Management of Container Weeds. Dr. James Altland

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1 Management of Container Weeds Dr. James Altland

2 Container vs. field production Containers No seed bank Bark substrates are free of weeds initially Isolated substrate volume Irrigated daily No postemergence herbicides No cultivation Field crops Abundant seed bank Abundant weed seeds and perennial propagules Soil is continuous Irrigated weekly or less Many postemergence herbicides (directed apps.) Cultivation equipment is common and efficient

4 Container weeds Seed have some sort of active dispersal mechanism Wind-blown Explosive dehiscence Splashed with water Germinate in low light levels Germinate in moist environments Short life cycles Prolific seed producers Small seeds

5 Container weed management Understand weed biology Understand how weeds propagate and spread Use unique aspects of the container environment to disrupt weed establishment

6 Container weed management Effective weed control Sanitation Weed seed Weeds in noncropland areas Herbicide management Maintain chemical barrier

10 Consistent message Sanitation Eliminate the weed source Culture Use practices that inhibit germination and slow weed growth Chemical Use proven effective herbicides Or substitute herbicides with mulch

11 Bittercress Cardamine sp.

12 Bittercress Cardamine hirsuta or C. oligosperma C. hirsuta 80% of flowers with 4 stamen 18% with 5 stamen 2% with 6 stamen C. flexuosa or C. stricta 100% with 6 stamen

14 Bittercress Cardamine hirsuta or C. oligosperma. Greek, literally translates to bitter cress Family Brassicaceae Mustard family Winter annual, short-lived, rapid life cycle Most problematic from October April Single plant can produce seed The crux of the problem

15 Bittercress seedlings Silique 2-sided, dry, dehiscent fruit.

16 Bittercress Seed germinates within 5 days Can produce new seed within 5 weeks Explosive dehiscence Shoots seeds up to 3 feet

17 Bittercress Sanitation is very important Control on gravel, weed fabric Sanitize ground between crops Remove debris, spilled bark, leaves, etc. If necessary, spray with postemergence herbicide to kill germinated weeds Use preemergence herbicides beneath containers

18 Bittercress seedlings Require little substrate for germination Germinate readily in Gravel Drain holes Weed fabric

19 Bittercress seedlings

21 Chemical control Most problematic in cool season Troublesome in over-winter structures Apply preemergence herbicide 3 weeks prior to covering containers for winter

22 Bittercress Expt. 1 Number germinated 3 weeks after herbicide application Control Broadstar Dim Dim + Pen Kansel OH2 Regal O-O Regal Star RegalKade Ronstar Weed number Rout Snapshot

23 Bittercress Keys to success Sanitation no weeds on gravel or near containers Preemergence herbicides Apply soon after potting Apply prior to overwintering

24 Creeping woodsorrel Oxalis corniculata Greek osys - sour Corniculata - horned

25 O. corniculata vs. O. stricta

26 Creeping woodsorrel Seed dissemination Seed are forcefully expelled up to 10 from mother plant. Seed are ridged and sticky

27 Creeping woodsorrel Small clump of foliage Spreads by stolons

28 Oxalis Expt. 1 Fresh weight 60 days after herbicide application Control Broadstar Dim+Pen Dimeth. Kansel+ OH 2 Regal O-O Regal Star RegalKade Shoot fresh weight (g) Ronstar Rout Snapshot

29 Creeping woodsorrel Easy to control from seed Most infestations come from liners!!!! Liners come infested with oxalis Regenerate from roots and stolons Most pre- herbicides will not control regeneration from roots

32 Creeping woodsorrel When containers have oxalis Thoroughly hand weed containers or liners Apply Snapshot at 200 lbs/acre

33 Creeping woodsorrel Keys to control Do not allow plants to grow near containers Check liners for infestations Use preemergence herbicides to prevent new infestations Use Snapshot at 200lbs to follow up on handweeding

34 Prostrate spurge Chamaesyce maculata Summer annual Seeds germinate within 5 days Plants mature in just 4 weeks

36 Prostrate spurge The most difficult-to-control species in the southeast Becoming more problematic in Oregon Seed dispersal??? Wind-dispersed in similar species.

