动态第707页 - 绿手指 - 养花技巧、花生病了怎么办、花园打理和设计

2017年09月19日

A major agricultural pest, the tomato fruitworm can feed on many different plants. Hence, the species has been given many different common names including cotton bollworm and corn earworm. It has also been known to consume tobacco, legumes, grain sorghum, and other vegetables and fruits.[图片]The pest occurs throughout the Western Hemisphere. In warm areas several generations occur annually. North of Interstate 70 the pupae cannot overwinter in the soil. Most populations enter Missouri as migrating swarms of moths from the southern United States. Symptoms and Diagnosis Tomato Fruitworm The evidence of tomato fruitworm is usually a visible black hole at the base of the fruit stem. When the tomato is cut, tunneling is evident and the cavity may contain frass and decay as well as the worm itself.[图片]Corn Earworm Most evidence of corn earworm is at the tip of the ear—damaged kernels, frass, the worm itself, and possibly resulting fungal disease. Life Cycle The eggs of this pest are each about ½ the diameter of a pinhead. They are spherical with a flattened base and white or cream in color, developing a reddish-brown band just prior to the young hatching. Depending on the temperature, the young hatch in 2-10 days.[图片]The larvae measure 11/2-2 inches when fully grown and may be green, brown, pink, yellow, or even black. They have tan heads and alternating light and dark stripes run lengthwise on the bodies. The skin is coarse and has small, thorn-like projections called tubercles. The larval stage lasts 14-21 days. When the larvae are finished feeding the worms drop to the ground and enter the soil near the base of the plant where they transform into shiny brown pupae. During summer adults emerge in 10-14 days and start the cycle over. In the fall, south of Interstate 70 the pupae survive winter 2-6 inches below the soil surface. The moths emerge from overwintering pupae during late April and May.[图片]Adult moths are usually light yellow-olive in color with a single dark spot near the center of each forewing. Each forewing has 3 slanted dark bands. Their hind wings are white. The cycle repeats itself with the moths laying eggs at dusk on host plants on warm days. The total generation time is 28-35 days. The moths lay eggs on the foliage of the tomato plants. With corn the moths usually lay eggs on corn tassels and silks but the larvae will migrate down the silk to the ear tips within one hour of hatching where they will feed on the developing kernels protected by the husk. When larval development is complete the larvae chew through the husk and drop to the ground to begin the pupal stage.[图片]Integrated Pest Management Strategies Tomato Fruitworm 1. Sanitation. Collect and dispose of any infested fruit before the insect completes its life cycle. 2. Introduce parasitic wasps. Do not remove parasitized caterpillars. Instead, leave them to assist as a natural, biological control. 3. Dusting with diatomaceous earth may kill larvae. 4. Use of a biological pesticide such as Bt can kill larvae during the warmest months.[图片]5. Use chemical pesticides. The pest has developed a resistance to many pesticides but the following pesticides are often used: esfenvalerate (Asana), methomyl (Lannate), azinphos-methyl (Guthion), carbaryl (Sevin), or pyrethrin. These must be applied before the worm enters the fruit. 6. Minimize local food sources. Avoid planting tomatoes near corn or other hosts of the fruitworm to minimize populations.

