June 18 2004.cdr
INSECTS
June 18,
2004
Issue 12
Gregory Hoover Ornamental Extension Entomologist
What's Hot! Japanese beetle adults are here. These beetles feed on the fruits, flowers and leaves of hundreds of different hosts. Roses and cannas are two highly preferred flowering plants. Preferred trees include maples, sycamore, birch, linden, and elms. Weekly sprays of Orthene, Turcam, Talstar. Sevin, Tempo 2, Merit, Scimitar or Astro T/O through July will provide only partial adult control. Traps are usually counter productive. Adults can be handpicked daily from special specimens.
FLETCHER SCALE, Parthenolecanium fletcheri, is currently active (crawler stage) on host plants in both landscapes and nurseries. This soft scale infests arborvitae, Thuja spp. and yew, Taxus spp. This species, also known as the "arborvitae soft scale", has been more common during the past several growing seasons. This key pest is found in the northern part of the eastern and midwestern United States. This species overwinters as a second instar nymph on the host plant. Nymphs develop rapidly to maturity in the spring. Adults normally are found on the twigs and stems of the host plant. Females are light brown to tan, almost globular, and about 3-5 mm in diameter. Females start laying eggs in late May. One female deposits an average of 500-600 eggs. These hatch in June into oval, flat, cream to yellow crawlers that migrate a short distance on a branch in search of a feeding site. They remain on the host plant for the remainder of the season, with very little growth or development occurring. This soft scale can reduce the health of a plant by removing fluid from vascular cells. In addition, heavily infested trees are often rendered unsightly by a heavy crust of black sooty mold that develops on the honeydew excreted by this scale insect. Heavily infested yews may also drop needles prematurely. This species produces one generation each growing season.
Cupping and curling of leaves are still evident from earlier aphid infestations. Beneficials are often present after the fact, so be careful in applying a control if the aphids are not there. You don't want to spray out of revenge and kill the beneficials.
Weak trees planted last year are obvious now. The warm weather is stressing the damaged root systems enough to cause major defoliation and branch dieback. It appears that many trees suffered from last year's excessive rain, resulting in drowned roots made more susceptible to soil-borne diseases. Affected trees may also have smaller than normal leaves or fewer leaves, making the crown look thin and sparse.
Effective management of an infestation of this pest should start with the use of a registered formulation of horticultural oil applied according to label directions at the dormant rate in early spring. Crawlers may be managed by using a registered formulation of horticultural oil (applied at the growing season rate), insecticidal soap, Merit, Scimitar, Sevin, or Tempo applied according to label directions from mid-June through mid-July.
DISEASES
Pine webworm larvae have been reported on white pine. Look for signs of mined needles on terminal shoots, now. Soon,
Bob Mulrooney Extension Plant Pathologist BOTRYTIS BLIGHT of foliage is showing up on different hosts that had flower or bud infections earlier in the year and now have infected tissue falling on the leaves, and causing infection. Botrytis will usually produce a large brown spot, often with a zonate pattern to the spot, but not always. I have seen this on flowering dogwood, 'Goldflame' honeysuckle, and rose. In the past, many annuals, including geraniums, have also been infected. Pick spent blossoms or remove the infected leaves. For preventative fungicides select something such as mancozeb, thiophanatemethyl, or chlorothalonil or other labeled fungicides and apply before rainy humid weather arrives. (Continued)
UNIVERSITY OF DELAWARE
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) Small mushrooms (nickel or dime sized) with fluted caps are appearing in lawns after the rains. These are harmless and can be raked away or mowed over. Most of these are in the genus Marasmius and are breaking down organic matter in the soil.
Editor: Susan Barton Extension Horticulturist
What's Hot (Continued)
older larvae will begin to consume needles while building and hiding in ugly nests composed of frass and silk surrounding terminal twigs. This is a minor pest of landscape pines. In small plantings, manually remove and destroy frass nests on terminals as soon as they are noticed. In large plantings, spray the terminals with Orthene, Sevin or Tempo 2 if much mining and needle webbing are present. In the UDBG, gall wasps were found on oak leaves and gall midges found on a camperdown elm. Galls result when leaf or twig tissue swells in response to chemicals produced by gall formers. Leaf galls are not serious unless abundant enough to cause early leaf drop. Pull off and destroy leaf galls while they are green. Dormant oil sprays can be used to reduce overwintering populations.
