Arthropods Associated with Two Crested

Wheatgrass Pastures in Central Montana

GEORGE B. HEWITT AND WAYNE H. BURLESON

Highlight: Two pastures of crested wheatgrass in central Montana were (percent cover) as determined by using surveyed for from May 10 through September 30, 1972, and 1973. A a point frame and taking 200 vacuum quick trap and the bagging of individual plants showed that five groups above-ground hits on the first plant of arthropods were important on the basis of abundance and above-ground species encountered was 39% crested biomass: grasshoppers, , , thrips, and mites. Adults of the first wheatgrass, 10% needleandthread, 2% three groups were identified to species. fringed sagewort, and 6% miscellaneous plants. The recording of According to Mercer (1938), damaged crested wheatgrass in New 200 ground level hits showed hits on bare ground averaged 65%. The second crested wheatgrass (Agropyron Mexico. However, the most important pasture (CW 2) was located 3 5.2 km desertorum (Fisch.) Schult.) is the pests of crested wheatgrass belong to the order , the genera north of Roundup, Mont., in most drought-, -, and Petroleum County. There 38% of the and known generally as disease-resistant forage and feed crop Labops Irbisia plants were crested wheatgrass, 3% grown in Montana. Williams and Post “black grass bugs” (Knowlton, 1967). needleandthread, 2% fringed sagewort, (1945) stated there are approximately For example, Knowlton and Roberts and 3% miscellaneous plants. Hits on one million acres of crested wheatgrass (1971) reported that these bare ground averaged 8 1%. Both in Montana that are used for grazing or reduced the amount of feed available pastures had been seeded many years for hay. This plant also furnishes a for both livestock and certain species previously, probably during the considerable amount of forage on of wildlife, impaired the rangeland as a 1930’s, though the actual date is unknown. Both pastures were also rangeland throughout other parts of habitat for other species of wildlife, grazed during the two summers; the West. and reduced the watershed capacity of the infested areas. Denning (1948) however, CW 1 was lightly grazed and Or t hoptera (grasshoppers) have CW 2 was moderately grazed. found that they damaged forage and caused considerable damage to crested Arthropods were collected from wheatgrass but at least two other caused loss of seed in Wyoming. Mills both pastures from May 10 through orders of insects contain species which (1939) and Pepper et al. (1953) found September 30 in 1972 and 1973 every are i nj urious : Thysanoptera and the bugs in Montana. Bohning and two weeks with a vacuum quick trap Hemiptera. Tingey et al. (1972) found Currier (1967) and Pepper et al. (described below). A s-m2 cage was t hrips (Thysanoptera) on crested (1953) reported that crested attached to a 4.9 m boom that was wheatgrass, rubber rabbitbrush, big wheatgrass plants were killed by the mounted on a three-wheeled sagebrush, and antelope bitterbrush in black grass bugs. motorcycle. Thus the cage could be released from a height of 2.4 m while Utah; but crested wheatgrass had the A study was therefore made to the machine was moving along one of most diverse fauna, 12 potentially determine whether thrips and black the predetermined transect lines. In damaging species. The authors grass bugs were indeed abundant in each pasture, at each sampling date, therefore felt that thrips may decrease two crested wheatgrass pastures in the cage was dropped 10 times with the grazing potential of stands by central Montana. At the same time, we 15.2 m intervals between drops. limiting the production of the seed assessed the abundance of other Arthropods trapped in the cage were required for natural reseeding. Watts insects that might limit the growth or vacuumed into a net placed in a 20.3 (1965) also reported that thrips seed production of this grass species. cm vacuum hose and were transferred from the net into Berlese funnels that were installed in a van truck. Heating Authors are research entomologist and Methods and Procedures elements in the Berlese funnels and agricultural research technician, Rangeland Insect Laboratory, U.S. Department of Two pastures were selected because lights used to attract the arthropods Agriculture, Agricultural Research Service, were powered by a portable generator Montana State University, Bozeman. they had vigorous stands of crested The authors gratefully acknowledge the wheatgrass and contained a minimum and allowed rapid extraction of the Cooney and Kimmel Ranches for use of of other plant species and because arthropods from the soil and plant land and the following taxonomists of the Systematic Entomology Laboratory for they were adjacent to shortgrass litter. The first year, the duff from insect identifications: T. L. Erwin, J. L. rangeland where grasshoppers had two of the 10 cages were checked by Herring, J. P. Kramer, D. R. Miller, L. M. previously been numerous. Thus, the Russell, D. R. Smith, T. J. Spilman, and W. examining it on a paper plate with a W. Wirth. effects of grasshopper feeding might magnifying glass for arthropods that Mention of a proprietary product in this be assessed for this plant. had not emerged. The examination paper does not constitute recommendation of this product by the IJ! One pasture (CW 1) was located 1.6 revealed that 99% of the arthropods S. Department of Agriculture. km south of Harlowton, Mont., in were recovered using the Berlese Manuscript received July 30, 1974. Wheatland County. The plant species funnels. Arthropods found to be

