Web on tomatoes how to save tomato beds from a dangerous pest

Little Red Spiders on My Tomato Plant

Keep tomato plants vigorous and healthy to prevent future mite infestations.

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Finding little red spiders on your tomato plant (Lycopersicon esculentum) can be a disheartening experience, especially after trying your best to keep this garden staple pest-free. The tiny red bugs plaguing your annual fruit-bearing plant are spider mites, a pest that feeds on the phloem sap inside the tomato plant. Home gardeners have several control options available to combat these annoying pests.

Spider Mites

Spider mites are tiny sap-sucking pests with red, yellow, green or brown-colored bodies, and typically appear as microscopic spiders or dots that move across the leaf surface. They tend to congregate on the undersides of leaves and insert their mouthparts into tender areas within the tomato plant, sucking out the cell content. White webbing on the leaves, stems and fruit is a sign your tomato plants may be hosting spider mites. Plants under water stress are more likely to come under attack by spider mites than plants with proper irrigation. Spider mites also are most prevalent in hot, dusty conditions and can overwinter under fallen plant debris.

As the spider mites feed upon the tomato plants, small dots will appear where the mites inserted their mouthpart. Their feeding results in poor plant growth, loss of vigor and discolored leaves that may drop from the plant. Thankfully, damage is rarely life threatening to the tomato plants unless the infestation is severe. However, if the infestation is large and the loss of leaves is significant, the plant may experience poor yield.

Non-Chemical Control

A simple way to control spider mites is to wash the annoying pests off the tomato plants with a water hose. The strong stream of water will forcefully remove the mites, keeping their numbers under control. However, you may have to repeat the treatment every few days to eradicate the mites from the tomatoes. Another non-chemical method to controlling spider mites is utilizing beneficial insects that prey on the mites. Lacewing larvae, spider mite destroyer lady beetle and minute pirate bug are a few of the insects that attack spider mites. Adding annual plants in the Umbelliferae and Compositae family — such as parsley (Petroselinum crispum) and sunflower (Helianthus annuus) — will lure beneficial insects to your garden, according to Cornell University.

Chemical Control

Spider mites generally become a problem when chemical pesticides are used, according to the University of California Statewide Integrated Pest Management Program website. These pesticides often kill beneficial insects that keep pests under control. Without them, the spider mites’ numbers begin to grow. If chemical control is the only option available, consider treating the tomato plants with ready-to-use insecticidal soap once every 7 to 14 days as needed. Insecticidal soap is a safer option with a low toxicity level to beneficial insects, humans and mammals. It also breaks down quickly, and won’t pollute the environment or your vegetables with toxins.

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Tomato Hornworms

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The Summer Solstice is Friday. Get ready!
Here are 10 things you should know about the first day of summer.

Big, fat, and green! Here are tips on how to identify, control, and get rid of tomato hornworms in your garden.

What Are Hornworms?

If you’ve ever grown tomatoes, chances are good that you’ve dealt with these green caterpillar pests. There are two main garden pest species, tomato hornworms and tobacco hornworms, which can be found in most regions of the U.S. and in southern Canada. Both species can ruin your tomato crop in record time! They also feed on other plants in the Solanaceae (nightshade) family: eggplants, peppers, tobacco, and potatoes. They blend in quite easily with the green foliage and feed non-stop, creating spotty and chewed leaves and fruit.

Tomato (and tobacco) hornworms live according to the following life cycle:

  • In late spring, large adult moths lay eggs on the undersides of foliage, which will hatch within a week. The adult moths are easily recognizable; they’re commonly called sphinx or hummingbird moths.
  • Caterpillar larvae will hatch in late spring and feed for 4–6 weeks before creating a cocoon, overwintering in their pupal state in the soil. If the weather is warm enough, larvae may only burrow for as little as 2–3 weeks.
  • Moths will emerge in the spring, and will then lay eggs once again. More than one generation a year may be possible in warmer climates.


Tomato hornworm moth (female). Look out for the moths in late spring. Photo by Didier Descouens/Wikimedia Commons.

How to Identify Tomato Hornworms

Hornworms can be up to 5 inches long—which can be quite a shock when you first come across one! They do the most damage in the caterpillar—or larval—stage. They are pale green with white and black markings, plus a horn-like protrusion stemming from their rear. (Don’t worry, they aren’t able to sting or bite!) The caterpillar also has eight V-shaped stripes on its green body. Tomato hornworms come from a mottled brown-gray moth (see picture, above).

