United States 

Department of 

Agriculture 

Forest Service 

Insects that Damage Northern Red Oak Acorns 

Northeastern Forest 

Experiment Station 

Research Paper NE-492 Lester P. Gibson 
hster Paul Gibson received his B.S. degree in 1954, his M.S. 

depee in 1962, and his Ph.D. in 1914, all from the Ohio 

State Universie. He joined the Forest Sewice in 1957 and 

has served as a Biologic& Aid (Survey Entomologist) and Research Entomologist at Columbus and Delaware, Ohio. He is 

a speeidist on insects (and their parasites) of nut crops and 

hardwood seeds, He is the world authority on the biology 

and systematics of Cureulio in the New World and of the 

braconid genus Urosigalphus. We has spent sever& years 

investigating the insect vectom of tree viruses. Currently 

he is engqed in research on the impact of insects on oak 

seed production and oak seedling establishment at the Northeastern Forest Experiment Station, Forestry SGiences 

Laboratovy at Delawaxr?, Ohio. 

Manuscript received for publication 

20 April 1981 

Abstract 

From 1961 to 1964 and in 1979, the insects found damaging 

acorns of northern red oak (Quercus mbra L.) in their relative order of abundance were: Cureulioproboscideus F., 6. 

suleatulus (Case y ), kissopus la tifernetanus (Wals.), 6. 

nasicus (Say), C. orthorhynehus (Chttn.), C. longidens 

Ch ttn., Gallirhy tis operator (O.S.), Callirhy tis fwetuosa 

Weld., Conolrachelus postieatus Boh ., Conotrachelus 

earinifer Casey, Conotmchelus naso LeC., and Vtalevstiraia 

glandulella (Riley). During 1961 to 1964,1979, and 1980 

insects damaged an average of 52.32 percent af &. mbra 

acorns (range 0 to 100 percent). 
Northern red oak, Quercus mbra L., is an important tree 

species in the emtern United States for timber and for wildlife. Each year insects heavily attack northern red oak acorns 

and destroy a large percentage of them, greatly reducing the 

numbr of acorns available to produce seedlings and feed 

wildlife. 

Methods 

Acorns from several locations throughout the eastern U.S. 

and Canada were collected and placed in chamkrs until 

larvae emerged. The emergent lawae were sorted by genus, 

counted, and placed in rearing containers to obtain adults 

and their parasites, After most lanrae had emerged, a sample 

of acorns from each collection was examined. The nuts were 

cracked open to determine their condition and the type of 

damage they had sustained. Larvae found in the acorns were 

combined with the emerged lamae to determine the degree of 

infestation. The amount of insect damry~e, the insect species 

responsible, and their relative importance were tabulated for 

various sites within the range of &. mbra. 

The distribution and relative abundance of individual species 

of Conotrachelus, Cureulio, Lepidoptera, and their parasites 

were computed on the number of emergent adults. 

Results and Discussion. 

Weevils of the genus Curculio cause the most insect damage 

to mature acorns. Five species sere found infesting northern 

red oak acoms. The majoriw of those reared from 1961 to 

1964 and in 1979 were Curculio pro boscideus E: (54.35 percent), followed by C. sulcatulus (Casc;?g) (31.77 percent). 

Curculio orthorhynclaus (Chttn.) were found infesting 4.07 

percent. Curculio nasicus (Say) infestations (which averaged 

9.76 percent) varied considerably; in the northern part of 

the range of &. m bra, northern Ohio, Massachusetts, Pennsylvania, New Brunswiek, Quebec, and Ontario, some collections produced only C. nasicus; in southem parts of the range 

some collections produced few or no C. nasicus. C. longidens 

Chttn, infested northem red oak only in the southern half of 

its range, and then only rarely (0.05 percent). These percentages are based on 1,600 adult Curculio reared from 

acoms collected throughout the range of northern red oak, 

Three species of Concr&achelus weevils have been reared 

from northern red oak: C. naso LeConte and C. posticatus 

Boheman were reared from the northem h Jf of the range 

and 6. posts'catus and C. ca~oiter Casey from the southern 

half of the range. Usually less than 3 percent of the acorns 

were infested by Conotrachelus. 

