Herbicide Timing

1. Herbicide Timing Dr. Elton Smith Extension Nursery Specialist The Ohio State University Extension-Lake County Ohio State Short Course 2010

2. To Contact Me ? • Email :Zondag.1@osu.edu • Website: lake.osu.edu – (presentation will be posted here ) • Fax: 440-350-5928 • Phone: 440-350-2584

3. What is a Weed? • It is a plant out of place or a unwanted plant; a nuisance. • competition for water, space and nutrients • causes the desired plant to die or be changed • changes the environment • is not what we desire • can harbor and spread plant pathogens • some weeds are a nuisance because they have thorns or prickles • some have chemicals that cause skin irritation or are hazardous if eaten

4. Annuals • Common chickweed  • Dwarf spurge • Garlic mustard  • Groundsel   • Hairy bittercress • Knotgrass  • Ragweed • Shepherd’s purse  • Nightshade  • Velvet Leaf • Spurge, Prostrate • Pigweed • Purslane

5. Biennials • Burdock • Wild carrot • Bull Thistle • Redstem filaree • Western Salsify

6. Perennials • Broadleaf plantain • Creeping Charlie • Dandelion • Goldenrod • Poison ivy • Wood sorrel • Canada thistle • Field bindweed • Nutsedge, yellow • Garlic, wild • Curly dock

7. Factors to Consider in Controlling Weeds • What stage of the life cycle should they be controlled? • When do they reproduce? • When are seeds dormant, germinating or emerging? • What options do I have for control?

8. Major Categories of Herbicides • An herbicide is a substance used to kill unwanted plants • Pre emergence : • Pre-plant incorporated - herbicides are soil applied prior to planting and mechanically incorporated into the soil • Post emergence : • Contact herbicides - destroy only the plant tissue in contact with the chemical • Systemic herbicides - are translocated through the plant, either from foliar application down to the roots, or from soil application up to the leaves • Selective herbicides • Non-selective herbicides

9. Preemergence

14. Preemergence Cool Season Application

16. Translocated • Vantage, Poast sethoxydim translocated selective for grasses • Envoy clethodim translocated selective for grasses • Fusilade fluazifop-p-butyl translocated selective for grasses • Roundup glyphosate translocated nonselective • Basagran bentazon translocated nutsedge • Manage halosulfuron translocated nutsedge • Lontrel clopyralid translocated composites and legumes • Many labels 2,4-D translocated selective for broadleaf weeds

19. Contacts Finale glufosinate contact nonselective Gramoxone paraquat contact nonselective Reward diquat contact nonselective Goal oxyfluorfen contact nonselective Scythe pelargonic acid contact nonselective

21. Fumigants

23. Granular Combinations

28. Weed seeds disperse both horizontally and vertically in the soil profile.

30. You Didn’t Match the Herbicide to the Field Environment. • Rates to soil types • Proper time of application and rates • Proper stage of plant growth • Did the product need to be incorporated? How?

31. You Disturbed the Soil with Cultivation. Preemergence form a layer 1 to2 inches on the soil surface. Few of these products can be disturbed and stay active.

32. You Failed to Incorporate the Herbicide with Cultivation or Irrigation. Many preemergence herbicides require up to ¾ inches of water to be activated.

33. You Fertilized with a Nitrogen Fertilizer Close to the Herbicide Application. You may have increased microbial action or salinity that breaks down the herbicide.

34. Your Herbicide Didn’t Include the Weed. That is a Problem. Everything but groundsel

35. You Applied the Herbicide to Sites Where Weeds May Have Already Emerged or Gone to Seed.

36. Poor Coverage.

37. Your Rates May Have Been Too Low.

38. How to Predict Weeds? • By the use of growing degree–days GDD. • By looking at what weeds had the chance to go to seed . • Germinate field soils indoors.

39. Charles Mohler, Cornell University ,Mark Schonbeck, Virginia Association for Biological Farming

40. How Can We Determine Weed Bank in Existence? To get a weed preview, you can germinate weeds indoors as you’re waiting to plant. For summer annual weeds, such as velvetleaf, foxtail, lambsquarters and pigweed, March–April is a good time to sample weed seedbanks. Using a soil probe or a garden trowel, take 20 samples to a 2” depth in a ‘W’ pattern from the field you’re interested in. Place the soil in a pie dish, put in a warm place (> 65 º F) and keep moist. Within one to two weeks, you should have an idea of what weeds will be emerging in your field as the soil warms.

41. Depth (inches) Dormancy Germination Mortality 0–0.5 Low2 High2 High 0.5–2 Low High Medium 2–5 Medium Low Low 5–10 High3 Very low3 low Effect of weed seed depth placement on dormancy, germination, and mortality1. 1 From Davis (2004).2 Dormancy and germination at 0–0.5 inches depth depends on seed size. Small seeded weeds tend to have low dormancy and high germination at the soil surface, whereas large seeded weeds have medium–high dormancy and low germination at the soil surface.3 Note, however, that shorter-lived seed with no or little dormancy mechanism tend to undergo fatal germination at this depth (C. L. Mohler, personal communication, 2008).

