绿手指
首页
动态
文章
百科
花园
设置
简体中文
已关注
+
关注
花园 (6)
动态 (3585)
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
There are over 1200 known species of whiteflies, most of which feed on only one or a few species of plants each. Some are pests on valuable crops such as the sweet potato whitefly (Bemisia tabaci). Others, like the greenhouse whitefly (Trialeurodes vaporariorum), feed on a broad range of herbaceous plants both inside the greenhouse and outside in the garden. Some of the host plants that the greenhouse whitefly attacks are the tomato, fuchsia, lantana, and coleus.
The silverleaf whitefly (Bemisia argentifolii) has been found on as many as 500 hosts such as canna lilies, bearded iris, crepe myrtle, lantana, petunia, and rose. Whiteflies are one of the most difficult insect pests to control. They are not true flies but are more closely related to aphids, mealybugs, and scale, which are also sap-sucking insects. In some parts of the country, some species of whitefly can transmit several plant viruses.
Symptoms and Diagnosis Identification of the whitefly is easy as a white cloud of insects rise from foliage when disturbed. The adults are about 1/16 to 1/10 inch in length, wedgeshaped, and appear powdery. Infested leaves may show little if any symptoms or may be mottled and yellow. Leaves will also become coated with a sticky substance called honeydew, which is secreted by feeding whitefly nymphs and adults. A black, sooty mold may sometimes grow on the honeydew. Sooty mold does not damage the leaf. The feeding, however, removes nutrients from the plant, which results in stunting, poor growth, defoliation, reduced yields, and sometimes death. On certain plants the silverleaf whitefly causes specific damage symptoms such as silvering of leaves on squash, irregular ripening in tomato, whitestalk in broccoli and cauliflower, light root in carrots, and white stem in poinsettia.
Life Cycle The whitefly spends its winters in weeds and ornamental plants, migrating to crops and gardens in spring and summer. Once temperatures warm up in the summer, populations can build rapidly with the highest populations probably occurring in late summer. They lay their tiny eggs on the undersides of leaves. Adult females usually lay between 200 to 400 eggs. Sometimes the eggs are deposited in a circular pattern (not true in all species) in groups of 30 to 40 as the female will often keep her mouth part in the plant to feed while moving in a circle to deposit eggs. Within about a week the eggs hatch into flattened nymphs, called crawlers that wander about the plant. Soon, they insert their mouth part and begin to feed. The first stage has legs and antennae, but these are lost after the first molt and the flattened, oval-shaped larvae stay fixed at one feeding site. The last part of the fourth instar is the pupa. Adults emerge from the pupa through a Tshaped slit and soon mate and reproduce. The adults live about one month. Within a population, all life stages are present and generations often overlap.
Integrated Pest Management Strategies 1. Inspection. Inspect all new plants planted in the garden for whiteflies. Inspect regularly and remove by hand older leaves that are heavily infested with whiteflies in a non-mobile nymphal stage. 2. Biological control. Whiteflies have many natural enemies in the garden setting including spiders, lady beetles, and lacewings. However, these predators are not effective if there is a frequent use of insecticides.
3. Mechanical control. The use of traps can be very helpful in controlling light infestations. Make yellow sticky traps about 12 x 6 inches and coat them with a sticky substance such as Tanglefoot, petroleum jelly, or heavy grade motor oil. Hang the traps vertically near the affected plants. The adults are attracted to yellow. Traps are also commercially available. Use one trap per plant. 4. Chemical control. Whiteflies have developed resistance to some chemicals. Because of this resistance, a certain product may work well in one area but not in another. Resistance may be delayed by alternating the types of chemicals used. In addition, the egg and non-feeding pupa stages are generally not as susceptible to insecticides as are the adults and nymphs. Consequently, eradication of a whitefly population usually requires four to five applications of a registered insecticide at five to seven day intervals. Be sure the applications are made to the lower leaf surface, and apply as soon as whiteflies are detected. Do not wait until populations become severe.
