September 23 2005.cdr
September 23, 2005
Issue 25
What's Hot!
INSECTS
Dewey Caron Extension Entomologist LOTS OF INSECT. On the Hort Research Expo PEST WALK this past Thursday there were many examples of heat stress to demonstrate, plenty of insect damage for me to show and Nancy Gregory showed lots of plant pathogen symptoms. Japanese beetle leaf lacing and grasshopper feeding damage was widely evident. Populations of lace bugs are locally heavy with hosts displaying sickly looking, bronzed foliage. Bagworms are having an exceptional year too, with disfigurement evident on some hosts from the large fully-formed bags now present. Wasp nests, including the spreading yellow-jacket look-alike species Polistes dominulus, are common this time of year. (Note: Rayanne Lehman is trying to determine how widespread it is in PA – if you see it please let Rayanne at PDA know.) We were able to show Douglas Fir Needle Midge, which causes a disfigurement and yellowing of needles (thanks to a Bob Mulrooney discovery). Soon the home invaders (already led by crickets) will be evident.
DISEASES Bob Mulrooney Extension Plant Pathologist DRY. We continue to see the effects of the dry weather on many trees. Tulip poplar, scycamores, and Katsura trees continue to drop leaves prematurely due to the previous drought stress. Stressed trees will also show fall color prematurely as well. FALL FOLIAGE DISEASES that are becoming more evident include anthracnose on red oaks, Septoria leafspot on dogwood, anthracnose on black walnut, anthracnose on liriope, leaf blotch on horsechestnut and Volutella blight on pachysandra. This late in the season no control is necessary at this time. POWDERY MILDEW. This has been powdery mildew weather and it is increasing on susceptible hybrid tea roses and many perennial hosts such as bee balm, garden phlox, peony and many others.
Several timely articles are excerpted below from The P.E.S.T. Newsletter published by Dave Shetlar at Ohio State University. White grubs are actively feeding in infested turf. The very high populations of Japanese beetles this summer should translate to significant populations of grubs. Pull up suspect turf and if it rolls up and you find 5-6 or more grubs per square foot, control is warranted. Merit, MACH2 and Arena are recommended for grub control, but they may take up to 1420 days to work. Skunks and racoons will continue digging for grubs during that period, so if you want faster control, try Dylox (trichlorfon) or Sevin (carbaryl). When gardeners start to clean up perennial beds at the end of the season, they may discover that iris leaves are gone. Some people assume this loss is from summer heat and drought, but it is probably due to iris borer infestation. If you dig up an iris rhizome to for division, you might find a hollowed out rhizome filled with frass and possibly the nearly three-inch long pinkish caterpillar (the iris borer). The loss of the two insecticides used for iris borer control (lindane and Cygon) makes annual digging, division and physical removal of larvae or pupae, the only viable method of iris borer control. Perennial growers should be aware of black vine weevil damage in overwintering perennials. Adults have been laying eggs (Continued) 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
UNIVERSITY OF DELAWARE
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) in perennial plant containers all summer. Little damage occurs from feeding larvae in summer and fall because the larvae are still small. Instead the damage occurs when perennials are covered up for overwintering. Blackened tissue uncovered in the spring is often diagnosed as a fungal disease but could be black vine weevil damage. A preventative strategy is to mix bifenthrin into the potting mix--probably too late for that now. Or, you can use insect parasitic nematodes when you close up the perennial house for overwintering. Both Steinernema and Heterorhabditis nematode species can kill black vine weevils, but the Heterorhabditis are often preferred fro soil-dwelling pests. Get fresh nematodes, apply them with lots of water and keep the post evenly moist for a couple of weeks. The nematodes work best with a fall application because the pots are above 60 F.
Editor: Susan Barton Extension Horticulturist
G N I W GRO E DAYS
05 E R 20 , 20 r G e b E m DAS OF Septe
NA) 4= 0 ' ( 7 se 3 21 hou ty) = n e e ice Gr Coun Off A) her le Fisc Cast sion 04 = N n n e w (' Ext etow (Ne org ) nty ) = NA e u G o A r, tC nty nte 04 = N Ken t Cou ' . Ce n duc = NA ( E (Ke h & nty) u earc Res sex Co (Sus
Issue 25
What's Hot!
