By Dr. Ayanava Majumdar|August 9, 2012
As the summer heat continues, it is common to see spider mites on commercial and home-grown tomatoes. Heat, drought, water stress, the presence of a large number of weeds, and incorrect use of insecticides can lead to high buildup of mites on tomatoes.
Mites are 1/50 inch in diameter and usually feed on the underside of leaves close to the midrib. There are several species of spider mites and they typically have a short life cycle of seven to eight days. Eggs are attached to the webbing produced by the adults, and the nymphal stages have three pairs of legs (i.e., resembling an insect).
A Two-Spotted Spider Mite Attack
The two-spotted spider mite is a common species on tomatoes in the south and is distinguishable by a pair of dark spots visible through the orange body. The dark spots on spider mites are generally the accumulation of body waste under the skin, hence the newly formed individuals may lack the spots.
Use a hand-lens to directly study the infected parts and ascertain the number of living individuals per leaf where possible as a measure of population pressure. In an outbreak situation, spider mites could easily exceed more than 40 mites per leaf on vegetable crops.
This pest feeds on individual plant cells and causes damage at an astonishing speed when uncontrolled. By the time producers detect an outbreak, spider mites could have already completed several generations.
Due to extensive spider mite feeding, the upper side of tomato leaves may get a speckled appearance or the entire leaf may turn yellow and die.
During a spider mite outbreak, extensive webbing of tomato leaves can be seen along with masses of spider mites at leaf tips as shown in the picture on this page. Adult mites overwinter in crop debris and wild host plants.
This pest typically feeds on tomatoes, eggplants, squash, cucumbers, and other vegetables. The same species can feed on greenhouse crops and destroy produce. Spider mites can also destroy valuable fruit crops such as strawberries, blackberries, and blueberries.
Management And Control Options
As mentioned, spider mites are rapid breeders, hence it is essential to control increasing populations early in the season after correct identification of the species present. Check insecticide/miticide labels before treating an area. Hot-spots of spider mite activity can be targeted in enclosed structures like greenhouses and high tunnels.
Many insecticides like the synthetic pyrethroids and organophosphates commonly used for thrips and worm control can cause a flare up of spider mites by removing predatory mites and other beneficial insects. The dry weather in late summer can also aggravate the situation.
Vegetable producers should assess the need for insecticide sprays and follow some of the cultural practices mentioned here to prevent an outbreak. Here are some miticide options for vegetable producers:
• Abamectin (AgriMek, Syngenta Crop Protection, 8 to 16 fluid ounces per acre): Abamectin is actually a naturally derived substance and serves as a good rescue insecticide. AgriMek contains synthetic abamectin and provides long-term residual control of two-spotted spider mites.
AgriMek also has a locally systemic action or translaminar activity and must be tank-mixed with a surfactant to enable the product to move inside the leaves. Do not apply more than two sequential applications of abamectin to tomatoes to prevent resistance buildup. The postharvest interval on tomatoes is seven days.
• Bifenazate (Acramite, Chemtura, 0.75 to 1 pound per acre): This is a contact poison against two-spotted spider mites with less toxicity to predaceous mites and beneficial arthropods. Acramite is a good knockdown product and also kills the eggs (ovicidal action). Do not make more than one application of bifenazate per season. The postharvest interval on tomatoes is three days.
• Spiromesifen (Oberon, Bayer CropScience, 7 to 8.5 ounces per acre) and fenpyroximate (Portal, Nichino America, 2 pints per acre): These are slow acting contact poisons. Oberon, a lipid biosynthesis inhibitor in insects, may also provide some whitefly control. These products can take up to four days to activate after application and two applications may be necessary to get control of a spider mite outbreak.
Industry sources indicate that fenpyroximate may provide a fast control of spider mites within two days. In some crops, spiromesifen has up to three weeks of residual action, if it is applied prior to spider mite outbreak. Both products have to be applied thoroughly to the leaf surfaces.
• Etoxazol (Zeal, Valent, 2 to 3 ounces per acre): Although Zeal is not labeled for use on tomatoes, it is worth mentioning because it is a new product. Zeal is a growth regulator specific to plant-feeding mites, and it doesn’t harm mite predators. Zeal has translaminar activity like abamectin and kills eggs and nymphs of the two-spotted spider mites plus it sterlizes the adults.
