April 13 2012 email
INSECTS
April 13,
2012
Brian Kunkel Ornamental IPM Specialist EASTERN TENT CATERPILLAR. This year has been very warm so far and we are well past the growing degree days (13-160 [59 peak] GDD50) signifying egg hatch. Larvae have migrated to the forks of tree branches, formed tents and laid trails of webbing down as they continue to feed on young leaves. Eastern tent caterpillars are black, have tan-colored hairs, irregular blue markings, a white stripe down their back with a yellowish-tan stripe on either side. This insect prefers to feed on wild cherry, but also readily eats crabapple, ornamental apple, plum, peach, and occasionally birch or ash. Caterpillars feed from 2-598 GDD50 or while Cornus florida is in full bloom before they mature and leave the tree to search for a suitable location to pupate. The adults emerge in two to four weeks, mate, and females lay eggs in gray foam-like masses with about 150-350 eggs in a mass. Eastern tent caterpillars egg masses are usually laid on twigs or small branches and there is only one generation per year. A number of natural enemies such as assassin bugs, parasitoids, birds and a naturally occurring virus help keep their numbers low. One cultural control option is to tear open the tent which helps these natural enemies get to the caterpillars. Pruning out egg masses and destroying the eggs in the fall or late winter before egg hatch is another effective cultural method to control eastern tent caterpillar. Some compounds used to control eastern tent caterpillar include: insecticidal soap, B. thuringiensis (Dipel), spinosad (Conserve), chlorantraniliprole (Acelepryn), or pyrethroid products such as bifenthrin. Applications when the larvae are small increases efficacy and applications should cover both the foliage and the tent.
DISEASES
Issue 3
What's Hot! Dry weather is the most significant news for landscape horticulture. Plants are just starting to leaf out, so they are not losing water yet, but as soon as the leaves are full, they will. Supplemental water will be required for all new plantings this spring and probably last fall. Even established plants may need water if we don’t get some rain soon. The website below has a great story about the first cherries donated to the US by Japan in 1909. They were supposed to be planted on the Mall in Washington, DC with lots of hoopla. But they were found to be infested with a number of exotic insect pests and had to be destroyed. While, this was unfortunate at the time, it identified a huge issue and importation of nursery stock became controlled. Healthy, uninfested trees were planted on the Mall in 1912. This really started the inspection and requirement for clean imports and exports! The mission of the NPDN remains early detection and rapid response. To learn more about Delaware’s role in the NPDN, contact Nancy Gregory ([email protected]). Read the whole story at this website: http://blogs.usda.gov/2012/04/04/celebratin g-100-years-of-washington-dc%E2%80%99scherry-blossoms/#more-39376
Bob Mulrooney Extension Plant Pathologist DRY WEATHER. The recent cool, dry weather has not been favorable for diseases this spring. Many deciduous trees are now in some stage of leaf emergence and expansion. This is usually the time when they are most susceptible to foliar diseases. This is the window for application of fungicides to protect the new leaves if foliar diseases have been a problem in the past. Most foliage disease of shade trees do not affect the health of the plants, just their appearance, so controls are rarely justified. Of course if you have a susceptible tree and the amount of leaf spotting that has occurred is unacceptable, now is the time to apply a fungicide. After the disease occurs it is too late to get satisfactory control. Once leaves emerge on the trees they will use more water and further deplete the available soil moisture. Keep an eye on recently planted trees and shrubs and those planted last year as well. Water as needed. (Continued)
UNIVERSITY OF DELAWARE
Fornfomromrae tion i
on pests & practices covered in this newsletter, call your County Extension Office Helpful numbers to know: Garden Line (for home gardeners only) New Castle County Extension Kent County Extension Sussex County Extension
831-8862 831-2506 730-4000 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) ANTHRACNOSE on liriope can be easily seen as irregular to elliptical spots with reddish-purple borders on the old leaves. Anthracnose is a minor disease on stressed plantings, but if the old foliage has not been removed yet there still may be time to cut back lirope. This spring clean-up removes most of the old infected leaves and most of the overwintering fungus. BLACK SPOT ON ROSES. It will be time to begin spraying hybrid tea roses for black spot soon. It bears repeating that a trial conducted here in the UDBG in 2005 on 'Tropicana' roses showed that spraying every two weeks throughout the season provided very good control of black spot with all of the homeowner fungicides tested. Those tested were Ortho Rose Pride Funginex, Spectracide Immunox, Bonide Infuse, Bayer Advanced Rose, Tree and Shrub Fungicide. Previous testing showed that applications of neem oil, horticultural oil, and potassium bicarbonate (Bonide Remedy) every two weeks did not control black spot under our conditions here. Clean up any old leaves and prunings from the rose beds to reduce overwintering spores of the fungus and begin spraying when the new leaves are expanding. Editor: Susan Barton Extension Horticulturist
G N I W GREGOREE DAYS D
, 2012 0 1 l i r Ap AS OF
) = 81 (’ 11 7 e lleg A) = 17 P e Co mor ounty, h t 61 ) r 1= Swa ware C e s 1 ('1 a l u 5 e o 1 h D ( n )= own Gree County rget her Geo 7) , r Fisc Castle e ent ('11 = 7 (New c. C Edu = 135 & h ) arc nty Rese ex Cou s s u S (
