Aid L The Yellw-Ppla Lef-inn Wevi Bulti2 A Gueto Reonto and Juy19 Alaam Exeiet AuunUiest Agiulua tto aiS CONTENTS INTRODUCTION ....................... METHODS ............................... RESULTS.............. ................................... ~.1 .2 ................................................... ..... .2 ................................................... Life Stages ............................. Damage and Symptoms of Attack Life History and Seasonal Cycle.. SUMMARY .............................. REFERENCES.......................... FIRST PRINTING .2 .3 .4 11 13 2.5M, JULY 1994 Information contained herein is available to all persons without regard to race, color, sex, or national origin. THE YELLOW-POPLAR LEAF-MINING WEEVIL A Guide to Recognition and Habits in Alabama L.L. HYCHE 1 INTRODUCTION The yellow-poplar leaf-mining weevil 2 occurs throughout much of the eastern United States from Massachusetts west to Michigan and Missouri and south to the Gulf of Mexico(]). Yellow-poplar (Liriodendron tulipifera L.), also known as tuliptree, is its most common host, and the weevil's range corresponds closely with the natural distribution of the tree. Magnolias (Magnolia grandiflora L., M. virginiana L.) and sassafras [Sassafrasalbidum (Nutt)] also are listed as hosts(],2). Weevil adults and larvae feed on and destroy foliage of host trees. Historically, infestations in natural hardwood forests have been localized, and the weevil has not been considered a threat to yellow-poplar timber. However, some serious outbreaks have been recorded. During the 1960s, several outbreaks caused serious loss of foliage on yellow-poplar in the Ohio River Valley and Appalachian Mountain regions(]). In Alabama, yellow-poplar is a valuable timber tree and a prized ornamental. Since the mid-1980s, localized infestations of the weevil have been observed periodically on yellow-poplar shade and ornamental trees in some areas of east-central Alabama(3). Infestations of greatest concern have been those occurring on young yellow-poplars transplanted into the urban and suburban landscape. Damage to foliage of these trees reduces their ornamental value and may affect survival. Consequently, research was conducted to determine the life history and habits of the yellow-poplar leaf-mining weevil on ornamental trees in the urban/suburban forest. 'Associate professor of entomology. 2 Odontopus calceatus (Say). Order Coleoptera, Family Curculionidae. No standardized common name has been established for O. calceatus. Yellow-poplar leaf-mining weevil is a name in common usage locally. ALABAMA AGRICULTURAL EXPERIMENT STATION :METYHODS Studies wAerc catrried out in Aubuirn duringi 1989-91I onyNellox -poplar shade trees and youngc ornamental yellowpoplars transplanted alonis a parkwAay. Trees were inspected daily or everyv ether day beg innins in F-ehruar\ prior to budbreak and conti nuing util lea\ es appeatred. When leav es began to appear. trees wAerc inspected dailI orevidence of emercence of 0\ et 'Ai teri nc adult w ccxil s and fot the stat ot teeding. tmatitng, atnd oviposition (egg layinc . Habits of eg la inrg females wAere noted. atid the oxiposition site and tiumher of eggs laid per site xx Cre recorded. Leav es contatining eggas of knowxn age wxere exaintted dailIy to detetrmine timte of hatch atnd start (ot larx al feedinuc. Fol loxxwing egg hatch, inf Iested leax es wAetc examined at one- to three-day itntervxaks to deter mine larxval habits and dex cloptietttimetid site ol pupattiti. and ti me of emetrcetice of niew adulIts. All ife stages of the wxee\ il wxere collected anad identiflied. sx mptoms of attack and ty pes of leat damace wAetc recorded. and lifIc habits and seasonal ~cketc deici mitied. x I Photo 1. Adult 0. calceatus just emerged from hibernation. Photo 2. Eggs in midrib of yellow-poplar leaf. The end-to-end, stackedarrangement is typical. R ES ULTS 4 T he adult ,cbril is ".. Li/e .Stages 'A ccxii (ph~oto Ii) .5 tun to 3.9 nu is I debug- Photo 3. Full-grown larvae in larval mine. Note conspicuous black strands of excrement extruded by larvae. anid 1.4 tut to 2.4 mm 'Aide. Most specimlens are black wxith dark broxwnt atitennal secments. tatrsi. and mouthparts. Speimen I rom southern areas Irequently hax e ... tarsi andi~ antetinal segmuenits yel loA. The anitentual club is usually dark