July 8 2005.cdr
July 8, 2005
Issue 16
INSECTS
What's Hot!
Dewey Caron Extension Entomologist st
JAPANESE BEETLES. We saw the 1 adult Japanese beetle June 17. Rain on the 26th helped trigger an impressive adult emergence. We found males on UDBG plants with their lamellate antennae fully extended hoping to catch a whiff of female beetles. The population of beetles was up somewhat in 2004 after three years of lighter numbers so the question is now how heavy will numbers be in 2005? Hot, dry weather with rapidly passing thundershowers promotes higher numbers but a rainy late June/early July reduces adult abundance. This easily recognizable green and brown beetle is a major economic pest both in its larval stage (on turf in August/September) and as an adult. Insecticides for preventive control of the larval stage, such as merit, MACH2 or Arena should be applied now. The adult stage now emerging is a generalist, feeding on a wide array of plants. It may rapidly skeletonize leaves and buds. Eggs laid in the soil need moisture to expand and hatch; watering lawns now can promote higher numbers but also support higher grub counts without damage symptoms if watering is continued throughout the summer. Remember Japanese beetle traps are not an effective means of control; they may in fact attract more beetles to a particular area. Hand picking is one option for some homeowners or nurseries. Picl or drop beetles onto a collecting cloth in the early morning or late evening for best success. Fine netting around valuable/specimen plants is needed in heavy population years. Insecticides include Sevin (not effective in exposed/wet conditions) or the array of pyrethroids. Neem and rotenone plus pyrethrum are “natural” alternatives. No studies support popular (but ineffective) extracts as a deterrent to beetles, such as garlic, pepper or orange peel.
DISEASES Bob Mulrooney Extension Plant Pathologist BROWN PATCH is now present on lawns especially tall fescue where it has been raining. As mentioned several weeks ago, this disease flourishes during periods of hot, humid weather and warm nights. Look for the irregular tan blotches on the leaves. Some, but not all, spots will have a thin reddish-brown border between the green and tan areas on the blades. Avoid over fertilizing in the spring and don't apply any nitrogen during the summer. (Continued)
UNIVERSITY OF DELAWARE
Lacebugs are present on many susceptible plants. We have found heavy lacebug infestations on Aster oblongifolius cultivars in roadside plantings. Look for leaf stippling and turn leaves over to determine how many lacebugs are present. You can treat with a wide variety of insecticides, being sure to cover both upper and lower leaf surfaces. In the past, lacebug infestation has not affected the bloom of asters on the roadside. Elm casebearers and larch casebearers were observed in last week. Larvae overwinter in cases attached to twigs and do most of their damage in May and June. Adult moths are about 1/4 inch long--tan with gray markings. Look for small brown spots between leaf veins. Each spot is caused by one casebearer larva. New cases will be formed in late summer and are attached next to the brown spots. This is a minor pest. Spray treatments (with Orthene) are only needed if most tree leaves contain more than one larva. A wide variety of scale crawlers are now present in the landscape. We have received reports of calico scale, cottony maple leaf scale, cottony taxus scale, elongate hemlock scale, euonymus scale, European fruit lecanium, Fletcher scale, pine needle scale and white peach scale. The crawler stage is provides a treatable opportunity. But, often beneficial insects will also control scale. In general, use a residual insecticide to control scale crawlers only if the damage is severe and beneficials are not present. Hort oils can be used to control some scale crawlers with less impact on beneficials.
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) Symptoms will disappear when the weather changes. Remember, it is a foliage disease and rarely kills the crowns of mature plants. BACTERIAL LEAF SPOT OF ZINNIA. This common bacterial disease is primarily seedborne, but can overwinter in old infected leaves. The small angular spots with yellow borders can progress from the lower leaves and cause extensive defoliation if ample rainfall and overhead watering splash the bacteria onto the upper leaves. The best control is to avoid wetting the leaves during watering and space plants apart to provide some air drainage so that the leaves dry more quickly. SLIME MOLDS AND MUSHROOMS. Wet weather brings out the slime molds and mushrooms. We have received several samples of the gray slime mold that can be seen on grass blades and other plants growing in turf. These are similar to the slime molds that are seen on hardwood bark mulch. Those large slime molds come in several colors, creamy white, pink, and light yellow. Both kinds are harmless, do not infect plants and can be removed with a rake, lawn mower, or a hard stream of water. Mushrooms are very common now as well. Many small inky caps can be seen in lawns as well as the common meadow mushroom. In mulched beds I have also seen the foul smelling stinkhorn fungi that are reddish orange with a brown stinky cap. Editor: Susan Barton Extension Horticulturist
G N I W GROREE DAYS
DEGOF July 5, 2005 AS
) 5 25 =1 4 0 ' ( 25 1 e ous y) = 1 h n 3) ice ree unt Off = 172 r G le Co n e o h t c wn nsi 4 ('04 F i s w C as eto xte org 707) y E = 1 31 (Ne t e n G ) r, ou =1 t C unty nte '04 . Ce 2 74 ( Kennt Co c u 1 d ( Ke &E )= rch ounty a e Res ssex C (Su
Issue 16
INSECTS
What's Hot!