INSECTS
Dewey Caron Extension Entomologist LOTS OF INSECT. On the Hort Research Expo PEST WALK this past Thursday there were many examples of heat stress to demonstrate, plenty of insect damage for me to show and Nancy Gregory showed lots of plant pathogen symptoms. Japanese beetle leaf lacing and grasshopper feeding damage was widely evident. Populations of lace bugs are locally heavy with hosts displaying sickly looking, bronzed foliage. Bagworms are having an exceptional year too, with disfigurement evident on some hosts from the large fully-formed bags now present. Wasp nests, including the spreading yellow-jacket look-alike species Polistes dominulus, are common this time of year. (Note: Rayanne Lehman is trying to determine how widespread it is in PA – if you see it please let Rayanne at PDA know.) We were able to show Douglas Fir Needle Midge, which causes a disfigurement and yellowing of needles (thanks to a Bob Mulrooney discovery). Soon the home invaders (already led by crickets) will be evident.
DISEASES Bob Mulrooney Extension Plant Pathologist DRY. We continue to see the effects of the dry weather on many trees. Tulip poplar, scycamores, and Katsura trees continue to drop leaves prematurely due to the previous drought stress. Stressed trees will also show fall color prematurely as well. FALL FOLIAGE DISEASES that are becoming more evident include anthracnose on red oaks, Septoria leafspot on dogwood, anthracnose on black walnut, anthracnose on liriope, leaf blotch on horsechestnut and Volutella blight on pachysandra. This late in the season no control is necessary at this time. POWDERY MILDEW. This has been powdery mildew weather and it is increasing on susceptible hybrid tea roses and many perennial hosts such as bee balm, garden phlox, peony and many others.
Several timely articles are excerpted below from The P.E.S.T. Newsletter published by Dave Shetlar at Ohio State University. White grubs are actively feeding in infested turf. The very high populations of Japanese beetles this summer should translate to significant populations of grubs. Pull up suspect turf and if it rolls up and you find 5-6 or more grubs per square foot, control is warranted. Merit, MACH2 and Arena are recommended for grub control, but they may take up to 1420 days to work. Skunks and racoons will continue digging for grubs during that period, so if you want faster control, try Dylox (trichlorfon) or Sevin (carbaryl). When gardeners start to clean up perennial beds at the end of the season, they may discover that iris leaves are gone. Some people assume this loss is from summer heat and drought, but it is probably due to iris borer infestation. If you dig up an iris rhizome to for division, you might find a hollowed out rhizome filled with frass and possibly the nearly three-inch long pinkish caterpillar (the iris borer). The loss of the two insecticides used for iris borer control (lindane and Cygon) makes annual digging, division and physical removal of larvae or pupae, the only viable method of iris borer control. Perennial growers should be aware of black vine weevil damage in overwintering perennials. Adults have been laying eggs (Continued) 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
UNIVERSITY OF DELAWARE
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) in perennial plant containers all summer. Little damage occurs from feeding larvae in summer and fall because the larvae are still small. Instead the damage occurs when perennials are covered up for overwintering. Blackened tissue uncovered in the spring is often diagnosed as a fungal disease but could be black vine weevil damage. A preventative strategy is to mix bifenthrin into the potting mix--probably too late for that now. Or, you can use insect parasitic nematodes when you close up the perennial house for overwintering. Both Steinernema and Heterorhabditis nematode species can kill black vine weevils, but the Heterorhabditis are often preferred fro soil-dwelling pests. Get fresh nematodes, apply them with lots of water and keep the post evenly moist for a couple of weeks. The nematodes work best with a fall application because the pots are above 60 F.
Editor: Susan Barton Extension Horticulturist
G N I W GRO E DAYS
05 E R 20 , 20 r G e b E m DAS OF Septe
NA) 4= 0 ' ( 7 se 3 21 hou ty) = n e e ice Gr Coun Off A) her le Fisc Cast sion 04 = N n n e w (' Ext etow (Ne org ) nty ) = NA e u G o A r, tC nty nte 04 = N Ken t Cou ' . Ce n duc = NA ( E (Ke h & nty) u earc Res sex Co (Sus
