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Phenology as a Tool
in Commercial 


Fruit & Vegetable 
Pest Management


Celeste WeltyExtension Entomologist

April 2015

Phenology & insects?

•  Predictions– Events hard to see

•  Methods– Calendar– Temperature–  Indicator plants

Phenology & insects?

•  Predictions– Events hard to see

•  Methods– Calendar: rough estimate– Temperature: better–  Indicator plants: best; easy to see

Topics today•  Strict phenology

– Apple – Cabbage

•  Related: predictions based on phenology + biofix + temperature– Codling moth– San Jose scale

•  Related: temperature-only models– Corn flea beetle– European corn borer

Apple & peach bud stages:
uses in IPM

•  When to set up traps•  When to scout•  Optimal timing of tactics

–  Insecticides– Pheromone mating disruption

Stages of

Apple Growth

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Apple buds

dormant silver tip

green tip Columbus: 3/24 - 4/11

Apple budshalf-inch

green tight cluster

pink

3/21 - 4/17

3/19 - 4/13

3/23 – 4/26

Apple buds

petal-fall

fruit set

bloom

3/28 – 5/2

4/28 – 5/16

king bud = king fruit

•  Bud in center of cluster•  Develops faster•  Makes the best fruit

Trap set-up time in applesTiming Target species

Green tip Spotted tentiform leafminerRedbanded leafrollerOriental fruit moth

Pink bud San Jose scaleBloom Codling moth

Lesser applewormPetal-fall Obliquebanded leafroller

Tufted apple budmothVariegated leafrollerDogwood borer

Mid-June Apple maggot

Trap set-up time in applesTiming Target species

Green tip Spotted tentiform leafminerRedbanded leafrollerOriental fruit moth

Pink bud San Jose scaleBloom Codling moth

Lesser applewormPetal-fall Obliquebanded leafroller

Tufted apple budmothVariegated leafrollerDogwood borer

Mid-June Apple maggotIn red: pest with trap-based control rules

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Apple pest scoutingTime Target pest

Early pink rosy apple aphid

Early petal-fall spotted tentiform leafminer

Early petal-fall white apple leafhopper

June green apple aphid

June San Jose scale, crawlers

June - August European red miteJune - August woolly apple aphid

Rosy apple aphid•  Scout once, at early pink•  Choose:

– 10 trees per block – 10 fruit clusters per tree– Best from inner canopy

•  Look for curled, distorted leaves

•  If ANY rosies found, then use aphicide at pink

Spotted tentiform leafminer•  Scout at early petal-fall•  Randomly choose:

– 5 trees per block– 3 fruit clusters per tree– Examine 2nd, 3rd, & 4th leaves

leaf from base•  Look for early mines

– Underside of leaf– Pale-green blisters

•  Treat if > 4 mines per cluster•  Sequential sampling graphs

available for more precise sampling

White Apple Leafhopper•  Scout at petal-fall•  Randomly choose:

– 10 trees per block– 5 fruit clusters per tree– 3 mid-cluster leaves per cluster

•  Look for young nymphs– Underside of leaf

•  Threshold at petal-fall:> 0.5 nymph per leaf

Spray programs Optimal timing of insecticide,
if pest present

Time Target pestpink rosy apple aphid

pink San Jose scale, adultspetal-fall spotted tentiform leafminerpetal-fall white apple leafhopperJune San Jose scale, crawlers

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Optimal timing of pheromone mating

disruption

Isomate dispensers being deployed in northern Ohio at apple bloom:

•  Crew of 10 workers •  Covered 70 acres •  1 day, 8 AM to 5 PM •  200 dispensers/A •  1 dispenser in every

tree, in every other row

Cabbage Maggot

Cabbage Maggot

•  4 generations / year•  Stages:

adult egg larva pupa(fly) (maggot)

•  Crop most susceptible if in seedling stage when new adults are laying eggs

•  Transplanted crops are most susceptible during the first 2-3 weeks after planting

Cabbage Maggot

•  Adults emerge at same time that certain well known plants are flowering

GEN. PLANT AVG. BLOOM (Ohio)1 yellow rocket early May2 day lilies late June3 Canada thistle early August4 New England aster early Sept.

