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HomeMy WebLinkAbout2003 10 08 Attached Distributed During Meeting (3)Date: OCTOBER 8, 2003 ATTACHED DISTRIBUTED DURING MEETING Page 1 Key Pests of Select Native Plants in Central Florida Landscapes by Eleanor Foerste, Dr. Cathy Neal and Celeste White University of Florida Extension Plant: Holly Ilex species Holly Key Pest List Insect Pest: Florida wax scale Recognition: The mature scale is round and convex, creamy in color and is found on sterns or tops of leaves. It is a soft scale, and supports the growth of sooty mold on the leaves beneath. Immature scales first appear as fine white dots, then develop a black body with a white fringe. Feeding damage results in chlorotic spots on the leaves and possible leaf drop. Contributing factors: As with most scale, it may be present year-round. Crawlers hatch in spring and should be monitored throughout the warm season. Management recommendations: If scale populations build to objectionable levels, oils or other approved insecticides maybe used. The crawlers are the easiest stage to control. Insect Pest: Tea scale Recognition: Tops of leaves show yellow markings typical ofpiercing-sucking insect feeding. Undersides of leaves are white from the white waxy threads produced by large numbers of scales. Leaves maybe distorted. Tea scale is a very small armored scale. The female scale is one twentieth of an inch long and brown in color; the male is even smaller and white. Contributing factors: Crawlers hatch in spring and summer; scale is present year-round. Management recommendations: Ifscale populations build to objectionable levels, approved oils or insecticides may be used. The crawlers are the easiest stage to kill. Disease Pest: Cylindrocladium leaf spot (Cylindrocladium spp.) Recognition: Although several fungi occasionally cause spotting on various hollies, Cylindrocladium can cause a serious disease. Symptoms are severe leaf spotting, defoliation, twig dieback, and sometimes death of new plantings. Leaf spots initially are minute chlorotic spots which enlarge and become circular and dark purple to black. Affected leaves drop easily; twigs may become infected and result in dieback. Contributing Factors: This disease occurs most commonly on Ilex vomitoria, but can also attack I. cornuta, I. crenata and I. opaca. Favorable environmental conditions are warm temperatures, high humidity, and excessive leaf wetness. Spores form on affected leaves on the plant or on fallen leaves, and spread by splashing water. Management recommendations: Adjust irrigation to keep the foliage as dry as possible. If disease Page 3 fertilizer to support new roots. No chemical controls are available for use on existing plants. When replacing plants, remove all roots and replace soil. Avoid replanting with susceptible species, or fumigate before replanting. Other: Magnesium deficiency Recognition: Yellowing along the margins of older leaves, often making a distinct yellow "V" shape on each leaf, is a symptom of magnesium deficiency. Contributing factors: Holly seems more sensitive to magnesium deficiency than some other species. Low soil pH and/or lack of magnesium in the soil results in deficiency symptoms. Management recommendations: Check and adjust the soil pH with dolomite. Apply magnesium sulfate (Epsom salts) or fertilizers with magnesium. Plant: Magnolia, Southern Magnolia Magnolia grandiflora Magnolia Key Pest List Insect Pest: Black twig borer (Xylosandrus compactus) Recognition: Twig dieback in otherwise healthy trees is conspicuous. The twigs will eventually break off and fall to the ground. Tiny entrance holes maybe found on undersides of affected twigs, where the female insect has bored holes in which to lay her eggs. The white grub-like larvae feed and pupate inside the twig. Contributing factors: none Management recommendations: Prune out and destroy infested twigs. The problem is primarily aesthetic. Insect Pest: Magnolia white scale (Pseudaulacaspis cockerelli). Recognition: Adults are pear-shaped, shiny white armored scales with yellowish brown bodies underneath the armor. The stationary adults maybe clustered along the midrib on the undersides of leaves, or scattered on both leaf surfaces. Feeding damage results in yellow spots on the leaves. Eggs are laid underneath the armor, and newly hatched crawlers (small yellow ovals) emerge which move along the leaves. and twigs. They are tiny and require a hand lens to detect. Contributing factors: Scales are present year round, but large numbers of eggs and crawlers are present in the early spring. Management recommendations: On established trees, the problem is primarily aesthetic rather than damaging to the tree. Mature scales are difficult to control. Round holes in the scale bodies indicate parasitic wasps have emerged and are helping control the pest population. Contact insecticides should be timed to control crawlers, since matures are well-protected by a waxy covering. Systemic insecticides maybe needed for severe