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2017年09月19日

The squash vine borer, Melittia cucurbitae, is native to Missouri. It is a serious pest of both summer and winter squash. The insect will also attack cucumbers, pumpkins, muskmelons, and watermelons.[图片]Symptoms and Diagnosis The first symptom is generally wilting of part or all of the plant. At the base of the plant, moist, sawdustlike debris (frass) can be seen piled outside small holes in the stem. If the stem is split lengthwise, frass and one or more fat, white caterpillars with brown heads can be found tunneling in the stem.[图片]Life Cycle Squash vine borers overwinter as pupae in a silken, dirt-covered cocoon one or two inches below the soil surface. Adult squash vine borers are day-flying clear wing moths a little over 1/2 inch long with reddish-white bodies and black bands on their abdomen. They have a distinctive wasp-like appearance. Their forewings are greenish-brown but their hind wings are transparent. The insect has a wing span of about 1-1/2 inches. The hind legs are orange and black, long, and hairy. Adults emerge in early to mid-June through July, first appearing about the time cucurbits begin to bloom, and lay 1/10 inch long, brown or reddish-brown eggs in rows or clusters on all parts of the plant but predominately on the stem. Upon hatching, the larvae immediately bore into the stems and remain there until full grown; then full-grown larvae move into the soil to overwinter. There is one generation a year.[图片]Integrated Pest Management Strategies 1. Remove and destroy the borers. Once detected the borers need to be killed or removed from the stem. The easiest way is to slit the stem above where the hole and frass is noticed and remove the insect or insects from the stem. Cover the stem area with soil to encourage new roots to form above the damaged area. This may save the plant, depending upon the severity of the damage. Dip your knife in a 10% solution of bleach before making the next cut in order to prevent transmitting wilt or rot organisms, which might be present.[图片]2. Biological control. Borers can also be killed by injecting a solution of Bacillus thuringiensis (Bt) into the infested stem, using a disposable syringe or wood working glue injector. Follow the disinfecting and mounding procedures discussed above. This method can also be used as a preventive if injected into the stem 1-1/2 inches above ground level when the plants first begin to flower. 3. Promote rooting along stems. About every five leaves or so, place a small mound of soil over the stem to encourage rooting. Then if borers kill the lower part of the plant, the upper parts will have roots to recover.[图片]4. Clean up plant debris. Plants killed by borer activity should be pulled up. Place these plants in a large, clear, plastic bag and leave it in the sun for a week or so. This will kill any borers still in the debris. In the fall, clean up and dispose of old plant debris. Leave the soil uncovered for a day or so to give birds a chance to clean up any insects on the ground. 5. Protect plants with a row cover. In subsequent years, early in the season, plants can be protected with floating row covers secured on all edges to prevent flying adults from laying eggs on the plants. The cover needs to be removed when the plants begin flowering.[图片]6. Use chemical controls with caution. Properly timed chemical pesticides can be effective. Scout plants early and often, watching for the first signs of borer’s frass at entrance holes in the stems indicating egg laying has occurred. Two insecticide applications spaced 5 to 7 days apart will control the majority of newly hatched larvae before they enter the vines. Chemical controls are not effective once the borer is inside the stem. Sevin can be applied to crowns and runners when the plants begin to vine. Apply late in the day because Sevin is very toxic to bees that frequent vine crops and facilitate pollination. Bees carry grains of Sevin dust back to the hive where it can kill many bees.[图片]

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2017年09月19日

Squash bugs, Anasa tristis, are sometimes mistakenly called stink bugs because they may give off a foul odor when squashed. Stink bugs have wider shieldshaped bodies than squash bugs. Squash bugs are pests on all cucurbits including cucumbers, muskmelons, pumpkins, squash, and watermelon. Squash and pumpkins are the most susceptible to squash bug attack.[图片]Symptoms and Diagnosis Squash bugs destroy plant tissue by sucking out the sap from leaves and stems and depleting nutrients from the plant. This feeding causes leaves to wilt and dry out. They eventually turn black and fall off the vine. Adult pests can be seen feeding on main stems. Nymphs are more likely to be found feeding on the undersides of leaves.[图片]Life Cycle Adult squash bugs are brown or black, flat-backed, and 1/2 to 3/4 inch long. In the spring when plants begin to develop runners, elliptical, yellow or brown eggs are laid in groups on the undersides of the leaves. Immature stages (nymphs) have gray-green bodies and red or black legs. Adults overwinter in garden debris and emerge the following spring. There is only one generation per year.[图片]Integrated Pest Management Strategies 1. The key to management is early detection and control. There are two critical times when plants are most vulnerable to damage. First is when plants are seedlings with undeveloped root systems and vulnerable to damage from overwintering adults. The second critical time is as plants begin to flower and eggs first begin to hatch. Handpick bugs and eggs and destroy them by dropping them in a bucket of soapy water. Egg masses are either orange-yellow or bronze in color and can usually be found on the undersides of leaves.[图片]2. Cover young plants with row covers of nylon netting or cheesecloth to deter bugs from feeding on them. 3. Plant resistant squash varieties like ‘Butternut’, ‘Royal Acorn’, ‘Sweet Cheese’, and ‘Black Zucchini’. 4. Do a thorough garden cleanup in the fall in order to remove overwintering sites. Tilling plants into the ground after the growing season helps to expose the overwintering stage of the squash bug and reduce their populations.[图片]5. Use an insecticidal soap every 3 days for the first 2 weeks after squash bugs first emerge in the spring. Insecticidal soaps are contact insecticides, so take care to make sure that all plant surfaces are covered, especially the undersides. 6. Dust plants with permethrin or sabadilla.