The larvae blend in really well with the plant greenery. Just get used to a daily patrol, looking for hornworm eggs and small caterpillars. Here are some cues of infestations:

  • Hornworms tend to start feeding from the top of the plant; look for chewed or missing leaves.
  • Look closely at the TOP of your tomato leaves for dark green or black droppings left by the larvae feeding on the leaves. Then look at the underside of leaves and you’ll likely find a hornworm.
  • Look for stems missing some leaves and wilted leaves hanging down. You may find white cocoons and their hornworm hosts nearby.


Tomato hornworm

Tomato vs. Tobacco Hornworms

There are a few species of hornworms that inhabit North American gardens, including tomato hornworms (Manduca quinquemaculata) and tobacco hornworms (Manduca sexta). Both species feed on common garden plants like tomatoes, potatoes, peppers, and eggplants. Here’s how to tell which caterpillar is which:

  • Tobacco hornworms have parallel white stripes; tomato hornworms have white V–shaped markings.
  • Tobacco hornworms have black spots lining each of their stripes; tomato hornworms do not.
  • Tobacco hornworms have a red “horn” on their tail end; tomato hornworms have a black horn.


Can you tell which hornworm this is? (It’s a tobacco hornworm! Notice the white stripes with dotted black lines and a red “horn.”)

Tomato Hornworm Damage

If you see leaves with large holes and severe defoliation, devoured flowers, and/or scarring on fruit surfaces, you might have tomato or tobacco hornworms. The fruit also may be damaged by sunscald because of the reduced foliage cover.

www.almanac.com

How the humble marigold outsmarts a devastating tomato pest

Scientists have revealed for the first time the natural weapon used by marigolds to protect tomato plants against destructive whiteflies.

Researchers from Newcastle University’s School of Natural and Environmental Sciences, carried out a study to prove what gardeners around the world have known for generations — marigolds repel tomato whiteflies.

Publishing their findings today (1 March) in the journal PLOS ONE, the experts have identified limonene — released by marigolds — as the main component responsible for keeping tomato whiteflies at bay. The insects find the smell of limonene repellent and are slowed down by the powerful chemical.

Large-scale application

The findings of the study have the potential to pave the way to developing a safer and cheaper alternatives to pesticides.

Since limonene repels the whitefly without killing them, using the chemical shouldn’t lead to resistance, and the study has shown that it doesn’t affect the quality of the produce. All it takes to deter the whiteflies is interspersing marigolds in tomato plots, or hang little pots of limonene in among the tomato plants so that the smell can disperse out into the tomato foliage.

In fact, the research team, led by Dr Colin Tosh and Niall Conboy, has shown that may be possible in to develop a product, similar to an air freshener, containing pure limonene, than can be hung in glasshouses to confuse the whiteflies by exposing them to a blast of limonene.

Newcastle University PhD student Niall said: “We spoke to many gardeners who knew marigolds were effective in protecting tomatoes against whiteflies, but it has never been tested scientifically.

“We found that the chemical which was released in the highest abundance from marigolds was limonene. This is exciting because limonene is inexpensive, it’s not harmful and it’s a lot less risky to use than pesticides, particularly when you don’t apply it to the crop and it is only a weak scent in the air.

“Most pesticides are sprayed onto the crops. This doesn’t only kill the pest that is targeted, it kills absolutely everything, including the natural enemies of the pest.”

Limonene makes up around 90% of the oil in citrus peel and is commonly found in household air fresheners and mosquito repellent.

Dr Tosh said: “There is great potential to use limonene indoors and outdoors, either by planting marigolds near tomatoes, or by using pods of pure limonene. Another important benefit of using limonene is that it’s not only safe to bees, but the marigolds provide nectar for the bees which are vital for pollination.

“Any alternative methods of whitefly control that can reduce pesticide use and introduce greater plant and animal diversity into agricultural and horticultural systems should be welcomed.”

The researchers carried out two big glasshouse trials. Working with French marigolds in the first experiment, they established that the repellent effect works and that marigolds are an effective companion plant to keep whiteflies away from the tomato plants.

For the second experiment, the team used a machine that allowed them to analyse the gaseous and volatile chemicals released by the plants. Through this they were able to pinpoint which chemical was released from the marigolds. They also determined that interspersing marigolds with other companion plants, that whiteflies don’t like, doesn’t increase or decrease the repellent effect. It means that non-host plants of the whiteflies can repel them, not just marigolds.

A notorious pest

Whitefly adults are tiny, moth-like insects that feed on plant sap. They cause severe produce losses to an array of crops through transmission of a number of plant viruses and encouraging mould growth on the plant.

