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Variety Selection in Pest Management

Variety Selection in Pest Management. Bruce Potter IPM Specialist University of Minnesota Extension Service SWROC “Remember, I’m only the messenger”. SW MN Counties. Which biotic and abiotic factors influence yield? What is the prevalence of factors influencing soybean production?

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Variety Selection in Pest Management

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  1. Variety Selection in Pest Management Bruce Potter IPM Specialist University of Minnesota Extension Service SWROC “Remember, I’m only the messenger”

  2. SW MN Counties • Which biotic and abiotic factors influence yield? • What is the prevalence of factors influencing soybean production? • How can county trials be used to predict variety performance?

  3. Yield and Biotic / Abiotic factors • Yield was POSITIVELY correlated with : • P soil test • K soil test • Yield was NEGATIVELY correlated with: • SCN soil samples at planting • Yield was NOT correlated with: • Soil test pH • Brown stem rot incidence

  4. Selecting a variety • High yield • Stable yield • Race horse vs. work horse • Do you need defensive traits? • There is no free lunch

  5. Soybean variety performance from county soybean grower association trials 1998-2000. % yield of indicator Freeborn

  6. What causes variability in yield? • Abiotic stress • Nutrients ( P, K, Fe, etc.) • Moisture • Temperature • Light • Chemical and mechanical stress • Biotic stress • Disease • Insects • Nematodes • Weed pressure

  7. Don’t ask genetics to solve too many problems! CAN’T LODGE DRGHT TOL. ANTI < WHITE MOLD YELLOW Rps1k PI 88788 BSR RES.

  8. Selecting defensive traits • What is (are) the worst problem(s) in the field? • There can be more than one • Can the problem(s) be dealt with through tillage, chemical, planting date etc.? • Which varieties have the best combination of defensive character(s), yield and other agronomic traits ?

  9. Tolerance vs. resistance Dropkin and Nelson 1960 nematodes

  10. Tolerance vs. resistance • Susceptible- Insects attracted to and feed/reproduce normally on plant. Plant growth suffers • Non preference – Insects not attracted to plant. • Antibiosis – Insects attracted but do not feed well (Bad taste or chemical compounds) • Tolerance – Insects attracted and reproduce well but plant growth little effected Painter 1951 - insect resistance

  11. Variety selection Phytophthora (rps and tolerance) Brown stem rot* SCN* White mold * Iron chlorosis * Roundup Ready No variety choices Insects* Other root rots* Other disease* *may be tolerance differences Soybean Pest ManagementThe variety selection problem First line of defense for predictable problems

  12. TOLERANCE is not RESISTANCE • Specific (vertical) resistance • One to few genes • Easiest to find, rate and breed • General (polygenic, horizontal,nonspecific) resistance • Several to many minor genes • General resistance (tolerance) • Crop yields well in spite of stress • No reduction in pest population

  13. The Problem with Vertical Resistance

  14. Defensive characters • Do not inherently increase yield • Should reduce yield variability caused by the matching pest or environmental stress • Are relatively inexpensive • A stress-proof soybean (or corn) plant has not yet been developed

  15. So what does this all mean and why worry? • You are paid for yield • Select high yielding varieties • High yield and stable yield are not the same • Look at consistency in many sites/years • You may need to give up short term yield for long term benefits • Defensive characters do not pay every year • Variety selection IS risk management

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