1. Weed IPM in Grape Production Jeffrey Derr Professor of Weed Science Virginia Tech IPM workshops 2014

2. 2014 Pest Management Guides Horticultural and Forest Crops http://pubs.ext.vt.edu/456/456-017/456- 017.html Weed control section for grapes http://pubs.ext.vt.edu/456/456-017/Section- 3_Grapes-3.pdf

3. Weed identification Books Weeds of the Northeast – Cornell Press Weeds of the South - University of Georgia Press

4. Additional Information http://oak.ppws.vt.edu/weedindex.htm www.ppws.vt.edu/ipm/weeds_container_nurs eries.html Virginia Tech Weed ID websites

5. Vegetation Management Plan Cover crop between the rows - Erosion control, ability to drive through vineyard soon after a rain Initially bare ground within the grape row - weeds, cover crops suppress vine growth

6. Site Preparation Goal is to reduce weed populations, especially for perennial broadleaf weeds Cover crops - cropping with competitive or allelopathic crops, such as rye or sudangrass, for 1 to 2 to two years before planting Grow alternative crops like corn where troublesome weeds like yellow nutsedge or broadleaf weeds can be controlled using herbicides that cannot be used in grape production Establish permanent cover before planting

7. Weed control in row middles Few options after planting grapes Aim (carfentrazone) - contact herbicide that will control small annual broadleaf weeds. Establish cover crop, control broadleaf weeds, kill cover crops in strips prior to planting

8. Site prep - Chemical control Glyphosate - apply in strips in fall for fescue, orchardgrass control - plant into killed strips

9. Perennial Cover Crop Evaluation for Enhanced Vineyard Floor Management Funded by the Virginia Wine Board/ VVA/VDACS Trials in Virginia Beach, Blacksburg, and cooperating vineyards Evaluate cool- and warm-season perennial grasses for use between rows of grapes Proposed new research – evaluate cover crops within the row, continue evaluating between row cover crops

10. Project Goals Evaluate ease of establishment and persistence for cool- and warm-season cover crops between vine rows. Evaluate weed suppression for each perennial cover crop. Determine crop suitability criteria such as: traffic, drought, and cold tolerance, as well as maintenance requirements. Evaluate cover crop influence on overall soil health.

11. Cover crops – Cool-season Tall fescue – standard + dwarf types Creeping red fescue Hard fescue Perennial ryegrass Kentucky bluegrass Hybrid bluegrass

12. Cover crops – Cool-season Prepackaged Combinations Companion grass – dwarf perennial ryegrass + creeping red fescue Rough and Ready- dwarf perennial ryegrass + turf type fescues + microclover

13. Cover crops – Cool-season glyphosate tolerant Big Horn GT – sheeps fescue Aurora Gold hard fescue Compared to Gotham hard fescue

14. Cover crops – Cool-season glyphosate tolerant Big Horn GT – sheeps fescue Aurora Gold hard fescue Compared to Gotham hard fescue

15. Cover crops – Warm-season Zoysiagrass Bermudagrass Blue grama Combinations with perennial ryegrass or hard fescue

16. Results – Warm season trials Difficult to establish in existing grape plantings due to the lack of safe herbicides for both the perennial grass and grapes Bermudagrass establishes much better from seed than zoysiagrass but will be more competitive Blue grama did not do well in our trials

17. Cool-season Establishment - Blacksburg All good establishment ‘Bighorn GT’ Sheep /Hard Fescue ‘DTT-43’ Dwarf Tall Fescue ‘DTT-20’ Dwarf Tall Fescue ‘Rough and Ready’ Microclover mix* ‘Companion Grass ‘ Cover Crop Mixture** ‘Applaud’ Perennial Ryegrass ‘Fawn’ K31 ‘Midnight’ Kentucky Bluegrass ‘Silverlawn’ Creeping Red Fescue

18. Cool-season Combination Seed Mixes ‘Rough and Ready’ Microclover mix - 34% Quatro Sheep Fescue, 30% Eureka II Hard Fescue, 30% PR8821 Perennial Ryegrass, 5 % Microclover ‘Companion Grass ‘ Cover Crop Mixture - 80% PR8821 Perennial Ryegrass, 20% Creeping Red Fescue ‘Southern States Premium Tall Fescue with Eco-Green’ - DTT 20 + DTT 43 tall fescue cultivars

19. Establishment – Virginia Beach Good – tall fescues (Fawn, DTT 43, DTT 20, Justice), zoysiagrass + Gotham hard fescue Poor – Kentucky bluegrass, hybrid bluegrass, Bighorn GT, Companion grass, Rough and Ready, Perennial ryegrass, zoysia + perennial ryegrass, blue grama

20. Traffic tolerance Good with the tall fescues, Companion grass, Rough and Ready Fair with Kentucky bluegrass Poor to fair with Bighorn GT, creeping red fescue

