Tomatoes can be prone to illness, especially of the fungal-borne variety. Fungal diseases like wilt, mildew, and especially blight are common problems for tomatoes.
Tomatoes can also fall victim to certain insect pests. While there aren’t a lot of insects that plague tomatoes, those that do can cause a lot of damage, very quickly. The damage they cause can destroy foliage and ruin the fruit, too.
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Treating and Keeping Tomatoes Growing with Minimal Environmental Impacts
As a food source, ideally, growers would like a solution that comes with minimal risk. Most prefer an organic solution that is friendly to pollinators and soils.
It should be noted that even organic interventions can present some risk to soils and pollinators if not used appropriately. If you choose a safer product and follow precautions and label instructions, you can protect your tomato plants, treat them for insects, pests, and diseases, and do it in a way that is kind to other beneficial insects and wildlife and soil, too.
4 Good Solutions for Kindly Treating Tomatoes for Common Pest and Disease Problems
These four products will treat all of the most common problems that tomato growers face. Use selectively as either a preventative or treatment, and you can continue to grow and produce good tomatoes, even in the most trying of years and in the worst conditions.
1. Neem Oil
Neem oil is a good choice for many things in the garden, berry beds, and orchards. It is a natural product, produced from the pressed oil of the seeds of the neem tree. It is naturally anti-fungal and a natural pesticide with insect-repelling properties.
For this reason, neem oil is an excellent all-purpose solution for most of what plagues tomatoes. It is natural and organic and will treat a broad spectrum of pest and disease issues.
What it treats:
Neem oil can basically treat any type of mold, mildew, or fungal type of disease. It can be used for blight and powdery mildew, among other tomato diseases. Neem oil is also useful for treating bacterial diseases in tomatoes.
Tomato diseases you can treat with Neem oil include:
- Early blight
- Late blight
- Mildew
- Powdery mildew
- Anthracnose
- Leaf spot
- Black spot
- Wilt diseases
- Rust
- Scab
- Stem rot
- Bacterial diseases
- Fungal diseases
Pest control:
Neem oil is also an effective insecticide that works on a broad variety of pests. It is a pesticide and also works as a pest repellent, though its repellent properties are typically less effective than when used as a pesticide.
Insects you can manage with neem oil include:
- Aphids
- Japanese beetles
- Worms
- Caterpillars
- Mites
- Thrips
- Whiteflies
- Fungus gnats
- Leaf miners
- Flies
- Moths
- Parasitic nematodes
One of the biggest benefits of using neem oil for your tomato troubles is that as you treat one problem, you will often prevent or treat another. For example, if you use neem oil to treat early signs of blight, you might also kill off damaging insect pests, all with one product. This can make neem oil an economical choice.
How to apply it:
Neem oil will either come as a pre-diluted spray or it will come as a concentrate that you mix with water.
The water should be warm so the oil disperses.
You can add a small amount of dish soap to help with adhesion.
The typical dilution recipe for neem oil is:
- 1 gallon of warm water
- 2 to 4 tablespoons of neem oil
- 1 to 2 teaspoons of liquid dish soap
Mix neem oil according to the label’s instructions for the product you buy, so that you make sure you are working with the right ratios for the concentration of the product you have purchased.
Apply with a spray bottle or a garden sprayer. Since tomatoes are large plants, mixing your own concentrate and using a garden sprayer will be the easiest and most economical choice.
You should mix a fresh batch each time you use neem oil.
When to apply it:
You can use neem oil as a preventative treatment when you know conditions are conducive to pests and diseases, which may help keep diseases away.
For example, if you are experiencing a rainy growing season or high humidity, that sets the stage for blight, mildew, and other fungal diseases to set in. Use neem oil weekly to keep fungal spores from colonizing.
Another example might be spraying neem at the time when you usually see a pest insect arrive (like June for Japanese beetles, or when hornworms and sphinx moths start arriving in your tomato patch).
Otherwise, start using neem oil at the first sign of insects or diseases.
The application schedule for neem oil is as follows:
- For disease prevention: apply every 7 to 14 days
- For disease treatment: apply every 7 days
- For insect control: apply every 7 days
- For heavy disease or infestations, you can apply as often as every 5 days
- Reapply after heavy rains (significant rainfall will wash neem oil off your plants, so it is safe to reapply more frequently if needed)
Safety of Neem Oil for Beneficial Insects and Pollinators:
Neem oil primarily works on insects that are either covered in it wet or on insects that eat the plants’ parts and ingest the dried spray.
