July 23 2004.cdr
INSECTS
July 23,
2004
Issue 17
Dewey Caron Extension Entomologist
What's Hot!
EUONYMOUS SCALE is a small introduced whitish scale that occurs on stems spilling over onto leaves primarily on portions of the host nearest to the ground. It is a major pest of evergreen Euonymous but also occurs on pachysandra, bittersweet, privet, honeysuckle, holly, camellia, plum and cherry. It can result in loss of plant vigor and even kill susceptible Euonymous japonica. Vigorously growing Euonymous varieties such as variegated and dwarf cultivars should be mulched and watered if drought conditions develop later this season. If current plants are heavily infested, prune them back severely and protect new growth with sprays.
Lace bugs and Japanese beetles are extremely abundant landscape pests this season. Determine if more directed control is needed for both of them. Alder in our landscapes are showing lots of blotch leafminer damage but are adding a new set of leaves to help compensate. Woolly alder aphids are abundant this season on alder. They appear as white, waxy, filamentous growths on stems. The leafminers are beyond control; the woolly aphids can be reduced with oil or soap but seldom cause significant damage.
This scale has 2 generations which overlap somewhat. The scale covers you see now are the 1st generation. They hatched during lilac boom this spring. The 2nd generation crawlers appear now (end of July-early August) in Delaware, so scout for the tiny yellowish-white flecks on infested hosts. The adult scales cannot be controlled now but will indicate places to focus your scouting. When you identify crawlers, spray infested material twice at 7-10 day intervals (eggs hatch over a 2-3 week time period) with hort oil, insecticidal soap, orthene or diazinon. Plan to cover the same hosts overwinter with a dormant oil spray when temperatures are above 40 degrees.
Peony blotch is now evident on garden and tree peony. Look for purple to dark red spots on the upper surface of the leaves and the corresponding lower surface will be chocolate brown color. The fungus Cladosporium will also infect the stems and produce circular spots with red borders. Be sure to remove and destroy infected leaves and stems in the fall to reduce overwintering spores. It's too late for any fungicide control this season, but the disease does not seem to affect plant health all that much, but makes a mess of the leaves.
Host material in shady locations have more predators and parasites to help control this pest since the beneficials suffer more in the hot dry exposed sites. A 2-spotted, tiny lady beetle has been introduced to help control the scale and, if evident, soap or oil should be the spray material of choice.
DISEASES
Bacterial leaf scorch is appearing already on susceptible oaks in the red oak group. Look for the typical marginal browning of the leaves that resembles drought damage. Infected trees may also be less vigorous than nearby healthy trees of the same species. The only way to definitely
Bob Mulrooney Extension Plant Pathologist GRAPES. Two diseases have been observed on backyard grapevines--black rot and downy mildew. Symptoms of black rot first appear as small yellowish spots on leaves. As the spots enlarge, a black border forms around the margins. The centers of the lesions become reddish-brown. By the time the lesions reach 1/8 to 1/4 inch in diameter, tiny black dots appear. These are spore-producing structures of the fungus. Often they are arranged in a ring pattern just inside the margin of the lesion. Lesions may also appear on young shoots, cluster stems, and tendrils. These lesions are purple to black oval in outline, and sunken. Fruit symptoms often do not appear until grapes are half grown. Small, round, light brownish spots form on the fruit. The rotted tissue in the spot softens and becomes sunken. The spot enlarges quickly, rotting the entire berry in a few days. The
For more ion format n i on pests & practices covered in this
(Continued)
Helpful numbers to know:
(Continued)
UNIVERSITY OF DELAWARE
Garden Line 831-8862 (for home gardeners only) New Castle County Extension 831-2506 Kent County Extension 730-4000 Sussex County Extension 856-7303
COOPERATIVE EXTENSION
Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating. Janice A. Seitz, Director. Distributed in furtherance of Acts of Congress of March 8 and June 30, 1914. It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age, or national origin.
Diseases (Continued)
What’s Hot (Continued)
diseased fruit shrivels, becoming small, hard, black, and wrinkled. Raised, black spore-producing structures of the fungus form on the blackened, shriveled fruit. The shriveled, infected fruit are commonly known as "mummies". These mummies usually remain attached to the fruit cluster. It's to late for control this season. Be sure to remove old infected fruit and remove old infected leaves from under the plants in the fall.
tell is to sample and run a test for the bacteria Xylella fastidiosa that causes bacterial leaf scorch. This pathogen is reportedly vectored by treehoppers or leafhoppers or other insects that feed in the xylem.
Downy mildew produces irregular yellow blotches on the upper surface of the leaf and on the corresponding undersurface you will see a small tuft of grayish white fungus growth of the downy mildew fungus. This disease can cause some leaf loss and reduction of sugars which affects fruit quality. Apply a labeled fungicide such as captan for control. Look for a fact sheet with more info at http://ag.udel.edu/extension/information/pp/pp-25.htm.
Anthracnose on oak is beginning to increase in the landscape. Look for the typical brown patches that follow the veins on oak. As the season progresses into the fall more disease will likely appear especially with all the showers we have been having. It is of minor concern to us and does not need to be controlled. Editor: Susan Barton Extension Horticulturist
Cooperative Extension Townsend Hall Newark, Delaware 19717
4 0 , 20 0 July 2 AS OF
GROWI DAYS DEGREE NG
23 = 15 '03 33 ( e ous = 18 enh unty) ) Gre fice f 4 1 O her e Co ion = 16 Fisc Castl tens 8 ('03 wn w 8 (Ne y Ex geto1) u nt y ) = 2 0 eor t r, G = 169 t Co 3 Ken t Coun ente c. C 066 ('0 (Ken Edu 2 h & nty) = u earc Res sex Co (Sus
)
July 23,
2004
Issue 17
Dewey Caron Extension Entomologist
What's Hot!