Go to the next page for management tips for organic producers.
For organic growers, maintaining stress-free plants is one of the best ways to prevent spider mite outbreaks from happening in vegetable fields. Here are a few pointers to keep organic fields mite-free:
● Control Weeds: Keep main production areas weed-free and follow basic sanitation practices diligently.
● Watch Your Fields: Scout crops closely and keep records.
● Keep The Pest In One Location: Avoid mowing grasses close to field crops during mid-summer and especially in drought conditions since mowing will help move the pest.
● Use Beneficials: Predatory mites belonging to the genera Amblyseius, Metaseiulus, and Phytoseiulus along with minute pirate bugs and lady beetles have been reported to be effective in controlling mites (release predatory mites ahead of an outbreak so that predators get a chance to establish on crop plants).
● Available Control Products: Insecticidal soap and neem oil have been suggested as possible low-impact environmental-friendly products for mite control. Do not use oil and soaps when it is too hot. Thorough coverage of plants with oils and soaps is essential along with many repeat sprays. Sulfur may also be used, but it can burn certain vegetable crops.
Majumdar is an Extension entomologist and state sustainable agriculture coordinator at Alabama Cooperative Extension System.
See all author stories here.
We received this question via my website, PLANTanswers.com in mid-June:
Sent: Tuesday, June 10, 2014 5:36 AM
To: Plant Answers: Ask the Answer Man
City or Zip Code: 78261
Subject: spots/specks on tomato plant leaves
My tomato plant leaves are covered with small specks. The leaves are starting to turn lighter toward yellow.
What can it be and how can it be controlled? Have gotten lots of blooms and have dozen tomatoes various sizes.
Any advice would be helpful.
This is one of the best descriptions of symptomatic damage of a beginning population of one of the most destructive hot-season pests we have on garden plants — especially tomatoes. The most prolific, elusive insects (which are really spiders) of any garden are the spider mites. These girls coined the phrase strength in numbers and they are committed to the cause! When conditions are optimum (hot and dry), they can double their population in 4 days. Don’t feel sorry for the requirements placed on the male in order to accomplish this feat – – their services are not required, but once. Isn’t that sick?! These gals have taken woman’s liberation too far; they only visit their male counterpart once during a lifetime. What’s worse is that some ladies eat the male after the encounter – – that’s gratitude for you!
Even though mites are small, their huge populations are mighty when potential plant damage is considered. These mighty small spider mites are often unnoticed by gardeners until the plant has been severely damaged. That is why it is very important to notice the subtle changes such as plant leaves being covered with small specks and the leaves are starting to turn lighter toward yellow becoming dull in appearance. Spider mites flourish in hot, dry conditions. They are named for the webs they make on their host plants while feeding. Spider mites usually feed on the green chlorophyll on the undersides of leaves and cause a stippled bronze coloration dotted with yellow specks on the surface of the leaf. Tiny webbing is usually present on the underside of leaves as the population increases to several million individuals!
Gardeners respond by using carbaryl (Sevin) or other insecticides. This often eliminates beneficial insects which consume spider mites. The predator elimination allows the mite populations to multiply rapidly. The mite is not an insect but rather related to spiders. They can NOT be controlled but rather the host plant should be eliminated or their population-explosion be slowed by the use of seaweed extract. There are several good organic controls for spider mites. Seaweed spray THOROUGHLY applied twice per week does the job. The new product Spinosad (Conserve and other product names) also seems to work. Add one teaspoon of a liquid soap per gallon of pesticide spray to insure good wetting of foliage and try to spray the bottoms of leaves as much as possible. Since mite eggs hatch ever 3-5 days and since sprays kill only the adults, consecutive sprays will hopefully destroy the young before they reach puberty.
NOTHING works when populations are dense and weather is hot and dry. The best control is destruction of infested plant materials when identified—DEFINITELY eliminate ALL infested plants before planting a fall garden.
That is my recommendations—here are some answers to other questions about spidermites:
Question: I have a raised bed garden and have battled spider mites to no avail. They have ruined my tomatoes. I use cypress mulch in my garden as well as a weed block. Do I need to get rid of these things to start the garden this year? Please help I want my garden back.