Before using any insecticide for whitefly control, make sure that the site and target plant are both listed on the label. Follow label directions carefully. 5. Chemicals. Some of the over-the-counter chemicals which could be used are malathion, imidacloprid, permethrin, or pyrethrins. Insecticidal soap, petroleum oil, and insect growth regulators can also be effective.
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Thrips are minute, slender-bodied insects less than 1/16 inch to about 3/16 inch in length. With magnification, you can identify the adults that range in color from yellow to black and have four long, narrow, fringed wings. The young nymphs are smaller, wingless, and range in color from yellow to white. Many thrips are plant feeders attacking flowers, leaves, fruit, twigs, or buds.
Symptoms and Diagnosis Thrips congregate by the hundreds and leave black, varnish-like fecal deposits on the underside of leaves. To feed, they puncture the epidermal layer of the host plant with their single large mandible, then slurp the cell sap as it flows into the wound. As a result of their feeding, the foliage appears dusty or silver and dull. Some species may burrow between the upper and lower leaf surfaces to feed. Blossoms can become streaked with brown and can wither prematurely. Injured leaves are twisted or discolored and scarred. The fruit of host plants is often pitted. A few species are beneficial predators of mites and small insects including other thrips, and some feed on fungal spores. Several species may bite people. Some species act as vectors of plant disease. Thrips are poor fliers, so that damage may first appear in one location and then slowly spread over the plant. Thrips will be most apparent on flowers, especially white, yellow, and other light-colored blooms.
Life Cycle Eggs are inserted into leaves, fruit, stems, or the bark of trees and shrubs. One to two weeks later, pale, wingless nymphs emerge and feed actively until they pupate. Some species enclose the pupa in a cocoon on the ground or on the host plant. The winged adult thrips emerge from the cocoon or pupal stage. Generations may occur every two to three weeks, but the largest populations are present from late spring to midsummer. Thrips overwinter in the egg stage.
Integrated Pest Management Strategies 1. Knock off thrips with a forceful spray of cold water in small gardens, preferably early in the morning. Use a nozzle that produces a fine spray of water, and thoroughly wash off the undersides of affected leaves. The control is most effective when repeated at least 3 times, either daily or every other day. 2. Keep plants well irrigated and adequately misted since thrips prefer a dry environment. 3. Prune and destroy injured and infested plants. Do not compost them. 4. Predacious spiders, mites, and pirate bugs help control thrips. Conserving naturally occurring populations of beneficial insects by avoiding persistent pesticides is important to biologically controlling thrips.
5. Aluminum foil and other disorienting mulches have been used with some success to reduce thrips infestations. 6. Two applications of pyrethrum applied 3 to 4 days apart will treat serious infestations. 7. Insecticidal soaps are effective for temporary reduction of thrips populations. Spray every 3 days for 2 weeks. To control iris thrips, spray insecticidal soap at the base of each plant every 5 to 7 days until the infestation has been controlled. To prevent thrips problems, soak iris divisions and gladiolus corms for 30 minutes in a hot water bath (110–125 degrees F). Dig up gladiolus bulbs early in the fall and let them cure in open trays in a shady location with good air flow such as a garage for a few weeks before soaking them. Then allow the bulbs to dry thoroughly before storing.
8. Spray infested plants with a systemic insecticide such as imidacloprid (Merit) since thrips frequently burrow inside the plant tissue. 9. If necessary, use chemical insecticides such as acephate (Orthene), bifenthrin, imidacloprid, or spinosad. Spray 2 or more times at intervals of 7-10 days to control thrips as they hatch.
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Two of the most damaging insects on perennial plants are the tarnished plant bug, Lygus lineolaris, and the four-lined plant bug, Poecilocapsus lineatus. These two plant bugs can cause serious problems because they have such a wide variety of host plants. The four-lined plant bug feeds on 250 plant species which are mostly herbaceous. The tarnished plant bug is a problem on a wide variety of ornamental flowers.
