The Most Common Tomato Diseases and Pests

Tomato plants are vulnerable to attack from a wide range of pests and pathogens. Insects, worms, viruses, bacteria, and fungi can all infest your plants, which can lead to disease, damage, stunted growth, and reduced yield; in short, a sad year for your tomato crop.

Keeping your tomatoes pest-free can often feel like an uphill battle, given the sheer number of enemies you have to fend off. However, ensuring the health of your tomato plants is entirely possible once you learn to recognize and avoid the most common pests and diseases.

What are the most common tomato diseases and pests?

Aphids

  • What are they?

Aphids are common tomato plant pests, especially in spring and summertime. The two aphid species you’re most likely to find on your tomato plants are the potato aphid and the green peach aphid.

Aphids feed by using their highly specialized mouthparts to pierce plant tissues and suck out the sap. If your aphid infestation is severe, this can cause tomato leaves to curl and may even lead to stunted growth.

  • How can you treat them?

If you find aphids on your tomatoes, don’t panic! There are several easy and effective control methods you can try to rid your plants of the bugs.

First, use a hose to thoroughly spray your tomato plants. This will physically remove the majority of the bugs.

To kill any remaining bugs, or to prevent re-infestation, try treating your plants with a DIY spray.

These can be easily concocted at home by mixing a few teaspoons of liquid soap with water in a spray bottle, then using this to douse your plants. Diatomaceous earth can also be used to effectively exterminate any remaining aphids, and to deter more from moving in. Dust your plants with the powder, to effectively protect them from bugs, as insects will on contact with the substance.

Hornworms

  • What are they?

The Tomato Hornworm is one of the most voracious tomato-eaters in the pest world and can cause devastating damage to your plants. A type of caterpillar, the hornworm is bright green, usually with a pattern of pale, V-shaped markings along the sides of its body and a black ‘horn’ protruding from its rear end.

These hungry caterpillars are especially fond of green, developing tomatoes, which won’t mature properly once attacked by hornworms.

  • How can you treat them?

The easiest way to get rid of hornworms is to physically remove them. Carefully inspect the leaves and stems of your tomato plants for hornworms, which are often camouflaged by their verdant coloring. Once you find them, simply pick them off and drop them into a bucket of soapy water to kill them.

If you are battling large numbers of the bugs, try sprinkling diatomaceous earth on the soil around your tomatoes to keep them away. You can also introduce beneficial insects (such as ladybugs) to your veggie patch, as these prey on hornworm eggs and a variety of other pest species.

Whiteflies

  • What are they?

There are several species of whiteflies that are known to infest tomato plants, but the two to be on the lookout for are the sweet potato whitefly and the greenhouse whitefly. Feeding by these insects can cause widespread damage to your tomato crop, causing leaves to yellow and curl and tomatoes to ripen unevenly.

You can usually find whitefly hiding out on the undersides of leaves, which is where they feed. These tiny, moth-like insects are white in color and will rise up in a cloud when their resting place is disturbed. You can check for whitefly on your tomatoes by giving the stems a gently shake and seeing what flies off.

  • How can you treat them?

To take care of adult whiteflies, blast your plants with a high-pressure hose to displace them. Alternatively, you can try using a handheld vacuum to remove them. Whitefly nymphs cling to leaves more tightly than the flying adults, however, so they’ll need a little extra work to get rid of. To eradicate your infestation entirely, consider treating your plants with an insecticidal soap spray or neem oil, both of which are known to kill whiteflies.

To prevent whiteflies from returning, set up yellow sticky pads around your plants. The color of these pads attracts adult whiteflies, which land on them and become trapped in the glue before they can make it onto your tomatoes.

Blights and wilts

  • What are they?

Blights and wilts are both diseases caused by fungal pathogens, and both can seriously damage your tomato plants. Late Blight (caused by the fungus Phytophthora infestans) is best known as the pathogen responsible for the Irish potato famine of the 1840s and is particularly destructive. Infection by Late Blight can lead to spotting on the leaves and stems of plants, fruit that doesn’t ripen properly and rapid plant death. Once established, Late Blight can also spread to other plants around your garden and greenhouse.

Fusarium wilt is another tomato disease that can decimate your crop. Caused by the soil-dwelling fungus, Fusarium oxysporum, this pathogen can cause tomato leaves to yellow and wilt and brown streaks to form on the stems and branches. Like Late Blight, it usually kills the plants it infects.

  • How can you treat them?

The best way to protect your tomatoes from the horrors of blights and wilts is to choose plant strains that are more resistant to the pathogens. Do your research before planting to make sure you pick a variety that has a better chance of withstanding attack from these microbes.

Important!

If you’ve already planted your tomatoes, keep an eye out for signs of infection and don’t hesitate to remove diseased tissues. For severe cases, there are chemical control options available, but fungicides should be used very carefully so as not to disrupt the surrounding ecosystem.

Conclusion

Tomato pests and diseases can cause devastating damage to your plants in the spring and summertime. A wide variety of bugs and pathogens are known to attack tomatoes, which can lead to stunted growth, reduced yield and even plant death. Setting up an integrated pest control plan and inspecting your plants regularly for signs of disease and infestation is the best way to keep them healthy!

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