Seed and Cone Insects Associated with Pinus Monophylla in the Raft River Mountains, Utah

Volume 44 Number 2 Article 18

4-30-1984

Seed and cone insects associated with Pinus monophylla in the Raft River Mountains, Utah

Michael J. Jenkins Utah State University

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Recommended Citation Jenkins, Michael J. (1984) "Seed and cone insects associated with Pinus monophylla in the Raft River Mountains, Utah," Great Basin Naturalist: Vol. 44 : No. 2 , Article 18. Available at: https://scholarsarchive.byu.edu/gbn/vol44/iss2/18

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. SEED AND CONE INSECTS ASSOCIATED WITH PINUS MONOPHYLLA IN THE RAFT RIVER MOUNTAINS, UTAH

Michael J. Jenkins'

.\bstract.— Dissection and reaiint; studies of second-vear cones disclosed six species of insects associated with the seeds and cones of singleleaf pinvon pine dining the spring and snmmer of 1976. Those most commonly encountered were: Dionjctha sp. probably albcnittcUa Hulst, Conoplithonis monophijUae Hopkins, and Pinetis coloraclensis Cillette. The three remaining species were of lesser importance. These included the gall midge, Asijnapta sp., a minor cone pest and two parasites, one of C. monophijUae. Acerocephala atroviolacea Crawford, and an unidentified parasite oi Dioriictria, of the family Ichnetunonidae. Dionjctria sp. probably alhovittella was regarded as the major insect destroying cones and seeds of P. monoplujilci

in this study. Dming the growing season it attained a maximum leyel of 29% infestation. Conoplithonis monophijUae occurred less frequently in this study, but probably has a higher potential for destruction in years of poor cone crops or high cone beetle popvilations. Pineiis coloraclensis caused negligible damage to seeds and cones, but was encountered frequently. Early in the growing season it infested a maximum of .38% of the cones.

Insects are probably the most important dollars worth of pine nuts. Pinyon timber has biotic agents reducing fruit and seed produc- also been used for fence posts, mine props, tion of trees and shrubs (USDA 1974). This and fuel wood, and pinyons serve as excellent study was conducted to determine those seed Christmas trees (Johnson 1970). and cone insects attacking the cones of the Since little value is placed on pinyon pines singleleaf pinyon pine, Pinus monophylla for timber products, there have been few Torrey & Fremont. studies describing the insects associated with

Singleleaf pinyon pine is a member of a them. This study was conducted to identify: group of closely related pines occupying vast the major seed and cone insects present on acreages in the semiarid regions of the south- singleleaf pinyon pine, to determine their rel- western United States and Mexico ative abundance, and to briefly describe their (Critchfield and Little 1966). It can form life cycles. pure, open forests, or, more commonly, grows in association with the Utah juniper, Methods Jiiniperus osteospenna (Torrey) Little, in the characteristic pinyon-juniper woodland (Har- Study Area low, Harrar, and White 1979). Pinyon-juniper woodlands cover over 75,000 square The study area was a 530-hectare single- miles of the southwestern United States (Lan- leaf pinyon-Utah juniper woodland in north- ner 1975), occupying more area in the Inter- western Utah's Raft River Mountains at an mountain Region than all other forest cover elevation of 1900 to 2300 m.

types combined (Cronquist et al. 1972). Quarter-hectare plots were used to deter- Little commercial value has been placed mine the relative number of pinyon pines on the pinyon pines for timber products, but and junipers. There was an average of 178 the seeds of these pines have been harvested pinyon pines and 72 junipers per hectare. for centuries by American Indians as a valu- The understory vegetation consisted of big able food supply (Lanner 1981). Various sagebrush, Artemisia tridentata Nutt., forms of wildlife depend upon pine nuts for Opuntia cactus, and a variety of grasses and survival, among them many birds and ro- forbs. Toward the western boundary of the dents. In good seed years, Indians of the stand was an increase in curlleaf mountain Southwest have collected and sold a million mahogany, Cercocarpus ledifolius Nutt.

'Department of Forest Resources, Utah State University, Logan, Utah 84322.