broA i or black(l ") (NOTE-: One inichi eqluals 25.4 mm.) THE YELLOW-POPLAR LEAF-MINING WEEVIL Weevils collected in east-central f it this description. Alabama generali They arc shiny to dull hilack w~ith li ~ht tan to y ellow\ish tar si (feect). The basal one-halt to twko-thirdls ol the f irst antennal segment and the antennal ci ub are dark browsn to black, and the sements e*ht in betwe en arc yelilowsi sh to li tan. Adults collected in L cc County, werie 34 mmn long. Eggs~ (Photo 2) are oh long os al. yellowsish to crcam in coior. and 0.6-0.7 mmn lon-. Then are laid cnd-to-end in a rows in the midihu of the ceaf. Larx ae (Photo 3) arc tnind in mine bets een leaf surtfaccs. The \ arc flathitish w5ith li ght tened. legless. and %k tan head capsules. Mean length of lullc~rossn larvae collected locally ssas 6 mm. Cocoons (Photo 4) arc spherical. 3.5-4.5 mmn (mean 4.1 mini) in diameter reddish brownii and loosely sso05en. Iat vac pupate in the cocoons iniside larv5al C mines. Pupae (Photo 5) arc 55ite and 3usual ly i sible 4 mmn long. They airc ss ithin the loosel wsos en cocoons. Damage and Symptoms of Attack Damage to f oliace is caused hs ado its feeding on ecat surf aces, h) females os ipositing in leat midribs. and by larvae minin wsithin leav es. In the spring, 05 erwsinti in g aduits emnerge from hibernation and Ieol on stipules Photo 6) and ness leases ( Photo 7, p. 6). Feeding si en on these structures es il activ5its. These sienmals the start ot ss adults Iced on the undci sortace of leas es. remos ing small cir culai to ohiong patches of tissue. Feeding- sites may he scattered os er thle lea! area hut commoniy are in the inici oiotthe leaf, Photo 4. Spherical cocoons constructed by larvae in which to pupate. 'r Photo 5. Typical weevil pupa. Ilk Photo 6. Adult feeding sign on stipules of yellow-poplar. ALABAMA AGRICULTURAL EXPERIMENT STATION often near the midrib (Photo 7). Subsequently, leaf tissue remaining on the upper surface at feeding sites turns orange-tan (Photo 7), then brown, and disintegrates, leaving holes where feeding occurred. These damaged leaves (Photo 8, p. 6) may persist until leaf drop in fall. Female weevils damage leaves by laying eggs in the leaf midrib (photos 9, p. 6; 17, p. 11). Midrib tissue at the oviposition site dies and turns brown (Photo 9). Weakened midribs often break, causing leaves to fold over at the oviposition site (Photo 10, p. 6). Some broken leaves may persist as such until leaf drop in the fall; others may be torn by wind action and remain on trees as ragged leaf stubs (Photo 11, p. 6). Larvae destroy leaves by mining between leaf surfaces (photos 12A-C, p. 7). There is usually one mine per leaf, but occasionally there may be two (Photo 12B). Heavily mined leaves may die and drop. Partially mined leaves may persist as ragged leaf stubs until fall (Photo 11). New-brood adults feed on leaf surfaces, with feeding usually beginning at or near leaf margins in the apical area of the leaf blade (Photo 13, p. 10). Feeding is primarily on the lower surface, but new adults also have been observed feeding on the upper surface. Damage by new-brood adults is more extensive than that caused by parent adults, and large areas of leaf or entire leaves may be killed (Photo 14, p. 10). Overall, weevil damage can result in serious reduction in the aesthetic value of shade and ornamental trees. Young transplants in urban and suburban areas may be particularly vulnerable to injury. With sufficient loss of foliage, growth may be retarded, twig and shoot die-back may occur, and form and survival of trees may be affected. Life History and Seasonal Cycle Yellow-poplar apparently is the primary host of the yellow-poplar leafmining weevil in Alabama. During the course of the study, no evidence of feeding or egg-laying was found on magnolias or sassafras growing in the vicinity. The weevil overwintered as an adult hibernating in trash or litter near and around host trees. In each year of the study, overwintering adults became active only after leaves on yellow-poplar began to appear. In the Auburn vicinity, appearance of host leaves was first noted on March 1, 1989; February 27, 1990; and March 4, 1991. The seasonal cycle and primary periods of development and activity of the weevil are presented in Figure 1. In 1989, emergence of overwintering adults