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2017年09月19日

The presence of white butterflies fluttering around the garden signals the start of a possible infestation of imported cabbageworm. The adult cabbage butterfly, Pieris rapae, is white with black tips and one or two black spots on the forewings. The larva (the cabbageworm) is a bright green caterpillar clothed in fine, short hairs that give it a velvety appearance. The imported cabbageworm will attack all growth stages in cole crops.[图片]Symptoms and Diagnosis When the adult butterflies are observed fluttering around the garden, the larvae and the damage they do will soon be obvious. All stages of growth in cole crops can be attacked by the larvae, but they are often observed on the underside of developing leaves. The outer leaves may become riddled with large ragged holes from the larvae's feeding. If leaves are parted, masses of greenish-brown excrement can be found at the base of the leaves. The larval feces often contaminate edible portions of the plant.[图片]Life Cycle The imported cabbageworm overwinters as a pupa attached to plant debris. The adult butterfly emerges the following spring and flies about the garden area during daylight hours. The elongated, yellow, ribbed eggs (shaped somewhat like a football) are laid on the underside of the foliage. The eggs hatch in 7 days. The emerging caterpillars are velvety green. Theyfeed on all cole crops for about 15 days. After this, they pupate, and new adults emerge in about 10 days. There are 2 or 3 generations of imported cabbageworm each year.[图片]Integrated Pest Management Strategies 1. Handpick the cabbageworms off of the underside of the leaves while plants are young. This procedure is effective when plants are young or if only a few larvae are present. 2. Use row covers. Position row covers or netting over plants to prevent egg laying by the butterflies. Start controls before the white cabbage butterflies are seen fluttering around the yard. 3. Fall sanitation. Clean up and remove infested plant material after harvest to eliminate overwintering sites of the pupae.[图片]4. Use Btk spray or dust. Dust plants with Bacillus thuringiensis kurstaki (Btk). Begin treating the plants when white butterflies are first noticed and the cabbageworms are still small. It may take several days before the insects die after feeding on Btk, but feeding will usually stop shortly after the plants are treated. 5. Chemical controls. Spray with insecticidal soap, carbaryl (Sevin), malathion, cyfluthrin, or permethrin when plants and larvae are young and damage is increasing. The larvae are more easily killed when young and this will minimize the amount of insecticide needed for control. Carbaryl (Sevin), the active ingredient in Sevin, is very toxic to honey bees; do not use near flowering plants.

