September 3, 2004.cdr
September 3,
2004
Issue 22
INSECTS
What's Hot!
Derby Walker Extension Agent
Tuliptree scale hatch has been reported on our native tuliptree. Adult females, which are orange with black spots are now dying and turning brown. Black crawlers are becoming active and will overwinter on twigs. Tuliptree scale prefers tuliptrees and magnolias but can also be found on linden, hickory, basswood and walnut. Small trees can be killed by this sucking insect and large trees may suffer yellowing, premature leaf drop and branch dieback. Honeydew and sooty mold is also a problem with this scale. Do not spray yet while eggs are still present. Wait until all eggs have hatched (end of September) and control with a residual insecticide such as Merit or Scimitar.
AZALEA LACE BUG adults can be found on feeding on azaleas. This is the last generation for 2004. Before spraying, check the leaves to be sure they are still present. In many cases the damage is done and the insects are gone so there is no need to spray. BAGWORMS. We have been finding a lot of empty bagworm cases from this year's hatch. Looks like the good guys have had some effect this year. OAK GALLS. Homeowners are curious about the growths they are finding on oak leaves. Oak leaves host a number of different insect galls. Little real harm is done to the trees and the galls are really more of a curiosity. HORNETS. Baldfaced hornet nests are now large enough and have enough hornets to concern homeowners. Those nests located high up in air are not much of threat unless they are challenged. But, low nests do pose a risk. A wasp and hornet aerosol is very effective for control. Apply a direct spray of the aerosol into the nest entrance after dark. Wait 24 hours before trying to take down the nest. Look for activity around the nest before disturbing it. A second treatment may be required before nest removal. The nests are only used once.
Fall webworm is in full force now surrounding outer limbs of many trees. Pruning out objectionable limbs is often recommended. That is fine if the tree is large and established. But, with small trees it may be better to let the insect run its course. Pruning several terminals may affect tree growth more negatively than the damage caused by the insect. At this point in the season, it really doesn’t hurt a tree to become partially defoliated. If the webs are very objectionable and the tree is small, consider disrupting the web
DISEASES Bob Mulrooney Extension Plant Pathologist BOTRYTIS FLOWER BLIGHT AND STEM CANKER is increasing on annuals and perennials. The cooler weather and prolonged dews will favor Botrytis. Remove spent infected blossoms to prevent the fungus from moving from the flowers to leaves or stems. Stem cankers can develop on roses if old flowers are not pruned and the fungus proceeds to the stems. Look for the tan to gray fluffy fungal growth on the flowers or stems. Fungicide applications of Daconil, or thiophanate-methyl can be helpful in controlling Botrytis in the landscape along with sanitation measures.
(Continued)
For more ion informat
ANTHRACNOSE on oak, maple, and walnut is increasing. On oak and maple, most of the leaf spots will follow the veins but some will be more or less round spots. This late in the season no control is necessary. On walnut, the spots are irregular in shape and numerous to the extent that they may cause premature defoliation. Again it is too late in the season for any control and the fungus does little to harm the health of the trees.
UNIVERSITY OF DELAWARE
on pests & practices covered in this newsletter, call your County Extension Office Helpful numbers to know: 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.
What’s Hot (Continued) mechanically and spraying the webworms off the foliage with a directed spray of water. Chuck Cornell covered several mites that will continue to cause problems to landscape plants this fall in his August 30th edition of Bug Bulletin. Here is the list: Spruce spider mites - look for activity increasing as the weather cools on many needled evergreens. Hort oil is a good choice for control on hemlocks since that plant usually has a complex of pests. Southern red mites - don’t forget this mite in the fall. Control with alternating miticides. Boxwood spider mites - multiple generations may occur into late autumn. Control is important since damage will be visible on this broad leaved evergreen all winter. Avercmectin is effective. Rust mites - are active now on a variety of evergreens. Use a beating tray and look for very small, spindle shaped mites (they do not look like spider mites). Hort oil is the only effective pesticide for landscape use. Editor: Susan Barton Extension Horticulturist
Cooperative Extension Townsend Hall Newark, Delaware 19717
GROWI DAYS DAESGORF EAuEgust 31, 2004 NG
70) = 25 '03 13 ( e ous ) = 28 y enh ice 91) Gre Count Off 6 her e 2 n o = i astl Fisc ens ('03 t wC (Ne y Ex 3 0 61 wn u nt = geto t Co unty) eor o Ken C r, G = NA) t 3 ente (Ken c. C 994 ('0 Edu 2 h & nty) = u earc Res sex Co (Sus
2004
Issue 22
INSECTS
What's Hot!