Answer: Spider mites do over winter in mulches and plant debris left over from the previous summer. But if you think that you will avoid mites by burning, scorching, “poisoning”, or otherwise sterilizing your garden soil, you are mistaken. Spider mites have an admirable capacity to find tomatoes even if the tomatoes are planted on virgin soil. They apparently do this via wind transport, or some other means we haven’t quite figured out.
Unfortunately, there are not many magic bullets on the market for spider mite control on vegetables. I recommend an integrated approach.
(1) Do not compost mite infested plant material (There’s no use giving mites a head start. Unless your compost pile is uniformly hot enough to kill mites, I’m convinced this is another way mites can infest a garden.)
(2) Inspect your tomato seedlings for mites and choose only mite free plants (Again, let’s not help the mites by giving them an early start). With a hand lens, check the undersides of a few leaves of every plant you purchase.
(3) At the first sign of infestation (assuming you do check your plants a couple of times a week for the first signs of spider mites on leaf undersides), do one of the following: try blasting mites off with a stiff stream of water directed at leaf undersides (this can significantly delay mite population buildups, if done thoroughly); apply horticultural oil or insecticide soap sprays; pick off and destroy any leaflets you find mites on.
(4) Get your spring tomatoes started early, and remove plants when they become mite infested. Instead of battling the mites, give in and focus on a late summer planting of tomatoes. Sometimes the fall tomato crop is easier to grow without spider mites.
Michael Merchant, PhD, BCE; Urban Entomologist; Texas A&M AgriLife Extension Service in Dallas, Texas
From Dr. Calvin Finch writes:
Spider mites become a real problem on tomatoes when the weather becomes hot. The generation time of the tiny sucking insects becomes as short as four or five days. Spider mites feeding cause the leaves to have a dusty faded look. In severe infestations, tiny webs cover the plant. There are several good organic controls for spider mites. Seaweed spray THOROUGHLY applied twice per week does the job IF STARTED early in the growing season and used as a preventive BEFORE mite populations explode. The new product Spinosad (Conserve and other product names) also seems to work. Neem oil is labeled for spider mites, but I have not found it very effective.
To determine if you have spider mites, flick a leaf with your forefinger over a white piece of paper. You should be able to see the red pinhead size mites moving on the paper.
Spider mites on a tomato leaf.
Q: We have 17 very healthy-looking tomato plants that have a total of 93 tomatoes on them so far. However, we are seeing little red spiders on the undersides of the leaves. Perhaps they are spider mites. So far we are treating them with Safer Insecticidal Soap. Is this the right treatment? Will they do serious harm to the plants?
A: That sure sounds like spider mites — possibly the two-spotted mite that favors tomatoes. It’s not a terribly common problem, but it can happen. And if predators don’t clean up the infestation for you, mites can do significant damage to the leaves and therefore affect your yield.
Insecticidal soap is the recommended treatment. There’s also an oil-based organic product called Mite X that’s specifically for mite control. That should do the trick, too.
But even a stiff spray or two of plain water helps. That knocks off the mites and kills some of them from the force of the water. Personally, I’d go with that approach first. Hose down the plants once or twice a day for a few days and see if that doesn’t end the problem.
I’d rather not turn to harsher pesticides since they also can wipe out lady beetles and predator mites, eliminating the natural help that usually and eventually brings pest mites under control.
- Natural insecticides against whiteflies on Tomato Plants
- The best natural insecticides against whiteflies on tomato plants
- Advantages of the natural insecticides against the whiteflies on tomato plants
- Tomato pests
- Exotic pest
- Common pests
- Tomato Tips, Tricks and Home Remedies
- Home Remedy Spray for Tomato Plants
- Home Remedy
- Conditions leading to tomato blight
- Avoiding downy mildew or tomato blight
- Treating tomato blight and downy mildew
- Tomato Plant Problems from Diseases to Pests & How to Fix Them
- Pests vs. Disease
- 3 Sure Signs of Pests
- 5 Sure Signs of Diseases
- Common Tomato Pests
- Common Tomato Diseases
- OTHER COMMON PROBLEMS
- How to Get Rid of Bugs on Your Tomato Plants
Natural insecticides against whiteflies on Tomato Plants
Whitefly pests are causing serious problems in the Spanish tomato crops, especially due to the transmission of viruses such as Tomato Yellow Leaf Curl Virus (TYLCV). Hence the importance of combating this problem through an integrated management that includes effective natural insecticides against whitefly on tomato plants.
