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About Enviroweather's Oriental Fruit Moth Assist Chart

By Enviro-weather staff

More information on Oriental fruit moth at IPM Resources

About the model:

Using 45 F as a base, degree-days (DD) for Oriental fruit moth activity are (starting April 1):

First generation

  • 175 DD first adult emergence (biofix 1)
  • 250 DD first eggs laid
  • 325 to 425 DD peak adult emergence
  • 525 DD peak egg laying

The observed date for the first adult emergence is the biofix for determining timing for sprays aimed at egg hatch. The first spray would be recommended approximately 200 DD base 45 F after biofix 1.

Second generation

  • 950 DD first emergence of second generation adults
  • 1,425 DD peak emergence of 2nd generation adults and first spray for 2nd generation larvae recommended

The date for 2nd generation adult emergence is the biofix for determining timing for sprays aimed at egg hatch of the next generation. The spray for this generation would be recommended approximately 200 DD base 45 F after biofix 2.

Third generation

  • 1,500 DD peak egg laying by 2nd generation adults
  • 1,900 DD first emergence of 3rd generation adults

Adults of the 3rd generation emerge in early to mid August, depending on the weather. This generation is a major cause of wormy fruit at harvest on late season peaches or apples, often with little or no external sign of injury. It may be difficult to distinguish lagging flight of the 2nd generation and the first flight of the third generation.

Use of the model:

The model is most useful for predicting egg hatch of the 1st and 2nd generations for timing sprays, especially with the use of biofixes to pinpoint the start of adult flight. By mid-August it is difficult to determine a distinct 3rd biofix. However, the model can be used to work backwards to determine when spray coverage was likely not sufficient to prevent larval hatch and fruit entries.

Using this report:

  • Locate the Biofix Date (date of first adult emergence) on the top row. (4/22 in this example).
  • Follow that column down to determine the Base 45F Degree Days (DD) that have accumulated between the biofix date and the date listed at the left side of that row. (Here, 206 DD between 4/22 and 5/12.)

Image of chart

  • Note that forecast data is provided (where available) to help with planning in the near-term.
  • Control is recommended at approximately 200 DD (check product) from the biofix date.
  • Repeat for additional blocks with a different biofix date.

References:

  • MSU Extension
  • Michigan State University Ag Bio Research
  • Project Greeen