July 29 2005.cdr
INSECTS
July 29, 2005
Issue 19
Dewey Caron Extension Entomologist
What's Hot!
BEETLES & WASPS as indicated in What's Hot last week, this has been a memorable Japanese beetle year. The lawn ornaments to trap adults have been bent over with success. Other than protecting valuable roses or fruit, spraying for adults is not indicated. Grubs might be a problem later in August but only if watering has been performed or if you are in one of those areas getting more frequent thunderstorms for the rest of us the egg hatch has not been very good due to the dry conditions. Still it will be worth checking on grubs in poorly performing turf. The Green June Beetle has also been very abundant this season. Adults come to lights at night and can be found flying over turf, especially with high organic content. They will gang up on developing fruit and sweet corn silk. If needed the same materials used for Japanese beetles will control Green June Beetle adults (Sevin, cyfluthrin and other pyrethroids). The grubs feed up-sidedown but only on the organic matter so are not a control issue. Scolid wasps search for the GJB grubs, flying just above turf. These are large, leggy individuals with a yellow strip around the abdomen. They will not sting humans or pets and as they are good guys should be left to parasitize the beetles. The other wasp we will now find is the cicada killer wasp. It burrows into side-banks and lighter soils, producing a large dimesized entry hole. Males establish territories and scare homeowners; Hosta flower spikes are a favorite yard perching site. Females can sting if handled but they lack the qualities in their venom that cause human reactions they have large ovipositors and they can hurt. Control if nesting in inconvenient locations with a soil approved insecticide.
DISEASES Bob Mulrooney Extension Plant Pathologist BACTERIAL LEAF SCORCH is appearing now on susceptible oaks in the red oak group. Look for the typical marginal browning (bordered by a pale halo band separating the dead or scorched and normal green tissue) of the leaves that resembles drought damage. Although it is getting dry in some locations, it is not likely to be drought damage at this point. The only way to tell definitively, is to sample and run a test for the bacteria Xylella fastidiosa that causes bacterial leaf scorch. Bacterial leaf scorch (BLS) is an infectious chronic disease caused by the fastidious, gram-negative, xylem-limited bacterium Xylella fastidiosa. This bacterium, which is transmitted by xylem-feeding (Continued)
UNIVERSITY OF DELAWARE
Septoria leaf spot, caused by the fungus Septoria rudbeckiae has been identified on a Rudbeckia sample. This is a common leaf spot disease of Rudbeckia. Symptoms begin as small dark brown lesions (angular or rounded) that enlarge to 1/8 - 1/4 inch in diameter. The fungus produces small, pinpoint-size black flask-shaped structures called pycnidia, which contain the threadlike spores typical of Septoria. Like most fungal leaf spot diseases, the spores require moisture to germinate and cause infection. While Septoria leaf spot is unsightly, the damage is primarily cosmetic, and infected plants will bloom. Infected leaves may die a little earlier in the fall than uninfected leaves. Since fungicides are protectants and do not cure infected leaves, control would have been required early in the season. At this point, just clean up fallen leaves to reduce the infectious spores for next year. Many newly planted shrubs are flagging during the extreme heat of the day. As plants try to cool themselves, they are transpiring more water than compromised root systems can supply. Keep newly planted specimens watered, but don’t overwater. When you check for soil moisture, be sure you are checking the actual root zone. You may find that surrounding clay soils are moist but the artificial medium that still contains all the roots of the newly planted specimen is dry. Be sure to wet the root system when watering.
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) insects, colonizes and physically "clogs" the tree's water conducting tissues or xylem. Water transport becomes disrupted in roots, branches, and leaves due to large amounts of multiplying bacteria and their by-products. The presence of the bacteria also triggers a reaction in the tree that plugs the xylem, further impeding water transport and eventually killing the tree. Bacterial leaf scorch spreads systemically and causes slow decline and death of a tree. It is not new but appearing more frequently in landscape trees, possibly as more people learn to recognize symptoms. There is no effective preventative treatment or cure for bacterial leaf scorch. Infected trees will be lost eventually, so the best remedy will be replacement. To keep a tree looking its best as it starts to decline, prune out dead wood and symptomatic branches. Trunk injections with antibiotics have been shown to suppress symptoms. Treatments must be made annually in late May or early June. The antibiotic oxytetracycline has been tested as a treatment, but it only caused the remission of symptoms; it did not provide a cure. Keeping the tree as healthy as possible with mulching, irrigation during periods of little rainfall, and fertilization if a nutrient deficiency is found, may keep trees from succumbing to BLS quickly. Controlling leafhoppers (the vector) is not practical since they are active during the entire growing season. Editor: Susan Barton Extension Horticulturist
G N I W O R G EGREE DAYS D
2005 , 6 2 July F O AS
) 02 20 = '04 3( 81 e 1 s ou y) = ) t i ce nh 77 ree Coun Off = 22 G n n r e io ow 04 che stl ens 06 (' get 37) t r F is w C a x o E e 2 ty = 19 r, G = 2 (Ne ) un nte ('04 Co unty e t n c. C 1871 Ke nt Co du & E ty) = (K e h n c ear Cou Res ssex ( Su
July 29, 2005
Issue 19
Dewey Caron Extension Entomologist
What's Hot!