In order to keep the whitefly population at bay, integrated pest management is the best method of action. Its objective is the rational and efficient control of pests and diseases, minimizing the amount of residues in the products to be harvested. It is necessary combine cultural measures, biological control and phytosanitary treatments, with priority of natural ones versus chemicals.
Farmers do not find it easy to find specialized, effective natural formulations that do not leave residues in the crop, but they exist.
The best natural insecticides against whiteflies on tomato plants
Among all the natural insecticides against whiteflies on tomato plants, Nakar product stands out given the good results it has demonstrated in trials and in commercial application, and given its high specialization. It is a biopesticide that presents excellent contact control of soft shell insects in all stages of development and especially of the whitefly in tomato.
Its state-of-the-art formulation gives it the ability to penetrate and fragment the lipoprotein matrix of insect cell membranes. The disruption of the membrane causes the evacuation of the cellular contents causing the dehydration and death of the insects.
Given its natural origin and its compatibility with the action of the natural predators and parasitoids of the whitefly is an ideal tool for Integrated Pest Management (IPM), so that the insecticide’s power is combined with the biological control action.
Along the same lines, Pirecris, an insecticide based on natural pyrethrins, is made with co-formulants of botanical origin, totally natural, so it does not use Piperonil Peroxide (PBO) as synergist. Its formula is patented.
Advantages of the natural insecticides against the whiteflies on tomato plants
1.- No security deadlines
These natural insecticides do not have safety period. In fact, both Pirecris and Nakar can be applied even the day before harvesting.
2.- Resistance management
Optimum result in resistance management strategies.
3.- Efficacy in all biological stages of insects
Although their efficacy develops over all biological stages of insects, the insects are more vulnerable to the effects of the active substance in its immature stages of development and non-flying phases.
4.- Wetting effect
The fact that whitefly populations are placed on the underside of the leaves conditions the effectiveness of the products that act by contact, so it is advisable to use wetters.
However, Nakar has achieved a potentiating and wetting effect, so that it improves adhesion in spray applications. Moreover, it increases the adhesion of other treatments because it decreases the surface tension of the water and increases the contact surface, as well as the contact time between the pathogen and the applied active material.
5.- Avoid molasses and bold in the crops
The whitefly secretes a species of molasses that hinders the growth of the plant because it interferes with photosynthesis and causes less vigor and, therefore, a worse quality in the fruits. This molasses favors the attack of the fungus that causes the bold in leaves, flowers and fruits, and also reduces the photosynthetic capacity of the vegetable and its respiration, depreciating the quality of the harvest, but also hindering the penetration of phytosanitary treatments.
Besides its potential as a natural insecticide, Nakar contributes to the cleaning of these molasses produced by attacks of sucking insects such as the whiteflies, in a way that avoids the fatal spread of fungi. In the same way, Nakar cleans the bold formed by the fungi.
6.- Efficiency comparable to chemicals
The different tests carried out with the bio-insecticide Nakar have shown that the efficacy of this natural insecticide equals the reference chemical in whitefly control, with the added value of not leaving residues and being suitable for integrated and ecological production.
In the last study carried out by researchers at the Technological Park of Almería (Tecnova) on integrated control of whitefly on greenhouse tomato, results confirmed the high efficiency of Nakar on immature and adult populations of this pest, cutting off their biological reproduction.
The synergy of this product with the action of Pirecris was conclusive in the control of the whitefly Bemisia tabaci.
The exotic Queensland fruit fly was first detected in Western Australia in green tomatoes in 1989 and subsequently eradicated.
The Mediterranean fruit fly sometimes attacks vine ripened tomatoes in suburban backyards. Spray with a splash bait containing spinosad weekly to reduce pest numbers. Place insect exclusion bags or sleeves, which are made from waxed paper or insect netting, over the green fruits.