For this reason, it is considered generally safe for pollinators and beneficial insects as long as you follow label instructions and avoid spraying neem oil directly on bees and beneficial insects. The best way to do this is to avoid spraying plants in bloom when possible and if you have to spray a plant in flower, then spray early or late in the day when those insects are not visiting the plants.
2. Copper Sulfate
Copper sulfate and other copper fungicides work by disrupting enzyme actions in the cells of molds, fungi, bacteria, and more.
In so doing, copper sulfate and other copper products can stop an infection from taking hold, minimize colonization, and stop colonies of spores from spreading to a point where they can kill a tomato plant.
Copper sulfate works as a preventative because it doesn’t really kill established spores and cells. But it can deny them the environment they need to infect a plant. It is a protectant more than a treatment. Copper sulfate can also be mixed with lime to create what is called a Bordeaux mixture; the Bordeaux mixture does have disease-fighting abilities.
What it treats:
Copper sulfate isn’t much good for treatments of things like late blight, but smart application can often prevent blight and other diseases in tomatoes.
Copper sulfate can slow and stop the spread of disease, including
- Anthracnose
- Fungal spores
- Powdery mildew
- Downy mildew
- Rust
- Fire blight
- Other mold and fungal diseases
How to apply it:
Copper sulfate will come either as a concentrated product or powder that you mix with water or as a premixed spray.
For large patches and applications, mixing your own from a concentrate and using a garden sprayer is most efficient and most cost-effective.
- Dilution ratio as a garden fungicide is one to two teaspoons of copper sulfate concentrate to one gallon of water
- Mix fresh for each application
- Apply to the stems, tops, and bottoms of leaves
When to apply it:
Copper can build up in the soil and can impact beneficials, so it is best to use it as advised and on the recommended schedule. It can also cause some damage to new growth, but that is vulnerable growth that is better off treated than left to be attacked by disease organisms.
- Apply on a warm, sunny day so that leaves and plant parts don’t stay too wet with the copper solution
- Spray every 7 to 14 days
- Spray at the 14-day interval for general disease prevention
- Spray on the 7-day interval if conditions are wet, rainy, or humidity is consistently high (times when fungal spores are most likely to take hold and spread prolifically
- Begin spraying early in the season or when humidity begins to climb, and spray as per the recommended schedule for the remainder of the season
Follow your product’s label instructions for dilution amounts and do not apply more frequently than is advisable.
Safety of Copper Sulfate for Beneficial Insects and Pollinators:
There is some risk that overuse of copper products will cause a negative impact and build up in garden soil. There is a potential risk to earthworms and some other beneficial insects.
That said, it would take a lot of copper product use to negatively impact the soil and its inhabitants. The average home tomato grower is not likely to use enough of the product to cause soil problems, especially with annual patch rotation.
However, this is why it is always wise to use copper products only as needed and as directed on your product’s label.
3. Bacillus thuringiensis (Bt)
Bacillus thuringiensis (Bt) is an organic product that is a naturally occurring bacterium. It is a targeted pesticide that targets worms, caterpillars, and similar organisms. It is highly effective on the larvae of moths and members of the Lepidopteran family.
Bt is not effective against other types of insects, like flying insects; but one of the biggest pests for tomatoes are hornworms and fruit worms. It is an excellent tool to use in tomato patches for this reason, and because it is so targeted to only this type of pest.
What it treats:
In terms of tomato pests, Bacillus thuringiensis will treat any caterpillar or worm. The most common uses are to combat
- Hornworms, both tomato and tobacco
- Fruit worms
How to apply it:
Bacillus thuringiensis is usually applied as a spray. It may come as a ready-to-use product, as a concentrate that you mix with water and apply via a garden sprayer, or as a spray bottle that is used on your garden hose and mixes as it sprays.
Wet the entire plant and the top and undersides of leaves.
There is also a powdered form of Bt if you prefer, though it may be more difficult to cover stems and the bottoms of leaves.
