University of Kentucky College of Agriculture
ENTFACT-66

Timing Control Actions for Landscape Insect Pests Using Flowering Plants as Indicators

by G.J. Mussey, D.A. Potter, and M.F. Potter, Entomologists
University of Kentucky College of Agriculture

 

Landscape managers in Kentucky contend with a wide vari- ety of plants and associated pest problems. In any given landscape, there may be hundreds of species and cultivars of native and exotic trees, shrubs, and garden plants. Throughout the growing season, these plants may be attacked by a similarly diverse assortment of insects, including wood borers, leafminers, scale insects, plant bugs, and leaf-feeding caterpillars.

 

Timing is everything when managing landscape pests. To be effective, insecticides or biological controls must be applied when pests are present and at their most vulnerable life stage. For example, scale insects are best controlled after the eggs have hatched but before the crawlers have formed a protective cover. Controlling wood borers requires treating host trees with insecticides to intercept the newly hatched larvae before they have penetrated the bark. Leaf-feeding caterpillars such as bagworms and tent caterpillars are easiest to control when the larvae are small. Timing is especially important when using short-lived materials such as summer oils, soaps, and Bacillus thuringiensis (BT).

 

Frequent in-field inspection is the most reliable means to detect insect problems and time control efforts. Unfortunately, regular monitoring is too time-consuming for many landscape managers. Field workers may not know when or where to look for vulnerable life stages or may not recognize them when encountered. Pests such as the holly leafminer, honeylocust plant bug, and potato leafhopper feed in advance of any recognizable damage. Pheromone traps are available for monitoring certain insects (e.g., clearwing borers) but require time and expertise to use effectively.

 

Forecasting Using Plant Phenology

Phenology is the science dealing with the effects of climate on seasonal biological events, including plant flowering and insect emergence. Insects are cold-blooded, and like plants, their development will be earlier or later depending on spring temperatures. Since both plant and insect development are temperature-dependent, seasonal appearance of particular insect pests should follow a predictable sequence correlated with the flowering of particular landscape plants. In a three-year research project, the seasonal development and emergence of 33 important insect pests were systematically monitored and tracked resulting in the creation of the timetable below. This information will help landscape managers and lay persons anticipate the appearance of important insect pests and effectively schedule control measures.

 

Using the Table

Beginning in early spring, the table predicts the sequence and date of emergence of particular insect pests of woody plants or turf (in bold type). Seasonal emergence of each pest is correlated with the flowering of 34 familiar landscape plants. First bloom (when a plant produces its first flower), 50 percent bloom, and 95 percent bloom (essentially full flower) are included to delineate distinct stages of flowering in the landscape. The table also lists average calendar dates of pest emergence during the three-year study, along with the range. Flowering tended to be a more reliable indicator of insect emergence than calendar date due to year-to-year temperature fluctuations.

 

Locate the pest you wish to monitor in the first column of the table. Flowering events that coincide with that pest's emergence appear in the same vicinity (above and below) of the table.

 

 