Aphids are most commonly seen in spring and autumn when the weather is mild and humid. They are small, soft-bodied, green, grey or black insects with thin legs. Aphids may be winged or wingless and are usually slow moving. The insects cluster on the tips of the plant shoots. By sucking the sap they reduce the vigour of the plants. Aphids can also be carriers of virus disease which can severely reduce yields and quality.
In a healthy garden aphids will be controlled by beneficial insects, but these normally take two weeks to build to sufficient numbers to reduce aphid populations. Aphids can be squashed with finger and thumb or reduced by spraying soapy water or knocked from the plants using a water jet from the hose.
Organic controls include horticultural (potassium) soap, horticultural oil and rotenone dust (derris). Imidacloprid is a low toxicity systemic. Other insecticides include dimethoate, cyfluthrin, tau-fluvalinate or pyrethrum and piperonyl butoxide.
These caterpillars are tough-skinned, brown, reddish or green and are about 40mm long when fully grown. They have irregular dark stripes on their back and a lighter stripe on each side of the body. Budworms bore holes in the fruit.
These pests are hard to kill and it is important that any infestation is tackled early in the season before the fruit becomes vulnerable to attack. They are common in summer.
The caterpillars pupate in the soil. The moths have light brown forewings and the hind wings have a darker brown margin on the trailing edge. They lay small white visible eggs on the plants, which are a sign of a pending attack.
Pick off the caterpillars or spray early as the small caterpillars are easier to kill and at this stage have caused less damage.
Bacillus thuringiensis is an organic spray. Spinosad (low toxicity), pyrethrin, cyfluthrin or tau-fluvalinate and fluvalinate can also be used on caterpillars.
Tomato Tips, Tricks and Home Remedies
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Step by step growing instructions for tomatoes with many home remedies and tricks included.
- Don’t plant your tomato plants in the same place every year. Rotating their location helps reduce risk of soil diseases.
- Grow sweeter, juicier tomatoes by adding a teaspoon of sugar to the watering can once the tomatoes begin to show color
- Produce sweeter, juicier tomatoes by adding powdered milk to their water. Milk is a great source for calcium, which nourishes the plant and can help prevent blossom end rot
- Protect your veggies with milk. Sprinkle outdoor plants with the water you swish around in an empty milk jug before recycling it. Tomatoes (as well as eggplant, peppers, and potatoes) love milky water because it can kill the tobacco mosaic virus.
- Another way to give your tomatoes all the calcium they need to prevent blossom end rot is put a small piece of wallboard or gypsum board in the ground close to their root zone. This will give them plenty of calcium to prevent this disorder. Gypsum can also be added to soften clay soil if the soil has a lot of sodium in it.
- Here is an amazing way to boost your tomato harvest. Build a Japanese tomato ring in your backyard if you want monster tomato bushes and a bumper crop. First, prepare a round bed in a sunny spot, about 6 feet in diameter. Wrap 10 feet of cattle wire into a cylinder and center it in the cleared bed. Fill it with alternating layers of fertilizer, compost, and shredded leaves, then soak it well. Plant four tomato plants around the cage and tie them to the wire trellis as they grow. Water the compost pile regularly. The tomato roots will find water plentiful food in the pile.
- Keep tomatoes at room temperature. Chilling in the refrigerator will diminish their garden fresh flavor.
- The best couple ever? Tomato and Basil! Though basil will grow anywhere, plant it next to a tomato plant, and this fragrant herb will fight off tomato pests and encourage the fruit to grow large and juicy. Then when they are ready eat thick slices of tomato with fresh basil and mozzarella cheeses. A favorite side dish at any Mediterranean table.
- Deter tomato worm by planting Borage or Pot Marigolds near by.
- Tomatoes and Cabbage make great companions! Tomatoes are repellent to diamondback moth larvae, which are caterpillars that chew large holes in cabbage leaves.
- Bee balm, chives and mint improve health and flavor of tomatoes
- Marigold deters nematodes.
- Don’t plant tomatoes near corn. They are attacked by the same worm.
- Mature Dill retards the growth of tomatoes.