•  Do not transplant during time that plant is blooming•  Do not seed ~2 weeks before plant is blooming•  Ideal time to seed is toward tail end of bloom period

Temperature-based predictions

•  Common sense:– Calendar NOT good predictor of

when biological events occur– Development is slower when cool– Development is faster when hot

•  More precise:– Calculate degree-days

Degree-Days (DD or oD)

•  Way to summarize development time•  Can be used to predict insect activity•  For one day, degree-days =

(average temp) minus (threshold temp)•  Accumulate DD over consecutive days

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Degree-Days: methods

•  Calculate yourself using simple min & max temperature

•  Look-up chart•  Interactive websites

– MSU, Cornell, or UCal

Degree days: starting point?


•  Calendar date– In places with cold winter, start

on January 1st or March 1st

•  Biofix:– Use a biological event, such as

catch of first moth in a trap

Degree-Days (DD): For one day, 
DD = (avg temp) minus (threshold temp)





Accumulate DD over consecutive days.



Example, base temp = 50o F:Day Tmax Tmin Tavg DD50

1 62 52 57 7

2 66 50 58 8

3 58 54 56 6

4 70 56 63 13

Degree-Days (DD): For one day, 
DD = (avg temp) minus (threshold temp)





Accumulate DD over consecutive days.



Example, base temp = 50o F:Day Tmax Tmin Tavg DD50 DDcumul

1 62 52 57 7 7

2 66 50 58 8 15

3 58 54 56 6 21

4 70 56 63 13 34

Insect Development Rates•  Each species has limits

– Minimum temperature (often 50oF)– Maximum temperature (often 90oF)

•  Between min & max is linear

Apple IPM Tools: Degree-day models

•  Codling moth

– Egg hatch

•  San Jose scale

– Crawler emergence

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Predicting Codling Moth Egg Hatch

•  Apply insecticide when eggs begin to hatch•  Rule developed 30+ years ago in Michigan (1976)•  Eggs begin to hatch

– 2 to 3 weeks after moths begin to fly– 250 degree-days (base 50F) after moths begin

sustained flight•  Use pheromone trap for moth flight•  ‘Biofix’ is the date that flight begins

Traps for monitoring codling moth

•  Trap choices:– Sticky trap– Multi-Pher (bucket) trap

•  Use pheromone lure•  3 traps / orchard block

DD look-up chart for codmothmin max

Timing for codling moth

•  1st spray: – 250 degree-days after biofix

(for most products)

•  2nd spray: – 14 days after first spray

Timing for 1st spray for codling moth DD after biofix

Approximate timing

Products*

250 1st cover Imidan, Altacor, Delegate, pyreth-roids, Avaunt

150-250 late petal-fall Assail, Calypso, Belay

100-200 mid petal-fall Intrepid, Confirm 50-75 early petal-fall Rimon

* & related home garden products

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0

1

2

3

Apr/22 May/3 May/15 May/27 Jun/7 Jun/19

Codling Moth Pheromone Trapping at O.S.U. Orchard, Columbus

Mea

n nu

mbe

r of m

oths

per t

rap

per d

ay

biofix5/18

optimalspray6/4

pink4/24

petalfall5/9

bloom5/2

1st cover5/17

normal2nd cover

5/31

normal3rd cover

6/14delayed2nd cover

6/4

250 DD

Range of biofix for codmoth in Columbus

•  Average 5/7-5/11

•  Earliest 4/20

•  Latest 5/24

San Jose scale

•  Sucking pest •  Overwinters on bark

•  Disperses to fruit in crawler stage (starts mid-June)

San Jose scale

When are crawlers crawling? •  Start about 4-6 weeks after bloom •  Emergence lasts several weeks •  Monitoring methods:

– Predict using trap & temperature – Detect with black sticky tape

San Jose scale When are crawlers crawling? •  Use pheromone trap

– Set up trap at pink bud stage – First adults usually caught at

bloom •  Track temperature

– Crawlers expected 300-350 DD degree-days (base 50°F) after catch of adults in trap

adult

trap

San Jose scale

When are crawlers crawling? •  Use black sticky tape

(electrical tape) – Wrap sticky-side out around

branch – Look for tiny bright yellow

crawlers

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Temperature models

•  Winter temperature•  Degree-day development

Pest Forecasting by Winter Temperature Model

•  Corn flea beetle on sweet corn– Vector of Stewarts bacterial wilt– Disease depends on survival of beetle– Beetle does not overwinter well if too

cold•  Management:

– Host plant resistance– Systemic insecticide– Most critical in years with mild

winter

Corn Flea Beetle•  Vector of Stewart’s bacterial wilt

– Varies among varieties– Worst on early yellow varieties– Greatest effect if infection < 7-leaf stage

•  Worse after mild winter

Corn Flea Beetle Index

•  Winter temperature model•  Sum of mean temperatures

Dec. + Jan. + Feb.

•  Used to predict severity of Stewart’s bacterial wilt

Corn Flea Beetle IndexFlea beetle index

Predicted Stewarts Wilt Severity

>100 Severe

95-100 Moderate

90-94 Light

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Temperature-based predictions•  Length (in days) of life stages

– Egg– Larva– Pupa– Pre-mating adult– Pre-egglaying adult– Complete generation

•  % of population in a life stage– 1% (start)– 25%– 50%– 100%

Degree day example:
European Corn Borer

•  Pest of sweet corn & peppers•  Start DD count:

– January 1st– OR when 1st spring moth caught

•  Threshold temp. = 50oF

egg 1st instar larva

pupa adult5th instar larva

European Corn Borer 
Base 50oF, start Jan. 1st

% Pupa Adult Flight Egg 1L 2L 3L 4L 5L

1 250 420 550 610 750 970 1140 1290 1420

25 340 540 690 790 920 1070 1220 1360 1490

50 390 600 740 850 960 1110 1250 1390 1520

75 450 650 790 900 1000 1140 1280 1420 1550

peak 560 760 900 990 1090 1210 1350 1490 1620

European Corn Borer 
Base 50oF, start 1st moth

DD Event Avg # days

Activity

212 egg hatch to 1st instar

16 Pin hole leaf feeding

318 2nd instar 7 Shot hole leaf feeding435 3rd instar 6 Midrib & stalk boring567 4th instar 7 Stalk boring792 5th instar 10 Stalk boring

1002 pupa 9 Changing to adult1192 Adult moth 8 Mating & egg laying

Vegetable pests with known DDLOCAL•  Cabbage maggot•  Carrot weevil•  Corn leaf aphid•  Crucifer flea beetle•  Green peach aphid•  Imported cabbageworm•  Onion maggot•  Onion thrips•  Seedcorn maggot•  Squash bug•  Two-spotted spider mite

MIGRATORY•  Beet armyworm•  Black cutworm•  Cabbage looper•  Diamondback moth•  Tomato fruitworm

Tomato Fruitworm

•  Lower threshold = 55oF•  Upper threshold = 92oF•  In California: if eggs found on leaves by

scouting in July, then use DD to predict egg-laying of generation in August that attacks the fruit

•  Takes 968 DD to complete a generation

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Challenge to us!

•  Gather phenology data for some key vegetable pests?

•  Some adult emergence data for past 27 years

Resources•  Cornell

– Apple insect phenology models and IPM forecasts: newa.cornell.edu/index.php?page=apple-insects

•  U. California– www.ipm.ucdavis.edu/WEATHER/

•  MSU’s Enviro-weather– www.enviroweather.msu.edu/

Apple bud stage pictures

•  https://www.pinterest.com/pin/396035360954363789/

•  http://www.hrt.msu.edu/faculty/langg/Apple_Critical_Temp.html

•  https://fruitgardener.wordpress.com/2012/05/01/apple-bud-stages/

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Peach bud stage pictures•  http://www.ent.uga.edu/peach/

peachhbk/pdf/stages.pdf•  https://www.pinterest.com/pin/

396035360954363863/•  http://county.wsu.edu/chelan-

douglas/agriculture/treefruit/Pages/Peach.aspx

•  http://www.hrt.msu.edu/faculty/langg/Peach_Critical_Temp.html

Info on veg. & fruit pest management 
old site: bugs.osu.edu/welty/


new site: u.osu.edu/pestmanagement/
 


Questions? 
e-mail: welty.1@osu.edu


office phone: 614-292-2803 
cell phone: 614-746-2429