349 350 Great Basin Naturalist Vol. 44, No. 2

Sampling characterize types of damage and to assess the number of individuals attacking a given A permanent plot center was selected in a cone. part of the stand found to be typical in terms Rearing began in July with collection num- of overstory density and composition. ber III. Cones were separated and grouped Ten sampling dates were .scheduled begin- based on external damage, placed in contain- ning in mid-April and continuing into Octo- ers covered with cheesecloth and left at room ber at two- to three-week intervals. The per- temperature (18-22 C) (Ebel 1959). Insect manent plot center was used as a starting specimens collected from rearing chambers, point for each collection. Prior to each col- whether adult or immature, were sent to spe- lection date, a direction was randomly se- cialists for identification. lected and traveled to collect the sample. Any tree falling partly or entirely on the line could be sampled. The restrictions to sam- Results pling were that not more than 10% of the The insect species collected and identified sample could come from any one tree and from seeds and cones of singleleaf pinyon are that all cones collected came from unshaded listed in Table 1. Following are discussions of branches of nearly average trees on average the nature of the damage caused by each in- sites. Collections were made using a pole sect and descriptions of their life histories. pnmer and consisted of 100 cones per collection date. ConophtJionis monophijUae Hopkins Analysis of the Sample (Coleoptera: Scolytidae)

The sample was returned to the laboratory Pine cones that dry and wither before they and cones were grouped based on the exte- are half grown are said to be "blighted." The rior appearance of insect damage. Cones usual cause of blighting is pine cone beetle showing no exterior evidence of insect activi- damage by the genus Conophthorus Hopk. ty were also grouped together. Half the cones (Keen 1958). Species in this genus were be- in the sample were dissected using a cone lieved by Hopkins (1915) to be specific to a cutter and the remainder were placed in particular member of the genus Piniis. Con- rearing chambers. Immature insects dissected ophthorus monophijUae is a unique species from cones were recorded and preserved in consistently associated with P. monophylla 70% EtOH for identification by specialists. (Wood 1982: 984). Rearing of early samples was not attempted, The range of C. monophijUae would be ex- as the small cones dried too rapidly. pected to correspond to that of P. mono- Once cones reached sufficient size, empha- phijUa, with the beetle being found wherever sis was shifted from dissection to rearing, to the singleleaf pinyon pine occurs. However, obtain adult specimens for identification. collection of C. monophijUae in the study Dissection of damaged and normal cones area represented an extension of its known continued using a smaller number of cones to range by more than 200 miles (Wood 1982).

Table 1. Insects associated with seeds and cones oi Pinus uKutopht/lla in the Raft River Mountains.

Order Family Scientific name

Coleoptera Scolytidae Conoplitliiinis monophiiUdc Hopkins

Lepidoptera Pyralidae Diorijctria sp. probably aUnnitieUa Hiilst Dioryctria sp. probably ahieteUa D. & S.

Homoptera Adelgidae Pineiis colomclcnsis Gillette

Diptera Cecidomyiidae Asynapta sp. Loew

Hynienoptera Pteromalidae Acerocepluihi atwviolacca Crawford Ichneumonidae One unidentified species April 1984 Jenkins: Seed and Cone Insects 351

ADULTS OVERWWTERINQ

EGGS

LARVAE

PUPAE

MAR APR MAY JUN JUL AUG SEP OCT NOV

Fig. 1. Life history of C. inoiKipliiilhu' slio\vin

Life history. Mating occurs in late spring trance hole made by the adult female was or early summer, and by early July the fe- visible near the base of the cone, with very male beetle lays her eggs in the second-year little resin or frass present around the hole. cones. The cone is killed by the attack of the Cones that were attacked later in the sea- adult beetle, as she bores a tunnel into the son opened prematurely and had an entrance base of the cone and up its central axis, de- hole near the base. The interior contained positing eggs in niches to the sides of the tun- larvae, pupae, or adults. Larvae boring in nel. The egg niches and tunnel are packed nearly mature cones preferred the individual with frass. The first larvae were observed seeds and were most commonly encountered within the cone by mid-July. The larvae feed there with only one larva feeding in any giv- on the seeds and cone scales, honeycombing en seed. They reduced the interior of the the interior of the cone. Pupation occurs in seed to strips of elongate frass and pupated mid- to late August with the adult emerging within the cone. The adult emerged the fol- two to three weeks later. The newly emerged lowing spring by way of a hole bored adults overwinter in the dead cone and feed through the cone scale. During the study on the drying tissue. They become dormant year, the number of cones attacked by Con- during the winter and emerge the following ophtliorus did not exceed 11% (Table 2, Fig.