Phenological sequence of woody plant flowering and insect events in Lexington, Kentucky.
Insects Phenological Indicator plants
Dates of pest emergence
Event
3-year avg.
Range
Acer saccharinum (silver maple)
1st bloom
18 Feb
12-23 Feb
Cornus mas (cornelian cherry dogwood)
1st bloom
21 Feb
10 Feb-04 Mar
Acer saccharinum (silver maple)
50% bloom
24 Feb
17 Feb-01 Mar
Cornus mas (cornelian cherry dogwood)
50% bloom
03 Mar
26 Feb-13 Mar
Acer saccharinum (silver maple)
95% bloom
10 Mar
03-22 Mar
Forsythia x intermedia (border forsythia)
1st bloom
12 Mar
27 Feb-27 Mar
Cornus mas (cornelian cherry dogwood)
95% bloom
13 Mar
29 Feb-23 Mar
Eastern tent caterpillar
Egg hatch
16 Mar
03-29 Mar
Forsythia x intermedia (border forsythia)
50% bloom
17 Mar
05-29 Mar
Magnolia stellata (star magnolia)
1st bloom
19 Mar
05-29 Mar
Rhododendron 'PJM' (P.J.M. rhododendron)
1st bloom
22 Mar
07 Mar-02 Apr
Magnolia x soulangiana (saucer magnolia)
1st bloom
22 Mar
04 Mar-04 Apr
Forsythia x intermedia (border forsythia)
95% bloom
23 Mar
09 Mar-01 Apr
Pyrus calleryana 'Bradford' (Bradford pear)
1st bloom
23 Mar
09 Mar-04 Apr
Magnolia stellata (star magnolia)
50% bloom
25 Mar
09 Mar-07 Apr
Magnolia x soulangiana (saucer magnolia)
50% bloom
29 Mar
09 Mar-11 Apr
Inkberry leafminer
Emergence
01 Apr
25 Mar-08 Apr
Pyrus calleryana 'Bradford' (Bradford pear)
50% bloom
01 Apr
21 Mar-08 Apr
Pyrus calleryana 'Bradford' (Bradford pear)
95% bloom
03 Apr
24 Mar-10 Apr
Rhododendron 'PJM' (P.J.M. rhododendron)
50% bloom
03 Apr
31 Mar-07 Apr
Amelanchier arborea (serviceberry)
1st bloom
05 Apr
30 Mar-11 Apr
Rhododendron 'PJM' (P.J.M. rhododendron)
95% bloom
06 Apr
02-10 Apr
Berberis x mentorensis (mentor barberry)
1st bloom
06 Apr
30 Mar-12 Apr
Acer platanoides (Norway maple)
1st bloom
06 Apr
04-10 Apr
Magnolia stellata (star magnolia)
95% bloom
07 Apr
04-11 Apr
Cornus florida (flowering dogwood)
1st bloom
08 Apr
01-14 Apr
Boxwood psyllid
Emergence
09 Apr
04-16 Apr
Berberis x mentorensis (mentor barberry)
50% bloom
09 Apr
30 Mar-18 Apr
Amelanchier arborea (serviceberry)
50% bloom
09 Apr
08-12 Apr
Viburnum x juddii (Judd viburnum)
1st bloom
10 Apr
08-13 Apr
Magnolia x soulangiana (saucer magnolia)
95% bloom
11 Apr
08-14 Apr
Acer platanoides (Norway maple)
50% bloom
11 Apr
08-14 Apr
Amelanchier arborea (serviceberry)
95% bloom
11 Apr
08-14 Apr
Malus floribunda (flowering crabapple)
1st bloom
11 Apr
08-15 Apr
Berberis x mentorensis (mentor barberry)
95% bloom
13 Apr
02-22 Apr
Viburnum x juddii (Judd viburnum)
50% bloom
13 Apr
11-17 Apr
Cercis canadensis (eastern redbud)
1st bloom
14 Apr
11-17 Apr
Malus floribunda (flowering crabapple)
50% bloom
15 Apr
13-20 Apr
Syringa vulgaris (common lilac)
1st bloom
15 Apr
14-18 Apr
Acer platanoides (Norway maple)
95% bloom
15 Apr
12-20 Apr
Aesculus x carnea (red horsechestnut)
1st bloom
16 Apr
03-30 Apr
Malus sargentii (Sargent crabapple)
1st bloom
16 Apr
13-22 Apr
Cornus florida (flowering dogwood)
50% bloom
17 Apr
15-19 Apr
Cercis canadensis (eastern redbud)
50% bloom
17 Apr
13-21 Apr
Viburnum x juddii (Judd viburnum)
95% bloom
17 Apr
13-19 Apr
Prunus serrulata 'Kwansan' (Kwansan cherry)
1st bloom
19 Apr
14-25 Apr
Prunus serrulata 'Kwansan' (Kwansan cherry)
50% bloom
19 Apr
17-21 Apr
San Jose scale
Egg hatch
20 Apr
20 Apr
Honeylocust plant bug
Emergence
20 Apr
13-29 Apr
Syringa vulgaris (common lilac)
50% bloom
20 Apr
18-24 Apr
Malus sargentii (Sargent crabapple)
50% bloom
20 Apr
16-26 Apr
Prunus serrulata 'Kwansan' (Kwansan cherry)
95% bloom
20 Apr
18-23 Apr
Birch leafminer
Emergence
21 Apr
20-23 Apr
Malus floribunda (flowering crabapple)
95% bloom
21 Apr
18-25 Apr
Cercis canadensis (eastern redbud)
95% bloom
21 Apr
18-24 Apr
Cornus florida (flowering dogwood)
95% bloom
22 Apr
20-24 Apr
Hawthorn lace bug
Emergence
22 Apr
19-27 Apr
Malus sargentii (Sargent crabapple)
95% bloom
23 Apr
20-28 Apr
Oystershell scale
Egg hatch
23 Apr
20-30 Apr
Magnolia weevil
Emergence
23 Apr
18 Apr-01 May
Viburnum plicatum var. tomentosum

