Pests
Symptoms Clusters of tiny soft green or black insects on the growing tips and the undersides of leaves, often so small they look like dots. Leaves may start to curl or feel sticky. You might notice ants walking up the stems; ants actually farm aphids for the sweet liquid they produce, so ants are a good early warning sign.Clusters of tiny soft insects on new growth and leaf undersides. Leaves curl, yellow, or become sticky with honeydew. Sooty black mold may follow. Cause Aphids are tiny soft-bodied insects that breed very fast in warm weather, so a few quickly turn into crowds on the soft new growth at the tips. Too much fertilizer makes that soft growth they love, so going easy on feeding helps keep them down.Several aphid species (most often green peach and potato aphids) colonize tomatoes. They reproduce asexually and explosively in warm weather, so a few founders become dense colonies on tender new growth within days. Soft, nitrogen-flush growth from over-fertilizing is especially attractive, which is why feeding history drives outbreak severity as much as weather. Organic treatment Spray the clusters directly with a strong jet of water from a hose; this dislodges most of them. For a persistent infestation, apply insecticidal soap or neem oil spray, making sure to coat the leaf undersides where the aphids cluster.Blast off with strong water jet. Apply insecticidal soap or neem oil directly to colonies. Introduce ladybugs or lacewings. Prevention Plant marigolds or nasturtiums near your tomatoes; both attract beneficial insects that feed on aphids. Avoid over-fertilizing with high-nitrogen fertilizer, which produces the soft, fast-growing shoots that aphids prefer.Plant marigolds and nasturtiums nearby. Avoid excess nitrogen fertilizer which creates soft, aphid-attractive growth. Encourage beneficial insects.
Symptoms Large sections of leaves or whole stems stripped very quickly, sometimes overnight. Look for fat green caterpillars up to 4 inches long that blend almost perfectly into the stems and leaves. The easiest way to find them is to look for the dark green or black droppings they leave on leaves below.Large green caterpillars (up to 4 inches) stripping foliage. Leaves disappear rapidly. Black droppings on leaves. Cause These are the caterpillars of a large moth. The moth lays eggs on the leaves in early summer, and the caterpillars grow big (up to about four inches) through mid and late summer, eating a lot of leaves fast. They spend the winter in the soil, so a bed left undug can carry them into next year.Larvae of the five-spotted hawk moth (Manduca quinquemaculata). Adult moths lay eggs on tomato foliage from early summer; the caterpillars feed and grow through mid-to-late summer, reaching up to about four inches and defoliating fast because a single large larva eats a great deal. They pupate in the soil over winter, so the prior season's population carries forward in an unworked bed. Organic treatment Hand-pick and drop them in a bucket of soapy water; it's simple but effective. If you find any with small white oval capsules stuck to their backs, leave those alone; parasitic wasps have already laid eggs on them and the wasps will take care of the rest.Hand-pick; they are well camouflaged but easy to remove. Apply Bt (Bacillus thuringiensis) spray. If white cocoons visible on back, leave them; parasitic wasps are doing the work. Prevention Turn or till the soil in autumn to expose and kill overwintering pupae. Planting dill or fennel nearby attracts predatory wasps that prey on hornworms.Till soil in autumn to kill overwintering pupae. Plant dill and basil nearby to attract predatory wasps.
Symptoms Lots of tiny round holes in the leaves, making them look like they've been peppered with a hole punch, most noticeable on seedlings and young plants. The beetles themselves are tiny, shiny, and black; they jump when disturbed, which is how they got their name.Tiny round shot-holes in leaves, especially on seedlings and young plants. Small shiny black beetles jump when disturbed. Cause Flea beetles are tiny black beetles that jump when you disturb them and chew small round holes in leaves. They come out in spring and hit young seedlings hardest, because small plants do not have many leaves to spare. Bigger, established plants shrug off the same chewing.Several flea beetle species. They overwinter as adults and emerge in spring, so pressure is heaviest early, on seedlings and freshly set transplants whose small leaf area makes the shot-hole feeding proportionally damaging. Established plants with ample foliage tolerate the same beetle numbers easily, which is why the timing of the attack matters more than its size. Organic treatment Cover seedlings with row cover fabric to keep beetles off young plants. Sprinkle diatomaceous earth (a fine powder made from fossilized algae) around the base and on the leaves; it damages soft-bodied insects on contact. Neem oil spray also works.Use row covers on seedlings. Apply diatomaceous earth. Neem oil spray. Prevention Wait to transplant until plants are large and well-established; flea beetles cause the most damage to small seedlings. Larger, established plants can usually tolerate some feeding without major harm.Delay transplanting until plants are large. Use transplants rather than seeds.