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2017年09月19日

The tomato hornworm, Manduca quinquemaculata, and the tobacco hornworm, M. sexta, are common pests of tomato, tobacco, eggplant, pepper, and potato throughout most of the United States. The hornworms are large (up to 4 inches long), bright green caterpillars with diagonal white stripes and a prominent horn at the rear. The two species have slightly different markings. The tomato hornworm has 8 diagonal white stripes on each side; the horn is straight and black. The tobacco hornworm has 7 diagonal white stripes; its horn is curved and red.[图片]Symptoms and Diagnosis Larvae of both species consume entire leaves and small stems and may chew large pieces from green fruit. Hornworm damage is obvious when the infestation is moderate to heavy because of the large amount of defoliation. Search for the large caterpillars. Large, black droppings on the leaves or ground beneath the plant will usually indicate the presence of hornworms.[图片]Life Cycle Hornworms overwinter in the soil as hard-shelled, brown pupae. Large adult moths, known as sphinx or hummingbird moths, emerge in May or June and deposit spherical green eggs on the undersides of leaves of host plants. The larvae hatch a week later and feed on foliage and fruit for three to four weeks until reaching full development. Pupation occurs in the soil and adults emerge 2 to 4 weeks later to lay second generation eggs. In Missouri there may be one or two generations depending on location.[图片]Integrated Pest Management Strategies 1. Handpick caterpillars. Handpicking is usually all that is needed to control these pests in a home garden. Larvae are most easily located in early morning, often on the exterior of the plant. Leave any caterpillars with small white cocoons on their backs; they are being parasitized by a braconid wasp, which will soon produce more wasps to control them. 2. Biological control. Bacterial insecticides containing Bacillus thuringiensis kurstaki (Btk) are effective when larvae are smaller. It may take several days for the caterpillars to die, but feeding generally stops shortly after treatment.[图片]3. Cultivation. Disking or rototilling after harvest destroys pupae in soil, reducing overwintering numbers. 4. Chemical control. An application of carbaryl (Sevin) or permethrin will effectively control hornworms if handpicking is impractical. However, chemical control will also reduce the numbers of beneficial insects.

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2017年09月19日

Cucumber beetles feed on all cucurbits from seedling emergence to harvest. Feeding by the adults causes scarring on stems and fruit of cucurbits. However, the most important damage by the insect is the transmission of bacterial wilt, which is lethal to the vine. Adult beetles also may feed on a number of different plants, including blossoms of rose and zinnia. Cucumber beetles are about 1/3 inch long. They have a black head and their wing covers are either green with 12 black spots or alternating black and yellow stripes. They fly readily when disturbed.[图片]Symptoms and Diagnosis Adult beetles damage cucurbits in several ways. They may feed on young seedlings or transplants, completely consuming stems and cotyledons, and killing or stunting the young plants. The adult also damages more mature vines and fruit by chewing holes in leaves and rinds. The worst damage by the beetle is the transmission of bacterial wilt when the plants are young. The infected vines will gradually wilt and die.[图片]Life Cycle Adult beetles overwinter in woodlands, fence rows, under fallen leaves, under bark, and on weeds. In early summer when temperatures near 70 degrees F, the beetles become active and feed on young plants. After mating, eggs are laid in the soil near plant bases. Emerging larvae feed on plant roots for 3–6 weeks. Emerging adults appear during midsummer and feed on above ground plant parts of host plants. There are 2–3 generations a year.[图片]Integrated Pest Management Strategies 1. Use row covers on young plants to exclude the beetles. Use floating row covers, screens, or cheesecloth to protect seedlings. Keep the covers in place until the plants begin to bloom. 2. Plant a trap crop of squash or pumpkin to attract beetles away from cucumber plants. Time the planting of the trap crop to emerge one week before the main cucurbit crop. The presence of cucumber beetles on the trap crop can help you time control practices. Trap crops can be pulled from the garden and the insects and eggs on the crop can be destroyed.[图片]3. Plant tolerant varieties. Varieties of cucumbers tolerant to bacterial wilt are available. A couple of these are ‘County Fair ‘83’ or ‘Saladin’. Some varieties are less appealing as food for cucumber beetles. These include ‘Ashley’, ‘Chipper’, and ‘Gemini’ cucumber. ‘Heart of Gold’ muskmelon and ‘Crimson Sweet’ watermelon also resist attack from beetles. 4. Delay planting time. Planting time can influence beetle feeding damage and wilt transmission. By planting early to mid-June, some beetle feeding can be eliminated. However, this eliminates early harvest and may be too late for some varieties.[图片]5. Insecticidal sprays may be needed if populations of cucumber beetles are high. Treat early in the season before over wintering beetles have a chance to lay eggs. Pesticides registered for use include carbaryl (Sevin), endosulfan (Thiodan), permethrin and pyrethrins.

