Presentation is loading. Please wait.

Presentation is loading. Please wait.

Weed Biology and Management Curtis Rainbolt Extension Weed Scientist Everglades REC.

Similar presentations


Presentation on theme: "Weed Biology and Management Curtis Rainbolt Extension Weed Scientist Everglades REC."— Presentation transcript:

1 Weed Biology and Management Curtis Rainbolt Extension Weed Scientist Everglades REC

2 Weed Biology and its Impact on Management What makes a plant a weed? What makes a plant a weed? Cost of weeds Cost of weeds Why do weeds always win? Biology Why do weeds always win? Biology Get to know the enemy Get to know the enemy Anatomy of a weed Anatomy of a weed Common south Florida weeds Common south Florida weeds Strategies for weed management Strategies for weed management

3 Definition of a weed: A weed is an undesired plant out of place A weed is an undesired plant out of place Water hyacinth in a aquatic garden: not a weed Water hyacinth in a aquatic garden: not a weed Water hyacinth clogging canals: a weed Water hyacinth clogging canals: a weed

4 Weed impacts  Weeds are costly  $24 billion in agricultural crop loss  $3 billion in control costs Pimentel et al. 1999

5 Weeds are costly It is estimated that without control, sugarcane losses would be 50% from heavy infestations of fall panicum It is estimated that without control, sugarcane losses would be 50% from heavy infestations of fall panicum In 2000, over $51 million was spent for weed control in US sugarcane In 2000, over $51 million was spent for weed control in US sugarcane

6 Why do weeds always win?  Dormancy: broken when conditions favor survival  Rapid early growth and expansion  Early and fast root growth  Efficient uptake and processing of nutrients and water

7  Ability to reproduce early in life cycle  Prolific seed production  Absorb resources in excess  Tolerate low levels of resources  Genetic and environmental adaptability  Ability to develop resistance to control measures Why do weeds always win?

8 Reproduction by seed  First infestation is dependant on seed  Estimates of the total number of weed seeds in the soil range from 4 million to 133 million per acre furrow slice

9 Vegetative reproduction  Less longevity in soil than seeds  Very small structures can reproduce  Canada thistle: ¼” piece of root results in new plant  Torpedograss can reproduce from very small segments of rhizomes  Can be as prolific as seed production  Yellow nutsedge: 1,900 new plants and 18,000 tubers in one year from one plant

10 Get to know the enemy: weed identification

11 Weed identification goals Impossible to learn the thousands of weeds found in Florida Impossible to learn the thousands of weeds found in Florida Learn the primary weeds Learn the primary weeds Keep field notes Keep field notes The goal is to learn how to identify a weed The goal is to learn how to identify a weed Plant anatomy Plant anatomy Plant keys Plant keys

12 Weed classification: life cycles  Annuals- reproduce by seed only  Biennial:  Life cycle completed in two years  Flowering and fruiting in second year  Examples: wild carrot, cudweed  Perrenials:  Simple- reproduce by seed only  Creeping- reproduce by seed and vegetative propagules

13 Differences between grasses and sedges: Sedges have a solid, triangular in cross section, stem. Leaves are arranged in threes (extend in three directions). Sedges have a solid, triangular in cross section, stem. Leaves are arranged in threes (extend in three directions). Grass stems may be round or flattened. Grass stems may be round or flattened.

14 Purple vs Yellow Nutsedge

15

16 Common Sugarcane Weeds

17 Fall panicum (Panicum dichotomiflorum) Most common grass in the area Most common grass in the area Relatively easy to identify Relatively easy to identify Stem can be hairy or smooth (hairy when young) Stem can be hairy or smooth (hairy when young) Ligule fringe of hairs Ligule fringe of hairs Round stem Round stem Widely dispersed seedhead Widely dispersed seedhead

18 Wild oats (Sorghum almum) Not really an oat Not really an oat Closely related to johnsongrass Closely related to johnsongrass No rhizomes No rhizomes Large, membranous ligule Large, membranous ligule Robust plant Robust plant Can look like sugarcane seedling when small Can look like sugarcane seedling when small

