Cedar-apple rust (Gymnosporangium juniperivirginianae), cedar-hawthorn rust (G. globosum), and cedar-quince rust (G. clavipes) are closely related rust diseases that require two hosts to complete their life cycle. All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Cedar-quince rust has the broadest host range and can affect many genera in the rose family including apple, crabapple, pears, quince, hawthorn, serviceberry, mountain-ash, flowering quince, cotoneaster, chokeberry, and photinia.[图片]Symptoms and Diagnosis Symptoms on juniper: Perennial, elongated swellings on the tips of twigs and branches, which may crack and form cankers, are symptoms of cedar quince rust on red cedars and junipers. In damp spring weather, cushion-shaped, orange, gelatinous blisters burst through the bark where the branches are swollen. Cedar-quince rust disease damages the ornamental value of susceptible cedars and junipers, killing young branches and weakening plants when cankers occur on the main trunk.[图片]Symptoms on apple and other hosts: Young branches and fruit (not leaves) are usually infected and symptoms vary widely among the various hosts. On hawthorn, the pinkish aecia (tubes) occur mainly on branches, thorns, and fruit. Hawthorn and serviceberry fruit often becomes heavily covered with aecia. Branch and thorn infections result in spindle-shaped, perennial cankers that expand each growing season. However, most infected branches are girdled by the canker during the second season, causing dieback to a bud or side-shoot.[图片]Life Cycle Basidiospores that are released from the juniper gall telial swellings infect stems and fruit of quince and the other deciduous hosts. Seven to ten days after infection, spots or swellings develop, followed a few days later by the formation of tiny black dots within the spots. Four to seven weeks later, aecia are formed. Aeciospores, released from the aecia during rain or as morning humidity lowers, become airborne and infect susceptible junipers during late summer and fall. The following spring (or one year later), swellings (consisting of both fungal and host plant tissues) develop on the juniper host. When the swellings are mature, a few hours of wet, cool (74 to 78 degrees F) spring weather are sufficient for repeated telial swelling and the release of basidiospores that infect quince and other deciduous hosts. The cedar-quince rust galls may remain infectious for 4–6 years or more (up to 20), whereas the cedar-apple gall is only infectious for one year.[图片]Integrated Pest Management Strategies 1. Prune. Prune out cankers associated with cedarquince rusts from landscape junipers and deciduous host plants. The spread of cedar-quince rust can be limited by reducing the infested plant parts. This is practical if a few plants are infected and the number of galls per plant is limited. 2. Co-exist. Live with the disease. It may disfigure plants when twigs are infected.[图片]3. preventive fungicide. Use preventive fungicides labeled for use on quince and other hosts. Fungicide sprays are aimed at protecting developing twigs and branches from infection during the time the galls on the junipers are orange and gelatinous. This usually lasts for several weeks and fungicide applications are not necessary once the galls become dry and inactive. Always read and follow label directions. Pesticides registered for use include captan, chlorothalonil (Daconil), mancozeb, sulfur, thiram, and ziram.[图片]4. Avoid planting susceptible plants together. Do not plant junipers close to susceptible varieties of apples, crabapples, or quince. 5. Resistant varieties. Remove and replace diseased plants with resistant varieties.

