2 to 3 inches (50 to 75 mm) long at in 10 to 12 days and young larvae maturity. Brown pupal skins tunnel into the bark and wood. ¬ protruding from entrance holes are tion occurs within the gallery during common in early summer. Adults are spring and lasts 3 weeks. A life cycle grayish, stout-bodied moths; the requires 1 to 2 years in the South, and hindwing in the male has an orange 2 to 4 years in the North. spot (figure 19b). Control. — Maintain high tree Identifying the Injury (figure 19c). vigor. Remove brood trees. Prevent — Earliest signs of attack are sap bark injuries. Natural enemies help. spots on the trunk. Later, frass (wood Control with trunk spray or gallery chips and pellets) is ejected from en¬ fumigation. trance holes. Burrows 2 inches (50

Figure 19. —(a) carpenterworm larva in gallery; (bj carpenterworm female moth; (c) tree trunk with carpenterworm attacks.

16 OAK CLEARWING BORER, Paranthrene simulans (Grote)

Importance. — This borer attacks Identifying the Injury (figure 20b). the lower trunk of red and white oaks — Sap spots and fine frass first ap¬ throughout the East. In the South, at¬ pear. Later, granular frass is ejected tacks are most common between root in clumps from .3 to .6 inch (9 to 15 flanges of large red oaks. Damage in¬ mm) entrance holes. There is little cludes degrade, entries for decay and mining under the bark. Galleries are nursery cull. .3 inch (9 mm) in diameter, 4 inches Identifying the Insect (figure 20a). (10 cm) long in the wood, and shaped — The larva is purplish gray, black much like those made by carpen- head, brown thoracic shield, and 1 terworms (figure 20c). inch (25 mm) long. Adults are color¬ Biology. — Moths emerge during ful, black and orange banded, ¬ June and July and deposit eggs in like moths with a wing expanse of 1.5 bark crevices. Eggs hatch in 15 to 18 inches (37 mm). days and the larvae tunnel into the bark and wood of host trees. Pupa¬ tion occurs within the gallery. A generation requires 2 years. Control. — Open-grown trees are most susceptible, thus maintain a well stocked stand. Identify and remove brood trees. Prevent or minimize in¬ juries. Larvae can be “wormed-out” with a knife and wire. Insecticides will protect valuable trees. Individual borers can be killed by gallery fumigation.

Figure 20. — (a) Male moth of oak clearwing borer; (b) oak clearwing borer entrance holes in bark; (c) gallery made by oak clearwing borer.

17 RED OAK BORER, Enaphalodes rufulus (Haldeman)

Importance. — Many of the large Identifying the Injury. — Initially, oaks in the East have been attacked tiny pin-holes with fine, extruded by this borer, resulting in defects and frass are present. Later, entrance serious degrade in the timber. holes become larger and sap-stained, Valuable shade trees in parks and followed by ejection of granular frass cities are sometimes injured. (figure 21b). A few excelsior-like Identifying the Insect (figure 21a). fibers are present in frass just before — Adult borers, are light brown, pupation. Tunnels are about .5 inch robust with long antennae and (12 mm) in diameter and 6 to 10 in¬ about 1 inch (25 mm) long. The shiny ches (15 to 25 cm) long (figure 21c). white, robust larvae have tiny legs on Biology. — The pest has a 2-year the thorax. life cycle. Eggs are laid in July and August on the bark. The larva mines under the bark during the first year, tunneling into the wood the second year. Pupation occurs and the adult exits through the bark near the en¬ trance. Control. — Maintain high tree vigor. Remove brood trees. “Worm- out” with knife or wire. Control in high-value trees with trunk spray or gallery fumigation.

Figure 21. — (a) Adult beetle of red oak borer; (b) sapstained bark and entrances typical of the red oak borer; (c) cross-section of oak trunk with red oak borer holes.

18 WHITE OAK BORER, Goes tigrinus (DeGeer)

Importance. — This borer is Biology. — Adult beetles emerge found in the East wherever its host during May to June and deposit eggs. species grow. Young trees 2 to 8 in¬ Eggs hatch in about 3 weeks and the ches (5 to 20 cm) in diameter, in the larvae tunnel directly into the wood. white oak group are attacked. Some Pupation occurs within the gallery degrade occurs. and lasts 2 to 3 weeks. A life cycle re¬ Identifying the Insect (figure 22a). quires 3 to 5 years. — The larva is moderately robust and Control. — Woodpeckers and cylindrical; 1 to 1.5 inches (25 to 37 sap-ooze are the most important mm) long; yellowish-white; head natural controls. Remove brood strongly depressed with dark brown trees. Follow practices that promote mandibles; and legless. The adult bee¬ stand vigor. Direct controls are oc¬ tle has a spine on each side of the casionally needed. thorax; about .8 to 1 inch (20 to 28 mm) long; white and brown mottled; and antennae about as long as the body. Identifying the Injury (figure 22b). — Egg niches .25 inch (6 mm) in dia¬ meter cut singly in the bark are fol¬ lowed by sap ooze and fine, moist frass. Later, the insects eject yellowish, ribbon-like pieces of frass containing pulverized wood and fibrous shreds. Galleries are about .5 inch (12 mm) in diameter and 6 in¬ ches (15 cm) long. Each borer leaves a small, elongate entrance hole and a circular .3 inch (8 mm) exit hole.

Figure 22. — (a) White oak borer larva in gallery; (b) brood-tree of white oak borer with numerous attacks and frass around the base of the tree.

19 TWOLINED CHESTNUT BORER, bilineatus (Weber)

Importance. — This borer attacks usually begin in the tree tops and ex¬ red and white oaks throughout the tend downward as the trees continue East. Trees weakened by drought, to weaken. D-shaped emergence defoliation, or other factors are most holes are evidence of infestation. susceptible. Larvae destroy the cam¬ Biology. — Adults emerge during bium and girdle the tree. Mortality spring and early summer and deposit has been extensive in weakened eggs in bark crevices. Eggs hatch in stands. 10 to 14 days and the larvae burrow Identifying the Insect. — Adult through the bark and cambium. They beetles are about .2 to .5 inch (6 to 12 overwinter in cells in the bark and mm) long, slender, and black with a pupate the following spring. There is light yellowish stripe on each wing one generation per year. cover. Larvae are white, slender, flat¬ Control. — Control is mainly a tened, about 1 inch (25 mm) long, matter of preventing attacks through and have two spines at the rear end. cultural practices that promote tree Identifying the Injury (figure 23). vigor. Spraying to protect foliage — Larvae excavate winding mines in from defoliators is recommended in the inner bark and outer sapwood of some areas. Trunk sprays offer some the main trunk and large branches, promise. frequently the tree. Attacks

Figure 23. — Twolined chestnut borer larvae and mines in inner bark.

20 OAK TIMBERWORM, Arrhenodes minutus (Drury)

Importance. — The oak tim¬ that expose the sapwood. White, berworm is a major cause of defect powdery frass at egg sites on exposed and degrade in the red and white oaks wood is good evidence of infestation. in the East. Attacks are most com¬ Winding tunnels .1 inch or smaller monly associated with wounds on (0.2 to 3 mm) in diameter, charac¬ mature trees. terize damage in lumber. Identifying the Insect (figure 24a). Biology. — During spring and — Adults are brownish black, brentid early summer, females chew cylin¬ weevils about 1 to 1.4 inches (25 to 35 drical holes into the sapwood and lay mm) long. The female has a narrow single eggs. Eggs hatch in a few days snout, while the male’s mouth-parts and the larvae bore almost through are broad and flattened. The larvae the tree then “U-turn” back across are white, elongate, cylindrical, and the grain to the point of origin. Pupa¬ curved (figure 24b). tion occurs in the gallery, and adults Identifying the Injury. — Attacks emerge through circular holes near usually occur at blazes, around other the egg site. The life cycle requires 2 borer entrances, and other wounds to 3 years. Control. — Avoid wounds and injuries, including other borer attacks to largely prevent infestation by the oak timberworm.

Figure 24. — (a) Oak timberworm adult female; (b)oak timberworm larvae and galleries in wood.