Dr Tosh said: “Direct feeding from both adults and larvae results in honeydew secretion at a very high rate. Honeydew secretion that covers the leaves reduces the photosynthetic capacity of the plant and renders fruit unmarketable.”

Further studies will focus on developing a three companion plant mixture that will repel three major insect pests of tomato — whiteflies, spider mites and thrips.

Longer term, the researchers aim to publish a guide focussing on companion plants as an alternative to pesticides, which would be suitable across range of horticultural problems.

Story Source:

Materials provided by Newcastle University. Note: Content may be edited for style and length.

www.sciencedaily.com

Pests & Disease

A number of tomato problems (insect, disease, environmental) can wreak havoc on your favorite plants. We identify them here and list earth-friendly solutions for getting rid of them.

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Home-grown tomatoes are a source of pride, a thing of beauty, and beyond-description delicious. Whether heirlooms of the sort our grandmothers knew or a tried and true northern variety that gives us success despite June and September frosts, a perfect tomato is an achievement. If that perfect tomato is organic, kept pest and disease free without the use of harmful chemicals, it’s priceless.

To produce that perfect tomato, be alert. Keep an eye on your plant’s health, look for larvae and other insects, watch for signs of disease. And if you find them, come here for advice on what to do. Remember: part of a quick reaction is having the most efficient tools, products, and methods ready for when trouble shows its head. Be prepared.

The first task when facing an unhappy tomato plant is to diagnose the problem. Websites with pictures can be enormously helpful here. One of the best is Texas A&M’s Tomato Disorders page, which presents photographs under five headings, green fruit, ripe fruit, stems, leaves, and roots. What you can’t do on that site, though, is type in a suspected issue and call up an associated picture. One of the best sites comes out of Maine titled Common Tomato Problems: Diseases and Disorders.

Garden Pests

If you see an insect on or near your beloved tomato plants, don’t rush for the nearest insecticide. Many insects are beneficial to the garden or at least neutral. That insect may be feeding on the very pests you’re having trouble with. Even if you’re looking at an enemy, one insect does not make an infestation. It’s best to identify the intruder and the level of damage it’s causing before implementing steps in managing insect pests in vegetable gardens (hat tip to Cornell University).

Aphids
These are those dense clusters of tiny insects you may see on the stems or new growth of your tomato plants. While small numbers are not a big deal — don’t be afraid to crush them with your thumb — large infestations can gradually injure or even kill plants. Pinch off foliage where aphids are densely concentrated, and throw these discarded bits into the garbage, not on the ground. If the problem then seems manageable, release beneficial insects such as ladybugs or lacewings. If it doesn’t, go for the insecticidal soap that uses natural fats and plant oils (Organic Material Review Institute listed) or natural sprays, many of which are listed for organic production.

Cutworms
These are the tiny grub-like caterpillars that feed on young plant stems at night, frequently felling seedlings by eating right through them at ground level. Prevent damage by placing collars around seedlings. You can make these of paper, cardboard, aluminum foil, or an aluminum pie plate about ten inches long and four high, bent to form a circle or cylinder and stapled. Sink the collars about an inch into soil around individual seedlings, letting three inches show above the ground to deter high-climbers.

Flea Beetles
A potentially devastating visitor, the flea beetle (so-named because it resembles and jumps like a flea) attacks from both sides: adults eat foliage, leaving numerous small holes, while larvae feed on roots. They’re not picky, these beetles; they’ll go for corn, cabbage, lettuce, and all members of the Solanaceae family: peppers, eggplant, potatoes, and tomatoes. Unless levels are very high, damage can be minimized and controlled by using preventative measures.

  • Clear away or plow under weeds and debris, in which adults over-winter.
  • Place yellow sticky-traps to monitor levels and capture adults.
  • Use row covers. Young plants are more vulnerable to damage, so cover them to keep beetles off.
  • Dusting plants with diatomaceous earth (a chalky stone composed of marine fossils, ground to powder) helps control adults feeding on foliage.
  • To attack the insect more directly, introduce beneficial nematodes into your soil to feed on the larvae and pupae.
  • In cases of high infestation and serious damage, botanical insecticides such as pyrethrin can be used.

Hornworms
These destructive caterpillars are so big — three inches long or more — that it would seem to be easy to control them just by picking them off. And so it is, sometimes. The dilemma is that their pale green color provides excellent camouflage, and the nymph and larval stages are far smaller and less obvious. If there are only a few, picking them off works well. (One site suggests spraying the plant with water, causing the caterpillars to, and I quote, “thrash around,” giving themselves away.) If there are more than a few, other measures may be called for. One of these is Bt, or Bacillus thuringiensis, an organic treatment that can control numerous other caterpillars as well.