Symptoms and Diagnosis Damage varies slightly from the two plant bugs. The four-lined plant bugs cause small (1/16 inch), discolored areas on leaves where they suck out cell juices. Injured areas will turn black or become translucent, and after several weeks, the dead tissue may drop out, leaving small holes. The adults feed on the upper surfaces of leaves and are voracious feeders. The topmost leaves will generally be the first to be injured.
Damage from the tarnished plant bug is in the form of distorted foliage or disbudded plants. This damage is caused by the overwintered adults which attack swollen and opening buds in the early spring. The disbudding will cause the plant to be short and bushy. If the attack takes place after shoot elongation begins, the tip will often turn black and die, or it will be so damaged that shoot stunting or distortion occurs. Stems frequently break at the injured area.
Life Cycle The four-lined plant bug overwinters as eggs inserted into a slit near the top of tender shoots. Nymphs emerge from the eggs in May. Nymphal coloring varies from bright red to yellow. The species requires about 30 days to complete nymphal development. Forewings of adults are yellow, but may turn bright green. However, the four black stripes that give the insect its name remain distinct. This species normally has one generation a year. Adults of the tarnished plant bug overwinter as adults in leaf litter. Beginning in the spring, they lay eggs mainly in the stems and flowers of herbaceous plants. After hatching, the young nymphs usually remain to feed on the same plant until they mature. The nymph is green or pale yellow and grows rapidly. Adults are capable flyers and readily move from place to place. There may be two to five generations per year. In midsummer, a life cycle may be completed in about 25 days. By late summer, populations can become very abundant.
Integrated Pest Management Strategies 1. Live with the damage. Since damage is often cosmetic, some damage can be tolerated. Often, natural predators will keep the insects under control. 2. Remove leaf litter. To limit problems in coming years, clean up leaf litter to avoid overwintering sites for tarnished plant bugs. 3. Prune out egg masses. Learn to identify the egg masses of four-lined plant bugs and prune them out in winter.
4. Use insecticidal soaps. If populations are high enough, spraying with an insecticidal soap may be necessary. Because the tarnished plant bug can go through many generations in a single year and cause great damage to a plant, it is best to initiate control when it first appears. 5. If necessary, use chemical insecticides. Plant bugs can be controlled with malathion, and carbaryl (Sevin).
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Stink bugs are attractive and distinctive insects that are generally easy to identify. Ranging in size from 1/4 to 1 inch long and about half as broad, they are shield-shaped with a triangle-like horny scale on their back. Also, as the name indicates, many stink bugs do produce an offensive odor when disturbed. The most common pest species are green, brown, gray, or yellow and some have red or yellow markings. Their host plants include blackberry, cabbage and other members of the mustard family, corn, tomato, eggplant, bean, soybean, and trees such as apple, peach, pecan, and cherry. Stink bugs may also be found on ornamental plants including columbine, snapdragon, and sunflower. The harlequin bug, Murgantia histrionica, a red and black-spotted species of stink bug, is an important pest of crops in the mustard family in the southern United States. The green stink bug, Acrosternum hilare, and brown stink bugs, Euschistus spp., can be of economic importance in soybean fields primarily by reducing seed quality and quantity. A few species of stink bugs are predatory on other insects.
Symptoms and Diagnosis In the "true bug" group, stink bugs feed by inserting their mouth parts into the leaves, flowers, buds, fruit, and seeds of host plants and sucking plant sap. Large infestations of stink bugs may cause plants, especially small plants and young tender growth, to wilt, become stunted and misshapen, or die. Other damage includes yellow or white blotches on leaves; misshapen or aborted fruits, seeds, and buds; calluses, blemishes or depressions; and black pits on nuts. Tomatoes exhibit pale yellow spots and a white pithy area just under the skin at the puncture site. Peaches and other fruits may develop scarring and dimpling resulting in cat-facing or a pitted appearance. The seeds in soybean pods may be deformed, small, discolored, or shriveled.
