1 / 7

Plant pests: Weeds

Plant pests: Weeds. Weeds = any plant growing in an unwanted location. Weeds reduce yields of horticultural crops through:. Weeds. Competition for nutrients, water, light. Allelopathy = chemical competition. Serving as hosts for insect pests. Plant pests: Weeds.

jennis
Download Presentation

Plant pests: Weeds

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Plant pests: Weeds • Weeds = any plant growing in an unwanted location • Weeds reduce yields of horticultural crops through: • Weeds • Competition for nutrients, water, light • Allelopathy = chemical competition • Serving as hosts for insect pests

  2. Plant pests: Weeds • Weeds successful in reproduction • Produce hundreds or thousands of seeds that are widely dispersed (e.g. Dandelion) • Weeds • Reproduce vegetatively (e.g. Quackgrass uses rhizomes that produce new plants at each node) • Long dormancy of seeds (e.g. Chickweed viable for more than 30 years)

  3. Plant pests: Weeds • Weed seeds can contaminate commercial seed lots; states have different regulations • Weeds • Weeds controlled by: • Physical methods • Pulling, hoeing, tilling, mowing, mulching • Often labor-intensive and impractical for large production areas • Chemical methods • Herbicides = chemical used to kill plants • Herbicides either nonselective or selective; traditional selective herbicides usually kill monocots or dicots but not both, but newer herbicides more specialized

  4. Plant pests: Weeds • Controlling weeds with herbicides • Herbicides applied at various times in growing season • Weeds • Before planting (pre-plant herbicides) • Before germination (pre-emergence herbicides) • After growth starts (post-emergence herbicides; must be selective) • Herbicides heavily used in U.S. • More than $5 billion spent on herbicides annually; more than 650 million pound produced • Most herbicides used for corn production, particularly in Midwestern states (e.g. Illinois, Indiana, Iowa)

  5. Plant pests: Weeds • Controlling weeds with herbicides • Most commonly used herbicides • Weeds • Atrazine (selective herbicide) • Dual (metoachlor; pre-emergence, selective herbicide) • Lasso (pre-emergence, selective herbicide) • Round-up (glyphosphate; non-selective herbicide that interferes with metabolism of plants it contacts) • Largest problem with herbicides is that weeds evolve resistance; most use more or different herbicides over time

  6. Plant pests: Weeds • Some weeds controlled biologically • Biological control agents must: • Weeds • Selectively feed on weeds • Reduce weed population to a level that does not interfere with crop • Be adapted to local environmental conditions • Not be consumed by natural predators • not disperse from area

  7. Plant pests: Weeds • Example of successful biological control • Opuntia cactus and cactus moth in Australia • Weeds • Prickly pear cactus (Opuntia) introduced in Australia to produce natural fences in rangelands • Cactus began taking over valuable grazing areas • Introduced cactus moth controlled Opuntia cactus • Unfortunately, few other successes of controlling weeds with biological agents

More Related