- Kohlrabi stunts the growth of tomatoes
- Don’t plant potatoes near your tomatoes. They are attacked by the same blight and viruses
Pests and Diseases:
- Prevent Blight, Blossom-end rot, and other common tomato diseases by sprinkling a handful of Nonfat Powdered Milk in the hole before planting transplants. After planting, sprinkle 2 more tablespoons on top of the soil. Repeat this topdressing every few weeks. You can also grind up chalk and do the same. These diseases are caused by calcium deficiency.
- Tomato and potato plants are particularly susceptible to fungal infections. Spray early in the growing season with a mixture of one teaspoon of baking soda, one tablespoon of mineral or canola oil and one gallon of water.
- Trap sap beetles with vinegar. Sap beetles, sometimes called picnic beetles, are tiny brown bugs that get into tomatoes. They are attracted by bruised, damaged or overripe fruit, but they also love the smell of vinegar. To get rid of them, take a couple of disposable, aluminum pie pans, cut some holes in the sides of one and attach it upside down on top of the other. Fill this trap with vinegar, set it out, and wait for them to go in and drown. This also works with other kinds of sweet seeking beetles.
- A simple way to keep control on tomato pests is to space your plants 6 to 8 feet apart. This prevents them from falling prey to pests like dominoes, one after the other.
- Be sure to wash your hands before you touch your tomato plants if you use tobacco. Nightshades are sensitive to the tobacco mosaic virus. To be on the safe side plant resistant varieties.
Other Tips Tricks and Home Remedies: Peppers; Cucumbers; Beans
Home Remedy Spray for Tomato Plants
Tomato plant image by Trombax from Fotolia.com
Tomatoes grow long, thriving vines in summertime and bloom repeatedly through the season to provide gardeners with a long and hearty harvest. These plants like full sun, lots of nutrition and consistent water, but come with some specific drawbacks, like pests and disease.
A tomato plant’s quick, thriving growth, juicy leaves and sweet fruit attract a number of different garden pests. These include tomato worms, leafminers, buster beetles, aphids, white flies, potato beetles, hornworms and stink bugs. The insects devour tomato leaves, stems and blooms, and can cause overall weakening of the plant.
Although garden shops offer a range of chemical and organic pesticides for these insects, many people prefer to prepare their own. Two tsp. of mild dish soap mixed into a spray bottle of lukewarm water is an effective repellent against most garden pests, and will kill some outright.
The soap in the solution washes away the waxy coating of aphids, exposing them to predation and dehydration. It kills worms, which have no protective coating, and stuns beetles and bugs for handpicking. The solution will also repel future insects by coating the leaves and stems of the tomato plant.
The best time to spray for tomato pests is in the morning, when bugs are still relatively sluggish and easy to spot. Coat the entire plant with the solution, and concentrate on the undersides of leaves or areas with heavy infestations. Hand-pick large worms and beetles off the plants after they’re stunned, and allow the solution to work its magic on smaller insects.
Many gardeners choose organic prevention methods for protecting their gardens from insect invasions. Borders of garlic, rosemary, chives, basil, borage and coriander all repel damaging insects or attract beneficial insects to the garden.
Tomato blight is one of the most devastating diseases because downy mildew spreads extremely quickly.
As soon as black spots appear on leaves, you should prepare for this worst of tomato blights: downy mildew.
Here is how to avoid this blight and treat this disease.
- Read also: how to grow tomatoes.
Conditions leading to tomato blight
Tomato blight is a fungus with latin name Phytophthora infestans that results in a devastating fungal disease.
As for all mushrooms, two factors meet to provide the most favorable conditions to its growth: heat and moisture.
Once contaminated, tomato plant leaves start to blacken. If not treated, the disease can spread to an entire crop in just days and destroy the harvest.
Avoiding downy mildew or tomato blight
Most important to avoid tomato blight is to space tomato plants well apart. If air circulates well, you will guarantee quicker drying of leaves.
Tightly packed tomato plants lead to a closed, stuffy environment that is exactly what downy mildew needs to grow. Downy mildew spreads along wet leaves, so the longer they stay wet, the higher the risk of becoming contaminated by the tomato blight.
When watering, never wet the leaves: only bring water to the foot of the plant.
Lastly, do all you can to avoid having leaves or fruits touching the soil. Soil propagates diseases and fungus such as downy mildew very well. Plants touching the ground will potentially be infected with mildew.
