LABORATORY AND FIELD EVALUATIONS OF ISOFENPHOS FORMULATIONS FOR SCARABAEID GRUB CONTROL 1,2

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1 LABORATORY AND FIELD EVALUATIONS OF ISOFENPHOS FORMULATIONS FOR SCARABAEID GRUB CONTROL 1,2 Paul B. Baker 3 and Paul R. Heller" Department of Entomology ew York State Agricultural Experiment Station Cornell University Geneva, NY Abstract: Laboratory studies of soil incorporation of five formulations of isofcnphos in different soils and exposure of three different species showed varying degrees of mortality. In general. all formulations in Upstate NY soil provided acceptable mortality of Anomala orienta/is and Rhizolrogus moja/is, while Long Island, NY, soils reduced the effectiveness of all formulations on A. orientalis. Field results confirmed laboratory studies. All formulations of isofenphos in the laboratory using Pennsylvania soil gave excellent control of PopiUia japanica. Key Words: White grubs, Scambncidae, isofenphos. control. J. Agric. Entomal. 3(3); 26[,-271 (July 1986) The Scarabaeid white grub complex remains the number one pest of commercially maintained cool season turfgrass in the Northeastern U.S. Historically, this complex has been controlled by a variety of insecticides. In the early 1970s, as a substitute for the reduced efficacy in chlorinated cyclodiene insecticides, the organophosphate insecticides were introduced for grub control. Presently, the organophosphates are the preferred products in our grub control program. One of the newest materials, with a relatively long residual activity of up to 3 mon (Tashiro et al. 1982) in this class, is isofenphos (Oftanol ). Registered in 1980, isofenphos became the preferred material for our region (Tashiro et al. 1982). In 1982, however, failures were reported on Long Island, NY (Baker 1985). These failures could not be correlated to a particular factor such as thatch, irrigation, or timing. Thus, it was suspected that the failures might be related to the formulations since changes were made in the fonnulations from 1978 through In cooperation with Mobay Corporation, we tried to determine the effectiveness of various formulat.ions of isofenphos in the laboratory and the field on third-instal' grubs from New York of the European chafer, Rhizotrogus maja/is (Razoumowsky), the Oriental beetle, ArlOmala orientalis Waterhouse, and from Pennsylvania of the Japanese beetle, Popillia japonica Newman. MATERIALS AND METHODS NY Laboratory Soils were acquired from two sources in New York. Long Island soil, obtained from the Fresh Meadows Country Club, was a sandy loam soil with a ph of 5.0 I COLEOPTERA: SClIrabneidne. 2 Accepted ror publication 26 August Current nddress: Council ror Environmental Studies, Universit) or Antona, TucKon, AZ Depanment. or Entomology. The Penns)'l'iania Slate liniver.<;it)'. University Park, PA