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相关图片 [图片][图片]#豹蠹蛾 分布与危害 国内分布较广，为害月季、紫荆、洋蹄甲、日本晚樱、山茶、山杏、石榴、碧桃、白玉兰、广玉兰、梅兰、黄杨、栀子花、香樟和法桐等。在我国南方还发生咖啡木蠹蛾（Z.coffeae Nietner）又名咖啡豹蠹蛾等，除上述花卉外，还为害香石竹、杜鹃、柑橘、橙、咖啡、海棠等。 又称六星黑色蠹蛾，属鳞翅目豹蠹蛾科。主要危害枝条。幼虫多自枝杈或嫩梢的叶腋处蛀入，向上蛀食。受害新梢很快枯萎，幼虫以后向下转移，再次蛀入嫩枝内，继续向下蛀食，被害枝条内部被咬成孔洞，孔壁光滑而直，内无粪便，在枝条向阴面排粪。 形态特征 成虫：雌成虫体长20-23毫米，翅展40-45毫米，触角丝状。雄虫体长17-20毫米，翅展35-40毫米，触角基部双栉齿状，端部丝状。翅展40-45毫米，触角丝状。雄虫体长17-20毫米，翅展35-40毫米，触角基部双栉齿状，端部丝状。全体灰白色，前翅散生大小不等的蓝黑色斜纹斑点。 后翅外缘有8个蓝黑色斑点，中部有一个较大的铜色斑点，胸部背面有3对近圆形的蓝黑色斑纹，腹部背面各节有3条纵纹，两侧各有1个圆斑。卵：长圆形，长径约1毫米，未受精卵米黄色，受精卵粉红色。幼虫：赤褐色，体长30-40毫米，前胸硬皮板基部有1黑褐色近长方形斑块，后缘有2横列黑色小齿，臀板及第9腹节基部黑褐色。 蛹：为裸蛹。体长19-24毫米，赤褐色，背面有锯齿状横带，尾具短臀刺。成虫白天隐藏在植株内部、叶片背面或枝条中下部，夜间活动，飞翔力强，具有较强的趋光性。 成虫多在下午16-20时羽化，羽化后的成虫次日1时左右交尾，1-2天后产卵，卵产于枝条中上部枝杈处或芽腋处，堆产量5-25粒。低龄幼虫有群集习性，长到10毫米后扩散为害。幼虫具有转移为害习性，老熟后在孔洞内吐丝缀屑堵塞两端，并向外咬一羽化孔，用环状间断的老皮盖住，做茧化蛹。 发生规律 豹蠹蛾在华北地区1年发生1代，以老熟幼虫或肾在寄主蛀道内越冬。翌年5月出现成虫，有趋光性，日伏夜出，卵产在伤口、粗皮裂缝处，卵期约20天。幼虫较活跃，有转移为害习性，先绕枝条环食，然后进入木质部蛀成孔道。由于地区不同及11月份的气温变化，该虫发育有异，则以老熟幼虫或蛹在蛀道内越冬。咖啡木蠹蛾生活习性与六星黑点蠹蛾相似，5-6月出现成虫。初孵幼虫先食嫩芽和叶柄，以后转蛀1-2年生枝条。资料报道，咖啡木蠹蛾在华南地区1年发生2代，翌年2-3月成虫羽化，8-9月为第二代成虫羽化期。 防治方法 ①及时清理花墩，收二茬花后，一定要在7月下旬至8月上旬结合修剪，剪掉有虫枝，如修剪太迟，幼虫蛀入下部粗枝再截枝对花墩长势有影响。 ②化学防治：尽量选择在低龄幼虫期防治。此时虫口密度小，危害小，且虫的抗药性相对较弱。防治时用45%丙溴辛硫磷（国光依它）1000倍液，或国光乙刻（20%氰戊菊酯）1500倍液+乐克（5.7%甲维盐）2000倍混合液,40%啶虫.毒（必治）1500-2000倍液喷杀幼虫，可连用1-2次，间隔7-10天。可轮换用药，以延缓抗性的产生。

Cedar-apple rust (Gymnosporangium juniperivirginianae), cedar-hawthorn rust (G. globosum), and cedar-quince rust (G. clavipes) are closely related rust diseases that require two hosts to complete their life cycle. All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Cedar-hawthorn rust, in addition to affecting apples, crabapples, and many hawthorns sometimes infects pears, quince, and serviceberry.[图片]Symptoms and Diagnosis Symptoms on juniper: The fungus produces reddishbrown galls on twigs and small branches of susceptible junipers. After reaching a diameter of about 1/8 to 1/2 inch, circular dimple-like depressions will appear resembling the surface of a golf ball. In the spring, small chestnut brown structures protrude from each of the dimples. During wet spring weather, these projections greatly expand into an orange mass of spore-bearing, jelly-like tendrils known as telial horns. Blown by the wind, the microscopic spores infect neighboring hawthorn trees. The galls produce spores at least two years in succession after which they dry out and harden. They can remain on the juniper host for several years.[图片]Symptoms on hawthorn: Cedar-hawthorn rust causes discoloring and yellow to nearly black spots on the leaves, fruit, petioles or new twigs. These spots contain black pimple-like fruiting bodies that produce spores. Life Cycle The disease overwinters as galls on infected junipers. During wet spring weather, "horns" extrude from the galls and produce spores. These spores are then windblown or carried by insects to the leaves of nearby susceptible hawthorn plants. The spores then turn brown, infect the leaf tissue, and form yellow spots on the leaves. In the late summer, spores are produced on hawthorn leaves. They are windblown back to needle bases or cracks in juniper twigs. After infection of the juniper, small galls form, thus completing the cycle. It takes two years to produce a spore-bearing gall.[图片]Integrated Pest Management Strategies 1. For both hawthorns and junipers, prune out diseased branches. The spread of cedar-hawthorn rust can be limited by reducing infested plant parts. 2. Live with the disease. The disease rarely kills trees. It can, however, disfigure plants when twigs are infected. 3. Use fungicidal sprays. Both junipers and hawthorns can be protected from infection with fungicide applications during periods of spore production. Spray hawthorns prior to spring bloom with a fungicide. Pesticides registered for use include chlorothalonil (Daconil) and mancozeb. Thorough uniform coverage of plant surfaces is essential for good disease control. Spray foliage to the point of runoff. Repeat on a 7–10 day schedule while cloudy and/or wet conditions favorable for disease development are common. Spray junipers three times, at two-week intervals, beginning in mid-July, with a fungicide such as Acme Bordeaux Mixture.[图片]4. Avoid planting susceptible hawthorns within a two-mile radius of junipers. (This may be impractical in an urban environment.) 5. Replace infected trees with genetically resistant hawthorn varieties.

