I found some very small black flies on tomatoes leaves and stems. (Please See the circled area in the photo. ) I also saw small small holes on leaves. What should I do ? Thanks for your help.
Thank you for contacting the Toronto Master Gardeners. I wish I could see the bugs in your picture better, but I think they might be flea beetles or aphids.
One of the leaves has damage that looks like the small holes you described. Adult flea beetles chew holes like this. They are a common pest found on many vegetables. They are tiny and can be black, brown, bronze or striped. They move very fast when disturbed, leaping out of sight; that is they jump, they don’t fly. Flea beetles are most harmful to seedlings, in the spring. Larger plants like yours are mostly able to withstand the damage. Heavy infestations can leave leaves with bleached or pitted spots, ragged holes, or even no leaves at all, which makes plants wilt or grow slowly. Adults overwinter in the soil and plant debris, emerging in spring to feed. They lay their ages in the soil and usually die by mid-summer. In a week, the larvae will hatch and start feeding on the roots. For a few weeks, they do not usually do much damage. The larvae pupate in the soil and mature into adults in 2–3 weeks. There is usually only one generation each year, sometimes more.
You can get yellow sticky traps at garden centers that you could put around your plants to see if you really do have flea beetles. Most of the time, you don’t need to treat flea beetles in the summer because they die off and won’t do much damage to older plants. From the picture, I can’t be sure, but I think your plants are in the garden instead of pots. If they are in the garden, you could use nematodes to kill the larvae and rotate your crops next year so that the tomatoes are replaced with something that flea beetles can’t eat. If they are in pots, get rid of the potting soil at the end of the season so that adult flea beetles don’t use it to spend the winter. Then, start over with new potting soil the following year.
The other possibility is that the insects on your plants are aphids. These are also very common. They are small (but bigger than leaf beetles), and they can be black, red, yellow, brown, green, or gray. Adult aphids can be winged or wingless. Their mouthparts pierce young leaves and stems and they suck the sap. They are usually found often in clusters on the undersides of leaves. The damage caused by aphids is twisted yellowing leaves and stunted or dead shoots. You can tell that something is an aphid by the sticky substance it leaves behind while feeding: honeydew. This attracts other bugs and helps a fungus grow called sooty mold. When you want to get rid of aphids, you can use a high-pressure spray from a garden hose or spray insecticidal soap on the whole plant, including the undersides of the leaves.
Here are a couple of links with information about these insects. Please keep in mind that these websites are in the US. If you live in Ontario, where pesticide use is strictly prohibited by law, the information on these websites will be very different. I have also attached a link about pesticide use in Ontario.
Dealing with Annoying Little Flies on Your Tomato Plants
As a tomato gardener, few things are more irritating than walking out to your plants and finding tiny flies buzzing around everywhere. These pesky insects seem to appear out of nowhere and can quickly become a nuisance. While flies around tomato plants are usually not harmful, they can indicate other problems and if populations become large, they may bother ripe fruit. Knowing what attracts flies, how to identify them, and control methods can help you take back your tomato patch.
Common Culprits: Fungus Gnats and Shore Flies
Two of the most likely flies seen flitting about tomato plants are fungus gnats and shore flies Identifying which one you have is the first step toward addressing an infestation
Fungus Gnats
Fungus gnats are dark gray or black flies about 1/8 inch long with long legs and antennae. The larvae feed on decaying plant material and fungi in moist soils. Adults lay eggs in soil, compost or potting mix, especially where organic matter is abundant. The larvae emerge and feed near plant roots.
Shore Flies
Shore flies are small dark flies about 1/16 inch long. They are often seen on damp soil, potted plants and around decaying vegetation. The larvae live in wet organic material. Shore flies are attracted to algae and fungus growing in wet sites.
Other occasional tomato flies include fruit flies, phorid flies and moth flies. Identifying the specific fly helps determine if breeding sites other than soil or decaying plants on which larvae feed need to be eliminated.
