TRACY ROWLANDSON UNIVERSITY OF GUELPH Model vs. Measurement: Evaluation of IPM strategies Discussion Topic

Need for re-evaluation Many IPM strategies have been based on leaf wetness duration (LWD) No standard has been set by the community regarding LWD What are the options going forward?

Measurement (Sensors) DecagonEnvirondataSpectrumNetsens OnSet Campbell Sci. RainwiseGlobal Water

Measurement (Sensors) Pros:  Several commercially available products  Provide site specific information  Visible  Capable of providing accurate LWD estimates

Measurement (Sensors) Cons:  Several commercially available products  Require calibration and maintenance  Placement requires consideration  Treatment is not standard; placement is not standard

Models Pros:  Both physically and empirically based models have been developed (both with success)  Require the input of standardized information  Representative for regions larger than sensors can provide; non- invasive  Data can be accessible  Entirely transferable (physical) with some adjustment (empirical)

Models Cons:  Some models require many, many inputs – particularly physically based  Data quality may be uncertain  Empirical models require calibration  No accepted standard

What we have proposed Adoption of a relative humidity based empirical model RH> threshold Why?  Requires a single variable (standard input)  A standard practice  Suggested method for threshold determination

RH > Threshold Ames, IA 83%; Elora, ON 85%; Florence, Italy 92%; Piracicaba, Brazil 90%

Discussion How can we provide RH data at a necessary resolution? IPM strategies have been developed based on LWD – should they be re-evaluated based on hours of RH> threshold? Concern has been expressed over quality of meteorological data – do we have a say in improvement?