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Cedar-apple rust (Gymnosporangium juniperivirginianae), cedar-hawthorn rust (G. globosum), and cedar-quince rust (G. clavipes) are closely related rust diseases that require two hosts to complete their life cycle. All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Of these alternate hosts, cedar-apple rust is primarily a disease of apples and crabapples. Cedar-hawthorn rust, in addition to affecting apples and crabapples, sometimes infects pears, quince, and serviceberry. Cedar-quince rust has the broadest host range and can infect many genera in the rose family. In addition to those plants already mentioned, mountain-ash, flowering quince, cotoneaster, chokeberry, and photinia are also hosts for this disease.[图片]Symptoms and Diagnosis Symptoms on juniper: Brown, perennial galls form on twigs. When mature (usually in two years), the galls swell and repeatedly produce orange, gelatinous telial horns during rainy spring weather. The galls of cedar-apple rust are often over 2 inches in diameter, while cedar-hawthorn rust galls are rarely over 2 inches in diameter. Occasionally the twig beyond the gall dies, but usually no significant damage occurs on the juniper host. Symptoms on apple (or crabapple): Circular, yellow spots (lesions) appear on the upper surfaces of the leaves shortly after bloom. In late summer, brownish clusters of threads or cylindrical tubes (aecia) appear beneath the yellow leaf spots or on fruits and twigs. The spores associated with the threads or tubes infect the leaves (needles) and twigs of junipers during wet, warm weather.[图片]Life Cycle On juniper, galls appear about seven months after infection, and they form gelatinous masses of spores after 18 months. Golf ball-like depressions form on the gall that will give rise to telial horns the following spring. The telial horns are brownish in color, but rapidly elongate and become bright orange with spring rain, shrinking and swelling with intermittent rainfall. After releasing their spores, the horns collapse, dry, and eventually fall off. The galls die at this point, but may remain attached to the juniper for a year or more. This rust is very obvious on red cedar and other junipers during spring, when the galls are covered with orange-brown gelatinous masses. Rust spores formed on the gelatinous masses cannot infect other junipers but can infect only certain susceptible species of the rose family.[图片]On apples and crabapples the circular, yellow lesions on the upper surfaces of the leaves appear shortly after bloom. Wet, rainy weather in early spring is conducive for twig, leaf and fruit infection of these deciduous hosts. Heavy rains within the first two weeks of budbreak and leaf expansion cause the disease to be more severe. As the disease progresses, the undersides of the leaves below the yellow spots will develop raised orange structures that will ooze from the center, turn black, and appear as black dots. In late summer, this area will produce the orange and brown rust-colored spores that infect the juniper host, completing the cycle. Severely infected leaves may drop prematurely, especially during a dry summer.[图片]Integrated Pest Management Strategies 1. Prune. Prune out the galls on junipers, if you wish, though be advised that the effectiveness of pruning out the galls or removing junipers is debatable since spores can travel long distances with the wind. 2. Co-exist. Live with the disease. It rarely kills trees. It may disfigure plants when twigs are infected. 3. Preventive fungicide. Use preventive fungicides labeled for use on apples. Fungicide sprays are aimed at protecting developing foliage from infection during the time the galls on the junipers are orange and gelatinous. This usually lasts for several weeks and fungicide applications are not necessary once the galls become dry and inactive. Pesticides registered for use include captan, chlorothalonil (Daconil), copper, mancozeb, maneb, sulfur, thiophanate methyl (Cleary 3336), thiram, triadimefon, and ziram.[图片]4. Mixing plants. Avoid planting juniper and rust-susceptible hosts in close proximity to each other. 5. Resistant apple varieties. Use only resistant varieties in planting. Remove and replace diseased plants with resistant varieties.

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Cane blight of raspberries is a late season disease caused by the fungus, Leptosphaeria conithyrium. Infected canes may blossom normally, but they usually wilt and die before they can set fruit or while they are heavy with fruit. Black raspberries are more susceptible than red or purple raspberries. Cankers on apples and roses are also caused by this fungus.[图片]Symptoms and Diagnosis Brown-purple areas develop around cuts or wounds in infected canes. The discoloration will slowly spread down the cane, encircling the stem. Small, smutty patches of olive-green fungal conidia (spores or conidiospores) develop on the bark. The spread of the disease through the canes blocks water movement through the plant, causing wilting and, eventually, death. Cane blight reduces yields because symptoms appear later in the growing season, when branches may be laden with fruit.[图片]Life Cycle Spores of the fungus overwinter on dead infected canes. In the late spring, fungal spores are spread from plant to plant by the wind and splashing water. Infection takes place when there is sufficient moisture allowing the spores to enter the plant through wounds. Spores may continue to live on dead, infected canes for 2 or more years.[图片]Integrated Pest Management Strategies 1. Prune and destroy all infected stalks. Blighted canes cannot be cured. 2. Do any pruning work during dry weather to allow wounds to dry out and prevent infection by the fungal spores.[图片]3. Prevent damage and wounds to canes by controlling cane borers. Vigorous, adequately fertilized and watered plants are more resistant to injury and less likely to attract harmful insects. If borers have infected canes, the tips will begin to wilt; prune these tips well below any insect punctures. 4. Plant resistant varieties. Red-fruited or purple varieties of raspberry are less susceptible to cane blight. 5. Use fungicides. Pesticides registered for use include copper and mancozeb.

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Black rot, caused by the fungus Guignardia bidwellii, is a serious disease of cultivated and wild grapes. The disease is most destructive in warm, wet seasons. It attacks all green parts of the vine – leaves, shoots, leaf and fruit stems, tendrils, and fruit. The most damaging effect is to the fruit. Note: Guignardia bidwellii forma parthenocissi causes a leaf spot on Boston ivy and Virginia creeper. Control is as for black rot of grapes.[图片]Warm, muggy weather in the spring and summer, along with unsprayed fruit of susceptible varieties, may cause fruit to become almost completely rotted by harvest time. Black rot is not difficult to control if good cultural practices are followed along with the use of protective fungicide sprays. Symptoms and Diagnosis Leaves: Reddish brown and circular to angular spots appear on the upper surface of the leaves starting in late spring. As spots merge, they form irregular, reddish brown blotches. The number of spots or lesions per leaf varies from 2 to more than 100 depending on the severity of the disease. The center of the leaf spot turns tannish brown and is surrounded by a black margin. Black, speck-sized fruiting bodies (pycnidia) are arranged in a definite ring just inside the margin of the lesion. Only young, rapidly growing leaves are affected.[图片]Fruit: Shortly after the flower petals fall, fruit infection can occur. Most infections start when the fruit is half to almost full size. A small spot will appear that becomes circular and whitish tan, often surrounded by a brown ring. This happens while the berry is still green. The spots grow rapidly and may cover half of the berry within 48 hours. Within a few days the entire berry becomes coal black, hard, and mummified. The surface of the withered fruit is soon covered with minute, black, pimple-like, sporeproducing pycnidia that are arranged in circular zones.