Weed Control Plant Science 280 - PowerPoint Presentation

Slide1

Weed Control

Plant Science 280

Mr. GomesSlide2

Seed Production

A live source of life! A mature fertilized ovule (embryo) that has stored energy reserves

A small plant packaged for shipment…just needs the right environment to go

Prevention of seed production, especially in annuals, is one of the biggest keys to reducing weed pressureSlide3

Seed Size/Abundance

Seed size is generally extremely small, most weeds can produce a tremendous amount

Shepherd’s purse can have as many as 5 million seeds/pound!!

Weed seed has a unique ability to survive in the soil based on archaic genetic traits

Estimates vary, but numbers vary anywhere from 120 million to as high as 1.4 billion seeds/acreSlide4

Seeds Produced by Common Weeds

Common Name

Barnyardgrass

7,160 seeds/plant 324,286 seeds/lb

Common cocklebur 440 seeds/plant 2,270 seeds/lb

Curly Dock 29,500 seeds/plant 324,286 seeds/lb Slide5

Weed Categories

Divided into three categories:

Broadleaves

Grasses

SedgesSlide6

Broadleaves

Broadleaf

Dicots

Veins in Leaves

Are Netted

Herbaceous or WoodySlide7

Grasses

Narrowleaf – Blade

Monocot

Veins are parallel Slide8

Sedges

Members of the family

Cyperaceae

Bear a close resemblance to grasses and can be distinguished by a thin triangular stem, the absence of a ligule, and the fusion of leaf sheaths forming a tube around the stem

Perennial sedges have underground tubers and/or rhizomesSlide9

Other Classifications

Summer Annual

Germinate in Spring, grow during summer, mature and die in the Fall

Winter Annual

Germinate in the Fall and Winter, Mature and die in Spring or early SummerSlide10

Life Cycles

Annual

Biennial

PerennialSlide11

Annuals

Annual Weeds germinate and spread by seed, having an average lifespan of one growing season. These include both winter and summer types. Winter annuals, like chickweed, germinate in late summer/early fall, go dormant in winter and actively grow during spring. Summer annuals, such as

lambsquarters

, germinate in spring, grow throughout the summer and are gone with the arrival of cold

weatehrSlide12

Lifecycle of an Annual Weed

germination

flowering

pollination

seed

set

plant

dies

growth

Shallow, tap root system

Reproduce by seed

Don’t need food reservesSlide13

Biennial Types

Biennial Weeds complete their life cycle in two growing seasons, germinating and forming rosettes their first year and producing flowers and seeds their second year. Examples of these types include bull thistle and garlic mustard.Slide14

Perennial Types

Perennial Weeds return every year and normally produce long tap roots in addition to seeds. These weeds, which include dandelions, plantain, and purple loosestrife, are the most difficult to controlSlide15

Perennial Types

Characteristics affecting timing

Deep root system

Rhizomes, tubers

Reproduce primarily by the above

Need food reserves to sustain plant through dormancySlide16

Life Cycle of a Perennial

germination or sprouting

growth and rhizome,

stolon, and/or

tuber production

Lowest amount

of stored carbohydrates

(flowering)

(pollination)

seed set or vegetative structure maturation

Highest amount

of stored carbohydratesSlide17

Managing Weeds

Maintain healthy orchard or fields

Prevent seed production

Prevent seed germination

Eliminate weed seedlings

Target susceptible growth stagesSlide18

Plant Development Stages

1. Seedling

Tender and vulnerable to stresses

2. Vegetative

Great uptake of water and nutrients

3. Seed Production

Slow uptake of water and nutrients directed to flower, fruit, seed

4. Maturity

Little uptake of water and nutrients

Low energy productionSlide19

What you need to know prior to developing a plan to control weeds

Be able to identify the weed

Know the weeds life cycle

Know the weeds habitat

Now a proper plan can be developed!!!Slide20

Types of Weed Control

Preventative

Cultural

Mechanical

Chemical

Biological Slide21

Preventative Weed Control

Preventative weed control refers to any control method that aims to prevent weeds from being established in a cultivated crop, a pasture, or a greenhouse. Examples of preventative weed control would be using certified weed free seed, only transporting hay that is weed free, making sure farm equipment is cleaned before moving from one location to another, and screening irrigation water to prevent weed seeds from traveling along irrigation ditchesSlide22

Cultural Weed Control

One of the easiest ways to control weeds is through prevention or cultural control. Close planting in the field can reduce weed growth by eliminating open space. Cover crops are good for this as well. Adding mulch will prevent light from getting to weed seeds and prevents growthSlide23

Mechanical Weed Control

Mechanical control of common weed plants can be accomplished through hand pulling, hoeing, digging or mowing (which slows growth and reduces seed formation). While these methods are effective, they can be time consuming and expensive.

Tillage such as discing and plowing

Mowing

Mechanical cultivator such as inline bed prepSlide24

Chemical Weed Control

Since many weeds, like dodder, hairy flea bane, spurge, and nut grass can become aggressive to the point of taking over, chemical control is sometimes necessary, and used normally a last resort. There are numerous herbicides, like glyphosate, available to help eliminate common weed plantsSlide25

Herbicide Classification

Selective

Kills some plant species, but does not damage other

Ex. Simplicity, Shark, Laudis, Weed-B-Gon

Nonselective

Generally kills all plant species.

Ex. Roundup, Goal

, RelySlide26

Herbicide Classification

Contact

Causes localized injury to plant tissue

Does not readily translocate.

Ex. Diquat

Systemic

Readily translocates on plant tissue

Ex. RoundupSlide27

Herbicide Classification

Pre-emergence – ex. Dual Magnum, Preen

Applied before weed seed germination.

Do not control emerged weeds

Post-emergence – Ex. Roundup,

Treevix

Applied after weed emergence.

Do not control un-emerged weedsSlide28

Herbicide Selection Factors

1. Identify the problem species

2. Identify the herbicides labeled for the site

3. Determine tolerance of desirable plants

4. Integrate management objectives

5. Obtain suitable safety and application equipment Slide29

Before you use herbicide

Identify desirable plant and weed

Read and UNDERSTAND herbicide label

Follow mixing, application, storage, disposal, etc. directions carefully

Use only recommended amount

Maintain and calibrate equipment

Do not use on desirable plants not listed on label (Off

LabelApplications

)Slide30

Biological

Biological weed control refers to any technique that involves the use of natural enemies of weed plants to control the germination of weed seeds or the spread of established plants. This is a rapidly expanding area of weed control with many examples. Examples of biological weed control include to sheep to control tansy ragwort or leafy spurge, cinnabar moth and the tansy flea beetle to control tansy ragwort, the chrysolia beetle to control St. Johns Wort, and the use of goats to control brush on rangeland.