Cooperative Extension Townsend Hall Newark, Delaware 19717
4 5, 20 0 June 1 AS OF
DEGREE
G GROWINDAYS
) 691 3= 9 ('0 e 104 ous enh nty) = e Gre u ffic ) O her stle Co A ion =N Fisc a tens 5 ('03 wn wC 9 (Ne y Ex geto) unt y) = 11 eor t r , G = 792 t Co 3 Ken t Coun ente c. C 170 ('0 (Ken Edu 1 h & nty) = u earc Res sex Co ( Su s
June 18,
2004
Issue 12
Gregory Hoover Ornamental Extension Entomologist
What's Hot! Japanese beetle adults are here. These beetles feed on the fruits, flowers and leaves of hundreds of different hosts. Roses and cannas are two highly preferred flowering plants. Preferred trees include maples, sycamore, birch, linden, and elms. Weekly sprays of Orthene, Turcam, Talstar. Sevin, Tempo 2, Merit, Scimitar or Astro T/O through July will provide only partial adult control. Traps are usually counter productive. Adults can be handpicked daily from special specimens.
FLETCHER SCALE, Parthenolecanium fletcheri, is currently active (crawler stage) on host plants in both landscapes and nurseries. This soft scale infests arborvitae, Thuja spp. and yew, Taxus spp. This species, also known as the "arborvitae soft scale", has been more common during the past several growing seasons. This key pest is found in the northern part of the eastern and midwestern United States. This species overwinters as a second instar nymph on the host plant. Nymphs develop rapidly to maturity in the spring. Adults normally are found on the twigs and stems of the host plant. Females are light brown to tan, almost globular, and about 3-5 mm in diameter. Females start laying eggs in late May. One female deposits an average of 500-600 eggs. These hatch in June into oval, flat, cream to yellow crawlers that migrate a short distance on a branch in search of a feeding site. They remain on the host plant for the remainder of the season, with very little growth or development occurring. This soft scale can reduce the health of a plant by removing fluid from vascular cells. In addition, heavily infested trees are often rendered unsightly by a heavy crust of black sooty mold that develops on the honeydew excreted by this scale insect. Heavily infested yews may also drop needles prematurely. This species produces one generation each growing season.
Cupping and curling of leaves are still evident from earlier aphid infestations. Beneficials are often present after the fact, so be careful in applying a control if the aphids are not there. You don't want to spray out of revenge and kill the beneficials.
Weak trees planted last year are obvious now. The warm weather is stressing the damaged root systems enough to cause major defoliation and branch dieback. It appears that many trees suffered from last year's excessive rain, resulting in drowned roots made more susceptible to soil-borne diseases. Affected trees may also have smaller than normal leaves or fewer leaves, making the crown look thin and sparse.
Effective management of an infestation of this pest should start with the use of a registered formulation of horticultural oil applied according to label directions at the dormant rate in early spring. Crawlers may be managed by using a registered formulation of horticultural oil (applied at the growing season rate), insecticidal soap, Merit, Scimitar, Sevin, or Tempo applied according to label directions from mid-June through mid-July.
DISEASES
Pine webworm larvae have been reported on white pine. Look for signs of mined needles on terminal shoots, now. Soon,
Bob Mulrooney Extension Plant Pathologist BOTRYTIS BLIGHT of foliage is showing up on different hosts that had flower or bud infections earlier in the year and now have infected tissue falling on the leaves, and causing infection. Botrytis will usually produce a large brown spot, often with a zonate pattern to the spot, but not always. I have seen this on flowering dogwood, 'Goldflame' honeysuckle, and rose. In the past, many annuals, including geraniums, have also been infected. Pick spent blossoms or remove the infected leaves. For preventative fungicides select something such as mancozeb, thiophanatemethyl, or chlorothalonil or other labeled fungicides and apply before rainy humid weather arrives. (Continued)
UNIVERSITY OF DELAWARE
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) Small mushrooms (nickel or dime sized) with fluted caps are appearing in lawns after the rains. These are harmless and can be raked away or mowed over. Most of these are in the genus Marasmius and are breaking down organic matter in the soil.
Editor: Susan Barton Extension Horticulturist
What's Hot (Continued)
older larvae will begin to consume needles while building and hiding in ugly nests composed of frass and silk surrounding terminal twigs. This is a minor pest of landscape pines. In small plantings, manually remove and destroy frass nests on terminals as soon as they are noticed. In large plantings, spray the terminals with Orthene, Sevin or Tempo 2 if much mining and needle webbing are present. In the UDBG, gall wasps were found on oak leaves and gall midges found on a camperdown elm. Galls result when leaf or twig tissue swells in response to chemicals produced by gall formers. Leaf galls are not serious unless abundant enough to cause early leaf drop. Pull off and destroy leaf galls while they are green. Dormant oil sprays can be used to reduce overwintering populations.
Cooperative Extension Townsend Hall Newark, Delaware 19717
4 5, 20 0 June 1 AS OF
DEGREE
G GROWINDAYS
) 691 3= 9 ('0 e 104 ous enh nty) = e Gre u ffic ) O her stle Co A ion =N Fisc a tens 5 ('03 wn wC 9 (Ne y Ex geto) unt y) = 11 eor t r , G = 792 t Co 3 Ken t Coun ente c. C 170 ('0 (Ken Edu 1 h & nty) = u earc Res sex Co ( Su s
