Tomato thrips are undoubtedly some of the most destructive insect pests that, if not well controlled, can cause massive losses to farmers. Unfortunately, some growers don’t know how to treat or prevent these disastrous insects, which allows the pests to thrive and cause unwanted damage to crops like tomatoes.
Here’s how to treat thrips on tomato plants:
- Identify thrips on your tomato plants.
- Determine the damage caused by thrips.
- Control thrips using a biological approach.
- Use organic sprays to control thrips.
- Get rid of thrips using cultural methods.
- Treat thrips infestation using chemicals.
- Protect your tomatoes from thrips infestation.
This article is a complete guide on how to treat thrips on tomato plants. It discusses how to identify thrips, the damage they cause to tomatoes, and how to get rid of them. So, read on to learn more.
1. Identify Thrips on Your Tomato Plants
There are about 5,000 species of thrips that destroy crops all over the world, including tomatoes, potatoes, and groundnuts. The pests are a significant threat to plant growth and development.
Therefore, it’s essential to know what these bugs look like and determine if they have attacked your tomato plants early to prevent severe losses.
How Thrips Look Like
Also known as Thysanoptera or thunder flies, thrips are tiny, slender, and winged insects. They can damage crops through direct feeding or by transmitting viruses. These pests can also move long distances floating in the air to infect new plants.
Most adult thrips have slender, elongated bodies. They are also minute – less than 0.04 inches (0.10 cm) long. In addition, they have two pairs of narrow wings fringed with fine hairs, although some are wingless.
Thrips are pale yellow to light or dark brown, with males being smaller and paler in color than the females. However, their appearance can vary depending on the temperatures at which they developed. Therefore, thrips that grow in cooler temperatures will appear darker.
If you suspect that these bugs have attacked your tomato plants and want to examine them:
- Beat or sweep the plants using a sweep net or a beating tray
- Study them closely using a hand lens
Note: Alternatively, you can close-examine your tomato flower heads, especially in spring and summer, when these pests are in large numbers.
Knowing what thrips look like at different developmental stages is also essential. Hence, let’s look at the pests’ life cycle:
The Life Cycle of Thrips
In spring, adult female thrips insert their cylindrical to kidney-shaped eggs into the tissues of flowers, stems, or leaves of plants. Each female thrip can produce up to 80 eggs without having to mate with the male.
The eggs then hatch after a couple of days in warm weather (or weeks to months in cold weather) to form wingless, slender, elongated larvae called nymphs. The larva is a feeding stage of the insect pest and feeds mainly on the sap of plants, hence a destructive phase.
After two or more nymphal stages, many thrips species fall into the soil or litter, where they develop into pupae. Some species pupate in plant crevices or galls of leaves, twigs, or roots of plants. Others undergo a pre-pupa stage before the actual pupa stage.
Later, adult thrips emerge and fly to the plant leaves, flowers, and stems, and the cycle repeats itself. Adult thrips feed on these plant parts, causing immense crop damage.
Female thrips have an average lifespan of 60 days, while their male counterparts live up to 30 days. Mating dramatically reduces the lifespan of male insects, reducing it to about half that of females.
Uniquely, mating in thrips doesn’t have to occur every time they want to reproduce. Female thrips store sperm after a mating encounter that fertilizes their eggs for their entire life.
How To Spot Thrips in a Tomato Plant
Since thrips are so tiny, it is difficult to see them without the aid of a magnifying instrument like a hand lens or a microscope. These winged pests like to hide under the leaves of the plant and inside the flower buds.
Since it is not easy to see the insects with the naked eye, the easiest way to spot a thrip invasion on your tomato plants is to look for signs.
Some of the signs you can look out for include:
- Dry or brown-spotted leaves
- Stippling (pale spots) in leaves
- Fallen leaves
- Splotches on tomato flowers
- Stunted growth
Additionally, thrips transmit the tomato spotted wilt virus, which makes your tomato plants produce undersized or discolored tomatoes. So, you’ll know that your plants are experiencing a viral attack (courtesy of thrips) if you notice the following symptoms:
- Brown (bronzing) leaves
- Cupping downwards of leaves
- Necrosis (death) of the plant
2. Determine the Damage Caused by Thrips
Thrips cause direct damage to tomato plants since they feed on the fruits, flowers, leaves, and shoots. The infestation significantly affects the appearance of a plant. However, not all thrip species cause immense losses.