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2017年09月19日

The bean leaf beetle, Ceratoma trifucata, is one of the most serious pests of commercial soybeans. It is an occasional pest of snap beans, soybeans and other similar crops in the home vegetable garden.[图片]Symptoms and Diagnosis Adult bean leaf beetles prefer tender young plant tissue and they can cause significant damage by defoliating and killing young plants. Older plants will be less vigorous and have decreased yields. Feeding damage to leaves appears as approximately 1/8 inch diameter round holes between major veins. (Grasshoppers or caterpillars cause larger irregular holes or jagged leaf margins; flea beetles cause smaller holes.) There may also be chewing damage on the pods. While this damage may cause complete pod loss or spread disease in commercial soybeans, it is generally just cosmetic in home gardens. Although the damage caused by the larvae is less severe, they feed on bean roots, especially the root nodules, decreasing the plant’s ability to fix nitrogen.[图片]Life Cycle Bean leaf beetle adults are about ¼ inch long and are commonly greenish yellow to tan with 4 black spots. However, they may also be red, orange, or gray with spots, stripes, both or none. They are distinguished from other beetles by the presence of a black triangle at the top of their wing covers. The beetles overwinter as adults in leaf litter and become active in spring when the temperatures reach 50 to 55 degrees F. The females lay 130 to 200 reddish oval eggs in the upper 5 inches of the soil at the base of plant stems. The larvae, which are white with a black head, emerge in 5-7 days and feed on underground plant parts for 3 to 6 weeks. After a pupal stage of about one week, the adults emerge and begin to eat, mate and lay eggs. In Missouri, a second generation matures in September and these adults will move to overwintering sites in October.[图片]Integrated Pest Management Strategies 1. Practice good garden sanitation by removing leaf litter and controlling weeds, especially those in the legume family. 2. Plant beans later in spring to avoid adults as they emerge from their overwintering sites.[图片]3. Handpick adults and drop them into a container of soapy water if the bean leaf beetle population is small. Since the beetles tend to tumble off the leaves when disturbed, it may help to hold the container under the plants. 4. Spray with an insecticide. Pesticides such as permethrin is an option. Be sure to use an insecticide that is registered for bean leaf beetles on your crop and follow the directions carefully.

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2017年09月19日

Several viruses infect tomatoes and peppers. The two most common are tobacco mosaic virus and cucumber mosaic virus.[图片]Symptoms and Diagnosis Symptoms vary depending upon the virus and strain, the plant, time of year, and environmental conditions. The most common symptoms include leaf mottling; puckering or curling; stem and petiole streaking; rough, deformed or spotted fruit; stunted plants; and blossom and fruit drop. Some viruses cause the leaves of tomatoes to become fernlike or develop a thin "shoestring" appearance. Symptoms may be confused with herbicide damage.[图片]Life Cycle Viruses have no active way of penetrating plant parts. They rely upon mechanical wounds, infected seeds, and being carried in the bodies of insects for transmission. The virus can also be present in tobacco and transmitted to plants by the hands of people who smoke. Once inside the plant cells, the virus replicates. The virus does not usually kill the plant and takes over the metabolic processes of the leaf, resulting in abnormal cell functioning and growth.[图片]Integrated Pest Management Strategies 1. Remove diseased plants. Once a plant is infected, there are no practical field methods of curing the plant of the virus. Remove infected plants as soon as they are noticed to reduce the chance of spreading the disease. 2. Follow strict sanitation. Persons handling plants must refrain from the use of tobacco or risk infecting the plants. Remove weeds in the area that could harbor the virus.[图片]3. Control insects. Because insects, especially aphids, vector cucumber mosaic, make every effort to keep insects under control using sticky traps or insecticides. 4. Plant resistant varieties. In subsequent years, plant varieties that are resistant to the most common viruses. Look for varieties that are marked TMV or CMV after the variety name.