The reason for the low infestation rate is that Conotrachelus 

cannot infest a sound nut. merefore only previously infested 

or physically darnaged nuts are avdlable for oviposition. 

The kpidoptera infesting northern red oak acorns were 

Melissopus la tifernanus (Walsinghm) and 'Valen finia 

glandublla (Riley). The latter is a secondary invader. These 

two species infested from 0 to 36.1 percent of acorns smpled from 1961 to 1964. In collections in Missouri from 

1973 to 1976, Steven Myers (1978) found from 0 to 63 percent of mature northern red oak acorns and from 0 to 30 

percent of immature acorns infested by lepidopterous larvae. 

Combining these data to make them comparable to my data 

(my data included immature acorns) yields an infestation 

rate ranging from 0 to 34.5 perce~t which clbsely agrees with 

the 0 to 36.1 percent rate I found. 

Three Lypes of galls were found in or on northern red oak 

acorns: 1) a large gall on the acorn cup produced by 

Am,phibol@spmnus Wafsh., 2) a pip gall in the side of the 

acorn shell produced by the agamic fall form of Callirhytis 

oper~tor (O.S.), and 3) a mass of stony gall cells that fills 

the entire interior of the nut, produced by Callirhytis fructuosa 

Weld. The last two usually kill the acorn: the pip gall causes 

the nut to fall prematurely and the stone gall replaces the seed. 

Samples showed that the infestation rate for Callirhy tis sp. 

galls varied from 0 to 31 percent in the United States collections and 0 to 37 percent in Canadian collections made during 1961 to 1964. Myers found the infestation rate to be 0 

to 31 percent in Missouri (0 to 48 percent in immature 

aeorns and 0 to 24 percent in mature acoms). 

Table 1 shows the percentage of acoms in each sample that 

were infested by any species of insect. The degree of infestation vades from year to year and from tree to tree in the 

same area as well as throughout the northern red oak range. 

Thus the data presented in Table 1 indicate only the infestation of the acorns on each sampled tree. However, the data 

do suggest the density and diversib of the insect infestation. 

Secondary invading insects similar to those found in bur oak 

(Gibson 1971) and white oak (Gibson 1972) were found in 

northern red oak acoms. Some of these added to the destmction of acorn viability. 

Table 2 shows the infestation rates for Curculio, Conotraehelus, Melissopus, and Callirhy tis spp. The rates for the 

first three are for individud insects per 100 acorns but the 

rate for Callirhytis is the percentage of galled acoms that 

may contain 1 to 2 dozen gall wasp larvae. The number of 

insects per 100 acoms sometimes exceeds the percentage of 

acorns infested. For example, in the Delaware Co. Ohio sample for 1979 the rates were 295.2 percent for Curculio, 0.9 

percent for Cono&achetus, 15.2 percent for Melissopus, and 

3.8 percent for CaNirhylis galls, for a total of 315.1 per 108. 

The infestation rate was 90.4 percent. This shows that several insects infested the same acorn. Usually acorns infested 

with Callirhygs bctuosa do not contain any of the other 

infesting insects. However, aeoms infested by Callirhytis 

operator (fall form) may also contain Melissopus 

lagferreanus larvae. The acoms infested by Cureulio usually 

conbin only one species of Curculio but nomally contain 

two to five Curculio larvae, and may contain one or more 

Cono&acheEus larvae or a moth larva, or both. 

