First and Foremost

1. First and Foremost Be curious Ask questions Cause a discussion Bring ideas and topics to class We will have outside reading assignments

2. How’s and Why’s PLNT 3112 stated the events without explanation. PLNT 4113 will discuss and challenge the students to understand how and why a weed science event occurs. Weed Science is NOT just the control of weeds; however, this is a very important component of Weed Science.

3. A Two-Part Course Weed Biology/Ecology Weed/crop interactions Techniques Interpretation on results Herbicide Families Behavior Fate Uses

4. Ecology and Weed Control Knowledge of the major mechanisms of weed survival (seed and propagule production and longevity) is needed to develop effective methods of weed control. Factors governing seed germination, sprouting of vegetative propagules, and plant development must also be addressed in planning an effective control program.

5. Ecology and Weed Control Seed dormancy and propagule unwillingness to sprout allows weeds to escape the effects of direct control measures such as tillage and herbicides and provides a mechanism for prolonged survival in soil, so this too must be taken into consideration.

6. Ecology and Weed Control Weed control methods are based on the assumption that dormancy will end and germination or sprouting will follow. Correctly estimating when maximum numbers of weeds will germinate and/or emerge will allow the agriculturalist to apply preemergence herbicides before weeds emerge.

7. Ecology and Weed Control After weed emergence, reactive rather than proactive weed control measures will have to be used. With the current herbicides today it is possible to manage weeds in this manner, but personally I dislike being in a “catch-up” system.

8. WEED BIOLOGY/ECOLOGY Essentially plant biology/ecology Recall definition of a weed? Least understood and appreciated component of Weed Science Looking for “weak links” or vulnerable points in the life cycle of the weed. Personal opinion – it is a “MUST”

9. Knowledge of weeds (plants) leads to the general appreciation of one’s environment in the same way as the recognition of other familiar things such as birds and animals. As one learns the identity of weeds (plants) and becomes familiar with their growth habits, positive attributes, and negative attributes, one’s perspective of life is broadened.

10. Why Do We Have Weeds It is natural Man or even a natural event has caused a change in the vegetation Nature is just trying to repair the damage This is called “Natural Succession” Flora going back to “climax vegetation” Man attempts to hold back succession

11. What is Climax Vegetation Prairie Hardwood Forests Swamp Cross-timbers Pine forests Desert Flat, fertile land without plants – NO WAY

12. In a Nutshell Man is trying to hold back or push back the natural processes of nature. For “man’s” purposes, we are trying to make the land produce more of what man wants than nature was providing. Without man pressing nature for more – many would starve today. 10 – 20,000,000 can survive as gatherers

14. Weeds are the First Stages of Natural Succession Rice noted 4 stages for OK farmland to return to prairie vegetation Weeds (ragweed, pokeweed, etc. – 2-4 yr.) Annual grasses (prairie three awn – 9-13 yr) Perennial bunchgrasses (little bluestem – 15-30 yr) True prairie vegetation (maybe as long as 40 yr) This same process has been documented to take 33 years in Kansas

15. Man/Succession For as long as a field is not in climax vegetation – man is trying to manage the natural process of succession. Man is the greatest disturber of environments that the “modern” world has ever known. Don’t forget the “Ice Age”

16. Food Belts Man has adapted his/her agriculture to the climate of the region – hence we have Corn, Soybean, Cotton, Wheat, Range, Forest belts These and other crops are seldom as well adapted as the species native to the area. These “better adapted” plants are what man calls weeds because those “plants” keep trying to reclaim their space and revert back to “climax vegetation”.

17. Why the Invasion of Weeds Crops grown in rows – gaps favor weeds Crops are grown in pure stands – the plan A single species generally fails to fully exploit the habitat. This applies even to climax vegetation. How many different species can you recall in a “climax?

18. Weeds are not Static Yesterday’s crops may be tomorrow’s weeds Johnsongrass, Kudzu, Bermudagrass, Genetically Engineered Crops New weeds or different plants filling a void where an old weed was, but is now controlled Cheat/Jointed goatgrass Pigweed & Crabgrass/Silverleaf nightshade

19. How do you recognize a weed You don’t! Man alone makes this determination and each of you may assess a plant differently (farmer, home owner, sportsman, RR) Poison oak & ivy, sandbur, pucturevine Morningglory, johnsongrass, bermudagrass, cheat, crabgrass, greenbriar, chufa, sericea lespedeza, and many, many more.

20. 14 of the World’s most serious weeds Smooth pigweed – North America (a) Spiny amaranth – Tropical America (a) Wild oat – Central Asia (a) Lambsquarters – Europe (a) Field bindweed – Europe (p) Bermudagrass – Tropical Africa (p) Yellow & purple nutsedge – India (p) Crabgrass – Europe (a) Junglerice & barnyardgrass – India (a) Goosegrass – China, India, Japan (a) Common purslane – Europe (a) Johnsongrass – Mediterranean (p)

21. Definition of a Weed A broadleaf plant A plant out of place A plant growing where it is not wanted A plant that has objectionable characteristics and is growing where “man” does not want it A plant whose virtues have yet to be discovered We have old weeds, new weeds (exotic/invasive), and maybe newer weeds are being made – GM crops and weeds crossing with GM crops.

22. Invasive Plant Species Invasive Exotic Exotic/Invasive Naturalized Many weeds, nearly all of our crops, and livestock are not native to the U.S.