(doublefile viburum)

1st bloom
23 Apr
22-27 Apr
Black cutworm
1st flight
24 Apr
22-26 Apr
Syringa vulgaris (common lilac)
95% bloom
24 Apr
20-29 Apr
Lilac borer
1st flight
24 Apr
18-30 Apr
Lonicera tatarica (tatarian honeysuckle)
1st bloom
25 Apr
20 Apr-03 May
Viburnum plicatum var. tomentosum

(doublefile viburnum)

50% bloom
26 Apr
23-30 Apr
American plum borer
1st flight
26 Apr
20 Apr-03 May
Holly leafminer
Emergence
27 Apr
24 Apr-01 May
Crataegus viridis 'Winter King'

(Winter King hawthorn)

1st bloom
27 Apr
23 Apr-04 May
Cornus kousa (flowering dogwood)
1st bloom
28 Apr
18 Apr-10 May
Chionanthus virginicus (white fringe tree)
1st bloom
28 Apr
22 Apr-06 May
Aesculus carnea (red horsechesnut)
50% bloom
29 Apr
26 Apr-03 May
Lesser peachtree borer
1st flight
29 Apr
24 Apr-07 May
Pine needle scale
Egg hatch
30 Apr
25 Apr-07 May
Viburnum plicatum var. tomentosum
  (doublefile viburnum)
95% bloom
01 May
29 Apr-03 May
Chionanthus virginicus (white fringe tree)
50% bloom
01 May
27 Apr-09 May
Crataegus viridis 'Winter King'

(Winter King hawthorn)

50% bloom
02 May
27 Apr-08 May
Redbud leafhopper (E. aclys)
Emergence
02 May
28 Apr-04 May
Redbud leafhopper (E. bistrata)
Emergence
02 May
28 Apr-04 May
Pyracantha coccinea (scarlet firethorn)
1st bloom
02 May
01-07 May
Lonicera tatarica (tatarian honeysuckle)
50% bloom
02 May
27 Apr-07 May
Boxwood leafminer
Emergence
03 May
02-04 May
Euonymus scale
Egg hatch
04 May
01-07 May
Aesculus carnea (red horsechestnut)
95% bloom
04 May
02-06 May
Cornus kousa (kousa dogwood)
50% bloom
04 May
26 Apr-15 May
Chionanthus virginicus (white fringe tree)
95% bloom
05 May
30 Apr-11 May
Crataegus viridus 'Winter King'

(Winter King hawthorn)

95% bloom
06 May
04-12 May
Potato leafhopper
1st activity
07 May
03-14 May
Pyracantha coccinea (scarlet firethorn)
50% bloom
08 May
06-10 May
Cladrastris kentukea (yellowwood)
1st bloom
08 May
05-11 May
Ilex opaca (American holly)
1st bloom
08 May
05-11 May
Lonicera tatarica (tatarian honeysuckle)
95% bloom
11 May
02-21 May
Ilex opaca (American holly)
50% bloom
11 May
08-14 May
Cladrastris kentukea (yellowwood)
50% bloom
12 May
10-15 May
Cornus kousa (kousa dogwood)
95% bloom
13 May
05-24 May
Pyracantha coccinea (scarlet firethorn)
95% bloom
14 May
13-16 May
Juniper scale
Egg hatch
15 May
13-18 May
Ilex opaca (American holly)
95% bloom
17 May
17-18 May
Cladrastris kentukea (yellowwood)
95% bloom
17 May
17-18 May
Bagworm
Egg hatch
18 May
18-20 May
Dogwood borer
1st flight
20 May
19-23 May
Crataegus phaenopyrum

(Washington hawthorn)

1st bloom
21 May
18-26 May
Bronze birch borer
Emergence
22 May
18-25 May
Tilia cordata (littleleaf linden)
1st bloom
23 May
02 May-07 Jun
Syringa reticulata (tree lilac)
1st bloom
23 May
19-30 May
Catalpa speciosa (northern catalpa)
1st bloom
24 May
21-26 May
Calico scale
Egg hatch
24 May
24-26 May
Crataegus phaenopyrum
  (Washington hawthorn)
50% bloom
24 May
21-28 May
Hydrangea quercifolia (oakleaf hydrangea)
1st bloom
27 May
23 May-02 Jun
Catalpa speciosa (northern catalpa)
50% bloom
27 May
26-29 May
Flatheaded appletree borer
Emergence
28 May
20 May-06 Jun
Crataegus phaenopyrum
  (Washington hawthorn)
95% bloom
28 May
26 May-01 Jun
Syringa reticulata (tree lilac)
50% bloom
29 May
24 May-05 Jun
Peachtree borer
1st flight
29 May
26 May-05 Jun
Twolined chestnut borer
Emergence
29 May
26 May-01 Jun
Magnolia grandiflora (southern magnolia)
1st bloom
30 May
23 May-12 Jun
Catalpa speciosa (northern catalpa)
95% bloom
31 May
30-31 May
Syringa reticulata (tree lilac)
95% bloom
02 Jun
28 May-07 Jun
Hydrangea quercifolia (oakleaf hydrangea)
50% bloom
02 Jun
31 May-06 Jun
Japanese beetle
1st flight
04 Jun
03-08 Jun
Tilia cordata (littleleaf linden)
50% bloom
07 Jun
04-09 Jun
Honeylocust borer
Emergence
07 Jun
26 May-15 Jun
Hydrangea quercifolia (oakleaf hydrangea)
95% bloom
07 Jun
05-11 Jun
Magnolia grandiflora (southern magnolia)
50% bloom
08 Jun
26 May-20 Jun
Walnut scale
Egg hatch
09 Jun
08-11 Jun
Tilia cordata (littleleaf linden)
95% bloom
09 Jun
06-13 Jun
Cottony maple leaf scale
Egg hatch
11 Jun
08-14 Jun
Koelreuteria paniculata (golden-rain tree)
1st bloom
16 Jun
13-18 Jun
Abelia x grandiflora (glossy abelia)
1st bloom
23 Jun
14 Jun-09 Jul
Koelreuteria paniculata (golden-rain tree)
50% bloom
24 Jun
21 Jun-01 Jul
Koelreuteria paniculata (golden-rain tree)
95% bloom
26 Jun
23 Jun-01 Jul
Obscure scale
Egg hatch
06 Jul
05-08 Jul

 

Determining Treatment Date

For most insects listed in the table, the ideal time to begin insecticide treatment is at or shortly after pest emergence. For bagworms, delay treatment one to two weeks after eggs hatch to ensure all young larvae have emerged from the old bags. For clearwing borers (dogwood, lilac, peachtree, lesser peachtree) and American plum borer, apply a bark spray 10 to 14 days after first flight. Apply a second bark spray one month later for better control of dogwood, peachtree, and lesser peachtree borers. For flatheaded borers (bronze birch borer, flatheaded appletree, honeylocust, twolined chestnut borer), apply a bark spray at or shortly after emergence and repeat after three weeks.

 

Revised: 4/07

 

CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.

 

Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!

 

Images: University of Kentucky Entomology