EUONYMOUS SCALE is a small introduced whitish scale that occurs on stems spilling over onto leaves primarily on portions of the host nearest to the ground. It is a major pest of evergreen Euonymous but also occurs on pachysandra, bittersweet, privet, honeysuckle, holly, camellia, plum and cherry. It can result in loss of plant vigor and even kill susceptible Euonymous japonica. Vigorously growing Euonymous varieties such as variegated and dwarf cultivars should be mulched and watered if drought conditions develop later this season. If current plants are heavily infested, prune them back severely and protect new growth with sprays.
Lace bugs and Japanese beetles are extremely abundant landscape pests this season. Determine if more directed control is needed for both of them. Alder in our landscapes are showing lots of blotch leafminer damage but are adding a new set of leaves to help compensate. Woolly alder aphids are abundant this season on alder. They appear as white, waxy, filamentous growths on stems. The leafminers are beyond control; the woolly aphids can be reduced with oil or soap but seldom cause significant damage.
This scale has 2 generations which overlap somewhat. The scale covers you see now are the 1st generation. They hatched during lilac boom this spring. The 2nd generation crawlers appear now (end of July-early August) in Delaware, so scout for the tiny yellowish-white flecks on infested hosts. The adult scales cannot be controlled now but will indicate places to focus your scouting. When you identify crawlers, spray infested material twice at 7-10 day intervals (eggs hatch over a 2-3 week time period) with hort oil, insecticidal soap, orthene or diazinon. Plan to cover the same hosts overwinter with a dormant oil spray when temperatures are above 40 degrees.
Peony blotch is now evident on garden and tree peony. Look for purple to dark red spots on the upper surface of the leaves and the corresponding lower surface will be chocolate brown color. The fungus Cladosporium will also infect the stems and produce circular spots with red borders. Be sure to remove and destroy infected leaves and stems in the fall to reduce overwintering spores. It's too late for any fungicide control this season, but the disease does not seem to affect plant health all that much, but makes a mess of the leaves.
Host material in shady locations have more predators and parasites to help control this pest since the beneficials suffer more in the hot dry exposed sites. A 2-spotted, tiny lady beetle has been introduced to help control the scale and, if evident, soap or oil should be the spray material of choice.
DISEASES
Bacterial leaf scorch is appearing already on susceptible oaks in the red oak group. Look for the typical marginal browning of the leaves that resembles drought damage. Infected trees may also be less vigorous than nearby healthy trees of the same species. The only way to definitely
Bob Mulrooney Extension Plant Pathologist GRAPES. Two diseases have been observed on backyard grapevines--black rot and downy mildew. Symptoms of black rot first appear as small yellowish spots on leaves. As the spots enlarge, a black border forms around the margins. The centers of the lesions become reddish-brown. By the time the lesions reach 1/8 to 1/4 inch in diameter, tiny black dots appear. These are spore-producing structures of the fungus. Often they are arranged in a ring pattern just inside the margin of the lesion. Lesions may also appear on young shoots, cluster stems, and tendrils. These lesions are purple to black oval in outline, and sunken. Fruit symptoms often do not appear until grapes are half grown. Small, round, light brownish spots form on the fruit. The rotted tissue in the spot softens and becomes sunken. The spot enlarges quickly, rotting the entire berry in a few days. The
For more ion format n i on pests & practices covered in this
(Continued)
Helpful numbers to know:
(Continued)
UNIVERSITY OF DELAWARE
Garden Line 831-8862 (for home gardeners only) New Castle County Extension 831-2506 Kent County Extension 730-4000 Sussex County Extension 856-7303
COOPERATIVE EXTENSION
Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating. Janice A. Seitz, Director. Distributed in furtherance of Acts of Congress of March 8 and June 30, 1914. It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age, or national origin.
Diseases (Continued)
What’s Hot (Continued)
diseased fruit shrivels, becoming small, hard, black, and wrinkled. Raised, black spore-producing structures of the fungus form on the blackened, shriveled fruit. The shriveled, infected fruit are commonly known as "mummies". These mummies usually remain attached to the fruit cluster. It's to late for control this season. Be sure to remove old infected fruit and remove old infected leaves from under the plants in the fall.
tell is to sample and run a test for the bacteria Xylella fastidiosa that causes bacterial leaf scorch. This pathogen is reportedly vectored by treehoppers or leafhoppers or other insects that feed in the xylem.
Downy mildew produces irregular yellow blotches on the upper surface of the leaf and on the corresponding undersurface you will see a small tuft of grayish white fungus growth of the downy mildew fungus. This disease can cause some leaf loss and reduction of sugars which affects fruit quality. Apply a labeled fungicide such as captan for control. Look for a fact sheet with more info at http://ag.udel.edu/extension/information/pp/pp-25.htm.
Anthracnose on oak is beginning to increase in the landscape. Look for the typical brown patches that follow the veins on oak. As the season progresses into the fall more disease will likely appear especially with all the showers we have been having. It is of minor concern to us and does not need to be controlled. Editor: Susan Barton Extension Horticulturist
Cooperative Extension Townsend Hall Newark, Delaware 19717
4 0 , 20 0 July 2 AS OF
GROWI DAYS DEGREE NG
23 = 15 '03 33 ( e ous = 18 enh unty) ) Gre fice f 4 1 O her e Co ion = 16 Fisc Castl tens 8 ('03 wn w 8 (Ne y Ex geto1) u nt y ) = 2 0 eor t r, G = 169 t Co 3 Ken t Coun ente c. C 066 ('0 (Ken Edu 2 h & nty) = u earc Res sex Co (Sus
)