Why Flies Are Attracted to Tomato Plants
There are several reasons you may see small flies flocking to your tomato plants:
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Wet soil from excessive watering or rainfall provides ideal breeding conditions for fungus gnat and shore fly larvae.
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Decaying plant debris attracts flies seeking food for larvae.
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Over-ripened or damaged tomatoes lure fruit flies wanting to lay eggs.
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Tomato flowers provide needed nectar for adult shore flies.
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Nearby compost piles or manure give flies a place to breed.
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Over-mulching with fresh green material creates moist fly habitat.
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Weedy garden areas provide alternative fly breeding and feeding sites.
Simple Ways to Control Flies on Tomato Plants
The key is to control flies through cultural practices first before resorting to pesticides if needed:
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Allow soil to dry out between waterings to deter fungus gnats and shore flies. Improve drainage if needed.
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Remove garden trash and overly wet mulch promptly to eliminate fly breeding sites.
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Till in or remove spent plants immediately after harvest to avoid decaying debris.
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Use yellow sticky traps near plants to monitor and catch adult flies.
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Pick ripe tomatoes promptly to prevent fruit fly issues. Dispose of any damaged fruit.
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Remove weeds around the garden to eliminate alternative food sources and habitat.
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Cover compost piles securely to contain fly populations.
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Apply a thin layer of sand or diatomaceous earth on top of potting soil to desiccate emerging larvae.
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Use Bacillus thuringiensis (Bt) biological insecticide to target larvae in soil if needed.
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In severe cases, use pyrethrins or insecticidal soap sprays following label directions to control adult flies.
Preventing Future Fly Problems
Good sanitation and cultural practices are the best defenses against future fly infestations:
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Allow soil to dry adequately between waterings. Improving drainage can help.
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Eliminate excess mulch, leaf litter and garden debris where larvae can breed.
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Solarize soil or incorporate beneficial nematodes to reduce larva populations.
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Rotate plants to avoid building up soil pests in one area.
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Cover compost and use proper composting methods to destroy larvae.
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Use row covers early in season to exclude adult flies from plants.
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Use sticky traps continuously to monitor for increases in flies and catch adults.
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Remove spent plants and till under debris after harvest to disrupt breeding sites.
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Control broadleaf weeds and grasses throughout the garden that can harbor flies.
While flies are more of nuisance than direct threat to tomato plants, taking sensible precautions to reduce their numbers through sanitation and soil moisture management will allow you to reclaim your garden and enjoy pest-free tomatoes. Combining preventive cultural practices with selective control methods when needed offers the best control.
Identifying Aphids on Tomato Plants and Using Soapy Spray – The Rusted Garden 2013
FAQ
Why are there tiny flies around my tomato plant?
How do you get rid of gnats in tomatoes?
How do I get rid of little flying bugs in my plants?
How do you get rid of tomato flies?
Wash off the eggs, larvae, and adult tomato flies from on top and under the leaves. Spray weekly in case the infestation is still there. If you use insecticidal soap, don’t increase the amount required to avoid plant damage. Discard any heavily infested tomato plants to prevent spreading to other plants.
What flies eat tomatoes?
Fruit flies are some of the most common flies you’ll find around tomato plants, especially around harvest time. These flies will typically congregate near flowers and fruits, including immature fruits, and will feed off both fruits and the leaves and stems of the tomato plants.
Are white flies harmful to tomato plants?
However, it has been known to be toxic to some aquatic life, so avoid using it near an inhabited water feature. Whiteflies are pesky pests that are often annoying and damaging to tomato plants. This article describes how to get rid of whiteflies on tomatoes.
How do you get white flies out of a tomato plant?
Spray both sides of the potted tomato plant’s leaves with a blast of water. Attach a sprayer head to your garden hose and wash away the immature and adult whiteflies from the leaves. Repeat weekly, or if you notice a reinfestation. Avoid increasing the dish or insecticidal soap, as this can damage the plant.