21 COLUMBIAN TIMBER BEETLE, Corthylus columbianus (Hopkins)

Importance. This beetle occurs Control. — There is no apparent over much of the East and attacks the relationship between tree vigor and white oaks and, to a lesser extent, the susceptibility. No natural enemies red oaks. It attacks the trunks of live have been found. Protection of trees of all sizes. Damaged wood is veneer-quality trees with insecticides degraded for such uses as veneer, seems possible. cooperage, and furniture. Identifying the Insect (figure 25a). — Adults are black to reddish- brown, cylindrical beetles about .2 inch (4 mm) long. The larvae are white, legless and C-shaped. Identifying the Injury (figure 25b). — Holes less than . 1 inch (1 to 2 mm) in diameter, are bored straight into the sapwood until the tunnel nears the heartwood, then it turns right or left. Damage is conspicuous in log ends. Streaks of stain originating from the tunnels are known as flagworm defects. Biology. — Adult beetles con¬ struct galleries. Eggs are laid in cham¬ bers along the main tunnel where the larvae live and develop. Larval food is a white fungus that grows on the gallery walls. There are two to three generations per year.

Figure 25. — (a) Columbian timber beetle adult in brood cell; (b) Columbian timber beetle galleries and "flag” stains in white oak.

22 PIN-HOLE BORERS, Platypus spp. and Xyleborus spp.

Importance. — These ambrosia mm) in diameter, branched or un¬ beetles are best known for their branched, stained black, extend into damage to fresh-cut logs and un¬ the wood. The lower trunk may seasoned lumber. They also readily sustain hundreds of attacks (figure attack weakened, stressed, and dying 26b). trees and healthy trees with bark in¬ Biology. — The beetles are at¬ juries. Damage is largely in the form tracted to wood with a moisture con¬ of degrade. tent above 48 percent. They do not Identifying the Insect. — Adult feed on the wood, but instead feed beetles are black to brown; .1 to .2 upon ambrosia fungi which they inch (3 to 6 mm); elongate and cylin¬ culture within the galleries. In the drical with a wide head in Platypus Gulf States, beetles are active most of and cylindrically compact in the year. There are two or more Xyleborus species. Larvae are white, generations per year. slightly curved to curculiform, Control. — Maintain tree vigor. legless, and .1 to .2 inch (3 to 6 mm) Salvage infested timber immediately. long. Promptly use logs during summer Identifying the Injury (figure 26a). months. Store logs under water or — White to light brown boring dust water spray. Green lumber is often in small piles in bark crevices is good kiln dried or chemically dipped to evidence of attack. Numerous round prevent attack. holes about .1 inch or less (1.5 to 3

Figure 26. — (a) Pin-hole borer attacks indicated by frass on bark; (b) numerous holes made in wood by pin-hole borers.

23 TWIG PRUNER, Elaphidionoides villosus (Fabricius)

Importance. — The twig pruner tached) 12 to 40 inches (30 to 100 cm) occurs throughout the East. It prefers long litter the ground under infested | the oaks but also attacks other trees. The end of the severed twig pre¬ deciduous species. Larvae bore into sents a smoothly cut surface. Split the the stems and cut off or prune twigs, pruned twigs to reveal the larva. terminals, and branches about .25 to Biology. — Adults emerge during 1 inch (6 to 25 mm) in diameter. spring and deposit eggs in small twigs. Severe adversely affects tree The larva burrows down the center of form and the aesthetic quality of or¬ the stem and severs the twig, which namental plantings, and creates falls to the ground, in late summer or clean-up problems. fall. Pupation and adult emergence Identifying the Insect (figure 27a). occur the following spring. There is — Larvae are cylindrical, white, and one generation per year. measure about .5 to .8 inch (12 to 21 Control. — Collect and burn mm) long at maturity. Adult beetles severed twigs during the fall and win¬ are gray mottled. ter. Natural enemies help control the Identifying the Injury (figure 27b). twig pruner. Insecticides are rarely — During the summer, fall, and win¬ needed. ter, pruned twigs (with leaves at¬

Figure 27. — (a) Ends of girdled twigs, tunnel, and larva of twig pruner; (b) young tree with top recently severed by twig pruner.

24 TILEHORNED PRIONUS, Prionus imbricornis (Linnaeus) BROADNECKED ROOT BORER, Prionus laticollis (Drury)

Importance. — These root borers gradual decline of the tree, charac¬ occur throughout the East. are teristic of severe, prolonged stress, often hollowed or severed. Open- i.e., leaves sparse, small, and grown trees and those weakened by yellowish. Examination of roots disease are most susceptible. Young, reveal the burrowing larvae and root vigorous trees are occasionally cut off damage (figure 28c). at the ground. Biology. — Adult beetles emerge Identifying the Insect (figure 28a). from the soil in early summer and — Larvae of both species are fleshy, deposit 300 to 500 eggs in the soil. creamy white with three pairs of small Young larvae burrow through the soil legs. They have cylindrical bodies and to the roots and begin feeding. The attain lengths of up to 3 inches (75 feeding period lasts 3 to 5 years. mm). The adult beetles are robust, Control. — Disease, drought, broad, dark brown, somewhat flat¬ mechanical injury, and poor soil con¬ tened, and up to 1.5 inches (37 mm) ditions increase tree susceptibility. long (figure 28b). Therefore, follow cultural practices Identifying the Injury. — Because that will keep trees thrifty and injury occurs to the roots below vigorous. Insecticides are seldom ground, correct diagnosis is difficult. needed. The above-ground symptoms are

Figure 28. —(a) Larva of Prion us species tunneling in root; (b) adult beetle of Prionus sp.; (cj root damage by Prionus sp.

25 MINOR BORERS Insect Injury Control* Little carpenterworm, Trunks and branches of sawtimber 5 Prionoxystus macmurtrei (Guerin); and shade trees; prefers red oaks; 7 larva (figure 29) pink to white, dark mine under bark, and gallery in wood 8 head and thoracic shield, 2.25 inches .4x6 inches (1 x 15 cm); frass of 9 (57mm); adult gray-mottled moth; wood chips and excrement pellets; 11 life cycle 2 to 3 years. causes lumber degrade, disfigures 13 ornamental trees.

Beech borer, Goes pulverulentus Trunks of saplings and poles of red (Haldeman); roundheaded larva, oaks; attacks are clustered (figure 30); 1 white, legless, cylindrical, about 1.5 galleries are about .4x8 inches (0.9 x 5 inches (37 mm); adult brownish-gray 20 cm); grayish frass with fibrous 6 longhorned beetle; life cycle 3 to 5 shreds extruded in ribbons; degrade, 7 years. entries for decay, stem breakage. " 11

Spotworm borer, Trunks over .5 inch (12 mm) in 5 Agrilus acutipennis (Mannerheim); diameter in white oak group, larva is slender, flattened, white, particularly heavy on overcup oak in about 1.3 inches (32 mm) long; adult river bottoms; larvae tunnel spirally beetle is narrow, dark metallic blue, in outermost growth ring (figure 31); about .5 inches (12 mm) long; a spot stains and frass-packed tunnels generation requires 2 years. are defects that degrade lumber.

Flatheaded appletree borer. Trunks and branches of red and 5 Chrysobothris femorata (Olivier); white oaks of all sizes; larvae bore 8 larva (figure 32) is flatheaded, white, into phloem and outer sapwood; 9 about 1 inch (25 mm) long; adult mines girdle and kill small trees; 10 beetle is oval, flattened, greenish newly transplanted trees and those 11 bronze, about .6 inch (16 mm) long; weakened or stressed are most one generation per year. susceptible.

Oak branch borer, Small branches and terminals 1 Goes debilis (LeConte); about .3 to 1.5 inches (9 to 37 mm) in 3 roundheaded larva, legless, diameter, mainly white oaks; attacks 5 yellowish-white, about .6 inch (15 (figure 33) near crooks and branch 6 mm); adult longhorned beetle, crotches; galleries about .2x3 inches mottled reddish-brown and gray; life (6x75 mm); yellowish frass protrudes cycle 3 to 4 years. from elongate entrance hole; infested stems become swollen, and often break or die back.

Oak-stem borer, Seedlings and sprouts about .5 to 1 Aneflormorpha subpubescens inch (12 to 25 mm) diameter; red and (LeConte); roundheaded larva, white oaks; larva bores down center of slender, about .7 inch (18 mm) long; stem, cutting off sections, burrows to adult narrow, light brown, spine on stem base or roots to overwinter; frass the third and fourth segments of is ejected through row of small holes in antennae. One generation per year. bark (figure 34), kills large numbers of seedlings and sprouts in Southeast. *See CONTROLS page 66.

26 Figures 29-34. — (29) Little carpenterworm larva; (30) cluster of attacks on sapling by beech borer; (31) bark removed to expose larval mines of spotworm borer; (32) flatheaded appletree borer larva in mine under bark; (33) oak branch borer entrance, with yellow frass; (34) oak-stem borer larva in gallerv of stem with row of small holes.