[图片]Life Cycle The black rot fungus overwinters in canes, tendrils, and leaves on the grape vine and on the ground. Mummified berries on the ground or those that are still clinging to the vines become the major infection source the following spring. During rain, microscopic spores (ascospores) are shot out of numerous, black fruiting bodies (perithecia) and are carried by air currents to young, expanding leaves. In the presence of moisture, these spores germinate in 36 to 48 hours and eventually penetrate the leaves and fruit stems. The infection becomes visible after 8 to 25 days. When the weather is wet, spores can be released the entire spring and summer providing continuous infection. Cool weather slows growth of the fungus. It requires warm weather for optimal growth and a period of 2 to 3 days of rain, drizzle, or fog.[图片]New black rot infections continue into late spring and summer during prolonged periods of warm, rainy weather. During August, the pycnidia are transformed into the overwintering stage (pycnosclerotia) that gives rise to perithecia within which the spring ascospores are produced, completing the disease cycle. Integrated Pest Management Strategies 1. Planting. Space vines properly and choose a planting site where the vines will be exposed to full sun and good air circulation. Keep the vines off the ground and insure they are properly tied, limiting the amount of time the vines remain wet thus reducing infection.[图片]2. Sanitation. Keep the fruit planting and surrounding areas free of weeds and tall grass. This practice will promote lower relative humidity and rapid drying of vines and thereby limit fungal infection. 3. Pruning. Prune the vines in early winter during dormancy. Select only a few strong, healthy canes from the previous year’s growth to produce the following season’s crop. Remove these prunings from the vineyard and burn or destroy. 4. Cultivation. Cultivate the vineyard before budbreak to bury the mummified berries. Diseased berries covered with soil do not produce spores that will reach the developing vines. For homegrown grapes, use 2–3 inches of leaf mulch or fine bark to cover infected debris.[图片]5. Fungicides. Use protective fungicide sprays. Pesticides registered to protect the developing new growth include copper, captan, ferbam, mancozeb, maneb, triadimefon, and ziram. Important spraying times are as new shoots are 2 to 4 inches long, and again when they are 10 to 15 inches long, just before bloom, just after bloom, and when the fruit has set. 6. Cultivars. Cultivars with large, juicy berries are the most susceptible. In general, grapes that ripen late in the season are affected the least. Most commercial cultivars are sufficiently resistant if adequately protected with a fungicide spray program.

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Black knot is a name used to describe a disease of woody stems with black, knotty, outgrowths. It is most widespread on plum and cherry trees, but also infects apricots and peaches. Infection occurs in the spring, but symptoms of the disease may not be obvious until the following spring or even in later seasons.[图片]Symptoms and Diagnosis Initially the bark of infected twigs and medium-sized branches will begin to crack in the springtime. A light yellow discoloration and cork-like swelling occurs on infected areas. Knotted areas later turn an olive-green color and finally turn black and harden during the summer. The swelling weakens branches and may stunt or kill smaller branches due to decreased water and nutrient flow.[图片]Life Cycle Dibotryon morbosum is the fungus responsible for causing black knot disease on cherries and plums. Spores overwinter in the blackened "knots" of infected branches. Disease spores are spread to new hosts by wind during warm spring weather when temperatures are between 55–75 degrees F and there is rain or high humidity. Trees are weakened because the knots disrupt the normal flow of water and nutrients throughout the branches. Twig dieback is common.[图片]Integrated Pest Management Strategies 1. Plant resistant varieties. Plums such as ‘President’, ‘Santa Rosa’, or ‘Fellinberg’. 2. Prune and destroy all knotted branches in the winter or before March 1. Prune 3–4 inches below the knot to remove all fungal material. Dip tools in a solution of 1–part bleach and 9–parts water between cuts.[图片]3. Remove any wild cherry and plum trees surrounding your property. These trees may be harboring black knot and it spreads easily to cultivated varieties. Pruned material should be disposed of or burned. 4. Apply a fungicide cover spray at bud break. Pesticides registered for use include copper, chlorothalonil (Daconil), mancozeb, and thiophanate methyl (Cleary 3336).

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The fungus, Armillaria mellea, occurs sporadically in this region and has been reported to infect over 25 species of ornamental trees and shrubs. The most distinctive sign of Armillaria infection is the honeycolored mushroom that grows from the roots and base of plants. The fungus is especially prevalent on oak but also affects many different kinds of fruit and nut trees, ornamentals, and herbaceous plantings. It is often referred to as oak root rot fungus because it is commonly found on oaks or in areas where oaks trees once were grown, such as cleared forest land.[图片]Symptoms and Diagnosis The symptoms of Armillaria are similar to those of other root disorders; height growth is reduced, foliage is sparse, and leaves that remain on plants are stunted and yellow. An abnormal flow of sap may be visible on the root collar. When soil is removed from the base of the trunk, black, root-like strands are visible and attached to larger roots. White to dark, fan-shaped mats of fungal strands develop between the bark and wood in infected root and trunk tissues. The most positive sign of infection is the production of clusters of honey-colored mushrooms at the base of the tree near the soil line. The mushrooms may have stalks 4 to 6 inches high with caps 1 inch high and 2 to 4 inches wide.[图片]Life Cycle Armillaria is found in the soil sporadically throughout the Midwest. The fungus spreads primarily by root-to-root contact or by root-like fungal strands. Root-like fungal strands grow through the soil and adhere to the host roots or root collar that it encounters. Successfully attacked trees do not die until infections girdle the base of the tree. On healthy, vigorous trees, Armillaria is not lethal but if present, it may begin to grow when the tree dies of other causes. Young trees are more likely to be killed by Armillaria. Trees that are 15–20 years old are more tolerant to attack.[图片]Integrated Pest Management Strategies 1. Remove and destroy infected material. Remove as much of the stump as possible. Sterilize tools with a solution of 1–part bleach with 9–parts water after use. 2. Provide adequate moisture in a well-drained soil to maintain vigor and resistance to infection. Plants suffering from drought are extremely susceptible to infection. Fertilize trees appropriately in late winter or early spring.[图片]3. No effective chemical controls are known. Plants reported by Auburn University to be resistant to Armillaria root rot include ginkgo, tulip tree, ash, bald cypress, cherry, Chinese elm, Chinese pistache, crabapple, cryptomeria, dawn redwood, eucalyptus, hackberry, holly, incense cedar, Leyland cypress, maidenhair tree, maple, privet, smoke tree, sweetgum, tree-ofheaven, white fir, and wisteria. These should be considered for replacement of diseased trees. New soil should be used to amend the planting site. All diseased material and associated roots, as much as possible, should be excavated before replanting.

