Issue 15
July 6,
INSECTS
2012
Issue 15
What's Hot!
Brian Kunkel Ornamental IPM Specialist BLACK VINE WEEVIL adults are active from 87 to 3644 [1259 peak] GDD50 and feed on over 100 different plants such as Taxus, hemlocks, euonymus, mountain laurel and rhododendrons. Our plant phenological indicator for the beginning of adult activity is when Magnolia x soulangiana is in full bloom. This flightless weevil feeds during the night and rests at the base of plants during the day. Adults are gray to brownish black. Larvae are cshaped, legless, and creamy colored with brownish colored heads. Larvae feed in early spring and emerge from pupae from late-May into June. Adults (all female) need to feed for 21 to 45 days before egg laying begins and sometime in July each female lays eggs in the soil or leaf litter around plants. Adult feeding appears as notches on leaves and is easier to see on larger leaved plants. Larvae prefer to feed on young roots, but as roots become scarce or soil becomes excessively moist they will feed on the plant stem and this damage may eventually be extensive enough to girdle plants. TWOBANDED JAPANESE WEEVIL adults are active from 1267 to 1897 [1555 peak] GDD50 and feed on ash, cherry laurel, pyracantha, privet, rose, spirea, forsythia, lilac, barberry, flowering dogwood, broad-leaved evergreens, and others. This weevil is light to dark brown with striped elytra. This flightless weevil feeds during the day on new leaves, shoots and inner foliage, but drops to the ground when disturbed. Remove excessive mulch to prevent overly moist soils around susceptible plants. Place burlap around the base of susceptible plants to examine existing populations. Entomopathogenic nematodes, Heterorhabditis and Steinernema spp., have provided variable control of larvae in field plots but have performed better in potted plants in greenhouses. Chemical control for adults includes acephate, pyrethrins, piperonyl butoxide, and cyfluthrin and imidacloprid. The twobanded Japanese weevil is resistant to sevin and malathion.
DISEASES
What’s Hot? Everything. While we’ve had some rainfall throughout this hot spell it has been inconsistent. Plants subject to heat stress will wilt in the hot afternoon sun even though it may have rained in the past day or so. Check soil moisture before you water. If the soil is dry, water wilting plants. If the soil is moist, the plant just may not be able to take up water fast enough and waterlogging the soil won’t help. It may even cause root rot, which will make the situation worse. Some plants need full sun but prefer to have cool roots. Clematis is the classic plant example of this. Some trees, such as Stewartia also require full sun for good bloom but need cool roots to thrive. A layer of mulch or better yet, a ground cover can cool roots while allowing the plant foliage to receive full sun. Epimedium is a great groundcover to use to provide root shade. It grows well under trees and can handle tree root competition. Its foliage is held above the ground so it provide better shade than a low matting groundcover. Editor’s note: At least 2 readers were confused earlier in the year and thought I was retiring. Bob Mulrooney retired this spring. I am definitely not retiring, although I am starting my 27th year at UD this July. Sue Barton
Fornfomromrae tion i
Nancy Gregory Plant Diagnostician
on pests & practices covered in this newsletter, call your County Extension Office
DIEBACK OF BOXWOOD has been seen in the landscape and samples have been sent in to the Clinic. Although there is a new disease called boxwood blight in the United States (primarily in North Carolina), most dieback in our area is cause by environmental stress and Volutella blight. We have not confirmed boxwood blight in Delaware, a fungal disease characterized by
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
(Continued)
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.
Diseases (Continued) black streaking along twigs, leaf drop, and death of plants. In our area, we commonly see Volutella blight caused by the fungus Volutella buxi, especially on environmentally stressed plants. Volutella blight is characterized by twig dieback, but bronze to yellow leaves usually remain on the plants. Pink to salmon colored spore masses of Volutella may be seen on the undersides of leaves and along twigs, especially under humid conditions (visible with a hand lens). Boxwood decline and Phytophthora root rot may affect boxwood, but also are promoted by environmental stress such as drought. The saprophytic fungus Macrophoma may colonize dead tissue, producing black fruiting bodies on leaves and twigs. There are no good fungicides for these fungal pathogens of boxwood. The best control is to maintain boxwoods in a good state of vigor and avoid drought stress by watering the equivalent of an inch of water once a week if there is no rain. Trim out affected dead branches and twigs.
Editor: Susan Barton Extension Horticulturist
G N I W GREGOREE DAY0S12 D
3, 2 y l u J AS OF
) 50 1 =1 1 1 ’ 5( e 1 49 ) leg A) = l 46 1 o P =1 re C nty, 1 o 1 u m (' rth e Co e n 490 Swa lawar ow ous y) = 1 h n get 45) t r e n o e (De r ou G Ge = 16 e r, her tle C ent 6 ('11 Fisc w Cas C . 8 duc = 14 (Ne &E ch unty) r a o e Res ssex C (Su
INSECTS
2012
Issue 15
What's Hot!