27 MISCELLANEOUS INSECTS OAK PHYLLOXERIDS, Phylloxera spp.

Importance — Phylloxerids are lack cornicles and usually spiny in ap¬ very small, aphid-like insects that at¬ pearance. Winged forms have tack the foliage and buds of red and reduced wing veination. They are white oak trees of all sizes. Heavy in¬ usually found in clusters. festations stunt and weaken the trees. Identifying the Injury (figure 35b). The distorted foliage mars the beauty — Buds and young developing leaves of ornamentals. (undersurface) on terminals and Identifying the Insect (figure 35a). branch ends are attacked, causing the — Phylloxerids are small .01 to .02 leaves to curl and twist. Growth may inch (0.3 to 0.6 mm) long, aphid-like, be reduced or stopped. Mature and nearly mature leaves are unaffected. Damage occurs during spring and early summer. Biology. — The biology is not well known, but overwintering occurs as eggs in bark crevices. Eggs hatch during the spring. There appear to be several generations per year. Control. — Natural controls usually keep damage to a minimum. Ornamentals may require chemical control.

Figure 35. — (a) Close-up of oak phylloxerid feeding along leaf midrib; (b) left, leaves curled and deformed by phylloxerids; right, healthy leaves.

28 OAK LEAF APHIDS, Myzocallis spp.

Importance. — These aphids in¬ side of the leaves. Feeding injury fest the undersides of leaves, leaf curls and folds the leaves. Every leaf stalks, and tender twigs of trees in the on a tree may be curled and distorted red and white oak groups throughout during heavy attacks. Leaf surfaces the East. Heavy infestations distort become sticky with honeydew the foliage and weaken the plants. followed by growth of black, sooty Honeydew and sooty molds further fungus. mar the beauty of ornamentals. Biology. — Overwintering occurs Identifying the Insect (figure 36). as eggs deposited in bark crevices of — The aphids are .04 to .06 inch (1 to host plants. The eggs hatch in the 1.5 mm) long, soft-bodied, pear- spring and nymphs begin feeding on shaped, with a pair of cornicles at the leaves. There are several genera¬ posterior of abdomen. They may be tions per year, but the highest pop¬ yellow, green, pink, or brown, with ulations have been observed during darker pigmented blotches on the ab¬ the spring. domen, and dusky bands on wings. Control. — Natural enemies Winged and wingless forms occur. usually keep infestations in check. In¬ Identifying the Injury. — Clusters secticides are sometimes needed on of aphids feed largely on the under¬ ornamentals and other high-value trees.

Figure 36. — Oak leaf aphids.

29 OAK LACE BUG, Corythucha arcuata (Say)

Importance. — Adults and pecially during dry weather. nymphs feed on white oaks from Biology. — Adults overwinter in Alabama and the Carolinas to bark crevices and similar protected southern Canada. By the end of areas of their host. They arouse from August, the leaves may be discolored hibernation during spring and attach and perform little photosynthesis. eggs to the underside of leaves. Upon Identifying the Insect (figure 37). hatching, nymphs begin feeding on — Nymphs are black and covered the underside of the leaf. A complete with spines. Adults have broad, cycle from egg to adult may develop transparent, lacelike wing covers; in 30 to 45 days; several generations flattened; and about .25 inch (6 mm) occur each year. In late summer, all long. active stages may feed together. Identifying the Injury. — Infested Control. — Natural enemies are leaves have chlorotic flecks on the up¬ usually effective. Chemical controls per side of the leaf. Heavily infested may be needed on shade and or¬ trees may be partly defoliated, es¬ namental trees.

Figure 37. — Adults and nymphs of oak lace bug.

30 PERIODICAL CICADA, Magicicada septendecim (Linnaeus)

Importance. — (locusts) — Females puncture the twig in attack oaks as well as other species straight rows to lay eggs and often and are widely distributed in the East. damage twigs so severely that their Egg-laying punctures by the adults terminal portions die. Large numbers often severely damage young, of molted skins of the nymphs may be transplanted trees and branches of found attached to trees trunks. large trees. Biology. — The adult female cuts Identifying the Insect (figure 38a). the bark of twigs and lays 24 to 28 — Adults are heavy bodied, and 1.6 eggs. Newly hatched nymphs drop to inches (40 mm) long. Their wings are the ground, burrow into the soil, and transparent with prominent veins. feed on the roots for 13 to 17 years. The female is completely black on Control. — Protect small trees top, while the male has four or five with netting. Properly timed insec¬ orange-brown abdominal segments. ticides may be necessary. Identifying the Injury (figure 38b).

Figure 38. — (a) Periodical cicada; (b) branches with egg-laying puncture injuries by periodical cicada.

31 LECANIUM SCALES, Lecanium spp.

Importance. — The lecanium Identifying the Injury. — Trees of scales are distributed throughout the poor vigor or with branch and crown United States. High scale populations dieback should be examined closely severely reduce vitality, weaken the for scale insects. Lecanium scales are tree, and cause branch or crown most prominent on twigs during the dieback. They have been of greatest spring and early summer. concern to shade and ornamental red Biology. — Eggs are produced and white oaks. underneath the female in late spring. Identifying the Insect (figure 39). Eggs hatch in early summer and the — The body of the adult female is cir¬ immature insects seek feeding sites on cular to ovoid, strongly convex or the underside of leaves. In late sum¬ tortoise-shaped, and about .2 to .3 mer, they migrate to twigs where they inch (4 to 7 mm) in diameter. Young overwinter. They complete their females may be tan or mottled with development in the spring. There is black, but older females are reddish usually one generation per year. or dark brown. After their eggs Control. — Parasites and hatch, the female body shells remain predators are effective in controlling loosely attached to the bark. Scales infestations. However, insecticides commonly overlap and encircle por¬ are often used and are most effective tions of infested twigs. against immature scales.

Figure 39. —(a) Lecanium scale insects on a branch.

32 GOUTY OAK GALL, Callirhytis punctata (Osten Sacken)

Importance. — This gall is among Identifying the Insect. — Adults over 600 gall insects that attack the are small, black, cynip with an oaks in the United States. Gouty oak oval, shiny, and slightly compressed gall is most common on , red, abdomen. The larvae are white and pin, water, and black oaks. In heavy globe-shaped. infestations, twigs, large branches, Identifying the Injury (figure 40a). and occasionally entire trees may be — Galls are irregular, globose, killed. woody, 1.5 inches (38 mm) in diameter, and encircle the twigs and small branches. They sometimes oc¬ cur so close together that they form nearly continuous masses (figure 40b). Biology. — This species has alter¬ nate generations. The first produces small blisterlike galls on leaves in the spring. The second produces gouty galls during the summer. Control. — Natural controls are generally adequate. Prune galls from small trees and destroy. Chemical control is possible, but poorly defined.

Figure 40. — (a) Close-up of single gall showing gall insect emergence holes; (bjtrees heavily infested by gouty oak galls.

33 OAK-APPLE GALL, Amphibolips confluenta (Harris)

Importance. — This is one of midrib or stem of leaves. Galls for¬ many leaf galls that affect oaks. med during spring are green, but These galls usually damage the tree become light brown on drying with a less than do twig galls. However, thin, papery shell. Oak-apple galls oc¬ heavy infestations of this and other cur principally on red, black, and leaf galls can cause premature leaf fall scarlet oaks. and are unsightly on ornamental Biology. — Oak-apple galls trees. usually start during spring when the Identifying the Insect. — Adults young leaf is being formed, are very small and dark with an oval, sometimes appropriating the entire compressed abdomen. The larvae are leaf for its own purpose. The biology small and globe-shaped. is poorly known, but it probably has Identifying the Injury (figure 41). alternate generations on different — Galls are about .5 to 2 inches (12 host parts. to 50 mm) in diameter, and are filled Control. — Natural enemies are with a fibrous mass. Each contains a usually sufficient. Galls can be picked single larva inside a hard center cap¬ or pruned off small ornamental trees. sule. The galls are produced on the Direct controls are seldom necessary.

Figure 41. — Cluster of oak-apple galls.

34 ACORN WEEVILS, Curculio spp.

Importance. — These weevils at¬ Identifying the Insect (figure 42a). tack both red and white oaks and are — Acorn weevils are robust and found wherever the hosts grow. Also, brown. The beak is long and slender, weevils in the genus Conotrachelus sometimes longer than the body, in and moths in the genus Melissopus the female. The larvae are legless, account for some losses. A major robust, dirty-white, and C-shaped. portion of the crop may be destroyed. Identifying the Injury (figure 42b). — There may be one or more holes in the acorn. Dissecting the acorn will reveal signs of feeding and one or more C-shaped larvae. Biology. — Female weevils drill one or more holes into the acorn and deposit a single egg in each hole. Lar¬ vae feed until full grown, then cut exit holes in the shell. Full-grown larvae enter the soil where they spend 1 to 2 years before pupating and emerging as adults. Control. — Natural controls help to minimize losses. Chemical control may be needed in seed orchards.