Treating tomato blight and downy mildew
As soon as black or brown spots appear on the leaves, remove and destroy them to eliminate any trace of the fungus.
Use clean pruning shears sterilized with alcohol after each cut to avoid contaminating health plants.
After that, treat with Bordeaux mixture and repeat this surveillance on a regular basis until about 2 weeks before harvesting the tomatoes.
Another solution is to treat with baking soda soap spray: 1 table spoon baking soda and 1 table spoon liquid beldi soap for 1 quart (1 liter) water.
- Read also: how to grow tomatoes.
Tomato Plant Problems from Diseases to Pests & How to Fix Them
By Emily Murphy
Given the right conditions, tomatoes will practically grow themselves. The basic formula is heat, full sun, nutrient rich soil that’s free draining, consistent water, and room for them to breath. No matter if you’re growing patio tomatoes in containers or vining tomatoes in raised beds, the formula is the same. However, every once in a while problems creep in (quite literally), so it’s best to be prepared and ward them off at the pass.
What do pests and diseases of tomatoes look like and what can you do about them? Your first and best line of defense is to choose tomato varieties that are adapted to your unique climate and resistant to the diseases common to your region.
The next best line of defense is to buy starts that appear perfectly healthy or to grow seedlings to reduce the risk of disease. Nursery starts should be vividly green, perky, and free of any marks, spots, or discoloration.
Once you’ve selected the right healthy tomato varieties, it’s valuable to recognize common pests and diseases and understand simple solutions for remedying problems. To help, we’ll break down the process into 4 components:
- Pests vs. Disease
- Common Tomato Pests
- Common Tomato Diseases
- Other Common Problems
Pests vs. Disease
First, identify what part of the plant is being affected. Is it the leaves, stem, flower, or fruit that appears disfigured, discolored, or dying? This will help determine if it’s an animal, bacteria, a fungus, or something else entirely.
3 Sure Signs of Pests
- Leaves or fruits are partially eaten, have holes, or insect tracks are evident
- Visibly seeing animals, eggs or larvae of aphids, weevils, or caterpillars on or near plants
- Seedlings disappear completely or plants are defoliated
5 Sure Signs of Diseases
- Leaves start yellowing or develop brown or black spots
- Leaf tips turn brown, curl, or shrivel
- A white film develops on leaf surfaces
- Fruits have soft spots, rotted stems, or are moldy
- Seedlings tip over or bend near the base of the stem shortly after the germination process
Common Tomato Pests
- Aphids are tiny winged and wingless insects that are often found on the undersides of leaves or feeding in clusters throughout plant vegetation.
- Tomato horn worms are large caterpillars with a horn-like tail (see above image).
- Slugs and snails love tomatoes as much as you and me.
- Whiteflies are bright white, winged insects that form large colonies on the undersides of leaves.
- Cutworms are larvae or caterpillars that feed on young plants at night.
- Flea beetles are double trouble.
They can be difficult to see, but if ants are present, then aphids generally are too. (Ants like to feed off the sugary honeydew that’s a byproduct of aphid feeding.) Aphids are sap sucking creatures that cause plants to weaken, stunting growth and cause leaves to become misshapen. To rid your tomatoes of aphids, use a heavy stream with a Thumb Control Watering Nozzle to knock them off leaves. Then spray plants with soapy water. If the problems persist, encourage natural predators such as ladybugs.
You’ll find eggs or caterpillars on or near plants in the tomato family. Or you’ll discover the leaves of your tomato have disappeared. Tomatoes are the preferred host plants of these larvae. When you see them, pick them off plants and put them in soapy water. It’s also helpful to keep your garden weed free. These same tips also apply to other caterpillars.
If you find leaves and fruits with large holes, slugs or snails are near. Look for accompanying slime trails to positively identify. The best remedies for slugs and snails are four-fold. First, water directly above the root crown and not the entire garden. (Slugs and snails prefer moist environments.) Next, inspect plants regularly and handpick any unwanted visitors. If the problem persists, employ traps and/or barriers. Place a shallow dish filled with beer near plants to trap slugs and snails (they’ll climb in and die) or sprinkle a ring of diatomaceous earth around plants to prevent them from reaching crops.