Brian Kunkel Ornamental IPM Specialist BLACK VINE WEEVIL adults are active from 87 to 3644 [1259 peak] GDD50 and feed on over 100 different plants such as Taxus, hemlocks, euonymus, mountain laurel and rhododendrons. Our plant phenological indicator for the beginning of adult activity is when Magnolia x soulangiana is in full bloom. This flightless weevil feeds during the night and rests at the base of plants during the day. Adults are gray to brownish black. Larvae are cshaped, legless, and creamy colored with brownish colored heads. Larvae feed in early spring and emerge from pupae from late-May into June. Adults (all female) need to feed for 21 to 45 days before egg laying begins and sometime in July each female lays eggs in the soil or leaf litter around plants. Adult feeding appears as notches on leaves and is easier to see on larger leaved plants. Larvae prefer to feed on young roots, but as roots become scarce or soil becomes excessively moist they will feed on the plant stem and this damage may eventually be extensive enough to girdle plants. TWOBANDED JAPANESE WEEVIL adults are active from 1267 to 1897 [1555 peak] GDD50 and feed on ash, cherry laurel, pyracantha, privet, rose, spirea, forsythia, lilac, barberry, flowering dogwood, broad-leaved evergreens, and others. This weevil is light to dark brown with striped elytra. This flightless weevil feeds during the day on new leaves, shoots and inner foliage, but drops to the ground when disturbed. Remove excessive mulch to prevent overly moist soils around susceptible plants. Place burlap around the base of susceptible plants to examine existing populations. Entomopathogenic nematodes, Heterorhabditis and Steinernema spp., have provided variable control of larvae in field plots but have performed better in potted plants in greenhouses. Chemical control for adults includes acephate, pyrethrins, piperonyl butoxide, and cyfluthrin and imidacloprid. The twobanded Japanese weevil is resistant to sevin and malathion.
DISEASES
What’s Hot? Everything. While we’ve had some rainfall throughout this hot spell it has been inconsistent. Plants subject to heat stress will wilt in the hot afternoon sun even though it may have rained in the past day or so. Check soil moisture before you water. If the soil is dry, water wilting plants. If the soil is moist, the plant just may not be able to take up water fast enough and waterlogging the soil won’t help. It may even cause root rot, which will make the situation worse. Some plants need full sun but prefer to have cool roots. Clematis is the classic plant example of this. Some trees, such as Stewartia also require full sun for good bloom but need cool roots to thrive. A layer of mulch or better yet, a ground cover can cool roots while allowing the plant foliage to receive full sun. Epimedium is a great groundcover to use to provide root shade. It grows well under trees and can handle tree root competition. Its foliage is held above the ground so it provide better shade than a low matting groundcover. Editor’s note: At least 2 readers were confused earlier in the year and thought I was retiring. Bob Mulrooney retired this spring. I am definitely not retiring, although I am starting my 27th year at UD this July. Sue Barton
Fornfomromrae tion i
Nancy Gregory Plant Diagnostician
on pests & practices covered in this newsletter, call your County Extension Office
DIEBACK OF BOXWOOD has been seen in the landscape and samples have been sent in to the Clinic. Although there is a new disease called boxwood blight in the United States (primarily in North Carolina), most dieback in our area is cause by environmental stress and Volutella blight. We have not confirmed boxwood blight in Delaware, a fungal disease characterized by
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
(Continued)
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.
Diseases (Continued) black streaking along twigs, leaf drop, and death of plants. In our area, we commonly see Volutella blight caused by the fungus Volutella buxi, especially on environmentally stressed plants. Volutella blight is characterized by twig dieback, but bronze to yellow leaves usually remain on the plants. Pink to salmon colored spore masses of Volutella may be seen on the undersides of leaves and along twigs, especially under humid conditions (visible with a hand lens). Boxwood decline and Phytophthora root rot may affect boxwood, but also are promoted by environmental stress such as drought. The saprophytic fungus Macrophoma may colonize dead tissue, producing black fruiting bodies on leaves and twigs. There are no good fungicides for these fungal pathogens of boxwood. The best control is to maintain boxwoods in a good state of vigor and avoid drought stress by watering the equivalent of an inch of water once a week if there is no rain. Trim out affected dead branches and twigs.
Editor: Susan Barton Extension Horticulturist
G N I W GREGOREE DAY0S12 D
3, 2 y l u J AS OF
) 50 1 =1 1 1 ’ 5( e 1 49 ) leg A) = l 46 1 o P =1 re C nty, 1 o 1 u m (' rth e Co e n 490 Swa lawar ow ous y) = 1 h n get 45) t r e n o e (De r ou G Ge = 16 e r, her tle C ent 6 ('11 Fisc w Cas C . 8 duc = 14 (Ne &E ch unty) r a o e Res ssex C (Su