Nematodes
This is one of the most dreaded tomato problems. Actually, almost 20,000 different species of nematode have been identified, and billions of these usually microscopic worms occupy each acre of fertile earth, so it is fortunate that only a few cause gardening troubles. Some, insect pathogenic nematodes, can actually help control other gardening pests such as fungus gnats or flea beetles. But when a gardening friend says in a voice of doom, “I’ve got nematodes,” he generally means one thing: root-knot nematodes. This particular species invades various crops, causing bumps or galls that interfere with the plant’s ability to take up nutrients and to perform photosynthesis. They’re most common in warmer areas with short winters. Unfortunately, controlling nematodes is not easy.

  • Rotation: Since they take several seasons to get established, rotating garden crops denies this pest the chance to get entrenched. It’s crucial, though, that you follow tomatoes with crops that are not vulnerable to the same problem! Members of the same family are of course taboo; this includes peppers, eggplant, and potatoes. However, less likely crops are also vulnerable; these include okra and cotton, in the south, and peas, squash, beets, and numerous others anywhere. If you suspect nematodes — if you ever pull a plant that has odd-looking lumpy growths on its roots — have your county extension agent take a look at it, and get advice about crop rotation in your area.
  • Soil sterilization: Completely sterilizing the soil is one option on small plots, but it’s toxic and sometimes expensive. It also means that you’ve killed off all the beneficial organisms in the soil as well as the troublesome ones, so it’s particularly important to follow such treatment with a big infusion of clean compost. It would also be best to add earthworms, and an assortment of microorganisms as well, since doing so will restore the soil to full health and make it less vulnerable to further incursions by nematodes.
  • Nematodes: While eliminating nematodes is extremely difficult, it is possible to limit their damage by using resistant varieties, marked N. Doing so doesn’t kill the pests, but it does keep them and their effects under control.

Whiteflies
These tiny flying insects feed on plant juices, leaving behind a sticky residue or ‘honeydew,’ which can become a host for sooty mold. Rustle the leaves of infested plants, and clouds of these insects will rise. If you have a serious problem, you may be tempted to reach for a conventional insecticide, but don’t bother, as whiteflies have developed resistance to many.

  • The best bet is a horticultural oil, which effectively smothers all stages of this insect.
  • To deal with lower levels, place yellow sticky traps to monitor and suppress infestations.
  • Hosing down plants can be surprisingly effective, especially if you use a bug-blaster, a hose attachment designed to produce an intense multi-directional spray that easily reaches the unders >

Plant Diseases

Tomatoes can be stricken by an astonishing array of diseases. If you want to see the full list, go to the How to Manage Tomato Pests page at UC Davis, which discusses some 30 diseases that can afflict tomatoes. Tomatoes can get early or late blight, either white or grey mold (or both). Then they can have problems with diseases with quirky names like curly top and corky root rot. It’s amazing that tomatoes are ever healthy. But they are, and it’s largely because the quandary never gets thoroughly established. After all, it’s a lot less work to nip troubles in the proverbial bud.

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Avoiding Problems

If you’re at all susceptible to anxiety attacks, it will probably be of some comfort to know that disease is generally far less of an issue for backyard gardeners than for commercial producers. Furthermore, there’s a lot a gardener can do to minimize diseases in vegetable gardens (PDF).

Here’s how you can protect your tomatoes:

  • Give your plants good soil & fertilizer and regular watering; healthy plants are much more likely to resist diseases and other problems.
  • Keep gardening plots free of weeds and debris where insects can breed and diseases can incubate.
  • Rotate crops so that soil-borne pathogens never have more than a season to get established.
  • Clean your gardening tools and equipment, especially at the end of the season, to ensure that they don’t carry over or spread a disease.https://www.planetnatural.com/tomato-gardening-guru/pests-disease/
  • Remove unhealthy foliage; pull unhealthy plants to cut down on the spread of fungal spores.
  • Don’t compost diseased foliage or plants unless you know it is safe to do so.
  • Don’t use tobacco near tomato plants, to avoid communicating tobacco mosaic virus.
  • Avoid watering the foliage of your plants, especially in humid climates, as many diseases are encouraged by damp conditions.