19 Broadleaf panicum Panicum adspersum (Urochloa adspersa) Panicum adspersum (Urochloa adspersa) Relatively prostrate growth Relatively prostrate growth Wide leaves with wavy margins Wide leaves with wavy margins Round stems Round stems Usually dark green in color Usually dark green in color Very similar to alexandergrass Very similar to alexandergrass

20 Alexandergrass (Brachiaria plantaginea) Relatively prostrate growth Relatively prostrate growth Somewhat wide leaves with straight margins Somewhat wide leaves with straight margins Round stems Round stems Usually light green in color Usually light green in color Very similar to broadleaf panicum Very similar to broadleaf panicum leaves narrower (usually) leaves narrower (usually) margins straight rather than wavy (usually) margins straight rather than wavy (usually)

21 Alexandergrass vs Broadleaf panicum

22 Napiergrass (Pennisetum pupureum) Very robust plant Very robust plant Forms dense clumps in fields Forms dense clumps in fields Long, wide leaves with finely toothed margin Long, wide leaves with finely toothed margin Up to 12 feet tall Up to 12 feet tall Seedhead has “bottle brush” appearance Seedhead has “bottle brush” appearance

23 Paragrass (Brachiaria mutica) Prostrate growing, medium size grass Prostrate growing, medium size grass Long stems covered with hairs Long stems covered with hairs Short hairs on leaf surface Short hairs on leaf surface Swollen nodes Swollen nodes Grows in very wet areas Grows in very wet areas Often moves out of ditches Often moves out of ditches Pasture grass in Africa Pasture grass in Africa

24 Paragrass (Brachiaria mutica)

25 Goosegrass (Elusine indica) Found in many fields Found in many fields Low growing Low growing Very white, flattened stems Very white, flattened stems Looks like it has been stepped on Looks like it has been stepped on Probably not competitive Probably not competitive

26 Crabgrass (Digitaria spp.) Very wide first leaf Very wide first leaf Initial clumping growth progressing to prostrate, tillering Initial clumping growth progressing to prostrate, tillering Visible membranous ligule Visible membranous ligule Can be very hairy, or hairless, depending on species Can be very hairy, or hairless, depending on species

27 Torpedograss (Panicum repens L.) Perennial with robust, creeping, sharply pointed rhizomes. Perennial with robust, creeping, sharply pointed rhizomes. Leaf blade stiff and erect. Leaf blade stiff and erect. Hairs on upper and lower leaf surface. Hairs on upper and lower leaf surface. Seedheads with stiff, ascending branches. Seedheads with stiff, ascending branches. Occurs in wet areas. Occurs in wet areas.

28 Spiny pigweed (Amaranthus spinosus) Most common pigweed species Most common pigweed species Stickerweed Stickerweed Large, upright growth habit, entire leaves Large, upright growth habit, entire leaves Very evident spines located at nodes Very evident spines located at nodes

29 Alligatorweed (Alternanthera philoxeroides) Common in many areas of the EAA Common in many areas of the EAA Prefers wet areas Prefers wet areas Often spread by cultivation Often spread by cultivation Low growing Low growing Hollow stems when growing in wet spots Hollow stems when growing in wet spots Opposite leaves Opposite leaves Small white blooms Small white blooms

30 Common lambsquarters (Chenopodium album) Common some years Common some years Usually during the cooler months (Dec, Jan) Usually during the cooler months (Dec, Jan) Can be difficult to control Can be difficult to control Waxy leaf surface Waxy leaf surface Small “dots” of wax are useful for ID Small “dots” of wax are useful for ID Gives leaves a white-gray color Gives leaves a white-gray color Alternate leaves Alternate leaves Medium size lobes on leaves Medium size lobes on leaves

31 Common purslane (Portulaca oleracea) Very common Very common Probably not competitive Probably not competitive Prostrate growing Prostrate growing Succulent Succulent Leaves small, smooth, opposite or alternate Leaves small, smooth, opposite or alternate Small, yellow flowers Small, yellow flowers Red stems Red stems

32 Common ragweed (Ambrosia artemisiifolia) Often found on ditch banks and field edges Often found on ditch banks and field edges Deeply dissected leaves Deeply dissected leaves Many hairs on upper and lower surfaces Many hairs on upper and lower surfaces Long seedhead at top of plant Long seedhead at top of plant Yellow flowers Yellow flowers Similar in appearance to ragweed parthenium Similar in appearance to ragweed parthenium Different flower type Different flower type