21. Grass species CultivarSeeding rate lb/1000 sq ft Establish rate 1-10 Weed Supp 1-10 Hard fescueBighorn GT226 Dwarf tall fescue DTT20/DTT43 blend 246 (mix)Rough and Ready 578 (mix)Companion grass 158 Perennial ryegrass Applaud596 Tall fescueFawn286 Kentucky bluegrass Midnight114 Creeping red fescue Silverlawn2510

22. Grass species CultivarTraffic tol- erance 1-10 Appearance 1-10 Height inches Hard fescueBighorn GT3920 Dwarf tall fescue DTT20/DTT4 3 blend 10827 (mix)Rough and Ready 10821 (mix)Companion grass 10825 Perennial ryegrass Applaud9720 Tall fescueFawn9455 Kentucky bluegrass Midnight6716 Creeping red fescue Silverlawn3533

23. Why control weeds?

24. Reasons to Manage Weeds Competition - leading to reduced crop growth and yield (quantity, quality) for water (drought years) nutrients (especially nitrogen) –cannot correct with extra N light (viny weeds)

25. Reasons to Manage Weeds Harbor insect and disease pests (dandelion and tomato ringspot virus, buckhorn plantain/aphids) Attract bees (problem for those allergic to bee stings, concern when insecticides are being applied) Interfere with harvest (rash - poison ivy, spines - brambles) Allelopathy (natural herbicides) - juglone – black walnut Provide cover for rodents

26. Tomato ringspot virus and grapes - http://www.grapes.msu.edu/ringspot.htm http://www.grapes.msu.edu/ringspot.htm Transmission of tomato ringspot virus from dandelion via seed and dagger nematodes. Mountain, W.L. et al. 1983. Plant Disease 67:867-868. When seedlings from 5 TmRSV-infected Taraxacum officinale plants were assayed, an av. 24% were infected, but germination was unaffected. Xiphinema rivesi (nematode) acquired the virus from infected plants and transmitted it to healthy seedlings. Dandelion is a major natural reservoir of the virus in Pa. and the potential importance of this weed in the epidemiology of TmRSV-induced orchard diseases (especially Prunus stem pitting in peach and apple union necrosis in apple) is discussed

27. Distribution of tomato ringspot virus in dandelion in Pennsylvania. Powell, C. A. et al. 1984. Plant Disease 68:796-798. The percentage of dandelion infection with Tomato ringspot virus was higher in orchards with Peach stem pitting (29%) than in either orchards without PSP (7%) or non-orchards (5%). Results support the hypothesis that TmRSV is initially introduced in an orchard via either infected nursery stock or dandelion seed and subsequently becomes established in dandelion and other weeds over a period of years.

28. Vegetation Management Plan Killed strip within the row to reduce weed competition Mowed (grass) alleyways for erosion control, drivability soon after rain

29. Grape Weed Control Biological – little available Cultural Chemical

30. Cultural control Cultivation (mechanical) – suppress perennials, break crusts, soil erosion, root damage Cultivation (flame) – tree injury, fire hazard Black plastic, fabrics – habitat for rodents, cost Organic mulches – improve moisture penetration, habitat for rodents, cost

31. Chemical control Preemergence herbicides Match to weed problems Apply prior to weed germination (clean soil or add a postemergence) Apply proper rate for soil type (organic matter, soil texture) Need rain or irrigation for activation Shorter residual under wet conditions

32. Preemergence herbicides for grapes – annual grasses and small-seeded broadleaf weeds Surflan (oryzalin), Prowl (pendimethalin), Devrinol (napropamide) – annual grasses, some broadleaves Can be used at planting after soil settles

33. Preemergence control – small-seeded broadleaf weeds Trellis (Gallery) (isoxaben) Combine with Surflan (oryzalin), Prowl (pendimethalin), Devrinol (napropamide) – annual grasses, some broadleaves Can be used at planting after soil settles 165 day PHI

34. Pre and early POST control – annual grasses, small-seeded broadleaf weeds, suppression of yellow nutsedge, dandelion Matrix (rimsulfuron) Vines must be established 1 year Short residual Combined with Surflan, Prowl, etc. for broader-spectrum control 14 day PHI

35. Preemergence herbicides for grapes – annual grasses, small-seeded broadleaf weeds, suppression of yellow nutsedge Solicam (norflurazon) Vines must be established 2 years

36. Pre and early Post control – annual broadleaf weeds, annual grasses Goal (oxyfluorfen) vines established 3 years unless on trellis wire at least 3 feet above soil surface combine with Surflan, Prowl, etc. for improved annual grass control

37. Pre and early Post control – annual broadleaf weeds, annual grasses Chateau (flumioxazin) Vines established at least 2 years unless vines protected with grow tubes, waxed containers, etc.