1 
Table 1. - Conditions of northern red oak acorns (in percent) 

Locality 

Ottawa Co,, OH 

Union Co., OH 

Average 

1962 

Auglaize Co., OH 

Champaign Co., OH 

Champaign Co., OH 

Clinton Go., OH 

Madison Co., OH 

Madison Co., OH 

Ottawa Co., OH 

Pu tnam Co., OH 

Ross Co., OH 

Shelby Co., OH 

Tmmbull Co., OH 

Wmbull Co., OH 

La Crosse Co., WI 

New Haven Co., CT 

Average 

1963 

Auglaize Co., OH 

Marion Co., OH 

Marion Co., OH 

Ottawa Co., OH: 

York Co., N.B. 

Ste. Foy, Que. 

Berthier Co,, Que. 

Sault Ste. Marie, Ont. 

Kings Co., N.B. 

Penobscot Co., ME 

Berkshire Co., MA 

BeIknap Co., NH 

Chittenden Co., VT 

Chittenden Co., VT 

Schenectady Co., NY 

Middlesex. Go., NJ 

New Castle Go., RE 

Washington, D.C. 

Monongalia Co., WV 

McKean Co., PA 

Rowan Go., KY 

Franklin Co., TN 

Macon Co., GA 

Harris Co., CA 

Owen Co., IN 

Du Page Co., IL 

Hardin Co., IL 

Iowa Co., IA 

Oceana Co., MI 

Dane Co., WI 
Insect 

infested Locality Sound Rotten Malformed 

Marathon Co., Wf 

nempealeau Co., WI 

Larimer Co., CO 

Average 

1964 

Auglaize Co., OH 

Champaign Co., OH 

Crawford Co., OH 

Harrison Go., OH 

Marion Co., OH 

Tmmbull Co., OH 

Average 

(combined) 

3.6 

20.0 

3 .O 

2.7 

4 .O 

5 .O 

9.2 

6 .O 

0.9 

11.2 

0.9 

17.2 

7.8 

14.3 

13.7 

1.1 

0.2 

0 

2.6 

1979 

Delaware Co., OH 

Delaware Co., OH 

Delaware Co., OH 

Marion Co., OH 

Morrow Co., OH 

Morrow Co., OH 

Morrow Co., OH 

Centre Co., PA 

Centre Co., PA 

Huntingdon Co., PA 

Miffiin Co., PA 

Stone Creek Road, PA 

Licking Creek Dr., PA 

Dry den, NY 

McClure, NY 

Watkins Glen, NY 

Watkins Glen, NY 

Watkins Glen, NY 

Buffalo, NY 

Average 

1980 

Mt. Gilead, OH 

Dry den, NY 

Dry den, NY 

McClure, NY 

Hmmond Hill, NY 

Watkins Glen, NY 

Average 

Average of all years 

a1.16 percent error due to lack of data for Rotten and Malfomed columns for 

collections from Chittenden Co., VT and Washington, D.C. 
Table 2. - Insect infestation ratesl1OO acorns by location 

Locality 

Valen tinia and CaNirhy tis cu rculio Con o trachelus Me2issopus 

weevils weevils moths galls 

1961 

Auglaize Co,, OH 10.3 0 0 0 

Auglaize Co., OH 21.8 0 0 0 

Erie Co., OH 67.4 0 9.2 1.2 

Madison Co., OH 104.1 0 21.4 0.5 

Ottawa CO., OH 74.2 0.1 19.4 0.1 

Union Co., OH 77.4 0 11.6 0 

1962 

Auglaize Co., OH 

Champaign Co., OH 

Champaign Co., OH 

CIin ton Co., OH 

Madison Co., OH 

Morrow Co., OH 

Ottawa Co., OH 

htnam Co., OH 

Ross Co., OH 

Shelby Co., OH 

Trum bull Co., OH 

Trurn bull Co., OH 

La Crosse Co., WI 

New Haven Co., CT 

Greene, Co., OH 

Franklin Co., OH 

Marathon Co., WI 

Lawrence Co., PA 

Clinton Co., MI 

FranMin Co., TN 

Buncombe Co., NC 

Rabun Co., GA 

Rabun Co., GA 

Fort Collins, CO 

1963 

Auglaize Co., OH 

Marion Co., OH 

Marion Co., OH 

Ottawa Co., OH 

York Co., NB 

Ste. Foy, Que. 

Berthier Co., Que. 

Sault Ste. Marie, Ont. 

Penobscot Co., ME 

Belknap Co., NW 

Berkshire Co., MA 

Sehenectady Go., NY 

Chittenden Co., VT 

Chittenden Co., VT 

Middiesex Co., NJ 

New Castle Go., DE 

Washington, D.C. 

Monongalia Co., WV 

Tucker Co., WV 

Owen Co., IN 
Locality Cu rculio 

weevils 

McKean Co., PA 

Rowarm Co., KY 

FrmMin Co., TN 

Macon Co., GA 

Harris Co., GA 

Du Page Co., IL 

Hardin Co., IL 

Iowa Co,, IA 

Oceana Co., MI 

Dane Co., WI 

Rempealeau Co., WI 

Marathon Co., WI 

Dent Co., MO 

1964 

Auglaize Co., OH 

Champaiffn Co., OH 

Crawford Co., OH 

Harrison Co., OW 

Marion Co., OH 

Trum bull Co., OH 

1979 

Delaware Co., OH 

Delaware Co., OH 

Delaware Co., OH 

MaYion Co., OH 

Morrow Co., OH 

Morrow Co., OH 

Morrow Co., OH 

Centre Co., PA 

Centre Co., PA 

Huntingdon Co., PA 

Mifflin Co., PA 

Stone Creek Rd., PA 

Licking Creek Dr., PA 

Dryden, NY 

MeClure, NYa 

Watkins Glen, NY 

Watkins Glen, NY 

Watkins Glen, NY 

Buffalo, NU 

1980 

Mt. Gilead, OHb 

Dry den, NY 

Dryden, NUb 

McClure, NY 

Hmmond Hill, NY 

Watkins Glen, NY 

fialentinioand Callirhytis Conotrochelus Melissopus 

weevils moths galls 

a36.3% of acorns eaten by rodents. 

bSorne Curcukio emergence prior to acorn eolleetion. 
Literature Cited 

Gibson, L.P. fnsects of bur oak acorns. Ann. Entomol. Soc. 

Am. 64(1);232-234; 1971. 

Gibson, L.P. Insects that damage white oak acorns. 1972; 

USDA For. &rv. Res. Pap. NE-220. 7 p. 

Myers, S.A. Insect impact on acorn population in Missouri 

upland forests. Unpublished Ph.D. Dissertation. Univ. 

Nfissouri; 1978. 246 p. 

12 U.S. GOVERNMENT PRINTING OFFICE: 1982-505-01 2/42 
Gibson, Lester P. Insects that damage northern red oak acorns. 

Broomall, PA: Northeast. For. Exp. Stn.; 1982; USDA For. 

Serv. Res. Pap. NE-492. 6 p. 

Insect damage to northern red oak acorns is extensive throughout 

the range of northern red oak, and greatly reduces the number of 

acorns available to produce seedlings and feed wildlife. Five species 

of Curculio weevils (proboscideus F., sulcaklus (Casey), orthorhynchus (Chttn.), nasicus (Say), and longidens (Chttn.), three 

species of ConoCrachelus weevils @osticatus Boh., cars'nifer Casey , and naso LeC.), two species of moths (Melissopus latiferreanus 

(Walsh.) and Valendinia glandulella (Riley)), and two species of 

gall wasps (Callirhytis operator (O.S.) (f'all form) and C. 

frmctuosa Weld.) cause most of the damage. 

ODC: 453-145.5 x [-18.09 - 18.27 -19.91 -21.31 (81): 176.1. 

Keywords: Quercus ru bra L., acorn, weevil, Curculio