37 Prostrate spurge Shoot weight (g) Control Broadstar OH2 Regal O-O Rout Snapshot

38 Spurge control 3 months Spurge number/pot 0 Control Rout Ronstar Pendulum Regal 00 Snapshot Regal Star

39 Marchantia polymorpha Lower plant form (Hepatophyta) Reproduces sexually by spores Reproduces asexually by gemmae

40 How do they spread? Gemmae splash from irrigation or rain drops. Gemmae can splash up to 1 meter. Liverwort produce microscopic spores

41 Liverwort control?? Prevention is the best method. Make the container environment inhospitable for liverwort. Reduce moisture Reduce humidity Remove nutrition on the container surface.

42 Preemergence liverwort control Greenhouses Sanitize greenhouses prior to crops

43 Zerotol Hydrogen peroxide Peracetic acid Stabilizers Kills spores prior or soon after germination. Kills gemmae. No observable injury on crops tested so far.

44 1:500-2x week Non-treated controls

45 Liverwort control - preemergence Container stock Preemergence herbicides Do not over-water plants Avoid topdressing

46 Liverwort control - preemergence Percent coverage of the container surface 70 days after herbicide application Control Broadstar Dim+Pen Dimeth. Kansel+ OH2 Pendulum Pre Pair Regal O-O Regal Star RegalKade Ronstar Rout Snapshot

47 Liverwort control - preemergence Propagation, enclosed structures Sterilization of greenhouse structure Bleach (use quickly) Quaternary ammoniums Triathlon Hydrogen peroxide Zerotol

48 Killing existing liverwort Mogeton Being registered by Crompton/Uniroyal Co-registration with U.S. and Canada Provides excellent post liverwort control Little or no injury to ornamentals Terracyte at high rates Labeled for 15 lbs/1000 ft 2 Most effective early in the year (before April)

49 Burn-down of juvenile liverwort

51 Liverwort control Keys to success Greenhouse Sterilize greenhouse Use Zerotol regularly Kill small liverwort populations Container stock Use Pre-herbicides Broadstar, Rout, or Ronstar Avoid over-watering and topdressing fertilizers

52 Pearlwort Sagina procumbens Sagina Latin for fodder, once mis-classified in the spurrey genus. procumbens - prostrate

53 Pearlwort seedlings

54 Pearlwort

55 Pearlwort Substrate particle size Seed are extremely small. When coarse substrate is used, seeds fall too deep in pores, cannot germinate.

56 Pearlwort Expt. 2 Weed number 50 days after herbicide application, seed applied 30 days after herbicides. Control Broadstar Dim+Pen Dimeth. Kansel OH2 Pendulum Pre Pair Regal O-O Regal Star RegalKade Ronstar Rout Snapshot

57 Pearlwort Easy to control from seed with herbicides. Pearlwort already established in prop liners is extremely difficult to control. What s the solution? Better weed control in propagation

58 Northern willowherb a.k.a. fireweed Perennial Germinates year round Forms a rosette over cold winter months Grows upright and flowers in spring/summer

59 E. ciliatum Plants grow 2 to 4 feet tall. Foliage and stems can be purple-ish

60 E. ciliatum Flowers are white to pink Flowers are bi-lobed Seed are attached to tuft of hairs and wind dispersed

61 E. ciliatum -NWH Seed germinate within 4 days of natural sowing. Plants mature and produce new seed in 8 weeks.

63 Fireweed Expt. 2 Weed number 50 days after herbicide application, seed applied 30 days after herbicides Control Broadstar Dim+Pen Dimeth. Kansel OH2 Pendulum Pre Pair Regal O-O Regal Star RegalKade Ronstar Rout Snapshot

64 NWH sprayed herbicides NWH number 60 days after herbicide application, seeds applied the same time as herbicides RegalKade Ronstar Rout none Devrinol Factor Surflan none Devrinol Factor NWH numbers/pot Surflan RegalKadeRonstar Rout With Gallery Without Gallery

65 NWH Keys to success Cultural control Do not allow NWH in or around the nursery to bloom and produce seed. Chemical control products containing oxadiazon (Ronstar)

66 Summary Sanitation is the cornerstone to any weed management program Learn how each weed spreads Prevent the dispersal mechanism Herbicides are good tools Alone they are largely ineffective Nurseries in Canada

67 Total weed management program Effective weed control Sanitation Weed seed Weeds in noncropland areas Herbicide management Maintain chemical barrier

68 Website

Container Weed Management. Dr. James Altland

Container Weed Management. Dr. James Altland Container Weed Management Dr. James Altland Container vs. field production Containers No seed bank Bark substrates are free of weeds initially Isolated substrate volume Irrigated daily No postemergence