2 266 J. Agric. Entomol. Vol. 3, No.3 (1986) and a percent organic matter of 6.0. The upstate soil, obtained from the Geneva Experiment Station grounds, was a sandy loam with a ph of 6.3 and a percent organic matter of 3.0. Isofenphos formulations at the rate of 1.5 ppm 13.7 lb (1.7 kg) AI/hal were thoroughly incorporated in both finely screened soils. Six lots (five treatments and a check) were held in separate covered plastic containers maintained on a 12:12 D:L at 25 C with 75% RH ± 10. Soil moisture was held at en 12-14% on an air-dry basis. The isofenphos granular fonnulations used were as follows: 5G technical (formulation prior to 1980) with 1) Benonite clay carrier (SO-B.C.) and 2) Oil-Dri Carrier ( ); a current 5G commercial standard with a Benonite clay carrier (83~B.C.); 5G commercial standard with Benonite clay carrier purchased from a commercial supplier (84-S.C.); a liquid 2 I(A) fonnulation (# ); and the check. The liquid formulation was mixed in 25 ml of tap water and sprinkled over the soil, mixed, and rescreened. After mi..xing, soils were covered and held in walk-in rooms maintained at 25 ± 2"C with 12-hr photoperiod. Oriental and European chafer beetle grubs were field~collected during the fall of 1983 and stored at 100e in 0.15 X 0.45 X 0.08 m wooden boxes containing a mixture of collection site soil and grass. Oriental beetles were collected from Hempstead Country Club on Long Island, NY, and the European chafers were collected upstate at Drumlins C. C. in Syracuse. Boxes were removed from storage and held at 21 "C for 24 h prior to removal of grubs to infest treated soils. At 28-d intervals beginning 21 November (1983) through 13 February 1984, ca. 22 kg of each treated soil was removed and distributed evenly among five 18 cm X 14 em X 10 cm clear plastic trays with lids (five reps/treatment). To provide a food base, ca 10 gm of commercial grass seed mix (44% Annual ryegrass, Lolium multiflorum Lam., 15% perennial ryegrass, L. perenne L., 20% Kentucky bluegrass, Poa pratensis L., and 18% fescue, Festuca sp.) was incorporated into each tray. Ten grubs/tray were introduced and allowed to crawl into the soil. Any that did not crawl in were replaced. Mortality readings were taken at 14, 21 and 28 dafter introduction. Grubs were considered dead when their appearance denoted moribundity. Mortality readings, based on Abbott's formula (Abbott 1925), were subject to analysis of variance and mean separation by Duncan's Multiple Range Test (P < 0.05). NY Field Applications of the isofenphos formulations were made 23 April 1984, to the rough/fairway at Links Country Club on Long Island and to the fairway at Drumlins Country Club in Syracuse on 30 April Links Country Club, located ca 30 km from the soil collection site used in the laboratory, was selected because it contained a mixed population of Oriental beetle, Japanese beetle, and the Asiatic garden beetle, Maladera castenea (Arrow). The Syracuse site was selected because consistent field populations of the European chafer/japanese beetle have been found in the area. Each fairway turf consisted of Kentucky bluegrass (40%), annual bluegrass, P. annua L. (35%), bentgrass, Agrostis sp. (10%), and annual grassy weeds (5%). Granular fonnulations were applied to the recommended commercial rates with a precalibrated Gandy spreader (0.75 m). The liquid formulations were applied with a sprinkling can using liters (3 gal) of water per 9.2 m 2 (100 sq ft) of plot (30 gav1000 sq ft). Plots were 3.04 by 3.04 m (10 ft), with each treatment including untreated controls replicated four times in a randomized complete block design. Irrigation was not applied because of high

3 BAKER and HELLER: Scnrabaeid Grub Control 267 amounts of annual spring rains. Treatments were evaluated d later by cutting a 1 ft X 10 ft (0.3 X 3 m) strip lengthwise through each plot using a mechanical sod cutter (depth 5.6 em). Three consecutive l-ft (0.3 m) square samples were taken from each replicate with sod and underlying soil examined for grubs with mean survival per sq ft determined. Mortality readings were as previously described. PA Laboratory Soil with no previous history of insecticide used was collected from State College, PA, in November Textural class was Hagerlown silt loam with a ph of percent organic matter reading was taken. Isofenphos fonnulations at the rate of 1.5 ppm 13.7 lb (1.7 kg) AI/hal were thoroughly incorporated into screened soil. Five lots (four treatments and check) were held in separate covered plastic containers at 25 ± 1 C. Moisture was held at ca % on an air-dry basis. The isofenphos formulations used were 5G technical (formulation prior to 1980) with: I) Benonite clay carrier (80-B.C.), and 2) Oil-Dri carrier (80-0.D.), and two 21 liquid formulations, A (# ) and B (#83R68-68). The two liquid formulations were suspended in 25 ml of tapwater and applied using a flne mist sprayer, then mixed and rescreened. After mixing, soils were covered and held in controlled rooms maintained at 25 ± 1 C with 12 h photoperiod. Japanese beetle grubs wete field-collected during the fall of 1983 and stored at 10 C in 3 X 15 X 1.2 m plastic tubs containing a mixture of collection site soil and grass. Tubs were removed from storage and held at 21 C for 24 h prior to introduction of grubs to treated soil. At 14 d intervals beginning 29 November (1983) through 7 March (1984), ca. 20 kg of treated soil was removed and distributed evenly between five 13 X 18.5 X 8 em deep plastic trays (5 reps/ treatment). To provide a food base, ca. 28 gm of contractor grass seed mix (60% annual ryegrass, 10% perennial ryegrass, 10% Kentucky bluebtf8ss, 20% fescue) was incorporated into each tray. Fifteen grubs/tray were introduced and allowed to crawl into the soit. Any that did not crawl in within 30 min were replaced. Mortality readings were as previously described. Soil Analysis Soil analyses of micronutrients were determined for low survival of the checks as described by Aten et aj. (1980). RESULTS AND DISCUSSION Laboratory Results of the isofenphos formulations incorporated into the soil indicate differences not only between formulations but between soil types and species (Tables 1 3). In Long Island soil, none of the formulations provided acceptable (80% or better) control regardless of days after introduction (DAl) of the Oriental beetle, nor were there any significant differences among formulations (Table 1). Mean check mortality was considered high at 28 DAI, which would contribute to the nonsignificance. In contrast, in the upstate NY soil, au but 5G 84 B.C. and the 5G-80 B.C. formulations provided acceptable Oriental beetle control, with 5G-83 B.C. and 5G-80 O.D. providing significantly better control at 28 DAL A comparison