Life Cycle The stink bug overwinters as an adult in protected areas such as under dead weeds, leaf litter, or the bark of trees. In early summer, the female lays clusters of eggs on the underside of leaves. These eggs are barrel or keg-shaped with a circular lid. In one to three weeks, the young hatch into wingless nymphs that resemble small adult stink bugs, although the coloration may differ from that of the adult. The nymphs will molt several times before developing wings and becoming an adult. The number of generations per year depends on the species.
Integrated Pest Management Strategies 1. Sanitation. Control weeds in susceptible crops and in areas adjacent to gardens to decrease breeding and overwintering habitat. It is important to remove weeds early in the growing season before stink bug populations increase or the loss of habitat may force pests to move into the garden. 2. Collect insects. Hand pick and destroy eggs and bugs. 3. Use natural controls. Encourage other natural predators such as parasitic wasps and flies by growing small-flowered plants. The unpleasant odor produced by stink bugs deters many predators but several bird species do consume these pests.
4. Use trap crops. Plant trap crops of mustard and treat that area with an appropriate pesticide. 5. Use insecticides. If damage is severe, use insecticidal soap, sabadilla, pyrethrin or permethrin (Eight).
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Spider mites are very common pests of outdoor plants. The mites suck juices from the plants, causing the plants to look dull and unhealthy. Mites also cause plants to lose vigor so that they may be unable to overcome a severe infestation, resulting in the plant's death. In Missouri, the most common outdoor spider mite is the two-spotted spider mite. The spruce spider mite infects conifers such as spruce, juniper, and arborvitae. They are less than 1/60th inch in size and difficult to see without a magnifying lens. They are not insects but rather a member of the spider family in which all members have eight legs.
Symptoms and Diagnosis Spider mites are among the most ubiquitous of pests, attacking a wide variety of field, garden, greenhouse, nursery, and ornamental plants, as well as several weed species. Infestations of two-spotted spider mites result in the bleaching and stippling of leaves. Severe infestations may cause entire leaves to become bronzed, curled, and completely enveloped in sheets of webbing. Damage to the foliage may result in leaf drop and reduction in the overall vitality of the plant. When a leaf or branch is tapped over a white sheet of paper, the mites appear as small specks that resemble dust or pepper and may be seen to move.
Life Cycle Adult female spider mites overwinter under loose bark, in cracks in the soil, in leaf litter, and in other protected places. In the spring, adults emerge and begin laying eggs. Each female typically deposits 70 eggs and lives for only 30 days. Eggs hatch in 5–7 days. As many as 10 generations may occur each year. The young look similar to the adults, but newly hatched young have only six legs and do not possess the characteristic dark spots on the back. Reproduction of the two-spotted spider mite is favored by hot, dry conditions, so serious damage is likely to occur in mid-July to September. The spruce spider mite is most active durng cooler weather in Spring and Fall.
Integrated Pest Management Strategies 1. Knock mites off plants with water. Spraying with a strong stream of water (particularly the undersides of leaves) will provide some control. Spray plants frequently to control future buildups. For severe infestations, affected plants or plant parts can be removed and destroyed. There are several natural predators that feed on spider mites. The use of chemical insecticides to control other garden pests can result in the death of these beneficial insects and a subsequent increase in the population of spider mites. 2. Use insecticidal soap. Insecticidal soaps specially formulated to kill insects and not damage plants are effective if used frequently until the problem is under control.
3. Use superior horticultural oil sprays. Highly refined oils sold as superior or horticultural oils are also very effective in controlling spider mites. The oil suffocates the mites. Unlike dormant oils, these oils are highly refined and under proper conditions, can be applied to plant foliage without damage. Follow label directions to avoid damage to some plants that may be sensitive. Superior oils are considered nontoxic and are less likely to kill beneficial insects. 4. Use chemical insecticides or miticides. A very safe product made from the seeds of a tropical tree is called Neem. It is commercially available under the name Margosan-O. Other chemical controls include malathion, bifenthrin, cyfluthrin, and kelthane. Be sure to follow all label directions when using pesticides. Many pesticides are very harmful to bees and fish when used improperly.
