Pests and Damage.oo3

Transcription

1 Pests and Damage.oo3 LECTURE NOTES 1 Pests and Their Impacts Matthew J. Grieshop MSU Entomology 2 What is a Pest? Etiology From M.Fr. peste: "plague, pestilence" From Latin: pestis "deadly contagious disease." Meaning "noxious or troublesome person or thing" first recorded "The Short Answer" Organism that causes economic loss Biological and economic components to determining loss 3 Anthropocentric Pests interfere with human activities Economic view: Pests cause Economic Loss Ecological view: Pests consume or supplant primary (or secondary) productivity How we define pests and therefore pest management largely depends on how we view the world. 4 Systems and Worldviews A system is a representation of reality Systems have boundaries, components, and flows Mechanistic Vs. Ecological Worldview 5 Industrial agriculture = Mechanistic Worldview Linear system (whole = sum of parts)

2 Infinite resources or replacements available Unlimited growth Neglegable feedback loops few overlapping functions among components Minor dependence/connection with surrounding ecological or cultural communities 6 Organic Agriculture = Ecological Worldview Cyclic system (whole > sum of parts) Resources are finite Local interdependencies, partnerships, and connected networks Many feedback loops Components have overlapping functions System part of larger ecological and cultural communities 7 Pests in an Ecological Worldview In strict ecological terms there are no pests, only producers (competators) and consumers However, agricultural systems are not "natural" Thus pests can be viewed as indicators of system imbalance Insects and fungi are not the real cause of plant diseases but only attack unsuitable varieties or crops imperfectly grown. Their true role is that of censors for pointing out the crops that are improperly nourished and so keeping our agriculture up to the mark. In other words, the pests must be looked on as Nature s professors of agriculture: as the integral portion of any rational system of farming (Howard, 1943, p. 161).

3 That said, loosing your harvest to pests is a hard lesson to learn. 8 Bottom up Versus Top Down PM Organic strives for Bottom up Bottom up equals management by design rather than by reaction This is not always feasible We'll talk about this more in Unit 2 9 Matt's Pest Definition Eats a crop 10 Competes with a crop 11 Infects a crop 12 Pest Classification By Damage Direct: Pest damages harvestable portion Indirect: Pest damages non-harvestable portion Nuisance and Aesthetic By Incidence Key Occasional Secondary 13 Codling moth 14 Rosy apple aphid 15 German cockroach 16 Pest Severity and Status (Two major components) Pest species Damage characteristics (Biological/Social) Management Costs (Economic)

4 Population dynamics (Ecological) Crop Species Market Value (Economic) Wheat versus apple Susceptibility to Damage (Biological/Social) How closely does the consumer interact with raw ag. commodities? (Consumer tolerance) Close: Fresh produce/minimal processed food (i.e. yogurt with whole fruit; weed seed in seeds) Far: heavily processed (i.e. flour, juice, jelly) 17 Types of damage Consumption of Plant Parts Pests directly feed on plant parts Insects, Pathogens, Vertebrates Colorado Potato Beetle 18 Powdery Mildew 19 Voles feeding on Roots 20 Dodder 21 Chemical Toxins, Elicitors, and Signals Pests exude a semiochemical that damage or otherwise transform plants in a negative way Phytophthora on tobacco leaves 22 Allelopathy from weeds 23 Oriental chestnut gall wasp (Dryocosmus kuriphilus) hypertrophy: cell enlargement hyperplasy: cell multiplication 24 Physical Damage/Loss of Harvest Quality

5 Damage to the plant which leads to further pest problems Root knot nematode complex Cause Hypertrophy Later invasion by Fusarium 25 Wheat Stem Sawfly (Cephus Cinctus) 26 Cosmetic Damage Pest makes harvest less appealing to consumers Apple Scab 27 Vectoring of Pathogens Bacterial Wilt and Striped Cucumber Beetle (##) 28 Direct Contamination Weed seeds in Seed crops 29 Stored product pests and dockage 30 Control Costs $$ Cost of pest management Environmental cost of pest management Cultural costs of pest management 31 Embargo and Quarantine Medfly in CA eradication program in 80's 90's local quarantine and eradication programs currently