Symptoms A fine stippling or scattering of tiny yellow or white dots across the upper surface of leaves, making them look dull and washed out. In heavier infestations you may see fine webbing on the undersides of leaves. Spider mites are barely visible to the naked eye; hold a white sheet of paper under a leaf and tap; if you see tiny dots moving, that's them. Worst in hot, dry weather.Fine stippling or yellow dots on leaves. Fine webbing on leaf undersides. Leaves may bronze, dry out, and drop. Worst in hot dry weather. Cause Spider mites are tiny mites (so small they look like moving dust) that love hot, dry, dusty weather and multiply incredibly fast, so they tend to flare up late in summer. Plants that are short on water suffer the most, so keeping plants watered and dust down is the best defense.Twospotted spider mite (Tetranychus urticae) and relatives. They thrive in hot, dry, dusty conditions and complete a generation in under a week in summer heat, so populations explode late in the season. Drought-stressed plants are far more vulnerable, which makes consistent watering and dust suppression the primary cultural controls rather than an afterthought. Organic treatment Spray the plant, especially the leaf undersides, with a strong jet of water repeatedly over several days to knock off mites and disrupt their colonies. Follow up with neem oil or insecticidal soap applied to the undersides of leaves.Blast with water repeatedly. Apply neem oil or insecticidal soap to leaf undersides. Increase humidity around plants. Prevention Keep plants well-watered in hot weather; water-stressed plants are far more vulnerable. Avoid dusty, dry conditions around the garden if possible.Keep plants well-watered in hot weather. Avoid dusty conditions. Introduce predatory mites.
Diseases
Symptoms Dark brown spots with a target-ring pattern (concentric rings, like a bullseye) appearing on the lower leaves first. Those leaves turn yellow and eventually drop. The disease works its way up through the plant over time.Dark brown spots with concentric rings on lower leaves first. Affected leaves yellow and drop. Spreads upward through plant. Cause Early blight is a fungus that lives in old plant debris and the soil and splashes up onto the lowest leaves in warm, wet weather, which is why it starts at the bottom and climbs. Planting tomatoes in the same spot year after year builds it up, so moving them and mulching the soil are the main ways to prevent it.The fungus Alternaria solani. It overwinters on infected plant debris and in the soil, then splashes up onto the lowest leaves in warm, wet weather, which is why infection starts low on the plant and moves upward. Repeated tomato plantings in the same bed build the soil inoculum, so rotation and mulch (to block soil splash) are the core preventions. Organic treatment Remove affected leaves as soon as you spot them and don't put them in your compost; bag and bin them. Apply a copper-based fungicide spray to slow the spread. Mulching around the base of the plant helps stop soil splash, which is one of the main ways the fungal spores travel from the ground up onto leaves.Remove affected leaves immediately. Apply copper-based fungicide preventively. Mulch soil to prevent splash-up. Prevention Move your tomatoes to a different spot in the garden each year; early blight spores persist in the soil. Water at the base of the plant, never from above. Stake or cage plants so leaves stay off the ground and get good airflow.Rotate tomatoes every 3-4 years. Water at soil level. Space plants for airflow. Stake to keep foliage off ground.