Therefore, determining what species have invaded your crops and how severe the infestation is can enable you to identify the best control or management strategy. So, to identify the thrip species invading your tomato plants:
- Beat or gently shake the foliage leaves or flowers on a sheet of lightly colored paper or a beating tray.
- If you suspect that thrips are hiding in the flower buds or unexpanded shoot tips, cut the parts.
- Place the suspected plant parts in a container with 70% ethanol.
- Shake them vigorously to dislodge the thrips from the plant part.
- Filter the solution using filter paper to make the thrips more visible.
- Consult an expert to identify the thrip species invading your crops.
Note: You can also take the plants suspected of thrips infestation to a laboratory for expert advice on controlling the pests.
Let’s now look at the damage thrips can cause to each part of the tomato plant:
Western flower thrips have mouth parts that are adapted for piercing and sucking. Therefore, they feed on the epidermal and mesophyll tissues of leaves, causing:
- Distorted growth of leaves
- Leaf scarring and wilting
- Falling of leaves
- Sunken tissues on the lower side of the leaf
Additionally, such leaves develop a characteristic silvery appearance. Sometimes they can develop little black spots due to thrips defecating on them. The insects also damage the leaves by depositing their eggs in the plant tissue using their sharp ovipositors.
Thrips thrive on expanding plant tissues. As a result, they destroy the stems of tomato seedlings before they become hardy. Their attack on young stems causes stunted growth and even death of the tomato plant.
Fruits and Flowers
Thrips attack tomato fruits, causing yellow spots and discoloration. If the insect population is high enough, the fruits will not grow to full size, and some may not even become mature.
Thrips feed by sucking the content of the epidermal cells of plants. When they feed on the fruit, it results in a condition called flecking. However, you can only notice this when the fruit has matured, although it occurs when it is young.
The adults of the western flower thrips and larvae of all species of thrips cause flecking.
Thrips also feed on tomato flowers and flower buds. As a result, these floral parts become deformed. Furthermore, affected flowers don’t mature to produce fruits since most of them fall off the plant.
3. Control Thrips Using a Biological Approach
You can choose one or a combination of methods to control thrips after they’ve infested your tomato garden. For instance, a biological approach is ideal if you’re practicing organic farming since it doesn’t harm other organisms in the ecosystem.
The approach involves using thrips’ natural enemies to eliminate these pests from your tomato plants. Examples of such predators include:
- Green lacewings
- Minute pirate bugs
- Predatory mites
- Parasitic wasps.
The pirate bug and its relatives have shown great potential as thrips predators in greenhouse tomato crops. On the other hand, the predatory mite – commonly used to control fungi, can only provide some control against thrips that are pupating in the soil.
You can buy most of these natural thrips predators from agrochemical stores near you. However, using these predators may not always be practical. Hence, you can embrace an Integrated Pest Management Program to keep the pests at bay.
4. Use Organic Sprays To Control Thrips
Organic soap-based sprays are chemical-free substances you can use to control thrips infesting your tomato plants. It is advisable to use commercial organic sprays since they comprise the correct concentrations. Making them home using soap can produce very concentrated sprays, damaging tomato plant foliage.
However, if you decide to make your own spray, use mild soap and add a little amount of rubbing alcohol to help the spray stick to the tomato plants.
Commercial organic sprays comprise naturally occurring plant oils and fats and can knock down heavy thrips infestations without harming other beneficial insects.
5. Get Rid of Thrips Using Cultural Methods
Cultural pest control methods involve changing your farming practice or crop production systems to minimize infestations. These approaches work best for organic gardens.
Some of the cultural approaches you can use to control thrips in your tomato garden include:
- Removing old leaves that might be infected with thrips and disposing them of.
- Planting tomato varieties that are more resistant to thrips infestation.
- Pruning excess branches that might be infested with thrips and disposing them of.
- Irrigating your tomato plants correctly to minimize water stress.
- Planting crops like Spanish needles to help reduce thrip infestations on tomatoes close to the crop.
- Avoiding planting crops that are susceptible to thrip infestation.
6. Treat Thrip Infestation Using Chemicals
Chemical treatment is one of the most common ways to control thrip infestation in traditional (non-organic) gardens. You can use several insecticides to control thrips in your tomato plants. However, it’s not very easy to treat the pests using these insecticides mainly because of their mobility, feeding behavior, and the fact that the egg and pupa stages are protected.
Some of the reasons your insecticide may not eliminate thrips from your tomato plants include:
- Improper timing of application.
- Failure to apply the chemical to the proper plant parts.