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Annual winter weeds germinate in the fall and winter and grow actively in spring. Gardeners are often surprised how quickly these weeds can seemingly pop up overnight in their yards and gardens, being unaware that they may have been growing slowly all winter long. After they flower in spring they die and disappear for the summer only to return in fall or winter when new seeds germinate.[图片]Some of the more common annual winter weeds in the Midwest are henbit, deadnettle, common chickweed, annual bluegrass, wild mustards, prickly lettuce, Persian speedwell, horseweed, cheatgrass and rabbitfoot clover. Some people do not consider these plants as weeds, as some can also be used for food or have been used for medicinal purposes. Deadnettle and Henbit Deadnettle (Lamium purpureum) and henbit (Lamium amplexicaule) are often confused. These winter weeds are both in the mint family and have square stems with opposite leaves. Both plants have pink/purple flowers and can reach 16 inches high but more commonly reach only about 6 inches high in the Midwest. Henbit has circular or rounded leaves with rounded teeth on the leaf margin. Deadnettle has triangular shaped leaves and less deeply lobed than henbit and at times the upper leaves are purple or red. Both plants are decumbent in youth but more upright with age. Flowers appear in whorls in the leaf axis of upper leaves from March to May and are tube-like with 2 lips.[图片]Common Chickweed Common chickweed (Stellaria media) is a winter annual with a shallow fibrous root which grows in moist, cool shaded areas. The bright green leaves are about ½ inch long, smooth, pointed at the tip, and elliptic in shape. They have opposite branching, slender, creeping stems which root at the nodes. The white flowers of chickweed are ½ inch in diameter and star-shaped with five deeply notched petals. Flowering occurs from early spring to fall. Chickweed reproduces by seed and rooting at the nodes on prostrate stems. The fruit contains many seeds within a dry capsule which splits when mature, shaking out the seeds onto the soil. Seeds will germinate at any time of the year but particularly in spring and autumn. Seeds are dispersed in mud on footwear and tires as well as by animals. Chickweed is found in turfgrass as well as nursery, cultivated horticultural, and agricultural crops. It is a host of several damaging virus diseases of crop plants which can be carried in the chickweed seeds.[图片]Annual Bluegrass Annual bluegrass (Poa annua) is one of the most common weeds in the United States. It is a native of Europe. Golf courses consider it a particular problem. It is identified by its boat-shaped leaf tips which curve up like the bow of a boat. Annual bluegrass is upright growing (growing 3-12" high) and can be noticed by its pale green spring appearance. It can produce 100 seeds in 8 weeks. It germinates when the temperature falls below 70 degrees and throughout the winter. It usually dies in the summer.[图片]Prickly Lettuce Prickly lettuce (Lactuca serriola) is in the aster family. It can grow up to 5’ tall. Sometimes this winter weed can be a biennial. It has creamy yellow aster-like flowers. Butterfly larvae feed on this plant. Alternate leaves branch off the main stem. There is a prominent midvein on each leaf which contains a row of spines on the bottom surface. Several edible lettuces, such as crisphead, butterhead, cos, Romaine, loose leaf or bunching, and stem lettuce or celtuce were all derived from this species.[图片]Persian speedwell Persian speedwell (Veronica persica) is a winter annual with slender, weak stems that grow along the ground but turn up at the tips. In shaded areas it tends to grow more upright. The stems are covered with finely pointed, flattened hairs. The hairy leaf blades are oval to roundish with rounded teeth around the edges. The lower leaves are arranged oppositely and occur on petioles, but the upper leaves occur on the more erect flowering stems, are arranged alternately, and do not have petioles. The flowers occur singly on long, slender flower stalks which arise from the leaf axils. The small flowers are usually light blue in color with darker blue lines and a pale blue to white center. Prior to flowering, the speedwells are often misidentified as ground ivy, henbit, or purple deadnettle. However, ground ivy does not have hairy leaves and both henbit and purple deadnettle have leaves that are arranged oppositely along the flowering stem. Speedwell is primarily a weed of lawns, turfgrass, landscapes, nurseries, and winter small grains.[图片]Horseweed Horseweed or mare's tail (Conya canadensis) can grow to 6 1/2 ’ tall. A mature plant has alternate leaves that have no petiole. Young leaves are egg-shaped with toothed margins but mature leaves are 3-4 inches long, hairy, and oblanceolate in shape (broader and rounded at the apex, and tapering at the base.) Plant has a taproot. Small inconspicuous flower heads are at the top of the central stem. Flowers are about 1/4 inch in diameter, with white or slightly pink ray flowers. This is a composite flower and there are many tiny disk flowers in the flower head (like daisies and coneflowers). In the early stages, this plant resembles shepherd’s purse or Virginia pepperweed. The fruit (or seed) is a 1/16 inch long achene that does not split open when it is ripe. It tapers from the apex with many small bristles that aid in wind dispersal. This plant is susceptible to aster yellows.[图片]Cheatgrass Cheatgrass (Bromus tectorum) is a winter annual that has a fine feathery appearance, with slender light-green stems drooping at the tips where the seeds form. Seed spikelets and their bristles can be 2 inches long. Mature grass grows to 30 inches and turns first purple, and then brown, as it dries. Cheatgrass occurs throughout most of the United States and is on state noxious weed lists in 43 states. It grows on rangelands, pastures, prairies, fields, eroded sites and roadsides. Cheatgrass can alter ecosystems by maintaining dominance for years on sites where native vegetation has been eliminated or severely reduced due to grazing, cultivation, or fire. Moreover, it increases the frequency and timing of wildfires. At maturity the sharp-pointed bristly sections can injure wildlife species by working into the nose, ears, mouth, or eyes. Spikelets can also cling to clothing.