Pecan IPM Toolbox

Insect Monitoring and Control

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Temperature Prediction Method for Adult PNC Activity

Steps for Using Day Degrees as a Prediction of PNC Adult Emergence
  1. 1. Record daily maximum and minimum temperatures starting from ten days before 50% budbreak. Start your hygrothermographs early and then when budbreak occurs, count back 10 days and start accumulating day degrees from that date.
  2. 2.  Calculate day degrees using the formula below.
  3. 3.  Record day degrees for each date on the Orchard Weather Data Report form. 
  4. 4.  Keep a cumulative total of day degrees in the space provided on the form.
  5. 5.  When cumulative day degrees occur equal to or greater than 956, then tree bands for collecting pupae should be in place.
  6. 6.  When cumulative day degrees occur equal to or greater than 1,521, then 10 percent adult emergence has occurred.
  7. 7.  When cumulative day degrees occur equal to or greater than 1,822, then 10 percent oviposition has occurred.
  8. 8.  When cumulative day degrees occur equal to or greater than 1,831, then first significant nut entry has occurred. This is when controls should be made.

Formula for calculating day degrees:

(max. + min.) - 38° F = number of day degrees (See item 2 above)

Example:
(65° + 42°) - 38° F = 53.5 - 38 = 15.5 day degrees (2)

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