42. Temperature and duration of heat treatment required to achieve 100% mortality for each species. Weed species Temperature (C) 70 60 50 46 42 39 --------------------- duration for 100% mortality (h) ------------------- Annual sowthistle 0.17 0.25 4 15a 96 672 Barnyardgrass 0.17 0.25 9 16 d d London rocket 0.17 0.25 6 24 96a b Common purslane 0.67 3 56a c d d Black nightshade 0.67 2 71 213 384 d Tumble pigweed 0.67 1 113 312 d d a 100% mortality not obtained because of a few heat-resistant individuals in each sample. b Could not be evaluated because of fungal infection. c Seeds germinated inside packets. d Species not affected at this temperature. Ruth M. Dahlquist, Timothy S. Prather, and James J. Stapleton

43. Number of years required for 50 percent and 99 percent reduction in seed number in the seedbank of ten common agricultural weeds. Adapted from Davis et al. (2005). Years required for 50% reduction Years required for 99% reduction • Common lambsquarters (Chenopodium album) 12 78 • Field pennycress (Thlaspi arvense) 6 38 • Common cocklebur (Xanthium strumarium) 6 37 • Yellow foxtail (Setaria glauca) 5 30 • Prostrate knotweed (Polygonum aviculare) 4 30 • Shepherd’s purse (Capsella bursa-pastoris) 3 11 • Giant foxtail (Setaria faberi) less than 1 5 • Common sunflower (Helianthus annuus) less than ½ 2 • Kochia (Kochia scoparia) less than ½ 2

44. Factors other than mean daily soil temperature have a major impact on the timing of weed germination and emergence in the field. Adequate soil moisture - good seed–soil contact. Common chickweed and common purslane in seeder tracks roughly double those over the rest of the field, annual grass weeds and yellow nutsedge did not show this pattern. Many weed seeds are also stimulated to germinate by light. Fluctuations in temperature and moisture. Increases in oxygen or nitrate nitrogen (N) levels in the soil. Tillage is therefore a critical determinant of seed germination. The timing of N fertilizer applications can also influence the number of weeds germinating. Small-seeded weeds such as kochia, Canada thistle, and common lambsquarters germinate at very shallow depths (less than ½ inch).

45. Tactics for Weed Control • Shallow soil disturbance during periods of peak potential germination. • Delayed applications of N fertilizer. • Timely cultivated fallow is used to reduce the weed seed bank and in the establishment of a stale seedbed prior to planting. • One strategy for managing the weed seed bank, especially for smaller-seeded weeds, is to maintain seeds at or near the soil surface. • Inversion tillage places seeds below the depth from which they can emerge. This may be an effective strategy for species with short-lived seeds, but it may simply protect longer-lived seeds. • Seeds of 20 weed species that were mixed into the top 6 inches of soil persisted longer in untilled soil than in soil tilled four times annually (Mohler, 2001a) compared to a single tillage which can enhance the longevity of recently-shed weed seeds. • Ridge tillage - before planting, the tops of the ridges are removed by sweeps that push residues and the top inch or two of soil into the interrow valleys.

46. Tactics for Weed Control • Kill weeds before they set seed—before flowering to be safe. • Control creeping perennial weeds before they can form new rhizomes, tubers, or other propagules. • Keep crops ahead of the weeds- shade, competition, space. • Walk fields to remove large weed escapes before they flower. • Mow field margins to minimize seed set by weed species that have the potential to invade fields. • Mow fields promptly after harvest to interrupt weed seed production. • Utilize good sanitation practices to prevent introduction of new weed species into the field, and remove new invaders before they propagate. • Increase the diversity of crop rotations- new herbicides and cultural practices. • Till or cultivate to stimulate weed seed germination at a time when the seedlings can be easily knocked out by additional cultivation or flaming (stale seedbed), or will be freeze-killed before they can reproduce. Rolling after tillage can further enhance germination by improving seed–soil contact.

47. Tactics for Weed Control • If practical, time this tillage or cultivation to take place when seeds of the major weeds present are least dormant, and/or during the season of the weeds' peak emergence. • Time crop planting to facilitate destruction of flushes of weed seedling emergence. Plant later and allow a weed to germinate than till and plant. • Reduce or avoid tillage during critical times for weed seed predator activity. If a significant weed seed rain has occurred, leave weed seeds at the surface for a period of time. • Maintaining a high level of soil biological activity through good organic soil management might be expected to shorten the half-life of weed seed banks. • Cultivate at night or with light shields over the cultivation implement to minimize the light stimulus to weed seeds. • Leave a loose soil surface after planting or cultivation to reduce seed. The looser the soil the drier it is and slow germination.

48. Tactics for Weed Control • Minimize soil disturbance at or near the time of planting. Do major tillage in fall or very early spring several weeks before planting. Use flame or very shallow cultivation to prepare the seedbed. • Avoid practices that result in early pulses of nitrogen that may stimulate weed emergence • Avoid planting crops in fields with heavy populations of weeds with similar life cycles • Time crop planting to take place well before the most abundant weed species in the field are expected to emerge. • Time crop planting to take place after the expected major weed seedling flushes, and remove the latter by shallow cultivation or flame weeding. • Invert the soil to a depth from which weed seeds cannot emerge (most effective for weeds with small, short-lived seeds. • Incorporated green manures or surface residues of cover crops can reduce the establishment of small-seeded weeds through allelopathy and/or physical hindrance.

49. Mixing Order of Pesticides • DF-Dry Flowables • WP- Wettable Powders • AS- Aquas solutions • F- Flowables • L- Liquids • S- Solutions • EC-Emulsifiable Concentrates