JOURNAL OF RANGE MANAGEMENT 28(4), July 1975 301 abundant or to have a large dry weight crested wheatgrass plants. the greatest biomass per square meter. were separated to species in the Results and Discussion However, the values for the adult laboratory, dried at 6O”C, and grasshoppers are probably grossly Insect species collected with the weighed. The other arthropods were underestimated because the quick trap separated to order or group (aphids, quick trap and considered important did not quantitatively sample adult mites, spiders, and immature forms). because of abundance and size are (mobile) grasshoppers. The most In addition, on each collecting date, listed in Table 1 along with their abundant insect species were five plastic bags were placed quickly over biomass and density. The total species of ants, one species, five crested wheatgrass plants selected numbers and density of other insects and one species of Diptera (Table 1). at random and the plants were cut off collected by the quick trap and at ground level. The plants were then extracted from bagged plants are The three most abundant groups in removed from the bag and placed in the Berlese funnels. Arthropods shown in Table 2. Only a few adult descending order of abundance were recovered were separated to orders and grasshoppers were collected, mostly immature Homoptera (mostly groups. This showed which arthropods from CW 2, but they were the heaviest leafhoppers), mites, and thrips. (The were directly associated with the of the individual insects and also had species of mites and thrips were not

Table 1. Density (no./m’) and biomass (mg) of selected adult insect species (Large and abundant) collected with the vacuum quick trap from 2 crested wheatgrass fields in central Montana during a 2-year period, 1972-l 973. aso- aoo- Insect weight and Number 750- of insects collected by the biomass (mg) vacuum quick trap 700. Avg indi- Av8 vidual dry bio- 650- Identification Pasture Pasture (order, family, and species) CWl CW2 Total Avg weight’ mass2 600- 550- Coleoptera Anthicidae Notoxus calcaratus Horn 27 28 55 0.26 4.90(20) 1.27 Tenebrionidae Blapstinus spp. 1 18 19 .09 2.48(10) .22 Carabidae Metabletus americanus Dej. 6 7 13 .06 .30(10) .02 Diptera Ephydridae Philygrtk debilis Loew Lw. 274 58 332 1.54 .66(10) 1.02 Trixoscelididae lXxoscelis fumipennis Melander 0 15 15 .07 .34(10) .02 Hemiptera .ll .19 Fig. 1. Seasonal density at americaferus Carayon 14 9 23 1.82(10) pasture CW I showing total density for 5 Lygaeidae .62 square meters on each collecting date. Nysius tenellus Barber 27 122 149 .69 .89(50) Geocoris bull&us (Say) 6 41 47 .22 .73(50) .16 associatus (Uhler) 2 17 19 .09 .20(10) .02 Irb isia spp. 1 20 21 .lO 1.75(3) .17 850- Homoptera aoo- Cicadellidae 750- Aceratagalk fuscoscripta Oman 111 236 347 1.61 .41(50) .66 700- Hardya dentata (Osborn 650- & Ball) 20 3 23 .ll .29(20) .03 600- Cuerna alpina Oman & 550. Bearner 2 23 25 .12 1.98(10) .23 500- Hebecephalus truncatus E450- Beamer & Tuthill 35 28 63 .29 .37(10) .ll : 400- Psyllidae Aphalara artemistie Foerst. 59 69 128 .60 .08(50) .05 ; 350- A. veazei Patch 1 37 38 .18 .19(30) .03 300- Cercapidae 2 50- Philzronia bilineata (Say) 1 16 17 .08 3.27(10) .26 200- 150- Formicidae 3.96 .59 100- Tapinoma sessile (Say) 823 28 851 .15(50) .80 .28 50-h Formica lasioides Emery 120 53 173 .35(50) Myrmica americana Weber 97 92 189 .88 .89(5 0) .78 MAY ‘JUNE ‘JULY ’ AUG ‘SEPT ‘OCT Leptothorax rugatulus 113 54 167 .78 .03(50) .02 Fig. 2. Seasonal arthropod density at Emery 196 565 2.63 .20(50) .53 pasture CW 2 showing total density for 5 crypticus Wilson 369 square meters on each collecting date.

