IPPC Degree-Day Models including Douglas-Fir Needle Midge
(Contarinia spp.)
Len Coop, IPPC, OSU CorvallisFeb 22, 2013
Phenology and degree-day concepts
Some features of the IPPC "Online weather data and degree-days" website at http://uspest.org/wea
Development and use of the Douglas-fir needle midge model
Topics for today's session:
"Who?" and "What?"Identification keys, diagnostic guides, management guides
"When?" Phenology models (crops, insects, weeds), Risk models (plant diseases)
"If?" Economic thresholds, crop loss models, sampling calculators, other decision tools
"Where?" GIS, precision agriculture
Typical IPM questions/decision tools:
Insects have complex life cyclese.g. Douglas-fir needle midge
(Contarinia spp.)EggsLarvaePupae (most)Adults
-Timing of stages *is often*predictable using degree-days, which area two dimensional “heatunit“ of development for cold blooded organisms
Degree-day calculations – method varies:Simplest: (daily max + min)/2 – low
threshold
Single triangle compared with typical daily fluctuation
How fast are they going?
Weather and Degree-day Concepts
1)Degree-day models: accumulate a daily "heat unit index" (DD total) until some event is expected (e. g. egg hatch)
38
20
18
32
14
22
20
26
daily:
cumulative: 20
70
84
106
126
152
Eggs hatch: 152 cumulative DDs
Eggs start developing: 0 DDs
70o(avg)-50o(threshold)=20DD
Degree-day model development: A bit more detail
35 40 45 50 55 60 65 70 75 80 85 90 950
25
50
75
100
125
150
175
200
Temperature vs. development time
Development time (days)
Temperature (F)
Day
sDeveloping degree-day models from lab studies
35 40 45 50 55 60 65 70 75 80 85 90 950
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
0.055
0.06
Temperature versus development
Development time (days)
Rate (1/days)
Temperature (F)
Ra
te (
1/d
ays
)Degree-day models: x-intercept method (Arnold 1959)
x-intercept ~ Tlow = 37 F
1/slope = 1/0.0011 = 920 ~ DD requirement
Pest Management: Monitoring plays a major role
especially since populations are cyclical (due to natural enemies or to swarming conditions
perhaps?)2012: 22 traps in 22 fields, 44 flies total
2011: 23 traps in 22 fields, 206 flies total2010: 21 traps in 20 fields, 2 flies
total2009: 47 traps in 47 fields, >500 flies total; swarming notedBox
trapSticky trap
Need at least 3-4 years data from a variety of locations Doug fir needle midge – mostly from 1 trap/field, more than 20-47 fields 2009-2011 (provided by D. Silen) Plus data from OSU Extension 1990 Method is to vary the lower threshold and start date and use the value that provides lowest error
Phenology Models – developed by field data using lowest error methods
Here is how version 1 of the model looks:
Phenology Models – developed by field data using lowest error methods
Here is how version 1 of the model looks w/2012 data:
Phenology Models – developed by field data using lowest error methods
http.uspest.org/wea
DFNM linked from PNW Insect Management Handbook – ID photos and DD model
New interface to DD Models – Douglas-fir needle midge
http://uspest.org/cgi-bin/ddmodel.us?spp=dnm
Google maps for location selection
Nothing else to do but click
“Calc”
DD model example output – Corvallis 2013
DD model output(cont.)
DD model output (cont.)
Watch for missing data/bad QA (quality assurance) reports
e.g. Albany Weather Underground
Flag for missing/interpolated data
QA report not bad in this case
What the model is telling us: timing can vary by 5 weeks or more
for cool vs. warm years
Pest Management: Spray or let natural enemies do their job? (avoid late sprays to protect later-emerging
parasitoids) Genus Platygaster
Genus GastrancistrusParasitoid wasp - family Pteromalidae
Parasitoid wasp - family Platygastridae
- Economic thresholds are lacking for christmas tree pests in general, would be especially helpful for DFNM
- More work should be conducted to distinguish the ID, biology, phenology, and parasitism of the three or more Contarinia species
Pest Management: Other considerations (cont.)
Summary Points:
IPPC uspest.org/wea has evolved as a hybrid for support of State, Regional, and National needs (>100 models, 17,000 weather stations)
New model interface uses Google maps for easier weather station selection
The new Douglas-fir needle midge DD model appears to succeed in taking on much of the 4-5 week year-to-year variability caused by weather.
Further work on biology of this pest complex is recommended!