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Nancy E. Adams

Extension Educator, Agricultural Resources

UNH Cooperative Extension is working in cooperation with the New England Agricultural

Statistics and the NH Department of Agriculture to bring you weekly growing degree day (GDD)

information throughout the growing season. GDD can be used to help predict events in an

insect’s life cycle during the season by measuring growth in terms of temperature over time.

When control measures are warranted, growing degree days can be used, along with scouting,

as a guide for timing control actions.

The GDD method takes into account the average daily temperature accumulations which

influence insect development. Due to temperature differences, insect development varies from

year to year and among locations throughout New Hampshire. For each day that the average

negative numbers are ignored. GDD data is collected beginning March 1. Early in the season

the numbers will accumulate slowly but as the average daily temperature increases, the GDD

will accumulate faster.

The GDD for insects is listed on the accompanying pages. The time for pest control is

expressed in a range of numbers beginning with first perceptible feeding injury and continuing

until approximately the end of the insect’s plant injury cycle. For example, Cooley spruce gall

adelgid GDD are 22-92 and 1500-1775. This means the insect is active starting around 22 GDD

and control measures can be implemented until approximately 92 GDD. Cooley spruce gall

adelgid also has another period during the growing season when controls may be effective and

necessary. This period is between 1500 and 1775 GDD.

Scouting practices should be employed at some point before the GDD number is reached to

determine if a pest problem exists and if some type of control is warranted. Decisions as to

whether or not to use control measure will be dependent upon such things as the level of

damage or potential damage and the life stage of the insect. Treatment, if decided upon, would

be timed to correspond with some point within the GDD range. If more than one range is listed,

then multiple generations or control periods in an insect’s life cycle exist. The most recent

control recommendations can be found in: The New England Management Recommendations

for Insects, Diseases, and Weeds of Shade Trees and Woody Ornamentals, $20, UMass,

Bulletin Distribution Center, Draper Hall, Box 32010, Amherst, MA, 01033, (413) 545-2717.

GDD information may be found in a number of different locations

UNH Cooperative Extension’s web site contains a complete listing of GDD data from each of the

19 NH sites. A complete listing of insect emergence for different GDD ranges as well as an

explanation of GDD is also provided.

A recorded message will be updated weekly listing GDD date for only a selected number of

sites and insects.

Common names, scientific names of insects, and growing degree days (GDD) affecting ornamental plants.

Beech scale Cryptococcus fagisuga *

Honeysuckle aphid Hyadophis tataricae *

Aphids several species * 7 120 135 250

Cottony taxus scale Pulvinaria floccifera * 7 91 802 1388

Elm bark beetles Scolytus sp., Hylurgopinus sp. 7 120

Elongate hemlock scale Fiorinia externa * 7 120 360 700 2515 2625

European red mite Panonychus ulmi * 7 58 240 810

Golden oak scale Asterolecanium variolosum * 7 121 802 1266

Hemlock eriophyid mite Nalepella tsugifolia * 7 22

Kermes oak scales Allokermes spp. * 7 91 298 912

Northern pine weevil Pissodes nemorensis 7 192

Oak leaftier Croesia semipurpurana 7 35

Oystershell scale Lepidosaphes ulmi * 7 91 363 707

Pales weevil Hylobius pales 7 121

Southern red mite Oligonychus ilicis * 7 91 246 363 618 802

Spruce spider mite Oligonychus ununguis * 7 121 192 363 2375 2806

Taxus mealybug Dysmicoccus wistariae * 7 91 246 618

White pine aphid Cinara strobi * 7 121 121 246 1917 2271

White pine weevil Pissodes strobi 7 58

Tuliptree scale Toumeyella liriodendri * 12 121 2032 2629

Cooley spruce gall adelgid Adelges cooleyi- on spruce * 22 92 1500 1775

Juniper scale Carulaspis juniperi * 22 148 707 1260

Magnolia scale Neolecanium cornuparvum * 22 91 246 448 2155 2800

Pine bark adelgid Pineus strobi * 22 58 58 618

Spruce bud scale Physokermes piceae * 22 121 912 1388

European pine shoot moth Rhyacionia buoliana 34 121

Euonymus scale Unaspis euonymi * 35 120 533 820

European fruit lecanium Parthenolecanium corni * 35 145 1266 1645

Fletcher scale Parthenolecanium fletcheri * 35 148 1029 1388 2515 2800

Hemlock scale Abgrallaspis ithacae * 35 121 1388 2154

Balsam twig aphid Mindarus abietinus * 58 120

Honeylocust plant bug Diaphnocoris chlorionis 58 246

Maple bladdergall mite Vasates quadripedes * 58 148 98 155

Pine tortoise scale Toumeyella parvicornis * 58 148 618 1050

Eastern tent caterpillar Malacosoma americanum 90 190

Gypsy moth Lymantria dispar 90 448

Hickory leaf stem gall phyllo. Phylloxera caryaecaulis 91 246

Pine tube moth Argyrotaenia pinatubana 91 246 1151 1514

Balsam gall midge Paradiplosis tumifex 120 290

Cooley spruce gall adelgid Adelges cooleyi- on Fir * 120 190 1500 1775

Nantucket pine tip moth Rhyacionia frustrana 121 448 1514 1917

Spotted tentiform leafminer Phyllonorycter crataegella 121 192 363 533

Woolly elm aphid Erisoma americanum 121 246

Zimmerman pine moth Dioryctria zimmermani 121 246 912 1917 1917 2154

Black vine weevil Otiorhynchus sulcatus 148 400

Cankerworms (inch worms) 148 290

Dogwood borer Synanthedon scitula 148 700

Hackberry psylla Pachypsylla spp. 148 448

Lilac borer Podosesia syringae 148 299

Pine spittlebugs Aphrophora parallela, A. sara. 148 298

Snowball aphid Neoceruraphis viburnicola 148 298

Taxus bud mite Cedidophyopsis psilaspis 148 448 707 912

Arborvitae weevil Phyllobius intrusus 150 260

Birch leafminer Fenusa pusilla 190 290 530 700

Clover mite Bryobia praetiosa 192 298

Forest tent caterpillar Malacosoma disstria 192 363

Holly leafminer (Soil Tr't) Phytomyza ilicis 192 290 246 448

Honeylocust pod gall midge Dasineura gleditschiae

Imported willow leaf beetle Plagiodera versicolora 192 448

Larch sawfly Pristophora erichsonii 192 299

Linden looper Erannis tiliaris 192 363

Native holly leafminer Phytomyza ilicicola 192 298 1029 1266

Privet thrips Dendrothrips ornatus 192 618 1029 1266

Rhododendron borer Synanthedon rhododendri 192 298 533 707

Rhododendron gall midge Clinodiplosis rhododendri 192 363

Tussock moths Halysidota tesselaris 192 298 2145 2516

Lace bugs Corythuca spp. 239 363 1266 1544

American plum borer Euzophera semifuneralis 245 440

Arborvitae leafminers Argyresthia spp. 245 360 533 700 1700 2100

Boxwood mite Eurytetranychus buxi * 245 600

Lilac leafminer Caloptila syringella 246 363 1388 1644

Pine sawflies Diprion spp., Neodiprion spp. 246 1388

Boxwood psyllid Psylla buxi 290 440

Cherry and hawthorn

leafminer

Profenusa canadensis 295 610

Locust leafminer Odontota dorsalis 298 533 1029 1388

Pine eriophyid mites Eriophyidae * 298 533

Pine needle scale Chionaspis pinifoliae * 298 448 1388 1917

Pitch twig moth Petrova comstockiana 298 707

Privet rust mite Aculus ligustri * 298 802 1266 1515

Redbanded leafroller Argyrotaenia velutinana 298 618

Rhododendron stem borer Oberea myops 298 802

Satin moth Leucoma salicis 298 618 1917 2271

Elm casebearer Coleophora ulmifoliella 300 533

Fruittree leafroller Archips argyrospilus 300 618

Elm leaf beetle Xanthogaleruca luteola 363 912

Elm leaf miner Fenusa ulmi 363 530

Larch casebearer Coleophora laricella 363 618 2375 2805

Periodical cicada Magicicada septendecim 363 618

Sassafrass weevil Odontopus calceatus 363 618

Twospotted spider mite Tetranychus urticae * 363 618

Walnut blister mite Eriophyes erinea 363 707

Willow flea weevil Rhynchaenus rufipes 363 618 707 1029

Woolly beech aphids Phyllaphis fagi 363 707

Bronze birch borer Agrilus anxius 440 800

Azalea whitefly Pealius azaleae 448 700 1250 1500 2032 2150

Boxwood leafminer Monarthropalpus buxi 448 700

Hemlock looper Lambdina fiscellaria 448 707

Lace bugs Stephanitis spp. 448 618 802 1029

Moutain ash sawfly Pristiphora geniculata 448 707

Oak skeletonizer Bucculatrix ainsliella 448 707 1798 2155

Pine needle miner Exoteleia pinifoliella 448 802

Rose chafer Macrodactylus subspinosus 448 802

Spruce needle miner Endothenia albolineane 448 802

Azalea leafminer Caloptilia azaleella 450 800 1260 1500

Greenstriped mapleworm Dryocampa rubicunda 533 1645

Oak blotch leafminers Cameraria spp., Tischeria spp. 533 912

Rust mites Eriophyidae * 533 802 1644 2033

Leafhoppers several species 618 802 1266 1514 1917 2155

Pine root collar weevil Hylobius radicis 618 912

White prunicola scale Pseudaulacaspis prinicola * 707 1151

Elm leaf aphid Tinocallis ulmifolii 710 1500

Cottony maple scale Pulvinaria innumerabilis * 802 1265

Oak spider mite Oligonychus bicolor * 802 1266

Pine webworm Tetralopha robustella 802 2000

Roundheaded apple tree

borer

Saperda candida 802 1029 1514 1798

Honeylocust mite Eotetranychus multidigituli * 912 1514

European elm scale Gossyparia spuria * 1029 1388

Japanese beetle Popillia japonica 1029 2154

Dogwood sawfly Macremphytus tarsatus 1151 1500

Tuliptree aphid Macrosiphum liriodendri 1151 1514 1917 2033

Birch skeletonizer Buccalatrix canadensisella 1266 1580

Fall webworm Hyphantria cunea 1266 1795

European hornet Vespa crabra germana 1388 2271

Maple trumpet skeletonizer Epinotia aceriella 1388 2032

Peachtree borer Synanthedon exitiosa 1500 1800

Twobanded Japanese weevil Callirhopalus bifasciatus 1644 2271

Willow twig aphids Lachnus spp. 1644 2271

Juniper webworm Dichomeris marginella 1645 1917

Sugar maple borer Glycobius speciosus 2032 2375

Locust borer Megacyllene robiniae 2271 2805

Poplar and willow borer Crytorhynchus lapathi 2271 2806

life cycle.

season (before bud break) would be appropriate providing a pest problem is present. Do not use on Douglas fir, blue

spruce, Japanese red maples, hickory, walnut, or butternut.

1% to 2% (use 1% rate for conifers) otherwise threat as dormant. Apply the same precautions as in footnote 2.

This project was supported in part by a grant

from New England Grows.

Reprinted with permission from Scott Clark,