23. Invasivespecies.gov What is an invasive species? An “invasive species” is defined as a species that is 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. (Executive Order 13112).

24. Invasive Weeds in Oklahoma? Salt cedar Thistles – musk, Scotch, & Canada Eastern redcedar Sericea lespedeza Johnsongrass Field bindweed Yellow & purple nutsedge

25. Origin of Weeds Native – 39% Europe – 35% Eurasia – 13% Tropical America – 3% Asia – 2% Other – 8% Pretty much the order of immigration

26. Purposely Introduced Species Crops Animals Wheat Cattle Cotton Swine Rice Chickens Soybeans Horses Alfalfa Sheep Potatoes Goats Tomatoes Pheasants

27. Purposely Introduced Species Weeds? Pests Hydrilla Sparrows Waterhyacinth Starlings Morningglory Egrets Cheat Carp Johnsongrass Nutsedges

28. Migration of Weeds Movement of weeds has followed man’s movements. Mostly east to west, but some movement west to east (limited). North and south movement has been much more limited. Climatic differences are more extreme going longitudinally rather than latitudinally.

29. Negative & Positive Aspects of Weeds Many – refresh yourself by looking at your PLNT 3112 notes or any Weed Science text book. Regardless of which group you put these plants in – you MUST properly identify them! Proper identification is “essential” to knowledge and management.

30. Biological Characteristics of Weeds Rapid growth rate High seed production capacity Dormant seed Erratic germination Several dispersal methods Variable flowering and germination More than one method of propagation Seed mature at different times

31. SWSS Monday, Jan 26 and Wednesday, Jan 28 – NO CLASS Make-up time Monday Feb 2, 5 to 6:40??? Tuesday Feb 3, 5 to 6:40??? Thursday Feb 4, 5 to 6:40???

32. Ecotype/Biotype A subdivision of a species that survives or behaves as a distinct group. May grow differently, react differently to herbicides. Generally not classified differently – taxonomically. Caddo maple, many bermudagrasses, cockleburs, there are ecotypes/biotypes of almost all of our weeds.

33. Classification of Weeds Annuals Biennials Perennials Simple Creeping Dicotyledons, monocotyledons, sedges

34. Perennials Propagated for seed they are seedlings and behave as “annuals” for a short period of time. This “seedling time span” is important! Much easier to control

35. Plant Families Groupings of plants which botanically or taxonomically have similar characteristics Families have some common genetic characteristics Solanaceae (tomatoes & silverleaf nightshade) Genus – more genetically similar than family Sorghum (grain sorghum & johnsongrass) Species – very genetically similar bicolor (grain sorghum & shattercane) Sativa (rice & red rice)

36. Pollination Most plants (crops and weeds) are self pollinated; however, a certain percentage are cross-pollinated. Cross pollination helps broaden the genetic base. Allows for more diversity Both good and bad Crops can be cross-bred, weeds can cross with crops, and weeds can cross with weeds

37. Pollination Naturally self-pollinated (<4% cross poll) Wheat, barley, oats, tomato, peas, soybeans, etc. Often cross pollinated (self more common than cross) Sorghum & cotton Naturally cross-pollinated Corn, clover, sugarbeet, many fruits, squash

39. Pollen Transfer With transgenic crops this is a major concern Rice > red rice Wheat > jointed goatgrass Grain sorghum > shattercane

40. Seed Production

41. Soil Seed Bank A Weed’s mechanism for long-term survival Lupinus arcticus (Legume) collected beneath permafrost in Yukon Terr. Estimated age 10,000 years – some seed germinated! Seeds from a British Museum herbarium that were 237 years old germinated Several other accounts can be given The “sleeping state” of a plant’s life cycle

42. Beal, Duvel & Turner Studies Beal, 1879 Buried seed, 3 out of 100 species germinated after 100 yr Duvel, 1904 27 out of 48 still germinated after 39 years of burial Turner, 1933 After 81 to 90 years of burial, 7 species germinated (all legumes)

43. Importance of soil-seed germination Not the level or magnitude, but the fact that it does occur. Evidence exists that tillage hastens depletion of the seed bank. Now we promote reduced tillage Seed longevity is increased if seed are mixed in the soil rather than left on the surface. Seems to conflict with statement above.

44. Depletion of the soil-seed bank Natural ageing, respiration, enzyme activity Germination Microorganisms Other soil organisms Birds and animals Climate/environment Fire

45. Recovery of the Soil Seed Bank Little definitive data on this subject Difficult to do and takes many years Scientists are impatient, must publish One year seeding, seven years weeding One year seeding, ten years weeding Very likely “species specific”

46. Factors Affecting Seed Production Quickness that this can occur Produce seed when flower is severed Nutrients Water Light Even under the most adverse conditions some seed is produced (likewise w/crops)

47. Resumption of Growth Germination can be defined as the resumption of growth of a seed or a vegetative part. Imbibition of water Increased respiration Mobilization of food reserves Digestion of reserved foods For our crops, this sequence begins promptly after planting and proceeds in an orderly fashion to the seedling emergence.

48. Requirements for Germination Water – the solvent for food reserves Some weeds can germinate in nearly dry soil Oxygen – required for respiration Some weeds (aquatic) can germinate in flooded soil Temperature – enzyme activity, cell division Very species specific Light A requirement for some Favorable pH