.spring (Fig. 1). The exact date of emergence 2). will vary with springtime temperatures. There is one generation per year. Dionjctria probably albovittella Hulst Damage. Cones that were attacked by C. (Lepidoptera: Pyralidae) monopJii/Ilae the previous year were readily identifiable by the numerous emergence Problems were encountered with the iden- holes in the cone scales. Previously attacked tification of the species of Dionjctria in- cones may either remain on the tree or fall to volved. A long series of larvae was identified the ground. Old injiuy was easily found in by D. M. Weisman as probably being D. al- the study area, although specific counts were bovittella Hulst. However, adults that were not attempted. obtained from rearing chambers containing Cones that were attacked early in the cur- cones infested with Dionjctria sp. appeared rent growing season were hard, brown, and to Weisman and D. C. Ferguson to be D. wrinkled by the end of the season. The en- ahieteUa D. & S. Weisman and Ferguson 352 Great Basin Naturalist Vol. 44, No. 2

fiable a large hole in the cone's exterior- OC. MONOPHYLLAE by AP, COLORADENSIS covered by frass, webbing, and resin (Keen 35-- 1958). D D. ALBOVITTELLA Dioryctria alhovittella is specific to cones of P. monophylla and should be encountered 30-- throughout the range of the singleleaf pinyon. The first recorded rearing of D. alhovittella was from collections made near Topaz Lake, Nevada, in 1939 (Keen 1958). It has a wide host range, affecting a number of co- 20-- niferous species. Life history. This species overwinters as eggs laid by females on twigs. The eggs hatch in early spring, and larvae are active in the cones from June through September. Pupae form in sparsely lined pupal cells in July, Au- 10-- gust, and September. Adults emerge from the cones in August and September. Mating occurs during this period and eggs are again de-

posited on twigs (Keen 1958; Fig. 3). Damage. The first larvae were encountered in early July, burrowing in young sec- APR MAY | I I JUN I JUL AUG I SEP I OCT ond-year cones. The activity was evident frass, Fig. 2. Percentage of cones attacked by major insect from a hole covered by webbing, and species at various times during the study. resin in the exterior of the cone. The frass existed as large spheres, differing from that of (pers. comm.) believed one of two possible C. monophyllae described earlier. The gallery situations existed: the first, and most likely, within the cone was packed with frass and was a mixed population consisting of D. albo- resin; the tissue immediately adjacent to the vittella and a few D. ahietella. If this was the gallery dried and turned brown. The cater- case, it appeared that the rearing techniques pillars fed without discrimination on scales used here might have selected for D. ahie- and seeds, with only one caterpillar active tella. The second possibility was that a new within any given cone. Small cones attacked species was involved, which Weisman consid- early in the season were totally destroyed, ered to be imlikely. but larger cones attacked later showed only The caterpillars of this species of moth fed partial destruction and could bear some nor- on the bracts, scales, and seeds of second-year mal seeds and open some scales at maturity cones, causing blighting, deformity, and (Little 1944). sometimes death of the entire cone. Usually a The first pupae were observed in late July variable percentage of seeds was destroyed in dry cones. It appeared that the larvae fed and the remainder were unaffected. The ac- for a determinate length of time and then pu- tivity of these caterpillars was easily identi- pated within the drying cone. Pupae and lar-

Table 2. Percentage of the 100-cone sample collected on each of the dates shown and attacked bv the three most mportant insect species. Data are shown for various collection dates in 1976. See also Figure 2. April 1984 Jenkins: Seed and Cone Insects 353 354 Great Basin Naturalist Vol. 44, No. 2

were made of P. coloradensis after 21 July common parasites of caterpillars. The one (Fig. 2). Development into alate adults and reared out in this study was associated with