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2017年09月19日

Viral infections can reduce plant vigor by disrupting cellular functioning, but do not commonly kill plants. Tobacco mosaic is one of the most highly persistent tomato diseases because it can remain viable without a host for many years and it is able to withstand high heat. The virus is spread primarily by mechanical methods. Gardeners can contaminate their hands when they touch tobacco products or infected plants and weeds and spread the virus to healthy plants.[图片]Symptoms and Diagnosis Tobacco mosaic virus is not as distinct as other viruses, but yellow-green mottling on leaves is the most characteristic symptom of the disease. Infected plants have stunted growth, and flowers and leaflets may be curled, distorted, and smaller than normal in size. Open blooms may have brown streaks through them. Yellow, chlorotic spotting is characteristic of pepper plants that are infected.[图片]Life Cycle Tobacco mosaic virus survives on infected seeds, plant debris, and even clothing for months or years. The virus enters plants through wounds sustained in transplanting or pruning. It spreads rapidly once it is in the host. The virus can remain viable for years on dried plant debris and is extremely tolerant of very high temperatures. Tobacco products are the most common source of inoculum; smokers can infect plants by handling them. The virus is not spread by aphids.[图片]Integrated Pest Management Strategies 1. Remove and destroy infected plants. Pull plants with mosaic symptoms immediately. Remove the debris from the garden area and bury them if possible. 2. Keep your garden weed-free. Some weed may be harboring the virus. These represent sources of inoculum.[图片]3. Always wash your hands thoroughly and disinfect tools. Before handling plants, wash with soap and water, especially if you're a smoker. 4. Plant resistant varieties of tomato. Suggested varieties include: ‘Big Pick’, ‘Celebrity’, ‘President’, and ‘Park's Extra Early Hybrid’. Other resistant varieties will be labeled TMV resistant.

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2017年09月19日

Septoria leaf spot is caused by a fungus, Septoria lycopersici. It is one of the most destructive diseases of tomato foliage and is particularly severe in areas where wet, humid weather persists for extended periods.[图片]Symptoms and Diagnosis Septoria leaf spot usually appears on the lower leaves after the first fruit sets. Spots are circular, about 1/16 to 1/4 inch in diameter with dark brown margins and tan to gray centers with small black fruiting structures. Characteristically, there are many spots per leaf. This disease spreads upwards from oldest to youngest growth. If leaf lesions are numerous, the leaves turn slightly yellow, then brown, and then wither. Fruit infection is rare.[图片]Life Cycle The fungus overwinters on infected tomato debris or on weeds in the nightshade family, the same family to which tomatoes belong. The fungus can also survive on equipment such as plant stakes and cages. Long periods of high relative humidity, temperatures of 60–80 degrees F, and leaf wetness are ideal conditions for development and spread of the pathogen. Integrated Pest Management Strategies 1. Remove diseased leaves. If caught early, the lower infected leaves can be removed and burned or destroyed. However, removing leaves above where fruit has formed will weaken the plant and expose fruit to sunscald. At the end of the season, collect all foliage from infected plants and dispose of or bury. Do not compost diseased plants.[图片]2. Improve air circulation around the plants. If the plants can still be handled without breaking them, stake or cage the plants to raise them off the ground and promote faster drying of the foliage. 3. Mulch around the base of the plants. Mulching will reduce splashing soil, which may contain fungal spores associated with debris. Apply mulch after the soil has warmed. 4. Do not use overhead watering. Overhead watering facilitates infection and spreads the disease. Use a soaker hose at the base of the plant to keep the foliage dry. Water early in the day.[图片]5. Control weeds. Nightshade and horsenettle are frequently hosts of Septoria leaf spot and should be eradicated around the garden site. 6. Use crop rotation. Next year do not plant tomatoes back in the same location where diseased tomatoes grew. Wait 1–2 years before replanting tomatoes in these areas.[图片]7. Use fungicidal sprays. If the above measures do not control the disease, you may want to use fungicidal sprays. Fungicides will not cure infected leaves, but they will protect new leaves from becoming infected. Apply at 7 to 10 day intervals throughout the season. Apply chlorothalonil, maneb, macozeb, or a copper-based fungicide, such as Bordeaux mixture, copper hydroxide, copper sulfate, or copper oxychloride sulfate. Follow harvest restrictions listed on the pesticide label.

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