Predicting Insect Growth and Development

1
Predicting Insect Growth and Development

• Sources http//www.ipm.uiuc.edu/, Dr. Saloms
  notes (VT)
• http//www.entomology.umn.edu/cues/book/dd.htm
• Insects are cold-blooded
• Temperature plays major role in
  growth/development
• as temperature ?, days required to complete
  development ?
• each sp. has optimum temperature, minimum
  temperature (threshold temperature) below which
  development stops, and maximum temperature (upper
  cutoff) above which development stops
• no development occurs when temp. lt48F for alfalfa
  weevil
• can use relationship btwn temperature rate of
  development predict when insects pass through
  certain stages
• used to predict biological events
• egg laying/hatching, synchronize insecticide
  sprays

2
Predicting Insect Growth and Development

• Degree day method method of estimating time
• degree day (DD) ave. of 1 degree over threshold
  temp. for 24-hour
• use biofix or Jan 1 for start
• Simplest means to calculate DD each day
• use min/max thermometer to record ave. of min.
  max. temp. each day
• threshold and cutoff temp. used to calculate DD
  for specific day
• 1 DD results when ave. temp. for a day is 1F over
  threshold temp.
• different min thresholds for different insects
• all have max threshold of 95F
• if daily ave. temp. gt 95, then DD for that day
  95 - lower threshold
• if daily ave. temp. lt lower threshold, then DD
  for that day 0
• if daily max and min temp. btwn 95 and lower
  threshold, then DD for that day daily mean -
  lower threshold

3
Predicting Insect Growth and Development

• add daily max and min temp. and divide by 2
• example
• min 45F, max 75F, ave temp (7545)/2 60F
• if threshold 50F, then 10 DD would have
  accumulated on that single day
• add the daily total from all previous days
• example
• threshold for alfalfa weevil 48F
• day when ave. temp. was 49F, 1DD accumulated
• daily accumulations added
• used to predict insect development
• azalea lace bug emerges at 130 DD
• boxwood leafminer emerges at 250 DD