subsequent dispersion apparently occurred Dioryctria sp., but its positive identification quite rapidly, resulting in this marked de- was not possible due to the previously dis- crease in the insect population present on the cussed problems in identifying the Dioryctria cones. sp. found in this study. Damage. The secretion of wax and ovipos- iting by females of P. coloradensis did no ap- Discussion parent damage to the cones of P. monophijUa internally or externally. Observations made Very few insect species have been de- on cones displaying P. coloradensis showed scribed in association with P. monophylla. subsequent normal development during the From the literature, three species have been time the insect was present and after it dis- listed as the most important pests of second- persed. Adult females can lay up to 100 eggs, year singleleaf pinyon pine cones. These are, it has that the feeding activi- and been noted according to Keen (1958), Conophthorus ty of immatures on growth can harm- new be monophyllae, Dioryctria alhovittcUa, and Eu- ful, especially to young trees, if the insect is cosnia bohana. Little (1943, 1944) also em- present in abimdance (Doane et al. 1936). In phasized the importance of the genera Con- the introduction to this section, it was noted ophthonis and Dioryctria on P. edulis. Keen that an imsightly condition on ornamentals and Little mentioned the activity of uniden- can result from the presence of species in this tified gall midges of the family Cecido- and related genera. myiidae as having an impact on cone crops, Previous reports of this insect have re- especially on first-year cones. stricted its occurrence to needles and twigs. In this study, D. probably alhovittella and This study demonstrated that cones repre- C. monophyllae were the most serious pests sented an important additional habitat. reducing seed production in P. monophylla. The adelgid, Pineiis coloradensis, was of Other Insects widespread occurrence, but caused little damage in the study area. The cecidomyiid of Three additional insect species were ob- the genus Asynapta was encountered only tained from the cone samples. One was a once and was considered to be of minor im- cone pest identified only to the genus Asy- portance. E. bohana was not collected in the napta. The two remaining insects were para- study area. sites, one of D. albovitfella and the other of Dioryctria probably alhovittella was wide- C. monophyllae. Tlie gall midge genus Asy- spread and regarded as the most damaging napta (Diptera Cecidomyiidae) (USDA 1965) insect species attacking second-year cones of is capable of causing destruction of first-year P. monophylla. The caterpillars were present cones (Felt 1935). First-year cones were not and active in cones throughout much of the considered in this study, and Asynapta sp. growing season, feeding without discrimina- was collected from a sample of second-year tion all parts of the cone. cones. The limited publications, isolated oc- on currence, and the fact that only inunatiues The singleleaf pinyon cone beetle, C. monophyllae, has a high potential for reducing were obtained made it impossible to determine the life cycle or specific identification. seed production. Large numbers of offspring Two parasites were identified. One was an developed in and emerged from a single adult specimen of Acerocephala atroviohicea cone. In this study, no cone found to be at- Crawford that develops on larvae and pupae tacked by cone beetles contained any normal of Scolytidae (Clausen 1940), in this case C. seeds. The incidence of attack in the study monophyllae. It has previously been reared area, however, was low, though typical Con- from C. edidis-infested cones of P. edulis at ophthorus populations do increase during Ute Pass, Colorado, and Las Vegas, New years of heavy cone production, then affect a Mexico (Gahan 1946). The other parasite was large percentage of cones the following year a member of the Ichneumonidae, which are (Forcella 1980). One significant outcome of .

April 1984 Jenkins: Seed and Cone Insects 355

ASYNAPTA?YNAPTA SP. (larvae)

C. MONOPHYLUVE (adults, larvae;

B, ALBOVITTELLA (larvae)

P, COLORADENSIS (adults, nymphs)

APR MAY JUN JUL AUG SEP OCT NOV

Fit^. 4. Time of activity of various insect species during the growing season. this study was the extension of the known or cone worm populations during the year of range of C. monophijUae by 200 miles. the study.

Pineus coloradensis is a species of minor There was some correlation between the economic importance. Its collection and time of attack by the major insect species and identification in this study was of value be- the seasonal history of the cone. Pineus colo- cause it represents the first recorded observa- radensis was most active on the cones during tion of this insect species on P. monophijUa the early part of the season. At this time, the In addition, P. coloradensis was not pre- cones were producing the most resin for the viously reported. Further research on this adults and immatures to feed upon. D. albo- species in the study area would be valuable vitteUa was active during the early and in determining the primary host and in ob- middle portion of the growing season, when taining a more thorough understanding of its the cones were growing rapidly and were complex life cycle. very succulent. Caterpillars can feed on any Larvae of the gall midge, Asynapta sp., of the cone tissues during this time. However, were encoimtered only once in this study. by late August, when the cones were reach- Keen and Little reported unidentified gall ing maturity, the occurrence of D. probably midges of the same family (Cecidomyiidae) as albovitteUa declined sharply. Conophthorus being the most important insects damaging monophyUae preferred to feed on the indi- first-year cones, but this study apparently vidual seeds within a cone. It did not become represents the first report of Asynapta sp. in active luitil the cone had matured to the the western United States. Because no adults point that individual seeds were evident (Fig. were obtained, identification to the species 4). level was not possible. Acknowledgments Two parasitic insects were also contained in tliis study. Acerocephala atroviolacea was The author thanks S. L. Wood of Brigham parasitic on C. monophijUae. The other para- Young University and D. C. Ferguson, R. J. site attacked D. albovitteUa and could be Gagne, E. E. Grissel, M. B. Stoegel, and D. identified only to the family level. Neither M. Weisman of the USDA Agricultural Re- was obtained in abmidance and was not be- search Service, Entomology Research Divi- lieved to be effective in reducing cone beetle sion, Beltsville, Maryland, for their prompt 356 Great Basin Naturalist Vol. 44, No. 2