Figure 42. — (a) Adult acorn weevil on acorn; (b) larva, feeding injury, and exit hole of acorn weevil.

35 MINOR MISCELLANEOUS INSECTS Insect Injury Control* Giant bark aphid, Terminals, twigs, and branches of 1 Longistigma caryae (Harris); red and white oaks; aphids feed by 11 (figure 43) with relation to other sucking the plant sap; heavily aphids, this species is very large, .25 infested stems badly weakened or inch (6 mm) long, long slender legs, killed; honeydew and sooty molds and is covered with a bluish-white mar beauty of ornamentals. “bloom”: several generations per year.

Pit scales, Found on twigs, branches, and 1 Asterolecanium spp.; adult females trunks of red and white oaks; prefers 11 are circular and enclosed in white oaks; maturing females yellowish, waxy, translucent produce ring-like swellings or pits on covering, .04 to .08 inch (1 to 2 mm) the bark (figure 44) causing a rough in diameter; one generation per year. appearance; branches and trees may be killed.

Kermes scales, Scales (figure 45) occur on twigs, 1 Kermes spp.; adult females are branches, near buds, near wounds, 11 globular or gall-like, yellow-brown- on leaf midribs, and petioles of red black, solid or mottled, about .1 to .3 and white oaks; dieback or inch (3 to 7 mm) in diameter. “flagging” of newly formed terminals, branch ends, and new leaves; early leaf drop; mar beauty of shade trees.

Obscure scale, Trunks and branches of red and 1 Melanaspis obscura (Comstock); white oaks; infestations are often 11 adult female cover (figure 46) heavy and layered, killing branches, circular, grayish to black — or resulting in general weakening, resembling bark in color .08 to . 1 and sometimes death of tree. inch (2 to 3 mm) in diameter; two generations per year.

Spider mites, Foliage and buds of red and white 1 Oligonychus spp. and Eotetranychus oaks; scattered chlorotic stippling on 11 spp.; .02 inch (0.5 mm) long, spider¬ leaves (Figure 47) later yellowing or like, eight legs, sucking mouthparts; bronzing, then browning and dying large numbers often present; many of foliage; mats of webbing often generations per year. present; weakens tree and mars beauty.

White grubs, Wide host range, including oak 1 Phyllophaga spp.; larva (figure 48) is seedlings and young trees; larval 11 milky white, C-shaped, about 1 inch feeding prunes and girdles roots; (25 mm) long, brown head; adult nurseries and young plantations beetle is robust, oval, brown, about often damaged; adults may defoliate .5 to 1 inch (12 to 25 mm) long. trees.

*See CONTROLS page 66.

36 rm

Figures43-48. —(43) Nymphs and adults of giant bark aphid; (44) pit scale on oak branch; (45) kermes scale on oak twigs; (46) obscure scale on oak branch; (47) left, healthy leaves; right, chlorotic stipling caused by spider mites; (48) left, white grubs and root injury; right, healthy roots.

37

DISEASES

39 DECAY FUNGI - canker rots HISPIDUS CANKER, Polyporus hispidus (Bull.) Fr.

Importance — Hispidus canker, small branch stub may be found near caused by P. hispidus, appears on the center where the started. oak, Nuttall oak, white oak, Biology. — Microscopic spores and hickory. Incidence of infestation are released from conks for a few varies by area and species, but may be weeks. They are spread by the wind, as high as 13 percent. Cankers but most travel no more than 140 lengthen about 6 inches (15 cm) yards (128 m). Spores reaching dead yearly. The decay column length ex¬ branches on healthy trees start new ceeds the canker length. Diseased . Conks will form after trees are quickly converted to culls. deadening or diseased trees. Identifying the Fungus (figure Control — Cut hispidus-diseased 49a).— Hispidus conks are about 2 trees as soon as possible for salvage to 12 inches (5 to 30 cm) wide, and to reduce disease spread by spongy, stalkless, yellowish-brown to limiting spore dissemination to red, with pores on the lower surface. healthy trees. No suitable treatment Conks are produced during the sum¬ is known for high-value trees in ur¬ mer or fall. They dry to a black mass, ban areas. fall, and can usually be found around the base of infected trees. Identifying the Injury (figure 49b). — Hispidus cankers are large, elongate, sunken in the center and bordered by callus folds. Infected stems become spindle-shaped. A

Figure 49. — (a) Polyporus hispidus conk; (b) Hispidus canker.

40 SPICULOSA CANKER, Poria spiculosa Campb. & Davids

Importance. — Spiculosa Identifying the Injury (figure 50). cankers, caused by P. spiculosa, may — Cankers appear as rough, circular occur on up to 10 percent of the swellings with depressed centers. bottom-land red oaks in some areas. Remains of a branch stub can usually The decay column increases about 10 be found in the center of the canker. inches (25 cm) in length, yearly. Biology. — Spores are released Identifying the Fungus. — Conks from the conks and carried by the of P. spiculosa develop flat under the wind to branch stubs on healthy trees bark and the brown fruiting surface where infection occurs. Trees respond becomes exposed with maturity to invasion of the cambium by following tree death. Doubtful infec¬ developing callous tissue. tions can be identified by chopping Control. — Cut diseased trees or into the canker center. The brown deaden them to allow room for fungus material will be exposed if the healthy growing stock. No suitable infection is well established. treatment is known for high-value trees in urban areas.

Figure 50. — Spiculosa canker, including cross section.

41 IRPEX CANKER, Irpex mollis Leys ex Fr.

Importance. — Irpex canker, branch stubs. Irregular cankers up to caused by /. mollis, occurs most fre¬ 2 feet (0.6 m) long may develop. quently on red oaks. Incidence of this There is white rot in the heartwood disease varies greatly in different behind these cankers. The canker face areas. It is the least common of the will have a number of sunken areas canker rots, affecting only a small with swollen margins resulting from percentage of the trees. However, the callous tissue formation. decay under Irpex cankers extends Biology. — Reproduction is by above and below the canker face as means of microscopic spores, much as 8 feet (2.4 m). The rate of produced and released by the conks decay is unknown. each fall. The spores are spread by Identifying the Fungus (figure 51). the wind to branch stubs on suscepti¬ — The conks of I. mollis are 1 to 5 ble trees where infection occurs. The inches (2.5 to 12 cm) wide and creamy wood is decayed and the cambium white, yellowing with age. They have killed, causing progressively larger short, jagged “teeth” on the lower cankers. surface. Conks usually occur during Control. — Control measures are late summer and fall. similar to those described for Identifying the Injury. — hispidus cankers. Infections are associated with dead

Figure 51. — Irpex mollis conks on canker surface, including cross section.

42 BUTT ROTS

Importance. — Butt rot, the Hedgehog Fungus Rot. — decay at the base of living trees, is the Hericium erinaceus (Bull.) Pers conks result of the invasion of one of a are 4 to 10 inches (10 to 25 cm), number of decay fungi (Polyporus globular, and occur singly or in spp., Hericium sp., and Pleurotus sp.) clusters. They are white, but yellow which enter the trees through with age, and have tooth-like projec¬ wounds. Fire wounds are the most tions pointing downward. This typical type. Data indicate that butt fungus is found mostly during the fall rot affects 29 percent of the white in butt hollows or where other open¬ oaks and 39 percent of the red oaks ings in the tree have developed (figure on loess and alluvial sites in the Mid¬ 52). south. It is the most serious cause of Polyporus Fungus Rot. — Poly¬ cull. porus fissilis Berk & Curt., produces Identifying the Fungi. — shelf-like, white, succulent conks 3 to Numerous fungi can cause butt rot; 8 inches (7.6 to 20.3 cm) wide, that however, five are responsible for yellow with age (figure 53). The lower about one-half of the identified cases. surface is made up of small pores. The following description will help to They usually appear during the fall or identify the most common fungi. winter.

Figure 52. — Hericium erinaceus conk. Figure 53. — Polyporus fissilis conk.