- The typical application ratio is one ounce of Bt solution or powder to one gallon of water
- Apply as a powder or as a spray mixture
- Follow label instructions
When to apply it:
It is best to apply Bt at the first sign of hornworms or caterpillars, or even before they appear, during the time when the caterpillars typically arrive.
Bt is not as effective on adult, mature hornworms or fruit worms as it is on smaller, younger worms. It is best to have it in place before eggs hatch, as that is when it is most effective. If you miss that window, start spraying as soon as you see fecal pellets or damage to plants.
Hornworms hide easily, but leaf damage, overnight defoliation, and green to brown cylindrical fecal pellets are sure signs that they are there.
- Spray plants every five to seven days
- If the infestation is heavy and not controlled, you can spray more frequently
- Bt breaks down in sunlight, so try to apply it in the evening or late in the day when the sun is less direct on your tomato plants
- Reapply after heavy rains, as this will wash Bt off your tomatoes
Safety of Bacillus thuringiensis (Bt) for Beneficial Insects and Pollinators:
Bt is considered one of the safer alternatives to the worst tomato pests, because it targets those pests. It will not harm beneficial insects and only kills larval stage caterpillars and worms.
Bt will not impact adult butterflies, moths, beetles, or bees. It does not harm parasitic wasps, which are quite helpful with hornworms, too.
Bt can potentially harm the larvae of other types of moths and butterflies, types that we like and want to protect. However, these are not typically found on tomato plants, so application on tomatoes is generally quite safe.
The key to safe, protective use of Bt is to avoid spraying on host plants for beneficial butterfly or insect larvae, like milkweed, and be careful not to overspray those plants.
4. Kaolin Clay
Kaolin clay is a clay powder made up of kaolinite and other minerals. It works by creating an actual physical barrier of protection on your tomatoes that denies fungi, mold, blight spores, and insects from being able to colonize your plants.
It is a safe and natural product that is gaining in popularity in the garden. Kaolin clay has been used commercially and in organic farming for quite some time.
In addition to disease prevention and insect control, kaolin clay can help protect sun-sensitive plants from sunburn.
What it treats:
Kaolin clay mostly works as a deterrent and keeps pests off your tomatoes to begin with. The clay covers up the plant, so insects can’t find the plants to lay their eggs on, and sap sucking insects can’t find them to feed on. The barrier also makes it extremely difficult, if not impossible, for worms and insects to chew through to the plant.
The barrier created by kaolin clay also denies a hospitable environment to fungal spores like mildew, blight, and other bacteria and viruses.
How to apply it:
For small, young transplants, kaolin clay can be mixed into a liquid, and then the transplants can be dipped in the liquid before planting.
For larger plants, kaolin is mixed into water and sprayed on. A garden sprayer is the best tool to use.
- The usual dilution for a kaolin clay mixture is three cups of powder to one gallon of water
When to apply it:
Kaolin clay can be used at any time throughout the growing season. Kaolin allows light particles through and also reflects sunlight to parts of leaves that don’t typically get light, so it does not usually negatively affect photosynthesis if it is applied as directed, even if it is applied frequently.
It is also best to apply the mixture before or after flowering. This is because insects and pollinators can also be confused away from the blossoms, and pollination in some plants can suffer. However, tomatoes are primarily self-pollinating and don’t rely much on insects, so this is not a big worry for tomato plants.
Kaolin can be applied frequently since it is not toxic, and light will not be blocked.
- A weekly application will usually suffice
- You can apply more frequently if needed
- Reapply after heavy rains, as the clay may be washed away in heavy rainstorms
Safety of Kaolin Clay for Beneficial Insects and Pollinators:
Because kaolin clay is not toxic, and because it acts more by barrier action and confusion than as a true chemical fungicide or insecticide, kaolin clay is quite safe. It may be one of the safest garden products you could use to prevent insect infestation or diseases.
It’s best to avoid directly spraying the clay on insects, but even then, it is not likely to damage beneficial insects or pollinators.
Because pollinators may be steered away from plants with kaolin clay, some experts recommend planting a flower patch nearby to keep the pollinators coming, but the clay should not kill them.
4 Good, Safe Products to Solve Your Tomato Garden Woes
With these four safe, reliable products in your tomato garden toolbox, you can counter most everything Mother Nature might throw at you. Having safer, more eco-friendly tools to use makes tomato gardening something you can enjoy again, and enjoy the productivity of the harvest!