BEETLES & WASPS as indicated in What's Hot last week, this has been a memorable Japanese beetle year. The lawn ornaments to trap adults have been bent over with success. Other than protecting valuable roses or fruit, spraying for adults is not indicated. Grubs might be a problem later in August but only if watering has been performed or if you are in one of those areas getting more frequent thunderstorms for the rest of us the egg hatch has not been very good due to the dry conditions. Still it will be worth checking on grubs in poorly performing turf. The Green June Beetle has also been very abundant this season. Adults come to lights at night and can be found flying over turf, especially with high organic content. They will gang up on developing fruit and sweet corn silk. If needed the same materials used for Japanese beetles will control Green June Beetle adults (Sevin, cyfluthrin and other pyrethroids). The grubs feed up-sidedown but only on the organic matter so are not a control issue. Scolid wasps search for the GJB grubs, flying just above turf. These are large, leggy individuals with a yellow strip around the abdomen. They will not sting humans or pets and as they are good guys should be left to parasitize the beetles. The other wasp we will now find is the cicada killer wasp. It burrows into side-banks and lighter soils, producing a large dimesized entry hole. Males establish territories and scare homeowners; Hosta flower spikes are a favorite yard perching site. Females can sting if handled but they lack the qualities in their venom that cause human reactions they have large ovipositors and they can hurt. Control if nesting in inconvenient locations with a soil approved insecticide.
DISEASES Bob Mulrooney Extension Plant Pathologist BACTERIAL LEAF SCORCH is appearing now on susceptible oaks in the red oak group. Look for the typical marginal browning (bordered by a pale halo band separating the dead or scorched and normal green tissue) of the leaves that resembles drought damage. Although it is getting dry in some locations, it is not likely to be drought damage at this point. The only way to tell definitively, is to sample and run a test for the bacteria Xylella fastidiosa that causes bacterial leaf scorch. Bacterial leaf scorch (BLS) is an infectious chronic disease caused by the fastidious, gram-negative, xylem-limited bacterium Xylella fastidiosa. This bacterium, which is transmitted by xylem-feeding (Continued)
UNIVERSITY OF DELAWARE
Septoria leaf spot, caused by the fungus Septoria rudbeckiae has been identified on a Rudbeckia sample. This is a common leaf spot disease of Rudbeckia. Symptoms begin as small dark brown lesions (angular or rounded) that enlarge to 1/8 - 1/4 inch in diameter. The fungus produces small, pinpoint-size black flask-shaped structures called pycnidia, which contain the threadlike spores typical of Septoria. Like most fungal leaf spot diseases, the spores require moisture to germinate and cause infection. While Septoria leaf spot is unsightly, the damage is primarily cosmetic, and infected plants will bloom. Infected leaves may die a little earlier in the fall than uninfected leaves. Since fungicides are protectants and do not cure infected leaves, control would have been required early in the season. At this point, just clean up fallen leaves to reduce the infectious spores for next year. Many newly planted shrubs are flagging during the extreme heat of the day. As plants try to cool themselves, they are transpiring more water than compromised root systems can supply. Keep newly planted specimens watered, but don’t overwater. When you check for soil moisture, be sure you are checking the actual root zone. You may find that surrounding clay soils are moist but the artificial medium that still contains all the roots of the newly planted specimen is dry. Be sure to wet the root system when watering.
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) insects, colonizes and physically "clogs" the tree's water conducting tissues or xylem. Water transport becomes disrupted in roots, branches, and leaves due to large amounts of multiplying bacteria and their by-products. The presence of the bacteria also triggers a reaction in the tree that plugs the xylem, further impeding water transport and eventually killing the tree. Bacterial leaf scorch spreads systemically and causes slow decline and death of a tree. It is not new but appearing more frequently in landscape trees, possibly as more people learn to recognize symptoms. There is no effective preventative treatment or cure for bacterial leaf scorch. Infected trees will be lost eventually, so the best remedy will be replacement. To keep a tree looking its best as it starts to decline, prune out dead wood and symptomatic branches. Trunk injections with antibiotics have been shown to suppress symptoms. Treatments must be made annually in late May or early June. The antibiotic oxytetracycline has been tested as a treatment, but it only caused the remission of symptoms; it did not provide a cure. Keeping the tree as healthy as possible with mulching, irrigation during periods of little rainfall, and fertilization if a nutrient deficiency is found, may keep trees from succumbing to BLS quickly. Controlling leafhoppers (the vector) is not practical since they are active during the entire growing season. Editor: Susan Barton Extension Horticulturist
G N I W O R G EGREE DAYS D
2005 , 6 2 July F O AS
) 02 20 = '04 3( 81 e 1 s ou y) = ) t i ce nh 77 ree Coun Off = 22 G n n r e io ow 04 che stl ens 06 (' get 37) t r F is w C a x o E e 2 ty = 19 r, G = 2 (Ne ) un nte ('04 Co unty e t n c. C 1871 Ke nt Co du & E ty) = (K e h n c ear Cou Res ssex ( Su