[图片]Rabbitfoot Clover Rabbitfoot clover (Trifolium arvense) is in the pea family. This winter weed has a multi-branched growth habit and is 4-16 inches tall. It came from Eurasia and is naturalized now. Both stems and leaves are densely hairy. Leaves consist of 3 narrow leaflets with minute teeth-like projections at the tip. Flowers are small and pink to purple in color. They are clustered in grayish soft and silky cylinder-shaped heads. It flowers in the spring, and reproduces by seed. Rabbitfoot clover is found in the Southeast United States, west to Louisiana and north to Missouri. Rabbitfoot clover contributes nitrogen to the soil, as do other clovers, but it grows in unimproved sandy soils in semi-arid grasslands.[图片]Bedstraw Bedstraw (Galium aparine) is a winter annual with square stems and short, downward pointing hooks on the stem corners. The stems are weakly branched, prostrate on the ground or climbing on other plants producing a tangled mass. The rough hairy leaves grow in whorls of six to eight. The tiny white flowers have four-lobed pointed petals on long flower stalks. Bedstraw is found in moist shady areas, thickets, valleys, roadsides, waste ground, under trees, and clearings. The hooked spines of the stems, leaves and seeds cling to just about everything and are difficult to remove. The burr-like seeds are produced in pairs and are covered with hooked hairs. This clinging characteristic minimized matting when bedstraw was used as a mattress filling.[图片]Shepherd's Purse and other mustards Shepherd’s purse (Capsella bursa-pastoris) is a winter annual with erect stems that grow 3 to 18 inches tall from a basal rosette quite similar to that of a dandelion. The rosette grows to be 4 to 8 inches in diameter. Shepherd’s purse has alternate leaves with the lower leaves more deeply lobed than the upper leaves. The flowers are small and white, appearing in clusters at the top of the stalk from early spring to early winter. Each flower has four petals and develops into a heart-shaped or triangular seedpod which, when the pod dries, splits in half releasing the mature seeds. The seedpods are supposed to resemble the purses of ancient shepherds. It does best in sunny, rich, disturbed soil, but it will also grow in partly shaded, extremely poor soils.. It can be found in flowerbeds, lawns, sidewalk cracks and along the edges of sidewalks and paths.[图片]Integrated Pest Mangement Strategies 1. Encourage grass. Keep lawn areas thick and mulch flowerbeds to help prevent weed seeds from germinating. 2. Removal. Dig or pull the weeds in the winter or spring before they flower and set seed for the next year. 3. Good sanitation. Use good cultural and sanitation practices to prevent the spread of weeds. Small weed seeds can be spread by machines, clothing, pets, and by contaminated seed.[图片]4. Use chemical herbicides. For established weeds the best time to apply herbicides is early spring when the weeds are actively growing but before they go to seed. Herbicides containing Dicamba and/or MCPA or MCPP are more effective than 2,4-D alone. After you have identified the weed you have, check product labels or resource materials to see which herbicides are most effective for that weed or combination of weeds. Use herbicides with caution around desirable plants that may be damaged. Read label directions and cautions carefully. 5. Use pre-emergent herbicide. To prevent germination of the seeds of these winter annuals, apply a pre-emergent herbicide, such as, Gallery in late summer or early fall before the weed seeds have germinated.

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A weed is a plant that is not valued where it is growing and is usually of vigorous growth, especially one that tends to overgrow or choke out more desirable plants. Summer annual weeds emerge in the spring or early summer, grow during the summer, produce seed in mid to late summer, and are killed by frost in the fall. Following are some of the more common summer annual weeds for the St. Louis area. General control measures are listed at the end of this article.[图片]GRASSES Barnyardgrass Barnyardgrass (Echinochloa crus-galli) is a summer annual grass that germinates from seeds from late winter or early spring throughout the summer. The stems are usually erect, thick, without hairs, often branched at the lower nodes, and may be tinted red to maroon at the base. The stems may reach 5 feet in height. The smooth, hairless leaves are rolled in the bud and contain neither ligules nor auricles. The dark green leaves, which range from 4 to 20 inches in length, have a distinct white midvein range. The seed head is green to reddish purple, with conspicuous, short stiff bristles or barbed spikelets. The roots are fibrous. Under close mowing, the broad, compressed purple sheaths of barnyardgrass lie flat on the ground and spread in a semicircular pattern. Barnyardgrass is found in moist soils, especially soils high in nutrients.[图片]Crabgrass Crabgrass, large and smooth (Digitaria sanguinalis, Digitaria ischaemum) are pale green summer annuals that has a prostrate or ascending growth habit. The two main species of crabgrass that occur in Missouri are smooth and large. Smooth crabgrass may be distinguished from large crabgrass by the absence of hairs on the leaves and sheath. Also smooth crabgrass does not root at the nodes like large crabgrass. Both species have a long, jagged membranous ligule and have no auricles. Crabgrass forms dense, unsightly patches that smother desirable turf grasses. Germination occurs when soil temperatures consistently reach 55 degrees F and is generally killed at the first frost. A crabgrass plant which needs warm soils and sunlight can produce 150,000 seeds. The seed head is composed of 2-6 branches (spikes) at the top of the stems forming 2 rows along the spike.