Symptoms A dark, sunken, leathery patch on the bottom (the blossom end) of the tomato, the end opposite the stem. It affects the first fruits of the season most often and is not contagious.Dark, sunken, leathery patch at the bottom (blossom end) of fruit. Affects first fruits most. Not contagious. Cause Blossom end rot is not a bug or an infection. It happens when the fruit cannot get enough calcium, and that is almost always because watering went from wet to dry and back. Calcium travels with water, so steady, even watering, not adding calcium, is what prevents it. Even soils with plenty of calcium get it when watering is uneven.Not an infection but a calcium-delivery failure in the developing fruit. Calcium moves with water, so when soil moisture swings between wet and dry (or roots are damaged), the fast-growing blossom end of the fruit is starved of calcium and its cells break down, leaving the dark sunken patch. It tracks watering consistency, not soil calcium levels, which is why even calcium-rich soils produce it under irregular water. Organic treatment Mulch around the plant and water deeply and consistently; blossom end rot is caused by uneven moisture, not a nutrient deficiency, so steady watering is the actual fix. Remove affected fruit so the plant can focus on developing the next ones.Mulch to maintain even soil moisture. Water consistently. Foliar calcium spray provides some relief. Remove affected fruit. Prevention The single most important prevention is consistent watering. Avoid disturbing the roots around the base of the plant, and don't over-fertilize with high-nitrogen fertilizer.Consistent watering is the key prevention. Avoid root disturbance. Do not over-fertilize with nitrogen.
Symptoms Small circular spots with a dark brown border and a pale gray or tan center, appearing first on the lower leaves. The spots may have a faint yellow ring around them. Over time, heavily spotted leaves turn yellow and drop.Small circular spots with dark borders and pale gray centers, starting on lower leaves. Spots may have yellow halos. Cause Septoria leaf spot is a very common tomato fungus. Like early blight it overwinters in old debris and soil and splashes onto the lower leaves in warm, humid weather, working its way up the plant. The same habits that stop early blight, moving the planting, watering low, and mulching, keep it in check too.The fungus Septoria lycopersici, one of the most common tomato leaf diseases. Like early blight it carries over on debris and infected soil and spreads by water splash onto lower foliage, favored by warm, wet, humid weather. It defoliates from the bottom up; the fix is the same set of moisture-management and sanitation practices rather than a single spray. Organic treatment Remove and discard affected leaves right away; don't compost them. Apply a copper-based fungicide. Make sure the plant has good airflow by keeping it staked and pruning any very dense growth.Remove affected leaves. Apply copper fungicide. Ensure good air circulation. Prevention Rotate your tomatoes to a new spot each year. Water at the base of the plant only, never from overhead. Mulch around the base to prevent soil splash.Rotate crops. Water at soil level. Mulch around plants.
Symptoms Water-soaked patches that turn brown and expand rapidly on the leaves and stems; this disease moves very fast and can destroy a plant in a matter of days. In humid conditions you may see white fuzzy growth on the undersides of leaves. Late blight is the most serious tomato disease in the garden.Water-soaked, rapidly expanding brown patches on leaves and stems. White fuzzy growth on undersides in humid conditions. Can destroy plants in days. Cause Late blight is a fast, destructive disease (the one that caused the Irish potato famine). Its spores blow in on wind and rain rather than starting from the soil, and in cool, wet weather it can kill a plant in just a few days. Because it arrives through the air, the best protection is choosing resistant varieties and pulling out any infected plant right away.The oomycete Phytophthora infestans, the same pathogen behind the Irish potato famine. Unlike the blights that start at the soil line, its spores travel on wind and rain over long distances and infect leaves, stems, and fruit directly, spreading explosively in cool, wet weather and able to kill a plant in days. Because the inoculum arrives airborne, resistant varieties and immediate removal of infected plants matter more than rotation. Organic treatment Remove and immediately bag and bin all affected plant material; do not compost any of it, as late blight spreads easily. Apply copper-based fungicide spray in wet periods as a preventive measure. If the plant is severely affected, remove it entirely.Remove and destroy all affected material immediately; do not compost. Apply copper fungicide preventively in wet conditions. Prevention Good airflow around the plant is your best defense: stake and space plants so air can move through. Never leave tomato plant debris in the garden over winter, as the pathogen can survive there. Plant resistant varieties if late blight has been a recurring problem in your area.Plant resistant varieties. Ensure excellent airflow. Never leave tomato debris in the garden over winter.