They’re highly visible and, when leaves are moved or disturbed, will fly off in small white clouds of bugs. Like aphids, they’re sap suckers that cause plants to weaken. Spray plants using a heavy stream of water with your watering nozzle and apply insecticidal soap.
If you find seedlings have disappeared by morning, they could be the culprit. To protect plants, place a collar made from cardboard, aluminum, or another recycled material at ground level and around stems to form a barrier.
The adults, which are small black beetles that jump like fleas, feed on foliage leaving pits and small holes on leaves. Their larvae feed on roots. These beetles can be controlled by sprinkling plants with diatomaceous earth, introducing beneficial nematodes to soil, and placing row covers over young plants.
Common Tomato Diseases
- Damping-off affects young sprouts and is caused by a fungus found naturally in soil.
- Bacterial leaf-spot forms small, rough black spots surrounded by yellowing leaves.
- Fusarium wilt and verticillium wilt are both fungi that access plants through soil moisture.
While different fungi, they have similar affects. If you see yellowing leaves, leaves that develop large brown splotches, and discolored stems, it’s most likely due to fusarium or verticillium wilt. If your tomato plants are suffering with these symptoms, it’s best to pull them and avoid planting tomatoes again in the same soil. Don’t throw infected plants into your compost, rather put them in the trash to avoid further contamination. Be sure garden tools are clean before your next planting.
Fusarium and verticillium wilt can be controlled much like leaf-spot. Grow disease resistant varieties, make sure soil has excellent drainage, encourage air circulation, weed when needed, and water at soil level and in mornings whenever possible.
- Early blight causes brown spots with concentric rings and yellow halos to form on leaves, and it eventually causes stems and tomatoes to rot.
- Late blight causes large, dark patches to form on leaves and leaf tips but without yellow halos.
If your seedlings suddenly tip over near soil level, wilting at the stem, it’s most likely due to damping-off. To prevent this disease, water seedlings when first planted and then water just enough to keep soil moist but not water logged. Make sure seedlings have room to breathe, giving them plenty of air circulation, and use clean containers and tools when planting and tending plants. If you see plants behaving as if damping-off is occurring, sprinkle cinnamon around the base of plants. It acts as a natural fungicide.
It can also occur on fruits. To prevent leaf-spot, grow resistant cultivars, keep your garden weeded, provide plenty of air circulation and sun, and manage water. It’s best to water tomatoes at soil level using a Thumb Control Watering Nozzle and Flexogen Hose. Water in the morning as this will give plants time to dry through the day.
Late blight then spreads to stems and fruits, where more brown spots and even white fuzz can be found. To prevent and control blights, grow resistant varieties, encourage air circulation, keep your garden clean and weeded, and water at soil level and in mornings.
OTHER COMMON PROBLEMS
- Blossom end rot is generally a sign that soil has a calcium deficiency or the pH is off and, therefore, plants can’t access available calcium.
- Cracked or split fruit is typically due to extreme fluctuations in watering and temperatures.
You can test soil for pH, but start by adding an organic source of calcium such as lime, kelp, or ground egg or oyster shells.
It can be difficult and often impossible to control outdoor temperatures and water that comes as rain. However, mulching soil and watering consistently is your best bet for preventing tomatoes from splitting or cracking.
How to Get Rid of Bugs on Your Tomato Plants
Growing and eating your own tomatoes is very rewarding but you have to be patient and put in an effort to get rid of bugs as soon as possible, to help ensure table-quality tomatoes.
Natural Pest Control
The best way to get rid of bug infestation on your tomato plants is to introduce lady bugs. Lady bugs are carnivores that eat aphids and bugs but will not harm your plants.
Home-made Insect Repellent for Tomato Plants
You can make your own bug spray by combining one tablespoon of canola oil, one quart of water and a few drops of liquid soap. Spray the solution on the leaves and underside of leaves where insects often hide. The oil will smother insects and you will have to reapply this solution after heavy rains.
Pest Control for Tomato Plants
If you don’t have patience with natural insect repellents and you can try one of these methods:
- An insect trap – you can buy or make home-made insect traps, and stake them to your tomato plants.
- An electric bug zapper will help control any bug infestation on your tomato plants by luring bugs into it and killing them with electricity.
- A non-organic bug spray – although this should be your last resort.