[图片]To control early in the season, use a pre-emergent herbicide as soon as soil temperatures reach 55 degrees F for a period of four days about the time forsythia blooms. A pre-emergent herbicide is recommended even if some crabgrass plants have germinated. There will still be crabgrass seed in the soil and the herbicide can prevent further infestation. Do not aerate after a pre-emergent herbicide application. For crabgrass control after germination, use a post-emergent selective grass herbicide. Fall Panicum Fall panicum (Panicum dichotomiflorum) is known as smooth witchgrass. It has a zigzag appearance as the buds turn out at the nodes. It has a very rounded stem, grows to 7’ and there is a purple tinge to its inflorescence. Sometimes it is confused with Johnson grass or barnyard grass, but fall panicum has a hairy ligule. Also its first true leaf has hairs on the underside of the blade, Johnson grass and barnyard grass do not.[图片]Witchgrass Panicum capillare is known as witchgrass or tickle grass. Culms are erect or spreading at the base. They are hollow, and pubescent at the nodes. They grow from 8 to 28” inches tall. The inflorescence is often ½ the length of the entire plant. It is purplish at maturity. It is softly hairy and the seeds are 1/16 of an inch. The head breaks off easily and rolls away in the wind, like a tumbleweed. Goosegrass Goosegrass (Elusine indica) is a prostrate-growing summer annual weed that grows in a clump. The leaves are distinctly folded in the bud and may be smooth or have a few sparse hairs at the base of the leaf. Goosegrass can be identified by the whitish stems at the base that are extremely compressed and flattened. The ligule is toothed and membranous with a cut in the center. There are no auricles. Goosegrass seed heads contain 3-7 spikes that form at the tip of the stalk. The seeds are attached in a zipper appearance on the spike. Goosegrass germinates about two weeks later than smooth crabgrass. Goosegrass can tolerate heavy traffic, dry compacted soils and low mowing heights.[图片]Sandbur Sandbur (Cenchrus longispinus) is a low-growing summer annual weed which is found in dense spreading patches most commonly in sandy soils. It roots at the nodes on the stems if they touch the ground. The leaves are folded in the bud, ¼ inch wide, and tapering to a point. The ligule is a short fringe of hairs and the auricles are absent. The seed head is a single spike with 6 to 20 rounded burs which contain 2 seeds in each bur. Sandbur seeds catch on clothing and animal fur and the barbed burs can easily pierce the skin and cause injury to livestock and people. Plants growing low to the ground can still produce burs. After a frost, entire plants become straw-colored, but stems with burs can persist through the winter. Seed dispersal occurs by animals, farm equipment, tires and in contaminated hay. Water is also important for seed dispersal, as burs float and may be carried for miles in irrigations ditches and other waterways.[图片]Yellow Foxtail Yellow foxtail (Setaria glauca) is a summer annual found especially in the Midwest and Eastern parts of the United States. It germinates when soil temperatures reach 65 degrees. Leaves are rolled in the bud. The ligule is a fringe of hairs. Auricles are absent. The collar is narrow and continuous. The blade contains hairs near the ligule. It has an upright growth pattern. The seed head is a bushy spike which resembles the tail of a fox. BROADLEAFS Black Medic Black medic (Medicago lupulina) is a summer annual that can act as a perennial. The leaf is similar to other legumes, but the center leaflet is on a separate petiole. The flower is a compressed cluster of bright yellow flowers in the shape of a globular spike on short branches. The seed pod turns black at maturity. It will produce seeds at normal mowing heights. It can be confused with lespedeza (Kummerowia striata) unless it is blooming. Lespedeza has a bright blue flower.[图片]Carpetweed Carpetweed (Mollugo verticillata) is a summer annual with smooth prostrate branching stems forming circular mats. It is light green in color, the leaves are lanceolate in shape, widest in the middle and narrow at tip and base. Leaves form whorls containing 3-8 leaves. The flowers are white, have 5 petals, and form clusters of 2-5 flowers. Flowers are formed in the leaf axils. It spreads by seed, and is found throughout North America. Carpetweed germinates much later than other summer weeds. It grows quickly, especially in thin turf. Mowing misses it. It prefers rich moist soils, but it can establish itself in dry, sandy soil. Lambsquarter Lambsquarter (Chenopodium album) is an erect growing summer annual that may appear highly branched in a mowed setting. The immature leaves appear to be covered with a white mealy substance, especially on the underside of the leaf. The first pair of leaves are opposite, and subsequent leaves are alternate along the stems. Leaf margins vary, but usually are irregularly lobed. The root of lambsquarter is a short, branched taproot. The flowers are found in small green clusters and lack petals. The clusters of flowers form in terminal spikes. Lambsquarter spreads by black seeds that germinate in the late spring to early summer. Each plant produces thousands of tiny seeds that may remain viable for years. When lambsquarter is abundant, it is reported to cause hay fever symptoms.[图片]Mallow Mallow (Hibiscus trionum) is a summer annual-- it is also called “flower of an hour”. There is a winter annual mallow, it is usually called the common mallow. H. trionum is grown in Europe as an ornamental. It is upright 10-18”. It is covered with hairs. The leaves are deeply cleft with 3-5 coarsely toothed lobes on long petioles. The lower stems and petioles are red to purple in color. It has a fibrous root system with a weak taproot. It has a showy flower. It is light sulfur-yellow in color with a deep red to purple center. It does last 2-3 hours then the petals drop. It spreads by seed. The seed can be dormant for 50 years. It is found throughout the U.S. Mallow can infest nurseries, orchards, roadsides, cultivated fields and open areas. It tolerates drought, alkaline soil, and gravelly soils. Pigweed Pigweed is actually toxic to pigs and cows. This summer annual has alternate leaves. There are 10 pigweeds (Amaranthus) identified through the corn belt area: redroot, smooth, rough pigweed, Powell, tumble, prostrate, spiny, tall, sandhill and another one. The difference is in the flower. The leaves are alternate, the seeds (1/25”) are shiny, round and flat. The plant can reach 2-4’ for the smaller ones and up to 61/2’ for the larger ones.