43 Varnish Fungus Rot. — Polyporus Oyster Fungus Rot.— Pleurotus lucidus Leys ex. Fr. produces conks 3 sapidus Kalchr. forms shelf-like conks to 10 inches (7.6 to 25. 4 cm) in size which are white to light grey. They and which appear yearly during the are soft and fleshy and may have a summer, usually near the soil line short stalk. Gill structures radiate (figure 54). The conks have a shiny, from the point of attachment on the reddish, hard upper surface; a short, lower surface (figure 56). Conks ap¬ stout stalk; and pores on the lower pear on living trees and slash during surface. The consistency is tough and most of the year except dry periods. woody. Identifying the Injury (figure 57). Sulfur Fungus Rot. — Polyporus — Conks, old wounds, hollows, ab¬ sulphureus Bull, ex Fries has conks 2 normal swellings or butt bulge in¬ to 12 inches (5 to 30 cm) wide. They dicate butt rot. Decayed wood may are soft, fleshy, moist, bright orange- be soft or brittle, and brown to white. red on the upper surface and red- The decay core may be small or in¬ yellow on the lower pore surface. The clude the entire heartwood. The core conks become hard, brittle, and white extends vertically from less than an with age. They appear singularly or in inch to several feet. Affected trees are clusters, usually during the fall (figure weak and subject to breakage. 55).

Figure 54. — Polyporus lucidus conk. Figure 55. — Polyporus sulphureus conk.

44 Biology. — Following tree wound¬ wound size, wood volume loss is ing, bacteria and non-decay fungi minimal when wounds are less than 4 flourish on the exposed woody years old. tissues, creating conditions for es¬ Control. — Because all infections tablishment of decay fungi. occur through bark wounds, injury Windborne microscopic spores prevention is the primary approach released for a few days to several to control. Severely decayed trees of weeks from conks on infected trees no value should be deadened. Con¬ germinate on wounds and penetrate sider early salvage for infected trees the tree. The decaying stage of the rot that have value because the lower, fungi follows and conks will be most valuable portion of the log is be¬ produced. The rate of decay varies ing decayed, with an increased with the tree species, fungus, and susceptibility to insect attack, wound size. Decay is most extensive windthrow and degrade from stain. when wounds are large; decay usually Repair valuable urban trees by does not develop in wounds less than removing the decay, treating the 2 inches (5 cm) wide. Regardless of cavity with a and filling it with a suitable material.

Figure 56. — Pleurotus sapidus conk. Figure 57. — Butt bulge indicates decay.

45 TOP ROTS

Importance.— Top rot results Biology. — The life cycle of heart from the invasion of the heartwood rot fungi, as top rots, is about the by many of the same fungi (Sterium same as was discussed for butt rots. spp. and Poria sp.) which cause butt The environment differs, thus some rot. The incidence of infection is different fungi are involved. Those similar to butt rot, but typically less. butt rot fungi which invade the roots However, the associated volume are not encountered and others, such losses are much less since this disease as Stereum sp., become more occurs in that part of the tree which is prevalent. not usually used for timber. Top rot 1 Control. — There are no mea¬ results in limb breakage, and thus sures for direct control of top rots. becomes important as a safety hazard Recognizing top decay and early har¬ in high use and urban areas. vesting of infected trees is the most Identifying the Fungi. — Three useful control method. Prevention of common top rot fungi, S. gausapatum injuries inflicted during could Fr., P. andersoni (Ell & Ev) Neuman help reduce top rot in growing stock. and S. subpileatum Berk. & Curt, In urban or high-use areas, early must usually be identified by cultural detection and appropriate removal of characteristics because conks rarely hazardous limbs should be carried are seen on dead branches. Others, out. such as Hericium erinaceus, Polyporus fissilis, Pleurotus sapidus and Polyporus sulphureus were described previously with butt rot fungi. Identifying the Injury.— The presence of broken limbs often in¬ dicates decay (figure 58). Examina¬ tion of the broken surface will con¬ firm its existence. Presence of branch scars alone indicates top rot. The in¬ cidence and amount of decay rise sharply with increased size and/or age of scars. The decay can be es¬ timated by judging the scar size and age in broad classes (table 1). Table 1. Expected length of decay in the main stem behind branch scars of oaks.

Diameter of branch scar inches • - - (cm) - - Age 1-3 4-6 7-10 (2.5-7.5) (10.2-15.2) (18-25) less than 1.2 4.8 30 15 years (3.0) (12.1) (76.2) more than 2.4 12 68.4 15 years (6.0) (30.4) (173.7)

46 ROOT ROTS CORTICIUM ROOT ROT, Corticium galactinum (Fr) Burt

Importance. — The fungus causes trees die. Trees may die in a growing root rot on many hardwoods and season and retain leaves until the conifers in the United States. It has a following year. Root damage can be wide host range and causes extensive observed by removing soil from damage to oaks growing on poor around the root crown. Trees may be sites. windthrown because of the root rot. Identifying the Fungi, (figure 59). — Biology. — The fungus can live as The white mycelial mat covers the a saprophyte on roots and stumps. root crown and roots. It can be de¬ The spread is caused by infected roots tected easily by removing the soil in close association with living roots. around the base of the tree. The fun¬ Insects also disseminate the fungus to gus produces a very inconspicuous healthy trees. fruiting structure that can be seen Control. — In intensively only with the aid of a microscope. managed plantations or in urban Identifying the Injury. — Thin forestry, remove dead trees to reduce crowns are the First symptoms usually spread to adjacent trees. Rate of observed. Some suckering and under¬ spread in soil is about 1 foot (0.35 m) sized leaves may appear before the per year.

Figure 59. — Mycelium of Corticium galactinum on oak seedling.

47 TEXAS ROOT ROT, Phymatotrichum omnivorum (Shear) Dug.

Importance.— Phymatotrichum readily detectable on young, newly omnivorum can cause root rot on established seedlings which may wilt many dicotyledonous plants in the and die suddenly. Southwest. Oaks planted on old farm Biology. — The fungus is soil- fields in reforestation projects or in borne and persists in the soil as subdivisions may become infected. sclerotia for many years. Infection Identifying the Fungus. — During occurs when mycelial strands cover warm, wet periods, the spore mat the root and enter between the may grow on the soil surface. Infected epidermal cells. The spores produced root surfaces are covered by a fluffy, on the mature mats rarely germinate yellowish mycelium which penetrates and their function in the spread of the the cortex (figure 60). Microscopic disease is uncertain. examinations show distinct cross¬ Controls. — Use soil amend¬ shaped hyphae by which ident¬ ments to increase soil acidity. The ification of the fungus can be made. fungus is not a serious pathogen in Identifying the Injury. — Diseased acid soils. The use of resistant plants, trees have a thin crown, top dieback such as monocotyledons, is recom¬ and poor vigor. The disease is more mended in areas that have a history of the disease.

48 SHOESTRING ROOT ROT, Clitocybe tabescens (Scop, ex Fr.) Bres, Vahl ex Fr. Importance. — Root rot trees may have low vigor. Roots may , C. tabescens and A. show various degrees of decay and mellea, cause major losses have rhizomorphs on the surface. throughout the United States. Frequently, root rot is evident only Windthrow of infected trees in urban on wind-thrown trees. The rate of and high-use areas contribute to the spread in the soil is about 1 foot (0.35 importance of root diseases. Ad¬ m) per year. ditional losses occur from loss of Biology. — The fungus can live in vigor. dead roots and stumps for many Identifying the Fungi (figure 61). years. Rhizomorphs spread through — In the fall, clumps of yellow the soil on infected roots near healthy mushrooms grow on the ground near roots that become infected. the tree and occasionally on the bole Mushrooms produce abundant several feet above the ground. Thin spores, but they are not important in black strands of mycelia infection of living trees. The fungus is (rhizomorphs) are produced on the most pathogenic on slow-growing root surface which resemble black trees. shoe laces. C. tabescens is a southern Controls. — Spread can be con¬ form of A. mellea. The mushroom trolled by removing the infected tree. has decurrent gills and produces Sterilize the soil before replanting. white spores. Any cultural practices that reduce Identifying the Injury. — Infected stress and increase tree vigor will prolong tree life.

Figure 61. — Clitocybe tabescens mushrooms on oak.

49 WILTS TEXAS LIVE OAK DECLINE, fagacearum (Bretz) Hunt

Importance. — “Live oak de¬ itial symptoms are chlorotic leaf mot¬ cline” is a major disease that kills tling, leaf browning, and defoliation thousands of high value live oaks an¬ (figure 62a). Later, the tree develops nually in Texas. Live oaks in small leaves, water sprouts, twig and Louisiana, Mississippi, and Florida limb dieback, and eventually the tree have shown symptoms similar to dies (figure 62b). Cankering fungi those observed in Texas. also cause dieback and death after Identifying the Fungus. — The trees are stressed by wilt. primary pathogen, C. fagacearum, Biology. — Live oak trees in can be identified by isolating it from Texas are infected by C. fagacearum, infected sapwood and through and develop initial symptoms mainly microscopic observation. Cultures during the spring and fall. The fungus are gray to tan and exhibit a fruity spreads through root grafts and by odor. Blunt, cylindrical microscopic insect vectors. Dieback from canker spores are produced. Black, flask¬ fungi develops mainly during the shaped fruiting structures may summer months. develop. Control. — Control procedures Identifying the Injury. — The in¬ are the same as for oak wilt.