Dewey Caron Extension Entomologist st
JAPANESE BEETLES. We saw the 1 adult Japanese beetle June 17. Rain on the 26th helped trigger an impressive adult emergence. We found males on UDBG plants with their lamellate antennae fully extended hoping to catch a whiff of female beetles. The population of beetles was up somewhat in 2004 after three years of lighter numbers so the question is now how heavy will numbers be in 2005? Hot, dry weather with rapidly passing thundershowers promotes higher numbers but a rainy late June/early July reduces adult abundance. This easily recognizable green and brown beetle is a major economic pest both in its larval stage (on turf in August/September) and as an adult. Insecticides for preventive control of the larval stage, such as merit, MACH2 or Arena should be applied now. The adult stage now emerging is a generalist, feeding on a wide array of plants. It may rapidly skeletonize leaves and buds. Eggs laid in the soil need moisture to expand and hatch; watering lawns now can promote higher numbers but also support higher grub counts without damage symptoms if watering is continued throughout the summer. Remember Japanese beetle traps are not an effective means of control; they may in fact attract more beetles to a particular area. Hand picking is one option for some homeowners or nurseries. Picl or drop beetles onto a collecting cloth in the early morning or late evening for best success. Fine netting around valuable/specimen plants is needed in heavy population years. Insecticides include Sevin (not effective in exposed/wet conditions) or the array of pyrethroids. Neem and rotenone plus pyrethrum are “natural” alternatives. No studies support popular (but ineffective) extracts as a deterrent to beetles, such as garlic, pepper or orange peel.
DISEASES Bob Mulrooney Extension Plant Pathologist BROWN PATCH is now present on lawns especially tall fescue where it has been raining. As mentioned several weeks ago, this disease flourishes during periods of hot, humid weather and warm nights. Look for the irregular tan blotches on the leaves. Some, but not all, spots will have a thin reddish-brown border between the green and tan areas on the blades. Avoid over fertilizing in the spring and don't apply any nitrogen during the summer. (Continued)
UNIVERSITY OF DELAWARE
Lacebugs are present on many susceptible plants. We have found heavy lacebug infestations on Aster oblongifolius cultivars in roadside plantings. Look for leaf stippling and turn leaves over to determine how many lacebugs are present. You can treat with a wide variety of insecticides, being sure to cover both upper and lower leaf surfaces. In the past, lacebug infestation has not affected the bloom of asters on the roadside. Elm casebearers and larch casebearers were observed in last week. Larvae overwinter in cases attached to twigs and do most of their damage in May and June. Adult moths are about 1/4 inch long--tan with gray markings. Look for small brown spots between leaf veins. Each spot is caused by one casebearer larva. New cases will be formed in late summer and are attached next to the brown spots. This is a minor pest. Spray treatments (with Orthene) are only needed if most tree leaves contain more than one larva. A wide variety of scale crawlers are now present in the landscape. We have received reports of calico scale, cottony maple leaf scale, cottony taxus scale, elongate hemlock scale, euonymus scale, European fruit lecanium, Fletcher scale, pine needle scale and white peach scale. The crawler stage is provides a treatable opportunity. But, often beneficial insects will also control scale. In general, use a residual insecticide to control scale crawlers only if the damage is severe and beneficials are not present. Hort oils can be used to control some scale crawlers with less impact on beneficials.
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) Symptoms will disappear when the weather changes. Remember, it is a foliage disease and rarely kills the crowns of mature plants. BACTERIAL LEAF SPOT OF ZINNIA. This common bacterial disease is primarily seedborne, but can overwinter in old infected leaves. The small angular spots with yellow borders can progress from the lower leaves and cause extensive defoliation if ample rainfall and overhead watering splash the bacteria onto the upper leaves. The best control is to avoid wetting the leaves during watering and space plants apart to provide some air drainage so that the leaves dry more quickly. SLIME MOLDS AND MUSHROOMS. Wet weather brings out the slime molds and mushrooms. We have received several samples of the gray slime mold that can be seen on grass blades and other plants growing in turf. These are similar to the slime molds that are seen on hardwood bark mulch. Those large slime molds come in several colors, creamy white, pink, and light yellow. Both kinds are harmless, do not infect plants and can be removed with a rake, lawn mower, or a hard stream of water. Mushrooms are very common now as well. Many small inky caps can be seen in lawns as well as the common meadow mushroom. In mulched beds I have also seen the foul smelling stinkhorn fungi that are reddish orange with a brown stinky cap. Editor: Susan Barton Extension Horticulturist
G N I W GROREE DAYS
DEGOF July 5, 2005 AS
) 5 25 =1 4 0 ' ( 25 1 e ous y) = 1 h n 3) ice ree unt Off = 172 r G le Co n e o h t c wn nsi 4 ('04 F i s w C as eto xte org 707) y E = 1 31 (Ne t e n G ) r, ou =1 t C unty nte '04 . Ce 2 74 ( Kennt Co c u 1 d ( Ke &E )= rch ounty a e Res ssex C (Su