[图片]Prostrate knotweed Prostrate knotweed (Polygonum aviculare) is a summer annual which resembles a grass with long, dark leaves as the seedling emerges. Later, it forms a flat mat up to 2 to 3 feet in diameter on slender wiry stems that emerge from a tap root. There are papery sheath or ocrea at each node that give the stems a knotted or swollen appearance. The alternate leaves are small and narrowly oval, dull and bluish green, and 1 ¼ inches long by 1/3 inch wide. The flowers are small pink to white and form in clusters in the leaf axis. Knotweed is found in compacted, infertile soil or thin turf in the sun. Smartweed is a close relative of knotweed, but it has a purple ocrea encircling the stem. Spotted spurge may be confused with knotweed, but the spurges do not have an ocrea and emit a milky sap when cut, unlike prostrate knotweed.[图片]Puncturevine Puncturevine (Tribulus terrestris) is a summer annual weed with multiple stems prostrate along the ground. Stems may be up to five feet long originating from a taproot. Leaves are compound pinnate with four to eight pairs of hairy leaflets. Each leaflet is less than ½ inch long. The small yellow flowers have five petals and are about 1/3 inch wide. The flowers, which consist of 5 petals, produce hard, spiny, five-lobed fruit. Bloom is in late spring and early summer. At maturity the fruit breaks into tack-like structures each containing 2 to 4 seeds. Seed nutlets disperse by adhering to tires, shoes and clothing of people, fur, feathers, and feet of animals. These burs can injure people and animals and can damage bike and car tires. Foliage is toxic to livestock, especially sheep, when consumed in quantity. The fruit is used medicinally in India.[图片]Purslane Purslane (Portulaca oleracea) is a prostrate mat-forming summer annual that can reach up to 24 inches long. It has multi-branched red stems that root at the nodes wherever they contact the soil surface. The smooth, thick, fleshy leaves are usually alternate and are often clustered near the ends of the branches. The entire plant is very succulent and resembles a jade plant. Purslane is common to disturbed soil, new seedlings, sidewalk crevices and mulched planting beds. It prefers high light and warm conditions. This plant reproduces by seeds that are formed in a capsule with a lid that flips open in the spring. Solitary yellow flowers with 5 petals will only open with sunny conditions from May to September. Purslane’s use as a medicinal herb to treat dysentery, headache, and stomach ache dates back 2000 years. It was also used as a salad green by the Australian aborigines, by the Chinese, French, Italians, and the English. Ragweed Ragweed (Ambrosia artemisifolia) is a summer annual that produces pollen. One weed equals 1 billion grains of pollen, 100 million tons of pollen are produced per year. It grows up to 5’ tall. Opposite leaves are egg-shaped in outline and once or twice compound (pinnatified), they are hairy on their upper surface and margin. Leaves can be up to 6” long, The erect stems have long rough hairs. The fruit is an achene, which resembles a queen’s crown. It has a shallow taproot. There is a giant ragweed (Ambrosia tridida) which grows up to 14’ high. No animal eats ragweed.[图片]Spurge Prostrate spurge (Euphorbia supine) and spotted spurge (Euphorbia maculate) are summer annual weeds. Spotted spurge has a more erect growth habit than prostrate spurge. Prostrate spurge forms dense mats with its stems radiating out from a shallow taproot. Both species have similar leaves, which are small and oblong with an irregular maroon to purple spot in their center. However, the leaves of spotted spurge are slightly larger than those of prostrate spurge. Both spurges have leaves that grow opposite on the stem, but spotted spurge has fewer leaves per stem. When the leaves of both spurges are broken or injured they emit a milky white sap (similar to dandelion). Prostrate spurge roots at the nodes, but spotted spurge does not. Both spurges reproduce from seed. The flower of spotted spurge is small and green in color. Prostrate spurge has inconspicuous small, pinkish white flowers in the leaf axils. Vervain Vervain (Verbena officinalis) is known as the herb of enchantment. It is used medically in 30 complaints. Supposedly vervain staunched the wounds of Christ on the Mount of Calvary. It has a slightly bitter taste and it has no scent. Vervain is rarely perennial, the leaves are numerous, opposite, lanceolate to ovate ½ to 3” long. It is pinnately toothed, it can have 3 lobes, with the center lobe larger than the others. The leaves are hairy on both surfaces. The flower is a dense terminal spike 1-8” long, usually ascending. The flower is blue or purple with 5 lobes, the tiny flowers are almost hidden by conspicuous hairy bracts.[图片]Integrated Pest Management Strategies for Summer Annual Weeds 1. Use good cultural practices to prevent the spread of summer annual weeds. Maintain a dense actively growing turf through proper mowing, fertilizing and watering practices. Most lawns should be cut at least 2 inches or higher. Watering deeply (4-6 inches) just before the turf begins to wilt is a sound approach. Frequent light watering promotes weak turf with shallow roots which are more susceptible to insect and disease attacks as well as weed invasion. Complete soil testing is the key to proper liming and fertilization. Cultural practices for the control of summer annual weeds are aimed at shading and crowding the young weed seedlings by producing a dense sod.[图片]2. Dig up the weeds. 3. Coring and traffic control reduce compaction and encourage desirable turfgrass growth. Mulch flower beds to control weeds. 4. Use chemical herbicides. Use a post-emergent herbicide when the weed is young, usually three to four leaf stage. It is best to control summer annual weeds in late spring or early summer when they are young. They are easier to control at that time and both warm season and cool season turfgrasses have a greater chance to recover the areas previously occupied by weeds. There are also some pre-emergent herbicides available which form a chemical barrier in the soil and prevent the weeds from emerging. Check herbicide labels to verify that the herbicide you have chosen is effective in controlling your problem weed and when and how to apply.

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