4 268 J. Agric. Entomol. Vol. 3, No. j (1986) Table 1. Mean rate of toxic action of five soil-incorporated formulations of isofenphos in two New York soils on third stage Oriental beetles. Percent mortality Days after introduction (DAn" Soil Formulation 14t L.L 21 (A) 19.6 a 21.5 a 22.2 a 5C a 13.9 a 13.9 a 5G-80 B.C a 11.3 a 2.2 a 5G-84 B.C. 0.0 a 3.5 a 0.0 a 5G-83 B.C. 0.0 a 0.0 a 0.0 a Standard error (9.4) (11.9) (21.1) x check mortality (%) Upstate 5C-83 B.C a 86.7 ab 91.5 a 5G a 89.8 a 90.4 a 21 (A) 72.4 a 80.9 ab 82.2 ab 5G-84 B.C b 67.8 be 70.0 be 5G 80 B.C b 62.5 e 63.2 e Standard error (6.9) (7.1) (7.3) x check mortality (%) "Pooled results from three (L,t) and fouf (Upstutc) lests. t Means not followed by same letter in the same column differ significnnlly at.sri;; level (Waller and Duncull BSO Hulc). Table 2. Mean rate of toxic action of five soil~incol'porated formulations of isofenphos in two New York soils on third stage European chafer. Percent mortality Days after introduction (DAn- Soil Formulation 14t L.I. 21 (A) 5G-83 B.C a 5G e 67.9 e 5G-84 B.C b 96.4 ab 87.5 a 5G-80 B.C b 77.7 be 37.0 a Standard error (4.7) (6.6) (19.7) x check mortality (%) Upstate 21 (A) 97.3 a 99.4 a 5G ab 97.1 a 98.3 a 5G-83 B.C_ 65.2 b 71.1 b 73.8 ab 5G-80 B.C b 64.1 be 68.2 b 5G 84 B.C. 9.5 e 45.2 c 48.6 b Standard error (7.0) (7.9) (9.2) x check mortality (%) Pooled results from olle (L.!.) lind three (Upstate) tests. t Mealls not. followed by same letter in the same column differ significantly Ilt 5% level (\ValJer lind Duncan BSD Rule).

