PL SC352 Study Guide - Final Guide: Centaurea Maculosa, Centaurea Diffusa, Euphorbia Esula
30 Apr 2018
School
Department
Course
Professor
Classic Biological Control of Weeds
Based on the enemy release hypothesis plants are invasive because they have
escaped/moved ahead of their native pathogens, predators and competing plant
species.
Choice of Biocontrol Targets
Want to use for weed targets that are widely dispersed in the environment.
- loss of biodiversity
- changes in habitat structure, hydrology, fire regime
- competition with crops and pastures
- poisoning of livestock and wildlife
- human health effects (allergies, asthma, dermatitis)
Note: not legal to use herbicide around riparian areas (Tamarix spp. – saltcedar)
Potential Control Agents and Programs
Insects
- butterflies, moths (common)
- beetles (leaf beetles common), flies
- aphids (weevils common)
Mites (gall, spider mites common)
Nematodes
Fungi, Bacteria (not too many successful used so far)
Relatively few species are being controlled:
- leafy spurge
- spotted knapweed, diffuse knapweed
- St. John’s wort
Plant diseases
- rust fungi
- bacterial diseases
Types of Biological Control
Classical
- used against introduced weeds
- agents introduced from native range
o usually insects or mites, some fungi
- agents released initially in small #s
- goal: to become permanently established (provide long-term control)
- aided to increase and disperse
- so, classical biocontrol agent must be from same native rage as the introduced
weed
- cannot kill the host, just need to suppress the populations without killing
them off
- Steps:
- Target selection should be large, significant problems
o non-native species
o no conflicts of interest (ex, medicinal industry St. John’s Wort)
o preferably growing in stable, natural habitats
o taxonomically isolated (cannot be related to natural/valuable crops)
- Exploration of natural enemies in native range
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Based on the enemy release hypothesis plants are invasive because they have escaped/moved ahead of their native pathogens, predators and competing plant species. Want to use for weed targets that are widely dispersed in the environment. loss of biodiversity. Changes in habitat structure, hydrology, fire regime. Note: not legal to use herbicide around riparian areas (tamarix spp. Fungi, bacteria (not too many successful used so far) Relatively few species are being controlled: leafy spurge. Agents introduced from native range: usually insects or mites, some fungi. Goal: to become permanently established (provide long-term control) So, classical biocontrol agent must be from same native rage as the introduced weed. Cannot kill the host, just need to suppress the populations without killing them off. Target selection should be large, significant problems: non-native species, no conflicts of interest (ex, medicinal industry st. john"s wort, preferably growing in stable, natural habitats taxonomically isolated (cannot be related to natural/valuable crops)