infestations. Dead scales will still remain on the plant, however. Disease Pest: Algal leaf spot (Cephaleurus virescens) Page 5 healthy trees, but can be an extreme nuisance for a short period of time. Use an approved insecticide for high-value specimen trees with very high populations of caterpillazs if necessary. Remove and destroy tents of eastern tent caterpillazs when first noticed. Insect Pest: Galls (insect-induced) Recognition: Galls occur in many forms, colors, and shapes. They maybe hairlike projections, spheres, rosettes or woody swellings, and can occur on leaves or twigs and branches. The malformed plant tissue, or gall, forms in response to egg laying or feeding by insects (wasps, midges, mites, moths, aphids or beetles). The young insects develop inside, but cause little or no damage to the tree. Small holes on the outside indicate that the insects have already emerged, but the gall remains. Some beneficial organisms live in abandoned galls. Contributing factors: Infested trees will continue to support populations of gall insects. Management recommendations: Select gall-free plant material for installation. Stem and branch galls can be pruned out and destroyed if not on main trunks or branches. Galls on stems and main branches may have a girdling effect and will result in weak points and possible limb breakage if not removed. Leaf galls are harmless. Insect Pest: Twig girdler Recognition: Wilted or dead twigs hanging in trees or on the ground during the fall are symptoms of twig girdlers. The severed ends of the twigs appeaz to have been whittled to a dull point. The beetle which causes this damage is seldom seen. It is about 3/4 inch long, has agray-brown body and long antennae. Contributing factors: Twig girdler damage usually occurs in the fall. Management recommendations: Collect and destroy twigs from the ground, which contain the immature twig girdlers. No insecticidal control is usually warranted. Disease Pest: Oak leaf blister (Taphrina caerulescens) Recognition: Raised or wrinkled blisters form on new leaves in the spring, caused by a fungal pathogen. Initially pale green, the blisters turn brovJn and necrotic later in the season. Distortion of newly expanding leaves is symptomatic of severe infections. Contributing factors: Infection occurs on newly emerging leaves during mild, rainy spring weather. Management recommendations: It is asurface blemish influenced by weather. Fungicide use is not recommended. Rake fallen leaves to reduce inoculum for the following year. Disease Pest: Root and butt rots Recognition: Above-ground symptoms of root and/or butt rots include various degrees of crown dieback, loss or discoloration of foliage, and a generally unhealthy appearance. Internally, roots may show discoloration. Fruiting bodies (shelf fungi or mushrooms) at or near the base of the tree are signs of specific fungi, but are not always present. Contributing factors: Trees which have been injured during construction or similar activities are susceptible to these diseases. Poor soil conditions (compaction, excessive moisture, etc.) Also favor disease. Decay also occurs on trees nearing the end of their life cycle. Page 7 Plant: Palms Palmae Palm Key Pest List Insect Pest: Palm leaf skeletonizer Recognition: Palm leaf skeletonizers are small caterpillars which feed on the surfaces of palm leaves. The first conspicuous sign of this pest is usually large quantities of brown, fibrous excrement. Portions of the leaf, or entire leaves, turn necrotic. A closer look is necessary to determine if caterpillars are still present. Contributing factors: Only palms are host to this insect. Management recommendations: Use Bacillus thuringiensis or other approved insecticides if caterpillars are present. Prune out severe damage if desired. Insect Pest: Palmetto weevil (Giant palm weevil) Recognition: Palmetto weevils destroy the growing points of palms. Symptoms range from sporadic browning of the fronds to the loss of the entire top of the palm, which may fall over. The center spear and fronds pull loose easily. Tunnels, entrance holes, and/or frass may be found in damaged tissue. Large grubs, fibrous pupal cases, and/or adults maybe found inside. Contributing factors: Adults are attracted to stressed palms, most frequently newly transplanted ones. Cabbage palms and Canary Island Date palms are the most frequently attacked species. Management recommendations: Make all efforts to reduce transplant stress on susceptible species. A preventative application of an approved insecticide at installation and again a few weeks later has shown some success in preventing palmetto weevil damage. Remove and destroy infested palms as soon as possible. Insect Pest: Scale Recognition: Various armored and soft scales attack palm leaves, including thread scale, magnolia white scale, oyster scale, Florida red scale, and others. Contributing factors: Scales may be more of a problem in a shaded site or area with poor air circulation. Management recommendations: Minor scale infestations