Weeds Category E Turf and Ornamental Pesticide Applicator

Weeds Category E Turf and Ornamental Pesticide Applicator Training Manual Chapter 4

Introduction • In this chapter you need to understand: • Why weeds are important. • When a plant is a weed. • Damage weeds can cause. • Identify some Minnesota plants considered weeds.

Terms • Broadleaf weeds—dicots that are growing where they are not wanted. • Grassy weeds—monocots that are growing where they are not wanted. Category E--- Chapter 4 Weeds

Why Weeds are Important • Weeds: – Detract from the appearance of the landscape. – Compete with desirable plants for space, nutrients, and water. – Can provide habitat for other plant pests.

What’s a Weed? • Any unwanted plant. • A plant can be invasive into desired plants – Some produce large amounts of seed. – Some can reproduce vegetatively (roots and stems) through normal cultural practices e. g. Mowing. – Legally declared weeds by the State of Minnesota e. g. Canadian thistle or local governments e. g. common buckthorn in Minneapolis

Potential Damage from Weeds • Compete with ornaments for water, nutrients, light, and space. • Can interfere with management practices e. g. planting, thinning. • Some weeds produce substances that inhibit growth of other plants (allopathy). • Some weeds produce irritating or poisonous substances.

Weed Identification • Turfgrass weeds fall into 2 groups: – Grassy—monocots (have a single leaf on emergence). Examples: crabgrass, quackgrass, tall fescue. – Broadleaf —dicots (have 2 leaves on emergence). Examples: dandelion palntain.

Weed Identification Dandelion • • Low-growing perennial. Rosette habit. Thick roots. Plant can regenerate from small root or stem segments. • Tiny seeds can disperse great distances. • Thrive in weak, thin turf.

Weed Identification Common Chickweed • Creeping annual weed. • Small, pale green weeds and petioles. • Grows best in cool, wet weather. • Shade tolerant. • To help prevent— Maintain a dense turf and water infrequently

Weed Identification Crabgrass • Coarse blades, light green. • Can germinate the entire season after the soil warms. • To help prevent— maintain a dense, healthy turf. • Apply preemergent after soil reaches 55°F.

Weed Identification Foxtail • Annual grass, has long hairs on the upper surface of the leaf blade and cylindrical yellow seedheads.

Weed Identification Canada Thistle • Perennial weed spread by seeds and creeping roots (can extend up to 20 feet). • Large numbers of wind-dispersed seeds. • Destroy by digging out roots or some herbicides.

Weed Identification Quackgrass • Perennial grass spread by rhizomes. • Cannot be controlled with shallow cultivation— requires deep tilling.

Weed Identification Prostrate Knotweed • Annual, low-growing. • Very competitive in compacted , high traffic, infertile soil.

Weed Identification Prostrate Spurge • Annual, low-growing. • Reddish or green prostrate stems. • Often found on poorly fertilized soils. • To help prevent—maintain a dense, healthy turf. • Apply preemergents when soil 60 -65°F.

Weed Identification Bindweed • Perennial, vining herb. • Extensive root system, hard to control. • Pull out or cut root 3 -6 inches below the surface.

Weed Identification Purslane • Annual, fibrous root system. • Stems smooth, often reddish and prostrate. • Common in cultivated areas. • Difficult to control with cultivation.

Weed Identification Ground Ivy • Perennial, creeping growth habit, forms dense patches. • Grows well in shady, poorly drained areas.

Weed Identification White Clover • Perennial, low-growing. • Will root from nodes. • Competes effectively with established lawns —especially in moist conditions and low fertility.

Herbicides • Nonselective herbicide—a chemical that is generally toxic to plants without regard to species…. • Preemergent—prior to the emergence of the specified weed or crop. • Postemergent—after the emergence of the specified weed or crop. Credit: Ware, G. E. 2000. The Pesticide Book, 5 th Edition.