identification of the insect species sent to Harlow, W. H., E. S. Harrar, and F. M. White. 1979. them. Textbook of dendrology. .McGraw-Hill Book Co., New York. 510 pp. Hopkins, A. D. 1915. A new genus of scolvtoid beetle. J. Literature Cited Washington Acad. Sci! 5:429-433. Johnson, C. M. 1970. Common native trees of Utah. Annand, p. N. 1928. A contiiliiition toward a mono- Agr. Expt. Sta., Coop. Ext. Service, College of graph of the Adelginae (Phylloxeridae) of North Natural Resources, Utah State Lfniv., Logan, America. Stanford Univ. Pub. Biol. Sci. 6:1-146. Utah. 109 pp. Clausen, C. P. 1940. Entoniophagons insects. McGraw- Keen, F. P. 1952. Insect enemies of western forests. Hill Book Co., Inc., New York and London. USDA Mi.sc. Publ. 173. 280 pp. 688 p. 1958. Cone and seed insects of western forest Critchfield, W. B., a.\d E. L. Little. 1966. Geograph- trees. USDA Tech. Bull. 1169. 168 pp. ic distribntion of the pines of the world. USD.\, Lanner, R. M. 1975. Pinyon pines and junipers of the Forest Service Misc. Pnbi. 991. 97 pp. southwestern woodlands. In The pinvon-juniper Cronquist, a., a. H. Holmgren, N. H. Holmgren, and ecosystem: a symposium. LUah Agr. Expt. Sta- L. 1972. Interniountain flora: vascular J. Reveal. tion, Logan. 194 pp. plants of the Interniountain West, USA. Vol. 1. 1981. The pinon pine. A natural and cultural liis- Haftier Publishing Co., New York and London. tory. Univ. of Nevada Press, Reno. 208 pp. 269 pp. Little, E. L. 1943. Common insects on pinyon (P. DoA.NE, R. \V'., E. C. Van Dyke, W. Chamberlln, a.\d edtilis). 51:2.39-253. J. J. New York Entomol. Soc. H. E. Burke. 1936. Forest insects. McGraw-Hill 1944. Destructive insects on pinyon (P. edulis). Book Co., Inc., New York. 463 pp. USDA, Forest Service, Rocky Mt. Forest and Ebel, B. H. 1959. Laboratory rearing of the pine cone Range Expt. Sta. Res. Note 110. 4 pp. in.sect Dioryctria ahietcUa (D. S.). Econ. En- & J. U.S. Department of Agriculture, Agriculture toniol. 52;561-564. Research Service. 1965. A catalog of Diptera of Felt, E. P. 1935. gall on pine cones. \ midge J. New America north of Mexico. .Agricultural Handbook York Entomol. Soc. 43:48-49. 276. 169 pp. FoRCELLA, F. 1980. Cone predation bv pinyon cone U.S. Department of Agriculture, Forest Servic;e. beetle {Conophthorus edtilis): dependency on fre- 1974. Seeds of woody plants of the United States. quency and magnitude of cone production. Agricultural Handbook 450. 883 pp. Amer.Natur. 11:594-598. Wood, S. L. 1982. The bark and ambrosia beetles of Gahan, A. B. 1946. Review of some chalcidoid genera north and central .America (Coleoptera: Scoly- related to Cerocephala Westwood. Proc. U.S. tidae), a taxonomic monograph. Great Basin Nat. Nat. Mus. 96:370. Memoirs, No. 6. 1359 pp.