The last on that list may be one of the most important. Many plant diseases — verticillium and fusarium wilt, early and late blight, and various leaf spots — are all caused by fungi that prefer damp, cool conditions. Experts generally advise gardeners to water in the morning in part to avoid conditions that encourage fungal growth or molds. Using drip watering systems or soaker hoses keeps leaves dry, again reducing attractive sites for the fungus to get established. Though some of these fungi are airborne, many reside in the soil or in garden debris or weeds related to the tomato. It is important, therefore, to keep weeds and brush piles clear of garden plots. It also helps to keep tomato foliage off the ground and to avoid splashing water up from the ground onto foliage while watering. Mulches help achieve both these objectives.

Damping Off
Caused by any of several viruses, damping off disease is a tomato problem that affects young, seemingly healthy seedlings that suddenly develop a dark lesion at the soil line, then quickly wilt and die. Cool, damp soil, overwatering, and overcrowding all increase probability of infection. Use clean potting soil and germination trays and tools to reduce incidence, avoid crowded seed beds, and monitor watering carefully during the first two weeks after sprouting.

Fusarium Wilt
Caused by a soil-borne fungus that targets Solanaceous plants (tomato, pepper, potato, eggplant), fusarium wilt often causes no symptoms until plants are mature and green fruit begins to reach its full size. At that point foliage, sometimes on only one side of the plant, turns yellow, and a sliced stem will show brownish, discolored tissue. Control includes crop rotation, so that the wilt organisms, deprived of a host, will die down in affected soils where it winters. Since cool, damp conditions favor infection, avoid spraying leaves, especially in cool weather. Use resistant varieties.

Mosaic Virus
There are actually several closely related viruses (the tobamoviruses) that cause the wilted, mottled, and underdeveloped fern-like leaves characteristic of the tobacco mosaic virus. All are spread by what are termed mechanical means: something or something that’s been in contact with the virus touches an uninfected plant, and voila — you’ve got an infected plant. Sanitation is therefore of the utmost importance, starting with never smoking near tomato plants, as tobacco can carry the virus. Infected plants should be destroyed. Backyard plants purchased from a reliable nursery or grown from certified disease-free seed and handled in a tobacco-free environment by only one or two people, are unlikely to develop this disease.

Verticillium Wilt
Like fusarium, verticillium is caused by a fungus that, once established in soil, is virtually impossible to remove. Symptoms are almost identical to those caused by fusarium wilt, but are less lethal. The edges of large, older leaves turn yellow, then brown and crumbly, and stems show vascular damage. Unlike fusarium, verticillium wilt affects a wide variety of crops, but lowers yield without killing plants. Again, avoid spreading infected soil and watering foliage, and again, use resistant varieties.

Environmental Conditions

Blossom End Rot
If your ripening fruits develop a dark spot at the lower end, a spot that gradually widens and deepens, you’re looking at blossom-end rot. It’s an environmental problem most often caused by uneven watering or by calcium deficiency. (These can be related; uneven watering can interfere with the uptake of calcium.) The simplest treatment is therefore pre-treatment: make sure soil is rich in all necessary nutrients, including liquid calcium, and water regularly. Mulches also help maintain even moisture levels.

Catfacing
Cat faced tomato plants are deformed to a greater or lesser extent, having deep grooves or indentations running from the blossom end all the way around to the stem. The condition results from cool weather or insect damage while the plant is in blossom. Tomato varieties with large fruit are most susceptible and tomatoes are often rendered inedible — although considered safe to it. To avoid the problem select resistant varieties whenever possible.

Cracking
Several things can cause cracking in tomatoes. Cherry tomatoes, especially small ones, frequently split at the stem end, sometimes all the way to the blossom end, and it does not indicate any sort of disease or problem. The skin of a tomato becomes less resilient as it matures, so the fruit often outgrows the skin. Pick cherry tomatoes just before full ripeness to avoid this.

Circular splitting at the stem end, (concentric cracking) or cracks running towards the stem (radial cracking) usually result from a sudden increase in moisture after a dry spell. Once again, the tomato fruit expands beyond the skin’s ability to adapt. Keep soil evenly moist to avoid this phenomenon.

Sun Scald
The tomato’s skin will look bruised or leathery, the skin sunken and puckered. It is essentially what it sounds like, a sun-burn, tomato style, and it occurs when fruit is too exposed during hot weather. This issue primarily affects staked and trellised tomatoes, which are more aggressively pruned than are caged or free tomatoes. To prevent this problem, be sure to leave adequate foliage on plants when pruning. Reusable shade cloth can also be used to protect tender vegetable plants. Once sunscald has occurred, you cannot do anything for affected fruit, but you can provide shade for the unaffected ones.

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