April 13,
2012
Brian Kunkel Ornamental IPM Specialist EASTERN TENT CATERPILLAR. This year has been very warm so far and we are well past the growing degree days (13-160 [59 peak] GDD50) signifying egg hatch. Larvae have migrated to the forks of tree branches, formed tents and laid trails of webbing down as they continue to feed on young leaves. Eastern tent caterpillars are black, have tan-colored hairs, irregular blue markings, a white stripe down their back with a yellowish-tan stripe on either side. This insect prefers to feed on wild cherry, but also readily eats crabapple, ornamental apple, plum, peach, and occasionally birch or ash. Caterpillars feed from 2-598 GDD50 or while Cornus florida is in full bloom before they mature and leave the tree to search for a suitable location to pupate. The adults emerge in two to four weeks, mate, and females lay eggs in gray foam-like masses with about 150-350 eggs in a mass. Eastern tent caterpillars egg masses are usually laid on twigs or small branches and there is only one generation per year. A number of natural enemies such as assassin bugs, parasitoids, birds and a naturally occurring virus help keep their numbers low. One cultural control option is to tear open the tent which helps these natural enemies get to the caterpillars. Pruning out egg masses and destroying the eggs in the fall or late winter before egg hatch is another effective cultural method to control eastern tent caterpillar. Some compounds used to control eastern tent caterpillar include: insecticidal soap, B. thuringiensis (Dipel), spinosad (Conserve), chlorantraniliprole (Acelepryn), or pyrethroid products such as bifenthrin. Applications when the larvae are small increases efficacy and applications should cover both the foliage and the tent.
DISEASES
Issue 3
What's Hot! Dry weather is the most significant news for landscape horticulture. Plants are just starting to leaf out, so they are not losing water yet, but as soon as the leaves are full, they will. Supplemental water will be required for all new plantings this spring and probably last fall. Even established plants may need water if we don’t get some rain soon. The website below has a great story about the first cherries donated to the US by Japan in 1909. They were supposed to be planted on the Mall in Washington, DC with lots of hoopla. But they were found to be infested with a number of exotic insect pests and had to be destroyed. While, this was unfortunate at the time, it identified a huge issue and importation of nursery stock became controlled. Healthy, uninfested trees were planted on the Mall in 1912. This really started the inspection and requirement for clean imports and exports! The mission of the NPDN remains early detection and rapid response. To learn more about Delaware’s role in the NPDN, contact Nancy Gregory ([email protected]). Read the whole story at this website: http://blogs.usda.gov/2012/04/04/celebratin g-100-years-of-washington-dc%E2%80%99scherry-blossoms/#more-39376
Bob Mulrooney Extension Plant Pathologist DRY WEATHER. The recent cool, dry weather has not been favorable for diseases this spring. Many deciduous trees are now in some stage of leaf emergence and expansion. This is usually the time when they are most susceptible to foliar diseases. This is the window for application of fungicides to protect the new leaves if foliar diseases have been a problem in the past. Most foliage disease of shade trees do not affect the health of the plants, just their appearance, so controls are rarely justified. Of course if you have a susceptible tree and the amount of leaf spotting that has occurred is unacceptable, now is the time to apply a fungicide. After the disease occurs it is too late to get satisfactory control. Once leaves emerge on the trees they will use more water and further deplete the available soil moisture. Keep an eye on recently planted trees and shrubs and those planted last year as well. Water as needed. (Continued)
UNIVERSITY OF DELAWARE
Fornfomromrae tion i
on pests & practices covered in this newsletter, call your County Extension Office Helpful numbers to know: Garden Line (for home gardeners only) New Castle County Extension Kent County Extension Sussex County Extension
831-8862 831-2506 730-4000 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) ANTHRACNOSE on liriope can be easily seen as irregular to elliptical spots with reddish-purple borders on the old leaves. Anthracnose is a minor disease on stressed plantings, but if the old foliage has not been removed yet there still may be time to cut back lirope. This spring clean-up removes most of the old infected leaves and most of the overwintering fungus. BLACK SPOT ON ROSES. It will be time to begin spraying hybrid tea roses for black spot soon. It bears repeating that a trial conducted here in the UDBG in 2005 on 'Tropicana' roses showed that spraying every two weeks throughout the season provided very good control of black spot with all of the homeowner fungicides tested. Those tested were Ortho Rose Pride Funginex, Spectracide Immunox, Bonide Infuse, Bayer Advanced Rose, Tree and Shrub Fungicide. Previous testing showed that applications of neem oil, horticultural oil, and potassium bicarbonate (Bonide Remedy) every two weeks did not control black spot under our conditions here. Clean up any old leaves and prunings from the rose beds to reduce overwintering spores of the fungus and begin spraying when the new leaves are expanding. Editor: Susan Barton Extension Horticulturist
G N I W GREGOREE DAYS D
, 2012 0 1 l i r Ap AS OF
) = 81 (’ 11 7 e lleg A) = 17 P e Co mor ounty, h t 61 ) r 1= Swa ware C e s 1 ('1 a l u 5 e o 1 h D ( n )= own Gree County rget her Geo 7) , r Fisc Castle e ent ('11 = 7 (New c. C Edu = 135 & h ) arc nty Rese ex Cou s s u S (