can usually be tolerated and do not cause significant damage. Round holes in the scale bodies indicate parasitic wasps have emerged and are helping control the pest population. Use oils or approved insecticides if the problem warrants. Systemic insecticides maybe needed for severe infestations. Disease Pest: Bud rots Recognition: Bud rots caused by either bacterial or fungal (Phytophthora sp.) pathogens cause a collapse or browning of young foliage and the emerging leaf. Affected spear leaves can be pulled out easily. A foul odor frequently accompanies damage. Phytophthora can also cause leaf spots. Page 9 fungus produces grey-black fruiting bodies which rupture through both leaf surfaces. Pestalotiopsis leaf spot affects several palm species, but is a particular problem on Phoenix species. Lesions may appeaz on the rachis and/or on leaflets. Tiny black spots enlarge and often coalesce. Mature lesions are almost white with a black border and black spot in the center. Stigmina leaf spots develop first as small round yellowish lesions on older leaves. Enlarging spots become tan to brown, zonate, with a dark center. Spots aze often surrounded by a yellow halo. Spots may occur on leaflets or on the rachis. Contributing factors: Leaf spot diseases may develop during periods of high rainfall or frequent overhead irrigation, shade, and poor air circulation. Some leafspots are secondary on palm leaves that aze nutrient deficient or damaged. Stigmina is most severe during the cool season (late fall through spring), whereas the others are favored by warmer temperatures. Management recommendations: Limit overhead irrigation where possible. If only a few leaves are infected, removal of those fronds can be a simple and effective control. In addition to sanitation, preventive use of approved fungicides may aid in disease control. Disease Pest: Thielaviopsis trunk or bud rot (Chalara paradoxa) Recognition: New leaves emerge deformed, with reduced pinnae and black necrotic tips. Palms have reduced growth rates, may defoliate and die. The trunk is hollow due to decay, and roots maybe decayed. A reddish brown liquid may bleed from the decaying trunk. Affected palms will blow over or snap easily. Contributing factors: Many landscape species are susceptible, including Phoenix, Sabal, Queen, and Washingtonia palms. The fungus is soil-borne and generally enters through wounds or growth cracks. f Management recommendations: Avoid mechanical damage to the trunk. Infected palms should be cut, removed and destroyed. Other: Magnesium deficiency Recognition: Magnesium deficiency is quite common, especially in Phoenix species. Symptoms occur on the oldest fronds first. Typical symptoms are a broad yellow band along the leaf margins, with green remaining towards the rachis. In severe cases, the tips may become necrotic. Contributing factors: Magnesium deficiency is caused by insufficient magnesium in the soil and common in sandy soils with low cation exchange capacity. Management recommendations: It is best to treat magnesium deficiency preventively, by using a "palm special" fertilizer containing adequate magnesium. To correct a magnesium deficiency, apply magnesium sulfate to the soil at a rate of two to four pounds per tree, four times per year. Yellowed leaves will not recover and maybe removed after growth of new, healthy fronds occurs. Page 11 Pine Key Pest List Insect Pest: Borers (flathead borers, roundhead borers) Recognition: Borers are beetle larvae or caterpillars which bore into trees. Look for branch wilt and dieback, holes, sap staining on outer bark, and/or boring dust caught in cracks of bark or at the base of tree. Contributing factors: Trees affected are generally weakened or wounded by some other predisposing factors such as root rot, soil disturbance due to construction, drought, flooding, senescence or physical injuries to trunk or branches. Management recommendations: Keep trees healthy to avoid infestations. Identify and remove highly susceptible trees and those with lethal infestations. Once infested, little can be done. Temporarily protect other nearby trees with approved insecticides applied on trunk from spring to fall according to label. Insect Pest: Pine bark beetles Recognition: There are 3 types of bark beetles in Florida: black turpentine beetle (BTB), Ips engraver beetle, and the southern pine bark beetle (SPB). Species differences are important. Adults bore through the outer bark and construct egg galleries in the inner bark. Immature offspring (larvae) continue tunnels, further disrupting phloem tissue. Ips and SPB also introduce a fungus that blocks water flow in the xylem. Trees can survive limited BTB attacks since they do not carry with them these blue stain fungi. They can be distinguished by adult appearance, the shape of their galleries, and the location of pitch tubes. The entire tree canopy changes from green to yellow to orange/brown as damage progresses. By the time the color change begins to occur, it is too late to save the tree. Look on