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
The phlox plant bug, Lopidea davisi, is an eye catching true bug. It is reddish orange and black. It is a piercing sucking insect with a long proboscis. It feeds mainly on phlox and can cause serious damage to phlox.
Symptoms and Diagnosis The phlox bug’s feeding causes white or light green spots on the leaves and buds that later show yellow stippling. The leaves then turn brown, curl, dry out and drop. The plant may become stunted and die. The bug feeds on leaves, stem terminals, flowers and seeds. It may be hard to see because it hides on the underside of leaves.
Life Cycle The phlox bug overwinters in the egg stage in dead phlox stems. It has two generations per year. The first generation appears in late spring, the second in mid to late summer. It undergoes incomplete metamorphosis. Integrated Pest Management Strategies 1. Practice good sanitation. Cut back and dispose of badly infested stems and leaves. Clean up stem and leaf litter of phlox and neighboring plants in winter before early spring.
2. Scout for nymphs and treat. Apply insecticidal soap to both the upper and underside of the leaves. Use a light horticultural oil. 3. Use chemical controls if warranted. Products listed for use include pyrethrins, permethrin or acephate (orthene), a systemic.
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
The large milkweed bug, Oncopeltus fasciatus, is colored orange-red and black. It has a long proboscis and is a piercing sucking insect. It feeds on the seeds, leaves and stems of milkweed (Asclepias). It is found in small groups on milkweed often on the stems, leaves and on the seed pods. The bodies of milkweed bugs contain toxic compounds derived from the sap which they suck from milkweed. Milkweed bugs are true bugs (Hemiptera) . They are used as research insects because they are easy to use in the laboratory, have a short life cycle and are easy to manipulate.
Symptoms and Diagnosis Milkweed bugs are more of a nuisance than a threat to milkweed plants. They feed on the seeds by piercing the seed pod and can be found in all stages of growth on the plants in mid to late summer. Life Cycle The milkweed bug undergoes incomplete metamorphosis. The nymphs look like adults but do not have full wings and their color pattern is different. They have five instars before they reach adulthood. Black wing pads appear early in their development. Eggs are a light lemon yellow changing to a reddish color. Incubation period is about four to five days. Each molt lasts five to six days. An adult will live for about one month. The insect overwinters as an adult.
Integrated Pest Management Strategies 1. Live with the damage. Milkweed bugs do little damage and are only present for a short period of time. Just living with the insects may be the most prudent thing to do. 2. Sanitation. Remove leaf litter and spent stalks in the fall to eliminate overwintering sites.
3. Use insecticidal soap. For quick control of an infestation insecticidal soaps are very effective and safe. Good coverage of the insects with the spray is necessary for it to be effective. 4. Use chemical insecticides. If necessary use chemical insecticides such as malathion or carbaryl.
0
0
文章
Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Mealybugs get their common name from white waxy secretions that cover their bodies. They are in the order Homoptera, which includes scales, whiteflies, and aphids, some species of which also cover their bodies with white waxy secretions, making field identification confusing. In warmer climates, mealybugs are serious pests on many citrus and ornamental plants. In this area, a wide variety of indoor and tropical plants summered outdoors or maintained in greenhouses can be attacked, as can many outdoor woody trees and shrubs, perennials, and summer annuals (e.g. begonia and coleus).
Some mealybug species can overwinter as nymphs and eggs. However, outside resurgences in the spring often come from introduction of mealybuginfested plants, with young nymphs from the infested plant colonizing nearby plants. Ants may also transport mealybugs from one plant to another. Symptoms and Diagnosis The typical female mealybug is 1/16 to 1/8 inch long with a white, waxy, oval body and functional legs. Some species are up to1/4 inch long. Males are much smaller, usually winged, and seldom seen.