302 JOURNAL OF RANGE MANAGEMENT 28(4), July 1975 Table 1 continued determined.) Grasshopper nymphs were also present in fairly high Insect weight and numbers, 2.45/m*, and were biomass (rng)- Number of insects collected by the undoubtedly the most important in Avg indi- Avg terms of potential forage loss and vacuum quick trap vidual dry bio- Identification biomass. (order, family, and species) Cwl Cw2 Total Avg weight’ mass2 The seasonal pattern of the total arthropod density for CW 1 and CW 2 in Figures 1 and 2, clavatus is shown (Thomas 2 .03 36.93(5) 1.20 respectively. Total density was higher in the spring and fall and lower during (Scudder) 0 9 9 .04 26.78(8) 1.12 the summer months of July and pseudonietana (Thomas) 0 1 1 .Ol 82.40(l) .38 August during 2 years at both trifasciatus locations. This pattern is probably the (Say) 0 1 1 .Ol 146.95(l) .68 result of species adaptation to the viridis short, hot, dry summer common to 82.15(l) 1.15 (Thomas) 0 3 3 .Ol the plains area of Montana. Also, gladstoni S cudder 0 2 2 .Ol 90.14(2) .84 arthropods were more abundant in M. infantilis Scudder 10 17 27 .13 46.18(10) 5.80 both pastures in 1973. &I. occidentalis (Thomas) 0 1 1 .Ol 132.50(l) .62 A total of 13,998 arthropods were M. packardii Scudder 0 3 3 .Ol 117.5 3(2) 1.64 collected from both CW 1 and CW 2 17 17 .08 65.68(9) 5.19 M. sanguinipes (F.) 0 for an average of 65.11 arthropods per pardalinus (Saussure) 0 1 1 .Ol 227.86(l) 1.06 square meter. This figure is probably Psoloessa delimtula lower than the actual population (Scudder) 2 0 2 .Ol 27.85(2) .26 density since some arthropods escaped (Say) 0 2 2 .Ol 228.26(l) 2.12 equale as the sampling cage dropped and kiowa (Thomas) 0 1 1 .Ol 52.99(l) .25 many small ones such as mites, thrips, ’ The number of parenthesis is the number of specimens weighed to obtain average. and aphids could not be vacuumed 2 Average biomass/m’ is obtained by multiplying the average individual dry weight by the loose from the growing plants. When average number/m2.

Table 2. Additional arthropods (order or group) collected (no./m2) with the vacuum quick trap or extracted from crested wheatgrass plants in 2 fields in Montana during a 2-year period, 1972-1973.

Number of arthropods extracted Number of arthropods collected from crested wheatgrass plants with a vacuum quick trap’ Order Common Stage of Avg Avgl or group name development Cwl Cw2 Total no./plant CW 1 cw2 Total m2 Acarina Mites Nymphs & adults 2240 2600 4840 24.20 953 1493 2446 11.38 Aphidae Aphids Nymphs & adults 78 185 263 1.32 87 139 226 1.05 Araneida Spiders Nymphs & adults 25 25 50 .25 182 194 376 1.75 Coleoptera Beetles Adults 27 86 113 .57 78 85 163 .76 Collembola Springtails Nymphs & adults 11 13 24 .12 245 22 267 1.24 Diptera Flies Adults 12 10 22 .ll 180 110 290 1.35 Hemiptera Bugs Adults 2 18 20 .lO 37 44 81 .38 Hemiptera Bugs Nymphs 12 8 20 .lO 146 266 412 1.92 Homoptera Leafhoppers, Adults 5 7 12 .06 88 74 162 .75 etc. Homoptera Leafhoppers, Nymphs 694 1983 2677 13.39 2218 1315 3533 16.43 etc. Hymenoptera Ants, wasps, Adults 75 100 175 .88 163 140 303 1.41 bees Lepidoptera Moths & Adults 4 3 7 .04 23 27 50 .23 butterflies Neuoptera Lacewings, etc. Adults 0 1 1 .Ol 1 1 2 .Ol Orthoptera’ Grasshoppers Adults 2 4 6 .03 - - - Orthoptera Grasshoppers Nymphs 1 3 4 .02 82 444 526 2.45 Psoceptera Psocids Adults 14 58 72 .36 0 0 0 .oo Thysanoptera Thrips Adults 53 36 89 .45 18 4 22 .lO Thysanoptera Thrips Nymphs 957 715 1672 8.36 902 457 1359 6.32 Misc. larva Coleop tera ) Diptera ) Immature 164 149 313 1.57 243 181 424 1.97 Lepidop tera) Total 4376 6004 10380 51.90 5 646 4996 10642 Total of specimens from Table 1 2126 1230 3356 Total and average specimens collected. 7772 6266 13998 65.11 ’ All adult grasshoppers (Acrididae) collected by the vacuum quick trap are included in Table 1. s A total of 100 m2was sampled on CW 1 and 105 m2 on CW 2 during the 2-year period.

JOURNAL OF RANGE MANAGEMENT 28(4), July 1975 303