- Inadequate spay coverage.
It is also essential to learn and study the biology of the thrips species affecting your plants and compare them to the available insecticide characteristics before deciding on the best insecticide to use.
Larva and adult stages of thrips are more susceptible to insecticides than the egg and pupa stages. Therefore, it would be best to target the larval and adult stages when using insecticides to control thrips.
When applying the insecticides, ensure good coverage of the underside of leaves where thrips mostly hide. If the plants are bushy, it would be best to prune them before spraying the chemical.
If you’re using Integrated Pest Management Programs, ensure that the chemical spray you use will not harm other beneficial insects. If necessary, consult a specialist on this before buying an insecticide.
Note: Combining insecticides with cultural and biological pest control methods improves these approaches’ efficiency.
7. Protect Your Tomato Plants From Thrips Infestation
Prevention is always better than treatment. However, it’s challenging to prevent thrips from entering your tomato garden. Since thrips are tiny, lightweight, and primarily winged, the air blows them quickly, and they can land in your garden anytime.
Nonetheless, here are a few measures you can take to protect your tomato plants from attack by thrips, including:
Keeping Your Garden Clean and Weed-Free
Keep your garden litter-free by collecting any pruned leaves, twigs, or flowers lying on the ground, especially in winter. Additionally, remove and destroy any dead plants hosting thrips eggs. So, maintaining a clean, healthy garden will minimize the chances of thrips attacking your tomato plants.
Many types of weeds are hosts to various species of thrips. A study on how weeds contribute to thrip infestation showed that several weed species, including S. arvenis, are hosts to western flower thrips.
As a result, keeping your tomato garden and its surroundings free of weeds is always advisable.
Covering Your Tomato Plants
Covering your tomato plants with a fine mesh cloth can also prevent them from facing a thrips invasion. An alternative would be to plant your tomato plants inside a greenhouse. Although this option is costly, it can effectively keep off thrips from getting into your tomato garden.
You can use row covers to prevent thrips from attacking your tomato plants. These tightly woven fabrics allow water and sunlight to reach your plants but keep off thrips and other flying insects.
However, for tall plants like tomatoes, the most effective way to do this is to attach hoops over the tomato bed and then wrap the fabric over the rings. Alternatively, you can drape the fabric over potted tomato plants and then secure the material to the pots or the ground using sticks.
Minimizing Fertilizer Application to Your Plants
Applying excess nitrogenous fertilizers (more than the recommended quantities) leads to a severe infestation of all thrips species. For instance, an increase in the levels of aromatic amino acids in over-fertilized tomato plants makes the plants attract more adult female western flower thrips.
Therefore, applying the recommended amounts of fertilizer to your tomato plants can help minimize the attraction of thrips to your crops.
Using Ultraviolet Mulch
You can also protect your tomato plants from thrips by planting them in a bed spread with ultraviolet mulch. Also called metalized or reflective mulch fabric, this cover repels thrips and other flying insects by disorienting them. As a result, it’s an effective method of keeping thrips at bay.
Protecting Tomato Plants in Greenhouses From Thrips
Although planting tomato plants in a greenhouse is safer, it’s still not a fool-proof approach. You can try several methods to minimize or prevent a thrip invasion on tomatoes in your greenhouse.
- Checking and ensuring that you use thrip-free seedlings.
- Covering the doors and vents of greenhouses with an insect-proof netting.
- Repairing any broken glass or plastic in time to keep off thrips.
- Keeping the greenhouse clean by removing all weeds and crop remains – You can also fumigate the greenhouse or keep it hot and dry for at least a week.
- Keeping areas around the greenhouse free of weeds.
- Using hygienic plant propagation methods and keeping batches of seedlings separately to prevent transmission of thrips from one batch to another.
Keeping Your Tomato Plants Away From Thrip-Prone Crops
Plants like onions, cereals, and garlic often harbor large numbers of thrips. Therefore, you can protect your tomato plants from these destructive pests by avoiding intercropping them with thrip-vulnerable crops.
Moreover, it would help if you don’t plant your tomato plants close to these crops because thrips will move from them to your tomatoes.
Other methods to prevent thrip infestation include planting tomato varieties resistant to thrips and rotating tomatoes with non-host crops.
Thrips are insects that can damage various crops, including tomato plants. Although some species are not very destructive, most invasive thrip species can cause massive crop losses.
Luckily, following the proper procedures to control and prevent thrips can help keep your tomato plants healthy and productive.