Mealybugs infest all plant parts; feeder roots, root crowns, stems, twigs, leaves, flowers, and fruit. Here, mealybug infestations usually involve leaves (mostly undersides), stems, branches, and joints. They pierce and suck sap, excreting a sticky honeydew over leaves and stems that provides an excellent growth medium for a sooty-colored mold, giving the plant a dirty, sooty appearance. Ants are likely to be found feeding on the honeydew. Heavily infested plants will experience irregular or no growth, yellowed leaves, and significant leaf drop. Left untreated, plants can die.
Life Cycle Most species are egg layers, though some, especially under greenhouse-like conditions, give live birth. Normally, females lay about 500 eggs in a cottony mass. Hatching in 1 to 2 weeks, nymphs resemble adult females, but male and females then develop differently. Female nymphs increase in size with each molt, reaching adulthood in about a month. In contrast, male mealybugs go through two or so molts and then enter a pupal state in a flimsy cocoon before hatching as a tiny, fly-like, twowinged adult, incapable of feeding and soon to die. Outdoors, two generations a year are common. Eight generations a year are possible in optimal greenhouse-like conditions. Several developmental stages can usually be found simultaneously.
Integrated Pest Management Strategies 1. Prevent new infestations. Examine, quarantine for 2 or 3 weeks, and treat as necessary (see below) all new plants before placing them near mealybug-free plants. Examine all plants frequently for pests. 2. Conserve natural enemies. Predatory insects, such as lacewings, syrphid flies, ladybugs, and several small parasitic wasps, prey on outdoor mealybugs and can often keep their population within bounds. An introduced beetle, Cryptolaemus montrouzieri, the mealybug destroyer, is available commercially for release in greenhouses. Avoid unnecessary insecticide use to minimize damage to these beneficial insects.
3. Remove mealybugs manually. Depending on host plant size and scope of infestation, remove mealybugs with alcohol-dipped cotton swabs or physically knock them off plants with a forceful water spray and repeat as necessary. While unlikely to eliminate mealybugs, this approach can often keep the infestation within tolerable limits and will have no negative impact on beneficial insects. 4. Control ants. Ants are known to transport mealybugs from one plant to another, so physical barriers or chemical controls that do not adversely impact beneficial insects can be part of a prevention and control program. 5. Use insecticidal soap or superior horticulture oil sprays. If above methods fail to reduce mealybug populations to acceptable levels, use insecticidal soap sprays or superior horticultural oil spray following label directions carefully to avoid damage to sensitive plants and beneficial insects. If possible, treat when crawlers are present. Mealybugs hide under leaves and in crotches, so be sure spraying is thorough. Repeat application as necessary in accordance with label instructions.
6. Use chemical insecticides. Acephate (Orthene), bifenthrin, and pyrethrins are effective against mealybugs. Follow label directions carefully.
0
0
文章
97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112
相关用户
茉莉花
茉莉花
来自： Faye
朝阳
绿萝
绿萝
来自： 采元气少女✨
长沙
茉莉花
茉莉花
来自： 小松树快乐
长沙
绿萝
绿萝
来自： 水中月
赣州市
茉莉花
茉莉花
来自： 艺源
广安市
芦荟
芦荟
来自： 采元气少女✨
长沙
茉莉花
茉莉花
来自： 阿罗
南昌
芦荟
芦荟
来自： Bailu_Yuan
北京
白掌
白掌
来自： 韩凯
武汉
绿萝
绿萝
来自： 阿罗
南昌
举报 反馈

您有什么意见或建议，欢迎给我们留言。

请输入内容
提交
取消
设置
VIP
退出登录
关闭
分享

分享好文，绿手指（GFinger）养花助手见证你的成长。

关闭
请前往电脑端操作

请前往电脑端操作

关闭
转发
插入话题
提醒好友
发布
/
提交成功 提交失败 最大图片质量 成功 警告 啊哦！ 出了点小问题 转发成功 举报 转发 显示更多 _zh 文章 求助 动态 刚刚 回复 邀你一起尬聊！ 表情 添加图片 评论 仅支持 .JPG .JPEG .PNG .GIF 图片尺寸不得小于300*300px 最少上传一张图片 请输入内容