50 OAK WILT, Ceratocystis fagacearum (Bretz) Hunt

Importance. — Oak wilt is the (figure 63a) defoliation, and eventual¬ most destructive disease of oaks in ly death (figure 63b). Defoliated the upper Mississippi Valley. Red leaves usually accumulate under af¬ oaks are affected more than the fected trees. The red oaks develop white. The disease can kill oaks symptoms over the entire crown rapidly and cause heavy losses. shortly after infection, but white Identifying the Fungus. — The oaks slowly develop symptoms in a fungus can be identified in the field few limbs at a time. by presence of fungal mats and Biology. — Oak wilt is favored by pressure cushions under the bark of moderate temperatures. The fungus infected trees. Identification can also will not grow at high temperatures. It be made by observing the fungus spreads for short distances through microscopically (see “live oak root grafts between infected and non- decline”). infected trees. Insects spread the dis¬ Identifying the Injury. — Symp¬ ease over long distances. toms are bronzing or browning of Control. — Kill infected trees green leaves from tips and margins with silvicides to reduce inoculum downward toward the leaf base and prevent root graft transmission.

51 CANKERS NECTRIA CANKER, Nectria galligena Bres.

Importance. — Nectria cankers, develops around the expanding caused by N. galligena, are frequently canker annually and bark sloughs off found on some oak species. These the older parts of the canker. After cankers are most important in trees several years, the annual concentric less than 20 years old. The canker can callus ridges on the cankers resemble girdle and kill young trees or make a target. them weak and subject to wind Biology. — The fungus overwin¬ breakage. ters as a saprophyte in cankers and Identifying the Fungus. — The produces spores for new infections fungus can be identified by the during the spring. Windblown and creamy-white fruiting structures that water-splashed spores infect tree appear on cankers soon after infec¬ wounds and branch stubs. Secondary tion. It can also be identified by the infections result from spores small, red, lemon-shaped perithecia produced on new spring cankers. near canker margins after 1 year. Control. — Cankers may be Identifying the Injury (figure minimized in high-value areas by not 64). — Well-defined localized areas pruning during wet weather, avoiding of bark, cambium, and underlying wounds, pruning out branch cankers, wood are killed by the invading and sterilizing pruning tools before fungus. A concentric callus ridge moving to an uninfected tree.

Figure 64. — Nectria canker.

52 BOTRYODIPLODIA CANKER, Botryodiplodia theobromae Pat.

Importance. — B. theobromae, bark to expose dead cambium. Old or can cause cankers and dieback in oak inactive cankers appear sunken and species over a wide geographical area. are surrounded by callus tissues. It is a potentially destructive Dieback is frequently caused by B. pathogen under certain adverse en¬ theobromae, but can be confused with vironmental conditions, especially if injury resulting from other diseases trees are somewhat stressed. or stress conditions (figure 65). Identifying the Fungus. — Black, Biology. — The biology of stromatic fruiting structures of the Botryodiplodia cankers in oaks is fungus develop on bark over the poorly known. However, the cankers cankers. However, microscopic ex¬ are favored by high temperatures. amination of spores is necessary for Cankers and dieback can develop correct identification. Mature spores rapidly in stressed trees. Fungal are dark, two-celled, and elongate. spores are spread by the wind and in¬ Identifying the Injury. — It is dif¬ sects. ficult to identify the canker by symp¬ Control. — Cankers can be toms alone. Therefore, the fungus minimized by preventing wounds, must be isolated and identified. Ac¬ pruning out cankered and dead limbs tive cankers on trees with rough bark to reduce inoculum, and maintaining can be detected only after removing tree vigor when possible.

Figure 65. — Botryodiplodia canker, including cross section.

53 HYPOXYLON CANKERS, Hypoxylon spp.

Importance. Hypoxylon cankers affect most oak species in North America. Both H. atropunctatum and H. mediterranium have been reported in oaks. They af¬ fect mainly trees that have been stressed by wilt, drought, construc¬ tion damage, or other injuries. Limbs and boles weakened by Hypoxylon spp. can be a safety hazard in high- use areas. Identifying the Fungus (figure 66). — Hypoxylon spp. can be identified by the light-to-dark-colored crusty fungus tissue (stromata) over the cankered area. Numerous small black fruiting structures are embedded in the stromata. Identifying the Injury. — Bark sloughing and decay are associated with Hypoxylon cankers. Affected trees are subject to wind breakage. Biology. — The fungus infects stressed trees through wounds and either produces a canker or quickly kills the tree by colonizing the sapwood. Fruiting structures develop on the cankers and are discharged into the air and spread to new infection sites. Hypoxylon cankers are generally secondary to some other disease or stressing condi¬ tion in trees. Control. — Remove cankered limbs before they fall on someone, and to reduce the amount of in¬ oculum for new infections. Maintain tree vigor and avoid wounding and stubbing of branches to minimize conditions favoring cankers. Figure 66. — Hypoxylon canker, including close-up view.

54 LEAF DISEASES ANTHRACNOSE, Gnomonia quercina Kleb = Gloeosporium quercinum West

Importance.— Severely affected leaf most frequently along veins. Af¬ oaks may be defoliated by midsum¬ fected leaves often appear scorched, mer, which reduces growth, and may curl or twist and drop from predisposes trees to other diseases the tree. Infrequently, cankers on and makes the trees unsightly. White small twigs and dieback can occur. oaks are most severely affected. Biology. — The fungus overwin¬ Anthracnose does not result in major ters in dead leaves. Spores losses in forests. (ascospores) are windblown to the Identifying the Fungus.— Black, new, expanding leaves and shoots. dot-size, cushion-like, fruiting bodies Another spore type (conidia), which form on necrotic tissue where spores reinfects other leaves or shoots, is are produced. A beaked, flask¬ then produced. shaped, fruiting structure can be Control. — Collect and dispose found on overwinter leaves. of fallen leaves and twigs. Remove Identifying the Injury (figure unneeded branches to increase air 67). — Round to irregular, light- movement. Fertilize to increase vigor brown to black areas appear on the and use fungicide sprays.

Figure 67. — Oak anthracnose. including close-up view.

55 LEAF BLISTER, Taphrina caerulescens Tul.

Importance. — Because most of and vary in color from yellow to pur¬ the affected leaves remain on the tree, ple. The leaf is depressed on the oak leaf blisters do not cause losses corresponding lower surface. under forest conditions. Affected Biology. — Spores (ascospores) trees may appear unsightly, but there of the fungus are produced on the is little damage. surface of the blisters. The spores are Identifying the Fungus.— The carried by the wind to bud scales mycelium occurs intercellularly in the where they remain over winter. In the leaf tissue. Dome-shaped, spring when the buds are expanding, microscopic, fungus cells are formed the fungus enters the leaf through the beneath the cuticle, usually on the up¬ natural leaf openings (stomata) and per leaf surface. The distal cell the cycle is complete. becomes the sac (ascus) in which Control. —- Collect and dispose eight ascospores are formed. of leaves. Plant or manage for resist¬ Identifying the Injury (figure oak such as pin and Shumard. 68). — Affected leaves develop many Properly timed fungicide sprays can blisters on the upper surface. The control this fungus. blisters are round, raised, wrinkled

Figure 68. — Oak leaf blister.

56 ACTINOPELTE LEAF SPOT, Actinopelte dryina (Sacc.) Hoehn.

Importance. — Actinopelte leaf spots develop along the leaf veins. spot can reach epidemic proportions The spots are normally surrounded and cause major loss of foliage. by light brown areas and may merge Growth losses, increased stress on the to kill large areas of the leaf in late tree and unsightly conditions result. summer. Small twig cankers may be Overall, the disease normally remains formed. endemic and causes foliage loss only Biology. — The fungus overwin¬ in the fall, with no subsequent effect. ters in the affected twigs and foliage. Identifying the Fungus.— Small, Spores of the fungus are spread by brown, dot-like fruiting bodies are wind and rain-splash the next grow¬ formed on the necrotic tissue. Spores ing season. are elliptic and clear or colorless and Control. — Collect and dispose can be microscopically observed by of fallen leaves. Remove unneeded crushing a fruiting body. branches to increase air movement. Identifying the Injury (figure Fertilize to increase vigor and use 69). — Round to irregular, red-brown fungicide sprays.