the trunk for pitch tubes (globs of resin) and accumulations of boring dust. Contributing factors: Beetles are first attracted to weak, stressed and/or wounded trees; however, during outbreaks of SPB, healthy trees maybe attacked. Drought, old age, disease, injury, fire, construction damage, lightning, etc. are common underlying causes of weak trees. Management recommendations: Promote tree health by minimizing tree stress. Avoid altering soil level and other practices causing root injury. Remove weak and/or infested trees or branches to prevent attracting beetles to the area. If beetles are known to be in the area, surrounding trees may benefit from a preventative insecticide application to the trunk. Insect Pest: Pine sawflies Recognition: Pine sawfly larvae look like caterpillars. They are up to 1" in length, yellow to green with variably patterned black dots or stripes. Large numbers of larvae feed on pine needles, leaving stubby remains with a tufted appearance. Older foliage is consumed first, then younger foliage. Frass accumulates on ground under tree. Contributing factors: Sawfly populations are cyclical in nature and occur approximately at 8-10 year intervals. All pine species and ages of trees are susceptible. Page 13 Plant: Sycamore Platanus occidentalis Sycamore Key Pest List Insect Pest: Sycamore lacebug Recognition Lacebug damage. is recognized by yellowing or bronzing of foliage in late summer. Leaves maybe blotchy or stippled, and will drop prematurely from infested trees. Mature lacebugs are about 3 mm long, yellowish to brown, with lacy wings. The nymphs are darker colored and wingless. Dark brown excrement can be noticed on undersides of leaves. Contributing factors: Sycamore lacebugs are specific to sycamore, hickories, and ash, and are a different species than the azalea lacebug. Sycamore lacebugs occur in mid to late summer. Management recommendations: Healthy trees will be able to tolerate annual lacebug infestations. Controls are usually not warranted since lacebugs occur late in the season and leaves naturally drop in the fall. Tree injection has been used successfully on specimen trees where cost could be justified. Disease Pest: Bacterial scorch; xylem-limited bacteria (Xylella fastidiosa) Recognition: Early leaf scorch symptoms are olive-green discoloration of margins or interveinal tissue. Affected leaves then turn brown and crisp, and are cupped and curled, but remain attached to the branches. This "scorched" appearance is due to plugging of the xylem. Symptoms begin on older leaves then progress upward towards the branch tip. Terminal leaves may remain green or the branch may die. Dieback is most prevalent in the spring, after the first growth flush. Symptoms may affect individual branches, large portions of the crown, or the entire tree. Contributing factors: The bacteria are transmitted by insects such as leafhoppers and spittlebugs. Scorch symptoms appear during periods of hot, dry weather. Management recommendations: Minimize moisture stress by using additional Irrigation and mulch over the root zone. Prune out individual branches as dieback occurs. Disease Pest: Powdery mildew (Oidium sp./Micosphaera platani) Recognition: The characteristic white powdery growth on the surface of leaves and buds is the fungal mycelia. Leaf curling and distortion are also symptoms. Contributing factors: Cool, dry weather in spring and fall is favorable for powdery mildew. Management recommendations: Approved fungicides maybe used on small trees when environmental conditions are favorable. Spraying large trees is not practical. Page 15 carefully. There is no treatment for infected plants except removal and replacement. Since the fungus is not soil borne, fumigation is not necessary. Nematodes: Root knot nematodes Recognition: Nematodes impair the roots, causing poor growth, plant decline and thinning of the foliage. Infested roots may be brown and stunted and have obvious galls. Contributing factors: Highest populations of nematodes occur in well-drained sandy soils where previous crops have supported populations. Management recommendations:Keep plants as healthy as possible with adequate water and fertilizer to support new roots. No chemical controls are available for use on existing plants. When replacing plants, remove all roots and replace soil. Avoid replanting with susceptible species, or fumigate before replanting. Acknowledgments Script: Cathy Neal, Celeste White, and Eleanor Foerste Reviewers: Drs. Gary Simone, Don Short, and Bob Dunn Funding: Dr. Russ Mizell, Asst. Dean for IPM programs Graphic Art: Scott Weinburg Photos: Thanks to the Florida Department of Agriculture and Consumer Sciences, Division of Plant Industry, for providing several photographs. Thanks also to the following University of Florida, IFAS faculty for their Dr. Bob Black Dr. Ed Gilman Dr. Alan Meerow Dr. Cathy Neal Dr. Don Short Dr. Tom Yeager Celeste White photographs: Dr. Bob Dunn Tom MacCubbin Dr. Russ Mizell Dr. Lance Osborne Dr. Gary Simone Dr. Tom Weissling