38. Chateau (flumioxazin) – grapes Dormant applications preferred Treat in early spring and fall Could add a preemergence grass herbicide, especially under high annual grass pressure or lower rates Add a postemergence herbicide for control of emerged weeds Use directed sprays, do not apply overtop of grapes

39. Chateau (flumioxazin) – grapes 6 to 12 ounces of product per treated acre, which equates to 0.19 to 0.38 pounds active ingredient per acre. Maximum use rate per year is 24 ounces of product. Use of 6 ounces of Chateau per acre when applications are made to very sandy/gravelly soils and tree or grape vines are established less than 3 years.

40. Results withChateau Strength is annual broadleaf control Excellent control – common lambsquarters, pigweed, velvetleaf, jimsonweed, common ragweed, prickly sida, bittercress Buckhorn plantain, yellow woodsorrel from seed Good control – annual morningglories, cocklebur

41. Results with Chateau Fair to excellent control of annual grasses: Large crabgrass, yellow foxtail, giant foxtail, johnsongrass from seed No control of yellow nutsedge or bermudagrass at use rates

42. Preemergence control - annual broadleaf weeds, annual grasses Princep (simazine), Karmex (diuron) Vines established 3 years Inexpensive broadleaf control Match rate to soil type

43. Preemergence herbicides for grapes – winter applied – cool-season grasses, winter annuals Kerb, Casoron – winter-applied, cools season perennial grasses, winter annuals For control of quackgrass, tall fescue, orchardgrass, plus winter annuals

44. Pre – annual grasses, annual broadleaf weeds Alion (indaziflam) Vines established at least 5 years

45. Alion (indaziflam) -sprayable form 1.67 lb/gal caution label -Preemergence with significant post activity - different mode of action (cellulose biosynthesis inhibitor) -directed spray -use rate 5 fl oz/acre (0.065 lb ai/A) (only 1 appl/year at that rate)

46. Alion (indaziflam) Strength – controls annual grasses (crabgrass, goosegrass, foxtails, annual bluegrass, annual ryegrass) -many annual broadleaf weeds (jimsonweed, pigweed, horseweed, lambsquarters, velvetleaf, eclipta, spurge, henbit, chickweed, speedwell, bittercress) -Long residual Weakness Does not control morningglory or yellow nutsedge

47. Postemergence herbicides for grapes

48. Chemical control Postemergence herbicides Match to weed problem Apply to actively growing weeds (no drought stress) Apply under warm temperatures (60 – 85 F) See if a surfactant is needed (nonionic versus crop oils)

49. Postemergence Grass herbicides Perennial grasses – johnsongrass, quackgrass, bermudagrass Annual grasses – crabgrass, foxtails, etc. Do not control yellow nutsedge or any broadleaf weed Poast (sethoxydim), Fusilade DX (fluazifop) – 50 day PHI, Select Max – nonbearing Need to add a nonionic surfactant or crop oil

50. Aim (Carfentrazone) a 1.9 lb/gallon EW or as a 2 lb/gallon EC postemergence control of small annual broadleaf weeds. 1 to 2 fluid ounces per acre. Apply when annual broadleaf weeds are less than 6 inches in height and actively growing. does not control grasses. can be tank mixed within other postemergence herbicides for broader-spectrum control or with preemergence herbicides. Adding a crop oil concentrate or nonionic surfactant may improve weed control. Do not allow spray to contact green stems, leaves, flowers, or fruit of fruit trees. Can also be used for control of suckers – see label for rates and directions for this use.

51. Rely (glufosinate) Nonselective Contact with some translocation Less effective on perennial weeds than glyphosate but lower risk of crop injury Apply as a directed spray when weeds are small and actively growing

52. Alternatives to Rely (glufosinate) Nonselective paraquat (Gramoxone) Rapid acting contact No effect on underground tissue – rhizomes, roots, bulbs, etc. Restricted use due to toxicity Apply this contact herbicide as a directed spray when weeds are small and actively growing

53. Alternatives to Rely (glufosinate) Nonselective Scythe (pelargonic acid) Rapid acting contact No effect on underground tissue – rhizomes, roots, bulbs, etc. 3-10% solution, use high spray volumes 75- 200 gallons spray per acre Can be used for sucker control

54. Alternatives to Rely (glufosinate) Nonselective Glyphosate (Roundup, others) more effective on weeds (systemic) but poses greater risk of systemic damage apply using a shield spray or wiper application Keep off grape foliage, green stems

55. Glyphosate Off patent, available under a variety of trade names (Roundup WEATHERMAX, Touchdown, etc.) Check label for pounds glyphosate acid/gallon Check label for need for a surfactant Check spray water for calcium content (hard water) – add ammonium sulfate 8-17 lb/100 gal

56. Herbicide-Resistant Weeds in Virginia atrazine - corn – smooth pigweed, redroot pigweed, common lambsquarters Simazine (Princep) – turf – annual bluegrass diclofop – wheat – Italian ryegrass sethoxydim – soybean - johnsongrass ALS inhibitors (IMIs, Sus – imazethapyr, nicosulfuron, etc.) – row crops - shattercane, smooth pigweed, common chickweed glyphosate – row crops - horseweed, Palmer amaranth others?