Derby Walker Extension Agent
Tuliptree scale hatch has been reported on our native tuliptree. Adult females, which are orange with black spots are now dying and turning brown. Black crawlers are becoming active and will overwinter on twigs. Tuliptree scale prefers tuliptrees and magnolias but can also be found on linden, hickory, basswood and walnut. Small trees can be killed by this sucking insect and large trees may suffer yellowing, premature leaf drop and branch dieback. Honeydew and sooty mold is also a problem with this scale. Do not spray yet while eggs are still present. Wait until all eggs have hatched (end of September) and control with a residual insecticide such as Merit or Scimitar.
AZALEA LACE BUG adults can be found on feeding on azaleas. This is the last generation for 2004. Before spraying, check the leaves to be sure they are still present. In many cases the damage is done and the insects are gone so there is no need to spray. BAGWORMS. We have been finding a lot of empty bagworm cases from this year's hatch. Looks like the good guys have had some effect this year. OAK GALLS. Homeowners are curious about the growths they are finding on oak leaves. Oak leaves host a number of different insect galls. Little real harm is done to the trees and the galls are really more of a curiosity. HORNETS. Baldfaced hornet nests are now large enough and have enough hornets to concern homeowners. Those nests located high up in air are not much of threat unless they are challenged. But, low nests do pose a risk. A wasp and hornet aerosol is very effective for control. Apply a direct spray of the aerosol into the nest entrance after dark. Wait 24 hours before trying to take down the nest. Look for activity around the nest before disturbing it. A second treatment may be required before nest removal. The nests are only used once.
Fall webworm is in full force now surrounding outer limbs of many trees. Pruning out objectionable limbs is often recommended. That is fine if the tree is large and established. But, with small trees it may be better to let the insect run its course. Pruning several terminals may affect tree growth more negatively than the damage caused by the insect. At this point in the season, it really doesn’t hurt a tree to become partially defoliated. If the webs are very objectionable and the tree is small, consider disrupting the web
DISEASES Bob Mulrooney Extension Plant Pathologist BOTRYTIS FLOWER BLIGHT AND STEM CANKER is increasing on annuals and perennials. The cooler weather and prolonged dews will favor Botrytis. Remove spent infected blossoms to prevent the fungus from moving from the flowers to leaves or stems. Stem cankers can develop on roses if old flowers are not pruned and the fungus proceeds to the stems. Look for the tan to gray fluffy fungal growth on the flowers or stems. Fungicide applications of Daconil, or thiophanate-methyl can be helpful in controlling Botrytis in the landscape along with sanitation measures.
(Continued)
For more ion informat
ANTHRACNOSE on oak, maple, and walnut is increasing. On oak and maple, most of the leaf spots will follow the veins but some will be more or less round spots. This late in the season no control is necessary. On walnut, the spots are irregular in shape and numerous to the extent that they may cause premature defoliation. Again it is too late in the season for any control and the fungus does little to harm the health of the trees.
UNIVERSITY OF DELAWARE
on pests & practices covered in this newsletter, call your County Extension Office Helpful numbers to know: 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.
What’s Hot (Continued) mechanically and spraying the webworms off the foliage with a directed spray of water. Chuck Cornell covered several mites that will continue to cause problems to landscape plants this fall in his August 30th edition of Bug Bulletin. Here is the list: Spruce spider mites - look for activity increasing as the weather cools on many needled evergreens. Hort oil is a good choice for control on hemlocks since that plant usually has a complex of pests. Southern red mites - don’t forget this mite in the fall. Control with alternating miticides. Boxwood spider mites - multiple generations may occur into late autumn. Control is important since damage will be visible on this broad leaved evergreen all winter. Avercmectin is effective. Rust mites - are active now on a variety of evergreens. Use a beating tray and look for very small, spindle shaped mites (they do not look like spider mites). Hort oil is the only effective pesticide for landscape use. Editor: Susan Barton Extension Horticulturist
Cooperative Extension Townsend Hall Newark, Delaware 19717
GROWI DAYS DAESGORF EAuEgust 31, 2004 NG
70) = 25 '03 13 ( e ous ) = 28 y enh ice 91) Gre Count Off 6 her e 2 n o = i astl Fisc ens ('03 t wC (Ne y Ex 3 0 61 wn u nt = geto t Co unty) eor o Ken C r, G = NA) t 3 ente (Ken c. C 994 ('0 Edu 2 h & nty) = u earc Res sex Co (Sus
