July 22 2005.cdr
INSECTS
July 22, 2005
Issue 18
Gregory Hoover Ornamental Extension Entomologist
What's Hot!
EUONYMUS SCALE, Unaspis euonymi, is a key pest of deciduous and evergreen euonymus. Vine-type euonymus plants are extremely susceptible to injury by this scale. Pachysandra is another common host plant for this armored scale. This pest overwinters as mature, fertilized females. Fertilized females are 2 mm long, grayish-brown, pear-shaped, and flattened. Males have narrow, white, waxy covers that are about 0.8 mm long. Mature males emerge as small fly-like insects. Females begin laying eggs beneath their protective waxy cover in late April and May. The eggs hatch in 2-3 weeks into the first nymphal stage called a crawler. Crawlers wander over the host plant for a short time, and then settle down to feed. Four to six weeks are usually required for the nymphs to mature into adults (mid-July). Male scales feed and develop under their covers, mate with the females, and die. A second generation of crawlers is produced during late July through August. Pruning and destroying heavily infested branches and twigs may be one way to manage infestations of this key pest. This armored scale insect is most difficult to control at the base of the infested plants near the ground. It is especially true with various low growing cultivars of euonymus. To manage crawlers, apply registered formulations of horticultural oil according to label directions in late May-June (for the first generation) and again in late July-early August (for the second generation). Choosing to apply horticultural oil will conserve natural enemies (such as the lady beetle, Chilocorus kuwanae) that feed on life stages of this pest. Registered formulations of DeltaGard T&O, insecticidal soap, Scimitar, Sevin, Tempo, and TriStar are also labeled for management of this scale insect. Repeat applications when indicated and be sure to follow all insecticide label directions.
DISEASES Bob Mulrooney Extension Plant Pathologist 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 unless you are just seeing the first blotches, but the disease does not seem to affect plant health all that muchit just makes a mess of the leaves.
(Continued)
UNIVERSITY OF DELAWARE
Japanese beetle damage has been severe again this season. Linden trees along Paper Mill Road in Newark have been hit hard in front of MBNA. Some of the trees are almost completely defoliated. Cherries in the UDBG and throughout the area have been hit hard as well. In the case of the MBNA lindens, most of the beetles are gone and the damage is done, so there is really no point in offering control. It may be worth trying to control active populations on valuable individual plants, like roses, but applications should be repeated weekly. In a few more weeks the adults will be gone and we’ll be worrying about trying to control grubs feeding in lawns--mid to late August is good time for grub control. Bagworms have gone beyond the stage where Bt is a control option. Bags are being constructed as you read, but there is still some time to use a residual insecticide before the bag is totally sealed for overwintering. On a small scale, you can pick and destroy formed bags throughout the fall and winter to reduce next year’s population. Lace bugs were found on cotoneaster, hawthorn and aster in the UDBG, producing the typical bronzing of the foliage. Adults, nymphs, and frass were all present. Remember, effective control is only attained with good coverage of the foliage.
For more ion format n i on pests & practices covered in this 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.
Diseases (Continued) OTHER DISEASES. Powdery mildew continues to increase on many plants as well as black spot in rose, crabapple scab, and others. Many of these I have discussed in previous issues of Hotline. A crabapple, Malus sargentii, was seen with considerable defoliation from cedar-apple rust. CEDAR-QUINCE RUST has been showing up lately on serviceberry, Amelanchier. The fruit and green twigs are infected and the fruit terribly misshapen. Again it will not affect plant health just appearance of the plant. STINK HORN FUNGUS is this weeks' most popular miscellaneous fungi currently appearing in compost and mulched beds. These curiosities are slender tube-shaped fungi with reddish, pink stems and a small brown slimy head that smells, thus “stink horn.” There are several variations found in the landscape--usually they are a species of Mutinus, the dog stinkhorn. This has no real cap, just the brown evil smelling slime. These are not harmful; they are simply decomposing the mulch or compost. Just remove by raking or some other mechanical means. Editor: Susan Barton Extension Horticulturist
G N I W GROREE DAYS
5 , 20 0 9 G 1 E D S OF July A
) 33 18 = ('04 10 6 e 1 s ou ty) = e 8) nh ffic 208 O ree Coun = G 4 wn on r e nsi 9 ('0 eto 6) che Castl e g s t r i 8 x F E eo 206 w 16 ,G nty = (Ne ter ('04 = ou nty) n C e C 663 u nt u c. Ke nt Co Ed ) = 1 & y (Ke t rch oun C sea Re ssex (Su
July 22, 2005
Issue 18
Gregory Hoover Ornamental Extension Entomologist
What's Hot!