33 Ragweed parthenium (Parthenium hysterophorus) Primarily ditchbanks Primarily ditchbanks Less common than common ragweed Less common than common ragweed Leaves less deeply dissected Leaves less deeply dissected Divisions don’t go all the way to the stem Divisions don’t go all the way to the stem White flowers White flowers Single, not multiples Single, not multiples

34 American black nightshade (Solanum americanum) Occasional weed in EAA Occasional weed in EAA Problematic in vegetables (tomato, pepper) Problematic in vegetables (tomato, pepper) Same family (Solanaceae) Same family (Solanaceae) Resistant to paraquat in some areas Resistant to paraquat in some areas Alternate leaves Alternate leaves Usually entire to somewhat lobed Usually entire to somewhat lobed Purple fruit Purple fruit Seems quite competitive Seems quite competitive

35 American black nightshade (Solanum americanum)

36 Sources of Weed ID Information Picture books: Picture books: Southern Weed Science Society ID Guide Southern Weed Science Society ID Guide Excellent resource Excellent resource Very thorough (almost too many plants) Very thorough (almost too many plants) Web Picture/Taxonomic Sites Web Picture/Taxonomic Sites tm tm

37 Weed management strategies

38 Secrets to Successful Weed Control 1. Prevention 2. Prevention 3. Prevention

39 Only you can prevent weed invasion! Be careful what you plant Be careful what you plant Consider all points of entry Consider all points of entry Keep an eye out for new invaders elsewhere Keep an eye out for new invaders elsewhere Prevent reproduction of early invaders Prevent reproduction of early invaders

40 Ecological weed management is based on how a plant is built Annual vs. biennial vs. perennial Annual vs. biennial vs. perennial Growth stage – perennials act like annuals for a short period Growth stage – perennials act like annuals for a short period Timing relative to the seasons Timing relative to the seasons Control prior to seed production Control prior to seed production

41 Management timing relative to the seasons Perennial weed growth schedule: Perennial weed growth schedule: Spring: export carbohydrates from roots to new shoots Spring: export carbohydrates from roots to new shoots Summer: capture and assimilate new energy Summer: capture and assimilate new energy Fall: “pack it in” for winter – carbohydrates transported to the roots Fall: “pack it in” for winter – carbohydrates transported to the roots Winter: usually, minimal growth or activity Winter: usually, minimal growth or activity

42 Management timing relative to the seasons Perennial weed management – general terms: Perennial weed management – general terms: Spring: limit new growth – drain the roots Spring: limit new growth – drain the roots Summer: prevent energy capture Summer: prevent energy capture Fall: opportunity to attack the root storage system Fall: opportunity to attack the root storage system Winter: eliminate new seedlings Winter: eliminate new seedlings

43 Manual removal Hoeing, Pulling, Cultivation Success determined by population and distribution – is it feasible? Success determined by population and distribution – is it feasible? Annual weeds easily removed Annual weeds easily removed Perennial plants are often “subdivided” Perennial plants are often “subdivided” Vegetative root pieces often produce new plants Vegetative root pieces often produce new plants

44 Biological control Biological control of weeds in cropping systems is a difficult proposition Biological control of weeds in cropping systems is a difficult proposition The control agent must be very host-specific and not injure non-target species The control agent must be very host-specific and not injure non-target species The life cycle of the control agent must match that of the target species The life cycle of the control agent must match that of the target species Surrounding habitat should support control agent survival and reproduction Surrounding habitat should support control agent survival and reproduction In the future, possibility of bioherbicides In the future, possibility of bioherbicides

45 Herbicides Several good options for most crops grown in EAA Several good options for most crops grown in EAA Applications should be timed to minimize competition with crop Applications should be timed to minimize competition with crop Should be made prior to weed seed head formation Should be made prior to weed seed head formation

46 Questions??


Download ppt "Weed Biology and Management Curtis Rainbolt Extension Weed Scientist Everglades REC."

Similar presentations


Ads by Google