Figure 69. — Actinopelte leaf spots, including close-up view.

57 LEAF RUST: FUSIFORM RUST and EASTERN GALL RUST, Cronartium fusiforme quercuum (Berk) Miyabe Hedge & Long and C.

Importance.— In forest stands seldom affected. these diseases are of minor impor¬ Biology. — Leaf rusts require two tance on oak (alternate host). hosts to complete their life cycle. However, they affect the aesthetic Fungus spores (aeciospores) value of shade trees and ornamentals. produced on pine galls are Fusiform rust on pine (primary host) windblown and infect young oak is the most important disease of pine leaves. Spores (urediospores) are in the Southeast. produced on the oak leaf which re¬ Identifying the Fungi (figure infect oak. Spiny-like hairs (telial 70).— Both fungi develop brown, columns) on the lower oak leaf sur¬ bristly spine-like structures on the un¬ face release teliospores which derside of the oak leaf. produce another spore stage Identifying the Injury.— Small (basidiospore) that infects pine. This yellow spots develop on the leaf sur¬ infection results in a gall with faces in spring. Some defoliation may aeciospores, and the cycle is com¬ occur. Red, water and willow oaks pleted. are primarily affected. White oaks are Control. — No control needed.

Figure 70. — Rust telial columns on oak leaf, including close-up view.

58 SEEDLING DISEASES

DAMPING-OFF, Cylindrocladium spp.

Importance.— Soil-inhabiting radicle (pre-emergence damping-off). fungi such as Fusarium, Cylin¬ Seedlings may remain stunted (post¬ drocladium, Rhizoctonia, Pythium and emergence damping-off). Phytophthora species cause heavy Biology. — The fungi are mostly losses (25 to 50 percent) in pre- and soilborne and remain inactive in the post-emergence seedlings. Fungi at¬ absence of a host as chlamydospores tack the young developing radicles or sclerotia. The presence of host killing seedlings 30 to 45 days after roots stimulates the fungus, which the seedlings emerge. grows over roots and penetrates the Identifying the Fungus.— The epidermis and cortex. Cylindro¬ pathogens involved are minute and cladium spp. also produce airborne can be identified only by the use of a conidia which may cause leaf spots microscope. Tentative identification and defoliation. can be made by cultural charac¬ Control. — Grass cover crops teristics. Cylindrocladium spp. are the will reduce the inoculum potential; most important pathogens in however, clover and other hardwood nurseries. leguminous cover crops increase the Identifying the Injury (figure pathogen. Do not apply nitrogen fer¬ 71). — The first symptom is failure of tilizer until 45 days after the seedlings seedling emergence. The seed may rot emerge. or seeds may have a dead or damaged

Figure 71. — Damping-off of oak seedlings.

59 PHANEROGAMS

MISTLETOE, Phoradendron spp.

Importance.— Branches beyond Biology. — The sticky seeds are the mistletoe infection may be stunt¬ spread by birds and . The ed and even die. Trees usually are not seeds lodge on young branches, ger¬ killed. However, in heavy infections minate, grow into the young branch on water oak, trees may decline and and produce a mistletoe plant. be killed. This true mistletoe is used Control. — Control is normally for Christmas greens. not needed but mistletoe can be con¬ Identifying the Causal trolled by removing it and cutting (figure 72).— Leafy, evergreen tufts branches at least 1 foot below the in¬ of perennial shoots with dark green, fection point. leathery leaves occur as bunches on branches of oaks. The plant is opposite-leaved and the stems are rounded and jointed. The flowers are inconspicous. White to red berries are produced in the fall. Identifying the Injury.— The most conspicuous sign of the disease is the presence of the parasite. The af¬ fected branch may be slightly enlarged and multiple infections may result in tree decline. Excess shading of tree leaves by large mistletoe plants produces dieback and decline.

Figure 72. — Mistletoe infection, including close-up view.

60 CHEMICAL DAMAGE, AIR POLLUTION, PESTICIDES AND OTHER CHEMICALS

Importance.— The total impact Because of great variation of of chemical damage is unknown. susceptibility among trees and the Large losses have occurred in very combination of chemical and climatic localized areas. The losses normally factors, diagnosis is complex. Thus, can be traced to a point source such proper diagnosis may require a per¬ as a chemical spill or industrial waste. son with extensive training and ex¬ Not as easily recognized but perhaps perience. more damaging are the non-point Control. — Protect from source pollutants such as those chemicals or plant resistant trees. associated with a large city. Many oak species decline, dieback and suc¬ cumb over a period of years. On the other hand, some oak species are relatively resistant to many pollutants and are not affected. Identifying the Causal Agent.— Chemicals can arrive at the tree in a variety of forms through the air or soil. Several conditions must occur to cause damage. There must be a susceptible host in a receptive condi¬ tion, and the chemical must arrive in a quantity and form that will affect the host. Some chemicals damage on contact, others interact with tree processes. Identifying the Injury (figure 73).— Most chemicals have certain characteristic symptoms. Ozone causes small bleached or pigmented spots on the upper leaf surface. Sulfur dioxide kills some areas between the leaf veins. Fluoride kills tissue on the leaf margin or between the veins. Ammonia causes faded leaf margins and dead or dying tissue with green islands mostly near veins. Herbicides cause blotchy dead areas on the sur¬ face of mature leaves; expanding leaves curl and become distorted.

Figure 73. — Chemical damage — due to ammonia.

61 MINOR DISEASES Disease Agent Injury Control* Leaf spot, Septoria spp. Small round spots with straw- 4 The fungus overwinters on dead colored centers may be numerous; 5 leaves; spores are wind disseminated (figure 74); red oaks are preferred; 14 to young leaves in the spring. defoliation may result in growth loss, 15 but no mortality.

Powdery mildew, Microsphaera White, powdery mold patches on 5 alni and Phllactinia guttata. leaves and buds (figure 75); leaves 15 These fungi overwinter on dead may be distorted, stunted and leaves and their spores are spread by dropped prematurely. the wind to healthy leaves.

Twig canker, Dothiorella quercina. The fungi overwinter on dead Small sunken branch cankers and 8 tissues; in the spring, spores are wind twig dieback (figure 76). 14 disseminated to wounds and twigs. 15

Spot anthracnose, Elsinoe, Very small spots on leaf upper 5 quercus - falcatae. The southern red surface starting about mid-summer. 15 oak is preferred host; spreads by wind disseminated spores.

Smooth patch, Aleurodiscus Often regarded as a threat to stand oakesii (figure 77).The fungus by owner, but it is of minor impor¬ survives on the bark surface and tance; control rarely needed. releases spores which continues its spread.

Iron-deficiency chlorosis Yellow-green discoloration 16 (figure 78); iron deficiency may be a between veins; leaves may curl, turn common problem with pin and brown along margins and between willow oaks in some of the less acid veins. soils.

*See CONTROLS page 66.

62 Figures 74-78.— ( 74) Septoria leaf spot; (75) powdery mildew; (76) twig canker; (77) smooth patch; (78) iron-deficiency chlorosis.

63

PESTICIDES

EPA-registered chemicals for control of insects and diseases that attack oaks. (See labels for dosages and application methods.)

INSECT INSECTICIDE INSECT INSECTICIDE Bacillus thurin- Slug oak sawfly Carbaryl Elm spanworm giensis Pyrethrin Carbaryl Oak leafroller Carbaryl Bacillus thurin- Diazinon Fall cankerworm giensis Oak leaftier, Spring canker- Carbaryl Solitary oak Carbaryl worm Naled leafminer, Malathion Acephate Gregarious oak Diazinon Linden looper Methoxychlor leafminer Naled Oak skeletonizer Carbaryl Orangestriped Carbaryl oakworm Chlorpyrifos Insect borers Lindane Pinkstriped Methoxychlor Carbon disulfide oakworm Naled Carbaryl Spiny oakworm Oak leaf aphids Diazinon Malathion Yellownecked Chlorpyrifos Giant bark aphids caterpillar Acephate Carbaryl Carbaryl Malathion and Acephate Forest tent Gardona Oak lacebug mixtures caterpillar Dylox Lindane Methoxychlor Chlorpyrifos Carbaryl Bacillus thurin- Periodical cicada giensis Lecanium scales Carbaryl Carbaryl Pit scales Diazinon Gypsy moth Methoxychlor Kermes scales Malathion Acephate Obscure scale Methoxychlor Gardona Dicofol Variable oakleaf Carbaryl Diazinon Spider mites caterpillar Malathion Malathion Naled

65 PESTICIDES, (continued)

EPA-registered chemicals for control of insects and diseases that attack oaks. (See labels for dosages and application methods.)

FUNGI FUNGICIDE FUNGI FUNGICIDE~

Powdery miidew Benomyl Phymatotrichum Lime sulphur Corticium root rot Septoria leaf spot Ferbam Polyporus lucidus Actinopeltes Captan Sterum Dothiorella quercina Benomyl Irpex canker Lime sulphur Elsinoe falcatae Zineb Poria canker Anthracnose Copper (metallii Nectria canker Benomyl Copper (metallic) Botryodiplodia plus methoxy- Leaf blister Captan chlor Ferbam Captan Damping-off Fusiform rust Ferbam Clitocybe root rot Captan Eastern gall rust Oil plus lime Armillaria root rot Dexon sulphur

CONTROLS Controls for insects and diseases presented in table form

1. Natural controls often adequate. 9. Mechanically “worm-out” with 2. Place sticky bands around trunk. knife and wire. 3. Prune infected twigs and destroy. 10. Wrap trunk of newly 4. Rake fallen infected leaves and transplanted trees. destroy. 11. Control with chemical insecticide 5. Maintain high tree vigor with 12. Control with biological cultural practices. insecticide. 6. Open-grown trees most 13. Control with gallery fumigation. susceptible; maintain good 14. Remove and burn diseased stocking. materials from the tree and area. 7. Identify and remove brood trees. 15. Control with chemical fungicide. 8. Prevent or minimize injuries. 16. Control with iron chelate.

66 ACKNOWLEDGEMENTS

We are grateful to the following We also thank the following for for reviewing the list of proposed photographs or specimens for mak¬ pests and/or portions or all of the ing photographs of some pests: Ron manuscript: Vern Ammon, Mis¬ Baer, SEA, Stoneville, Miss.; L. Bar¬ sissippi State Univ., Mississippi ber, USDA For. Serv., Asheville, State, Miss.; Ron Baer, USDA N.C.; M. L. Dix, USDA For. Serv., Science and Education Administra¬ Bottineau, N.D.; A. T. Drooz, tion (SEA), Stoneville, Miss.; F. H. USDA For. Serv., Research Triangle Berry, USDA For. Serv., Delaware, Park, N.C.; John Gant, USDA For. Ohio; A. T. Drooz, USDA For. Serv., Asheville, N.C.; R. D. Gass, Serv., Research Triangle Park, N.C.; Missouri Dep. Conservation, Jeffer¬ G. F. Fedde, USDA For. Serv., son City, Mo.; William Hoffard, Athens, Ga.; W. H. Kearby, Univ. of USDA For. Serv., Asheville, N.C.; J. Missouri, Columbia, Mo.; M. F. A. Payne, SEA, USDA, Byron, Ga.; Laster, Delta Branch Exp. Stn., Mis¬ H. E. Williams, Agric. Extension sissippi State Univ., Stoneville, Miss.; Serv., Univ. of Tenn., Knoxville; S. J. R. McGraw, Agr. Ext. Serv., Jarrett, USDA For. Serv., Delaware, North Carolina State Univ., Raleigh, Ohio; E. E. Simons, N.C.; W. R. Phelps, USDA For. Dept. Environmental Resources, Serv., Washington, D.C.; W. J. Stam- Middletown, Pa.; R. F. Tallerico, baugh, Duke Univ., Durham, N.C.; USDA For. Serv., Broomall, Pa.; J. F. M. Stephens, Univ. Ark., Fayet¬ R. Cook, Mississippi For. Commis¬ teville, Ark.; F. H. Tainter, Univ. sion, Jackson, Miss.; J. C. Nord, Ark., Fayetteville, Ark.; E. P. Van USDA For. Serv., Athens, Ga. Arsdel, Texas A & M Univ., College Station, Tex.; E. F. Wicker, USDA For. Serv., Washington, D. C.

67 INDEX

INSECTS Page Page Aphids, giant bark .. 36 Mites, spider . 36 Aphids, oak leaf. 29 Oak skeletonizer . 13 Beetle, Columbian timber . 22 Oakworm, orangestriped . 4 Borer, beech . 26 Oakworm, pinkstriped. 14 Borer, broadnecked root . 25 Oakworm, spiny. 14 Borer, flatheaded appletree . 26 Phylloxerids, oak . 28 Borer, oak branch . 26 Sawfly, slug oak . 9 Borer, oak clearwing. 17 Scale, kermes. 36 Borer, oak-stem . 26 Borer, pin-hole . 23 Scale, lecanium . 32 Borer, red oak . 18 Scale, obscure . 36 Borer, spotworm . 26 Scale, pit . 36 Borer, twolined chestnut . 20 Spanworm, elm . 2 Borer, white oak. 19 Spider mites. 36 Borer— Tilehorned prionus .. 25 also see Tilehorned prionus Timber beetle, Columbian . 22 and Twig pruner, Little Timberworm, oak . 21 carpenterworm, Carpenter- Twig pruner. 24 worm, Oak timberworm, Columbian timber beetle Walkingstick . 10 Bug, oak lace. 30 Weevil, acorn . 35 Weevil, Asiatic oak . 14 Cankerworm, fall. 3 Cankerworm, spring. 14 Carpenterworm . 16 DISEASES Carpenterworm, little. 26 Actinopelte leaf spot . 57 Caterpillar, forest tent . 7 Anthracnose . 55 Caterpillar, variable oakleaf. 5 Anthracnose, spot . 62 Caterpillar, yellownecked . 6 Blister, leaf. 56 Cicada, periodical . 31 Canker, Botryodiplodia. 53 Gall, gouty oak. 33 Canker, Hispidus. 40 Gall, oak-apple. 34 Canker, Hypoxylon . 54 Grubs, white . 36 Canker, Irpex . 42 Gypsy moth . 8 Canker, Nectria . 52 Lacebug — see Bug Canker, spiculosa . 41 Leaf galls—see Gall Canker, twig . 62 Leafminer, gregarious oak . 12 Corticium root rot. 47 Leafminer, solitary oak . 12 Damping-off . 59 Leafroller, oak . 11 Decline, Texas live oak. 50 Leaf skeletonizer— Hedgehog fungus rot . 43 see Oak skeletonizer Leaftier, oak . 14 Iron deficiency . 62 Locusts — see cicada Leaf spot. 62 Looper, linden . 14 Leafspot, Actinopelte. 57

68 INDEX, (continued)

Page Page Mildew, powdery. 62 Shoestring root rot . 49 Mistletoe . 60 Smooth patch . 62 Oyster fungus rot . 44 Stereum fungus rot .46 Polyporus fungus rot . 43 Sulfur fungus rot . 44 Poria fungus rot . 46 Texas root rot . 48 Rust, eastern gall . 58 Varnish fungus rot.44 Rust, fusiform. 58 Wilt, oak. 51

69 CAUTION

Pesticides used improperly can be injurious to man, animals, and plants. Follow the directions and heed all precautions on the labels. Store pesticides in original containers under lock and key — out of the reach of children and animals — and away from food and feed. Apply pesticides so that they do not endanger humans, livestock, crops, benecial insects, fish, and wildlife. Do not apply pesticides when there is 1 danger of drift, when or other pollinating insects are visiting plants, or in ways that may contaminate water or leave illegal residues. Avoid prolonged inhalation of sprays or dusts; wear protective clothing and equipment if specified on the container. If your hands become contaminated with a pesticide, do not eat or drink until you have washed them. In case.a pesticide is swallowed or gets in the eyes, follow the first aid treatment given on the label, and get prompt medical attention. If a pesticide is spilled on your skin or clothing, remove clothing im¬ mediately and wash skin thoroughly. Do not clean spray equipment or dump excess spray material near ponds, streams, or wells. Because it is difficult to remove all traces of herbicides from equipment, do not use the same equipment for insecticides or fungicides that you use for herbicides. Dispose of empty pesticide containers promptly. Have them buried at a sanitary land-fill dump, or crush and bury them in a level, isolated place. NOTE: Some States have restrictions on the use of certain pesticides. Check your State and local regulations. Also, because registrations of pesticides are under constant review by the U.S. Department of Agriculture, consult your State forestry agency, county agricultural agent or State exten¬ sion specialist to be sure the intended use is still registered.

U.S. DEPARTMENT OF AGRICULTURE