EUONYMUS SCALE, Unaspis euonymi, is a key pest of deciduous and evergreen euonymus. Vine-type euonymus plants are extremely susceptible to injury by this scale. Pachysandra is another common host plant for this armored scale. This pest overwinters as mature, fertilized females. Fertilized females are 2 mm long, grayish-brown, pear-shaped, and flattened. Males have narrow, white, waxy covers that are about 0.8 mm long. Mature males emerge as small fly-like insects. Females begin laying eggs beneath their protective waxy cover in late April and May. The eggs hatch in 2-3 weeks into the first nymphal stage called a crawler. Crawlers wander over the host plant for a short time, and then settle down to feed. Four to six weeks are usually required for the nymphs to mature into adults (mid-July). Male scales feed and develop under their covers, mate with the females, and die. A second generation of crawlers is produced during late July through August. Pruning and destroying heavily infested branches and twigs may be one way to manage infestations of this key pest. This armored scale insect is most difficult to control at the base of the infested plants near the ground. It is especially true with various low growing cultivars of euonymus. To manage crawlers, apply registered formulations of horticultural oil according to label directions in late May-June (for the first generation) and again in late July-early August (for the second generation). Choosing to apply horticultural oil will conserve natural enemies (such as the lady beetle, Chilocorus kuwanae) that feed on life stages of this pest. Registered formulations of DeltaGard T&O, insecticidal soap, Scimitar, Sevin, Tempo, and TriStar are also labeled for management of this scale insect. Repeat applications when indicated and be sure to follow all insecticide label directions.
DISEASES Bob Mulrooney Extension Plant Pathologist 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 unless you are just seeing the first blotches, but the disease does not seem to affect plant health all that muchit just makes a mess of the leaves.
(Continued)
UNIVERSITY OF DELAWARE
Japanese beetle damage has been severe again this season. Linden trees along Paper Mill Road in Newark have been hit hard in front of MBNA. Some of the trees are almost completely defoliated. Cherries in the UDBG and throughout the area have been hit hard as well. In the case of the MBNA lindens, most of the beetles are gone and the damage is done, so there is really no point in offering control. It may be worth trying to control active populations on valuable individual plants, like roses, but applications should be repeated weekly. In a few more weeks the adults will be gone and we’ll be worrying about trying to control grubs feeding in lawns--mid to late August is good time for grub control. Bagworms have gone beyond the stage where Bt is a control option. Bags are being constructed as you read, but there is still some time to use a residual insecticide before the bag is totally sealed for overwintering. On a small scale, you can pick and destroy formed bags throughout the fall and winter to reduce next year’s population. Lace bugs were found on cotoneaster, hawthorn and aster in the UDBG, producing the typical bronzing of the foliage. Adults, nymphs, and frass were all present. Remember, effective control is only attained with good coverage of the foliage.
For more ion format n i on pests & practices covered in this 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.
Diseases (Continued) OTHER DISEASES. Powdery mildew continues to increase on many plants as well as black spot in rose, crabapple scab, and others. Many of these I have discussed in previous issues of Hotline. A crabapple, Malus sargentii, was seen with considerable defoliation from cedar-apple rust. CEDAR-QUINCE RUST has been showing up lately on serviceberry, Amelanchier. The fruit and green twigs are infected and the fruit terribly misshapen. Again it will not affect plant health just appearance of the plant. STINK HORN FUNGUS is this weeks' most popular miscellaneous fungi currently appearing in compost and mulched beds. These curiosities are slender tube-shaped fungi with reddish, pink stems and a small brown slimy head that smells, thus “stink horn.” There are several variations found in the landscape--usually they are a species of Mutinus, the dog stinkhorn. This has no real cap, just the brown evil smelling slime. These are not harmful; they are simply decomposing the mulch or compost. Just remove by raking or some other mechanical means. Editor: Susan Barton Extension Horticulturist
G N I W GROREE DAYS
5 , 20 0 9 G 1 E D S OF July A
) 33 18 = ('04 10 6 e 1 s ou ty) = e 8) nh ffic 208 O ree Coun = G 4 wn on r e nsi 9 ('0 eto 6) che Castl e g s t r i 8 x F E eo 206 w 16 ,G nty = (Ne ter ('04 = ou nty) n C e C 663 u nt u c. Ke nt Co Ed ) = 1 & y (Ke t rch oun C sea Re ssex (Su
