Growing Healthy Lawns Without Insec6cides David Smitley Michigan State University White Grubs are the Most Destruc6ve Family of Turf Pests in North America Exo6c Pest Species Japanese beetle European chafer Oriental beetle Asia6c garden beetle Aphodius granarius Displacement of Na6ve Grubs in Turf in Eastern United States by Exo6c Grubs Survey of 49 towns in Connecticut* (Hanula & Andreadis 1988) Species Total found Japanese beetle Popillia japonica 1,4 Asiatic garden b. Maladera castanea 594 Oriental beetle Anomala orientalis 454 Rose chafer M. subspinosus 144 European chafer Rhizotrogus majalis 65 N. masked chafer C. borealis 24 June beetles Phyllophaga spp. 43 *Golf course or park sites selected if at least 1 Japanese beetle grub was found in the first 2 samples (.1 m 2 ). Native: Phyllophaga spp. and masked chafers Alterna6ve Management Strategies Irriga6on to reduce grub survival Cultural prac6ces to increase root mass Irriga6on Fer6lity Mowing Resistant or tolerant turf types Biological control strategies Irriga6on Study in Michigan: Country Club of Jackson (Cappaert and Smitley) Grub plots in golf course rough (natural infesta6on) Treatments (4 replica6ons): No irriga6on Irriga6on in July only Irriga6on in August only Irriga6on in July and August
Larvae/ft2 JCC Ir r ig Plots, Japane s e be e tle 35 3 25 2 15 1 5 13-Aug 2-Oct Dry Early Late Total Larvae/ft2 3 2 1 JCC Irrig Plots, Europe an chafe r 13-Aug 2-Oct Dry Early Late Total Ir r igation Tr e atm e nt Irrigation Tre atm e nt Irriga6on and European chafer Smitley and Gilstrap 22 239 larvae introduced into each plot in early September. Plots harvested in November Daily irriga6on: 8.2 larvae/sq Z Weekly irriga6on: No irriga6on 17. larvae/sq Z 22.1 larvae/sq Z Turf Resistance to European chafer Turf Core Study in Greenhouse Smitley, Cappaert and Bughrara 22 Turf species Cultivar Root loss - grubs Fine fescue Dawson 7 % Kentucky bluegrass Brilliant 54 % Champagne 45 % Midnight 63 % Perennial ryegrass Affinity 53 % Palmer 55 % Premier 59 % Tall fescue Bonsai 35 % Falcon 26 % KY-31 45 % *Note: No visible foliage loss until about 7% of roots consumed Root loss/low larvae dendsity Root loss treatment due to grubs (%) 9 8 7 6 5 4 3 2 1 Grub Root Damage in Relation to Root Mass LBS Buf Ind Sed Zoy Ky-31 y = -4.1557x + 85.885 R 2 =.6755 5 1 15 2 Dry root mass (g) Ber Turf Tolerance to Grubs A large part of tolerance comes from having a large, rapidly growing root system. Some turf types (tall fescue, zoysia) are more tolerant/resistant even with the same root mass as more suscep6ble types We are also seeing differences in tolerance/resistance among cul6vars within a turf species
Turf types most likely to be tolerant of grub feeding injury Cool season Irrigated Kentucky bluegrass Not irrigated Tall fescue Warm season Irrigated Zoysia, Bermuda Not irrigated Tall fescue Cultural Prac6ces to Increase Turfgrass Root Mass Irriga6on Proper fer6lity Mowing height (higher is beaer) Alterna6ve Grub Management Plan for Home Lawns: Irrigated lawns Tolerant cul6var of Kentucky bluegrass (or zoysia in warm season turf areas) Good fer6lity Mow at 2.5 to 3.5 inches Inoculate once with Heterorhabdi2s nematodes and milky disease Alterna6ve Grub Management Plan for Home Lawns: Non- irrigated lawns Grow tolerant cul6var of tall fescue Good fer6lity program Mow at 2.5 to 3.5 inches In future: Inoculate with S. scarabaei when it becomes available. Turf Type Grubs Control Root wt Root wt w/grubs Root loss (%) Rating Tall Fescue KY31 4.5 11 15 87 5. Tall Fescue Bonsai 5.6 114 18 84 5.3 Tall Fescue Falcon 5.8 81 22 73 5.8 Ryegrass Palmer III 7.7 156 15 91 5.1 Ryegrass Premier 6.2 88 17 72 6. Ryegrass Affinity 6.8 146 27 81 4.4 Ky Bl Brilliant 9. 19 97 49 2.8 Ky Bl Midnite 7.2 195 6 69 5.1 Ky Bl Champaign 7. 187 56 7 2.2 Fine Fescue Dawson 7.2 133 33 75 3.4 Turf selection and mowing to prevent grub damage Smitley, Rogers, Steinke Mowing Height From Beard, Turfgrass Science More than 5% of roots must be consumed before damage is visible
Cultural Prac6ces to Increase Turfgrass Root Mass (no insec6cide) Turf Tolerance/ Resistance to Grubs Irriga6on Proper fer6lity Mowing height (higher is beaer) Turf selec6on MSU Hancock Turf Research Farm Conclusions From Grub Tests Timing of Merit, Allectus and Arena: All give excellent grub control when applied in May, June, July or early August Grub control less reliable in late August and early September (7 8%) Not effec6ve for grubs azer mid September Timing of Mach II: Excellent in June and July Conclusions- Products Most Effec6ve Against European Chafer Merit, Allectus and Arena are highly effec6ve against EC and JB Mach II was more effec6ve against JB than EC Sevin was more effec6ve against EC than JB
Homeowner Grub Control Products Product lb ai/a Date Type Chemical Grubs Merit 75.3 7/13 Spray imidacloprid.2 1 * Complete Killer.26 8/29 Granular Imidacloprid.5 * Season-long Grub Control.25 7/13 Granular Imidacloprid.8 * Grub Stop Once and Done 2. 7/13 Granular Halofenozide 1.8 * 24 Hour Grub Control 8.1 8/29 Granular Trichlorfon 3.5 Sevin Lawn Insect Granules 7.8 8/29 Granular Carbaryl 3.5 Grub Stop Once and Done 2. 8/29 Granular Halofenozide 4. Triazicide Insect Killer.5 8/29 Granular Cyhalothrin 1.7 Untreated Check - - - - 1.1 Department of Entomology Michigan State University 1 Number of grubs per 2. ft 2 * Indicates treatment is different from untreated at P =.5, LSD test. Photo by Dave Cappaert