was first detected March 14, two weeks after start of leaf development. Sign of feeding by adults on stipules and leaves (photos 6, 7) was first found on March 17. Mating was first observed on March 24, and the first evidence of oviposition was detected on March 26. Weevils were first found in 1990 on March 12, and in 1991 on March 24 - 14 and 20 days, respectively, after start of leaf development. Adult feeding sign was observed on these same dates, and sign of oviposition was detected two days later. THE YELLOW-POPLAR LEAF-MINING WEEVIL Overwintered® adults I 1989 I 1990 L Eggs 1991 Larvae Cocoons/pupae New-brood adults I I I I I I 1 10 20 1 10 20 April March I 1 I I 10 20 May 1 10 20 June 1 10 July Figure 1. Seasonal activity of the yellow-poplar leaf-mining weevil in east-central Alabama, 1989-91. The shaded section of each bar represents the major activity period for each stage. Unshaded portions represent a period of declining activity with weevil stages present only in low numbers. Larvae and pupae present late in this latter period apparently did not reach adulthood; no new-brood adults were observed in the field beyond dates indicated. Overwintered adults were common through April into the first week of May each year. Thereafter, weevils were scarce, but a few were observed occasionally on foliage into late May in 1990 and 1991 and early June in 1989. The period of parent adult activity overlapped the start of activity of new-brood adults. The principal period of oviposition was late March through April. Egg laying diminished noticeably in May, but some occurred as late as May 18, 1991; May 23, 1990; and June 9, 1989. Eggs were deposited in a section of the leaf midrib on the undersurface of the leaf. Commonly, there was only one group of eggs per leaf, but two groups were found on a few leaves. Midrib diameter, or some midrib characteristic indicated by diameter, was a factor in selection of sites for oviposition on yellow-poplar. Locations of oviposition sites by leaf size and midrib diameter were obtained for 82 leaves. In all cases, oviposition occurred exclusively where the midrib diameter at the base of the egg-laying site was 1.1-1.7 mm (Figure 2, p. 8). On 82% of the leaves, diameter of the midrib at the point where oviposition began was 1.3-1.5 mm. Distance from the base of the leaf blade to the site of oviposition varied with leaf size (Figure 3, p. 9). On the smallest leaves (mean length of midrib 41 mm), the mean distance from base of midrib to point of oviposition was 10 mm and diameter of the midrib was 1.35 mm. Distance to ALABAMA AGRICULTURAL EXPERIMENT STATION - ail. "* ri A? V Mme- A--vt 1 \ :*4 iy Photo 7 (top left). Newly emerged overwintering adults and typical damage caused by their feeding on the lower leaf surface. Photo 8 (top right). Leaf in midsummer with holes resulting from adult feeding on the undersurface in spring. Photo 9 (center left). Section of leaf midrib damaged by the egg-laying female. Photo 10 (center right). Leaf broken at oviposition site. Some broken leaves may remain on trees until fall. KE" ' T" ~C- -- T-~PII*CI~- qlt--fi~ si:,. Photo 11 (left). Ragged leaf stub retained on tree. Such stubs are the result of weathering which tears away portions of leaves damaged by oviposition, larval mining, or new-brood adult feeding. THE YELLOW-POPLAR LEAF-MINING WEEVIL the oviposition site increased progressively with increase in leat size, with all sites located in the area where midrib diameter at the base of the site was within the 1.1- to 1.7-mm range. In the ovipositional process(3). the female usually partially sexered the midrib at a point basal to where eggs were to be deposited (photos 15. 17: p. I 1. She then positioned herself on the midrib with her head toward the base of the leaf. She punctured the midrib with the her snout (Photo 15). xithdre snout, reversed her position to face the leaf apex. and deposited eggs into the puncture (Photo 16). The process was then repeated, moxing toward the apex Photo 12A. Leaf mine initiated by firststage larvae; usually the first visible evidence indicating hatch of eggs. of the leaf. Egg laying killed midrib tissue. Length of the dead section of midrib measured in 84 leaxes ranged from 3.5-10.5 mm with a mean ot six mm. 5c The number of egg punctures (Photo 17) per oxiposition site varied trom one to 10. with tour punctures being the most common (Figure 4. p. 10). The number- of eggs per puncture varied from zero to three, but 66% of the punctures contained two eggs each. Photo 128. Two larval mines from a single group of eggs; occurs only occasionally. When two or three eggs were present in a puncture. eggs were stacked one atop the other(Photo 2). The maximum nuin ber ot eggs tound at any oviposition site in this study was 19. However, one leaf examined contained 21 larvae. ini' . e dicating the possible deposition of 21 eggs. Sixty-six percent of the oviposition sites contained five to nine eggs. Egg hatch was indicated by the I appearance of larval mines in leaf tissue at the edge ot the oviposition site (Photo I2A). Larval mining was first observed in the field on April 5 in 1989. Photo 120. Mined leaf typical of late-stage larvae. ALABAMA AGRICULTURAL EXPERIMENT STATION 10 days after first oviposition was recorded; March 29 in 1990, 15 days after first oviposition; and April 5 in 1991, 10 days after first oviposition (Figure 1). However, duration of the period from oviposition to start of larval mining varied with the season, apparently an influence of weather conditions. Actual dates of oviposition and start of larval mining were recorded for 55 individual groups of eggs laid from mid-March to mid-May. The period from oviposition to hatch varied from 4-17 days. Among 17 groups of eggs laid between March 14 and April 15, larval mines appeared in 8-17 days (mean 12.4). Among 38 egg groups laid between April 16 and May 17, mining appeared in 4-9 days (mean 6.5). Larvae fed in groups in a common mine (Photo 3). There was usually only one mine per leaf (photos 12A, 12C), but occasionally there were two (Photo 12B). The number of larvae per leaf varied greatly, ranging from 1-21 among 120 leaves examined. Larvae mined extensively, often destroying much of the leaf area (Photo 12C). As development progressed, mines became inflated, and were partially filled with dark, continuous strands of excrement extruded by the larvae (Photo 3). Fully grown larvae constructed spherical, reddish-brown cocoons (Photo 4) and pupated in larval mines (Photo 5). Cocoon formation was first noted April 28, Number of oviposition sites 3531 30 2520 15 10 5 20 2 1.0 1.1 1.2 1.5 1.6 1.3 1.4 Diameter of midrib (mm) 1.7 1.8 Figure 2. Relationship of midrib diameter to location of oviposition sites. THE YELLOW-POPLAR LEAF-MINING WEEVIL Mean distance from midrib base to oviposition site (mm) 35 n=14 30 n = 12 0 midrib mean diam. =1.40 mm 2520 20 n = 23 midrib mean diam. =1.32mm 15-n2 10 15 n=13 n=20 _ midrib midrib mean diam. 1.41 mm 0 midrib _mean diam. =1.35 mm mean diam. =1.36 mm 5 0 35 40 45 50 55 60 65 70 75 Mean length of leaf midrib (mm) II I II I II I 80 I 85 Figure 3. Distribution of oviposition sites along the midrib by leaf size and midrib diameter. 1989; April 23, 1990; and April 20, 1991. Length of the larval development period varied. Time from the first record of egg hatch to presence of the first cocoons in larval mines was 23 days in 1989; 25 days, 1990; and 15 days, 1991 (Figure 1). The primary period of larval activity extended to about mid-May, but larvae were present in low numbers until late June. Pupae were most abundant during May, but were found as late as about the first of July in 1991. For the most part, these late-season larvae and pupae did not survive to adulthood. The reason for this was not established, but observations indicate that predation may have been a factor. New-brood adults began to emerge during the first half of May, 28 days after hatch of the first-laid eggs in 1991; 34 days in 1990; and 41 days in 1989. New adults usually fed in groups beginning at or near leaf margins on the apical portion of the leaves or leaf lobes (Photo 13). Feeding was usually on leaves not damaged by larval mining. Damage caused by new-brood adults was much more extensive (Photo 14) than that caused by overwintered adults. The primary period of new adult activity was May to about mid-June. Subsequently, adults moved from trees to trash and duff on the ground and remained inactive until the following spring. Only one generation occurred each year. ALABAMA AGRICULTURAL EXPERIMENT STATION Frequency of occurrence 100 95 90 25 20 15 10 0 J ] B n = 145 n A = 35 C n = 45 _ - _ - _ , E L [_1 12 3 4 5 6 7 8 910 0 1 2 3 0 1 2 3 4 5 6 7 8 9101112131415161718 19 Punctures per site Eggs per puncture Eggs per leaf Figure 4. Number of: (A) oviposition punctures per egg-laying site; (B) eggs deposited per puncture: and (C) eggs per leaf. F " .w~ . A. 0Ic 1 / ; '4 .4 ".-JISO 01 Photo 13 (above). New-brood adults and typical feeding damage. Photo 14 (right). Extensive leaf damage caused by new-brood adults. THE YELLOW-POPLAR LEAF-MINING WEEVIL SUMMARY p- F~i Photo 15. Female puncturing midrib of leaf in preparation for laying eggs. Photo 16. Female ovipositing in egg puncture. y.j Photo 17. Oviposition punctures in midrib. The yellow-poplar leaf-mining \ ccvil attacks foliage of yellow-poplar. Adults feed on the surfaces of leaves, and larvae mine between leaf surfaces. Destruction of foliage seriously reduces the aesthetic value of yellow-poplar shade and ornamental trees. Damage may affect growth, form, and survival of young trees transplanted into the urban landscape. The weevil overwinters in the adult stage in hibernation in trash and duff around host trees. Adults emerge from hibernation in early spring, about midMarch in cast-central Alabama. Overwintering weevils feed on the lower ,urfaces of leaves, removing small ciro:ular or oblong patches of leaf surface. \lating occurs and females lay eggs in leaf midribs on the undersurface. Most egg laying occurs from late March through April, but some oviposition continues through May. The female punctures the midrib with her snout and then turns and deposits one to three eggs (usually two) in the puncture. Normally. there are four or five punctures at each oviposition site and usually only one site per leaf. Midrib tissue dies and the leaf often breaks at the egglaying site. Eggs hatch and larval mines begin to appear in leaves around the first of April in the Auburn area. The primary period of larval activity extends to about mid May. Larvae feed side by side in groups in a common mine leading away from the midrib. Extensive mining may destroy entire leaves. Full-grown larvae pupate in silken, spherical cocoons in larval mines. 12 ALABAMA AGRICULTURAL EXPERIMENT STATION New-brood adults begin to appear during the first half of May. They feed primarily on the undersurface of leaves, as did parent adults, but may also feed on the upper surface. Typically, new weevils feed in groups, with feeding commonly beginning at leaf margins in the apical portion of the leaf. Feeding by new-brood adults may be extensive, and damage to foliage may be severe. New weevils are active for about four weeks; in east-central Alabama, activity usually ceases by mid-June. Adults move to trash and duff near host trees and remain inactive until the following spring. Only one generation occurs each year. THE YELLOW-POPLAR LEAF-MINING WEEVIL 13 REFERENCES (1)BuRNs, D. P. AND L. P. GIBSON. 1968. The Leaf-mining weevil of yellowpoplar. Can. Entomol. 100:421-429. (2)BuRNs, D. P. 1971. 5 Yellow-poplar weevil. USDA For. Serv. Pest Leafi. 125. pp. (3)HYCHE, L. L. 1990. Ovipositional habits of Odontopus calceatus (Coleoptera: Curculionidae) on yellow-poplar. J. Entomol. Sci. 25:493-495. With an agricultural research unit in every major soil area. Auburn University serves the needs of field crop. livestock. torestry. and horticultural producers in each region in Alabama. Every citizen of the state has a stake in this research program. since any advantage from new and more economical ways of producing and handling farm products directly benefits the consuming public. 9 11, 10 Main Agricultural Experiment Station, Auburn. E. V. Smith Research Center, Shorter. Tennessee Valley Substation, Belle Mina Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman Upper Coastal P a n Substat on, Winfield Forestry Unit, Fayette County Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County Piedmont Substation, Camp Hill Foresty Unit, Autauga County Prattville Experiment Field, Prattville 11 12 13. 14. 15. 16 17. 18 19 Black Belt Substation, Marion Junction The Turnipseed-Ikenberry Place, Union Springs Lomer Coastal Pla i Substation, Camden Forestry Unit, Barbour County Monroeville Experiment Field, Monroeville Wiregrass Substation. Headland. Brewton Experiment Field, Bremton Ornamental Horticulture Substation, Spring Hil Cult Coast Substation, Fairhope