5 BAKER and HELLER: Scarabacid Grub Control 269 Table 3. Mean rate of toxic action of fouf soil incorporated formulations of isofenphos in a Pennsylvania soil on third stage Japanese beetles. Percent mortality Days after introduction (DAlt Formulation G _8 a 21 (A) 94.6 b 97.8 ab 98.6 ab 21 (B) 92.1 b 97.8 ab 97.7 b 5G-80 B.C b 96.3 b 97.6 b Standard error (1.5) (0_9) (0.7) x check mortality (%) Pooled results of eight tests. t fi..leans not followed by the SlImc leuer in the SlIlllC column significantly lit 5% level (\Vallcr tlnd Duncan BSD nule). of only soil types on the Oriental beetle revealed that the Long Island soil reduced (.he effcctiveness of all the formulations by at least 40%. and some ovcr 80%. Mean check mortality of European chafer in Long lsland soil at 21 and 28 DAI was very high with no significant differences among formulations at 28 DAI (Table 2). At 14 and 21 DAI, the 21(A) and 5G-83 B.C. gave excellent control, but one must Question the significance in the 21 DAI because of the high mortality in the checks. Mortality in the checks in the remaining tests was above 900/.; and thus unacceptable. Mean mortality of European chafer in upstate soil was excellent;. with the 2I(A) and 5G giving excellent control after 21 d (Table 2). Soil analysis comparisons taken from fairways at the Fresh Meadows Country Club and Geneva by the Pesticide Analytical Laboratory (Geneva) using Aten et al. (1980) method, shq\...ed the Long Island soil to contain over 32 ppm of arsenic (Table 4). We initially suspected the arsenic as calise of the high mortality; however, this warrants further investigation. AU formulations of isofenphos on Pennsylvania soil gave excellent control of the Japanese beetle throughout the experiment (Table 3). The 5G formulation was significanuy better than the 21(B) and tbe 5G-80 B.C. formulations, but none of the I>ercent mortalities were below 97% and thus the significance is meaningless. NY Field Field application of the different isofenphos fonnulations confirmed results found in the laboratory. Isofenphos formulations applied to mixed European chafer/japanese beetle grub populations at an upstate golf course showed all formulations gave acceptable and significant controls (Table 5). The same formulations applied on a Long Island golf course gave unacceptable control, consistent with laboratory findings (Table 6).

6 270 J. Agrie. EntomoL Vol. 3, No.3 (1986) Table 4. Analysis of New York soil from Fresh Meadows Country Club (L.l.) and Geneva. Fresh Meadows (fainvays) Elemen~ 14th Ilth Geneva Kt 911 uglg 852 uglg 350 Na Ca 18,468 2,165 3,020 Fe 11,237 17, Zn Mg 6,748 2, Mn Cu B P 2,630 1, PB ASI Procedures: t - Flame AAS; t Hybrid AAS; all othenj ICP. Table 5. Activity of isofenphos fonnulation on mixed European chafer/japanese beetle grub populations in fairway turf. Drumlins Country Club, Syracuse, NY. Treated 30 April 1984; examined 1 June European-3 rd Japanese-3rd Totals Fonnulation~ x t % control; x % control x % control 21 (A) a 96 5G-83 B.C o a 93 5G-80 B.C o a 89 5G-80 O.D o 0.7 a 75 5G-84 B.C o 0.7 a 75 Untreated b 4.9 lb (2.2 kg) Allh. t Grubs/O.93 m2. t Control based on Abbott's formula. Means not followed by same letter in same column diner significantly at 5% level (\\faller and Duncan asd Rule). Table 6. Activity of isofenphos formulations on mixed OrientaVJapanese beetle grub populations in fainvay turf. Links Country Club, Long Island, NY. Treated 23 April 1984; examined 30 May Oriental 3rd Japanese-3rd Totals! Fonnulation~ x t % controu x % control x % control 21 (A) 2.4 a~ a a 74 5G-83 B.C. 3.7 a a a 60 5G-80 B.C. 3.9 a a a 57 5G-80 O.D. 3.5 a a a 55 5G-84 B.C. 7.8 a a a 22 Untreated 5.9 a 1.4 a 12.1 a 4.9 lb (2.2 kg) AI/h. t Grubs/O.93 m2 ;: Control based on Abbott's formula. Includes Asiatic garden bectle, Maladera cw;tllliea (Arrow). 11 Means not followed by the same letter in the same column dilfer significantjy at 5% le~'el (Waller and Duncan BSD Rule).

7 BAKER and HELLER: Scarabaeid Grub Control 271 REFERENCES CITED Abbott, W. S A method of computing the effectiveness of an insecticide. J. Econ. Enwmol 18: Aten, C. F., J. B. Bourke, J. I-l Martini, and J. C. Walton Arsenic and lead in an orchard environment Bull. Environ. Contam. Toxico!. 24: J Baker, P. B. J985. Spring control of white grubs on a Long Island golf course, Insecticide and Acaricide Tests: Vol. 10: 273. Tashiro, H., T. D. Spittler, and E. Greco Laboratory and field evaluation of isofenphos for SCOl'Obaeid grub (Coleoptera: Scarabaeidae) control in turfgrass. J. Econ. Entomol. 75: