How to Safe Thrips Treatment for Vegetables and Flowers?

type

status

date

slug

summary

1. What are Thrips?

Identify Thrips

The larva thrips show a rectangular translucent yellowish color body with no wings. The adult thrips are slender, about 1~2mm long, and have two pairs of slender wings with tassels. The body appears dark brown or black. Their needle-like mouths can pierce the surface of plants and then suck up plant sap.

We can identify different types of thrips by checking their looks and the host plant. For example, adult western flower thrips and onion thrips are larger than avocado and citrus thrips.

Some common pests thrips and host plants

Signs of Damage

Thrips damage the buds, leaves, and fruits of plants and affect plants' appearance. Thrips like to attack hydrangea, camellias, carnations, persimmons, cucumbers, eggplant, tomatoes, onions, etc. And thrips spread quickly among these plants, especially when these plants are young.

Leaves

Thrips feed on the undersides of leaves, causing the leaves' upper surface to appear silver or bronze. This hinders the growth of plants and causes their leaves to become crisp and twisted.

Sometimes, these pests produce small white spots on plant leaves, which fall off early because they pierce the leaf cells and suck out the sap.

Cuban laurel thrips can cause galled foliage on Ficus from midsummer to fall. Myoporum thrips cause plants to form galls-like tissue in which many thrips reproduce and survive.

Flowers

Western flower thrips mainly attack herbs. But large amounts of thrips will damage the flowers of woody plants, such as roses. Before the bud opens, thrips kill the petal tissue, causing the petals to change color. If dark stripes or spots appear on your rose's flowers, it could signify thrips infestation.

Fruits

Thrips can create scab-like brown or silver scars on avocados and oranges skin. However, these scars do not affect the taste or the inside of the fruit.

When thrips lay eggs on grapes, the fruits of the grapes show black scars. These sucking insects deform or scar the fruits of apples, nectarines, and raspberries.

Citrus thrips can cause severe damage to blueberry buds and leaves, leading to reduced fruit yield.

2. How Do Thrips Harm My Garden?

Stage 1: Egg Stage

The egg stage is the first phase of its life cycle. Thrips usually lay eggs in plant tissue or on the surface of plants. Its eggs are so small, typically translucent or white. The time for eggs to hatch depends on temperature and humidity, ranging from a few days to weeks.

Curled Indian laurel fig leaves, Cuban laurel thrips, Gynaikothrips ficorum, yellow nymphs, black adults, and pale eggs are exposed. Credit: Jack Kelly Clark. Cite: UC IPM

Stage 2: Nymph Stage

Once the eggs are hatched, the thrips enter the nymph stage, which usually lasts one to three weeks. Nymphs of wings have not fully developed. Nymphs experience molting in the growth process, and each molting represents that the nymphs are growing. Nymphs can eat up a lot of plant tissue and cause damage to plants.

Stage 3: Adult Stage

Unlike other pests, thrips have no actual pupa stage.

When the nymph completes its development, the thrips enter the adult stage. Adult thrips have wings and can fly. They still feed on plant tissue, piercing plant cells with needle-like mouths and feeding plant sap. Adult female thrips reproduce their offspring by laying eggs.

The life span of adult thrips usually ranges from a few weeks to several months.

During the year, thrips break out from mid-April to early October. I will take precautions in early April. If thrips already exist on plants, I will wipe them out by mid-October at the latest. Otherwise, I will isolate and burn the infected plant.

When the conditions are suitable for breeding, thrips can multiply quickly. Female thrips can produce 80 eggs once and reproduce many generations in a single growing season. This results in exponential pest number growth and overlapping generations.

Wind and plant transplants are both ways of passive transmission. The wind can carry thrips far away, allowing them to breed in new places. If there are thrips on cuttings or transplanted plants, they will also transfer with the plant.

Thrips are super annoying because they keep reproducing like crazy until the day they die. If you are not careful, the harm of thrips will spread in the garden like a plague.

3. Safe Treatment Options for Thrips

As long as you grow plants, you do not thoroughly eliminate thrips. However, once these pests propagate on a large scale, they are difficult to control. Therefore, the process of thrips control requires care and patience. In general, there are six ways to control thrips.

Monitor;

Exclusion Methods;

Mechanical Control;

Cultural Practices;

Chemical Control;

Natural Enemies.

3.1 Monitor

It is vital to regularly check plants for signs of thrips, specifically during the evening when they become active. Thrips tend to be dormant during the day and come out at night to feed on the sap of plants. When checking, we should closely observe the leaves' back for signs of stippling, twisted growth, and adult thrips. To monitor the activity of adult thrips, we can use sticky traps in yellow or blue colors.

3.2 Exclusion Methods

To protect delicate plants from thrips, cover them with row covers or netting that keeps thrips out. This is especially important during times when there are a lot of thrips around.

We need to pay attention to the size and temperature of the plant when using the row cover. We should remove covers when the plants grow fast, or the temperature rises. This ensures the plants have enough space and the right temperature.

3.3 Mechanical Control

When we first found thrips, we could use water guns to spray water to wash them away from the surface of plants. Then, trim and remove the infected parts to reduce their number.

3.4 Cultural Practices

Keep the garden neat and clean. Remove weeds from the garden in time, as these weeds are alternative hosts for thrips. After pruning, removing plant debris can reduce thrips' breeding sites.

Although nitrogen fertilizer is an essential nutrient for plants, don't overuse it. Excessive use of nitrogen fertilizer can damage the ability of plants to resist diseases and pests. Thrips, aphids, powdery mildew, and other pests and diseases easily break out with too much nitrogen fertilizer.

3.5 Chemical Control

Insecticides can also help us control thrips. However, this method can not kill thrips quickly. Insecticides usually don't work until the next growing season of plants. So, to prevent the transfer of thrips from diseased plants to healthy plants, using row covers is the most effective way to avoid thrips.

The toxicity of insecticidal soaps and neem oil is relatively low. When we use it, we should thoroughly cover the buds, stems, and leaves, especially the back of the leaves. As long as thrips exist on plants, we must reuse them regularly.

Compared with these two products, spinosad rid of thrips is more effective. Its effect can last for a week. But don't use spinosad on flowering plants because it kills bees.

We can also use chemical pesticides when necessary. Dinotefuran and Imidacloprid have sound effects on the control of thrips. These products are toxic. They kill not only pests but also beneficial insects in the garden.

3.6 Natural Enemies

There are many species of thrips, so different species of thrips have different natural enemies. For example, green lacewings are the natural enemy of Cuban laurel thrips. I have not tried to put these insects that control thrips in the garden because there is little research on this control method.

Bibliography:
Ananthakrishnan, T. N. "Bionomics of thrips." Annual Review of Entomology 38.1 (1993): 71-92. https://doi.org/10.1146/annurev.en.38.010193.000443
Stuart R. Reitz "Biology and Ecology of the Western Flower Thrips (Thysanoptera: Thripidae): The Making of a Pest," Florida Entomologist 92(1), 7-13, (1 March 2009). https://doi.org/10.1653/024.092.0102
John Diaz-Montano, Marc Fuchs, Brian A. Nault, József Fail, Anthony M. Shelton, Onion Thrips (Thysanoptera: Thripidae): A Global Pest of Increasing Concern in Onion, Journal of Economic Entomology, Volume 104, Issue 1, 1 February 2011, Pages 1–13, https://doi.org/10.1603/EC10269
Ataide, L.M.S.; Vargas, G.; Velazquez-Hernandez, Y.; Reyes-Arauz, I.; Villamarin, P.; Canon, M.A.; Yang, X.; Riley, S.S.; Revynthi, A.M. Efficacy of Conventional and Biorational Insecticides against the Invasive Pest Thrips parvispinus (Thysanoptera: Thripidae) under Containment Conditions. Insects 2024, 15, 48. https://doi.org/10.3390/insects15010048

My name is Arthur Mo. I am a gardener who loves gardening so much. I graduated from Ocean University of China. After I returned to Japan, I began to learn how to cultivate hydrangeas and daisies. Mr. Mitsuhiro (my master) taught me to sow, cut, fertilize, and manage diseases and pests. For nine years, I have been sharpening my planting skills. In 2022, my family and I moved to Florida. The warm climate of Florida gives me the impulse to continue cultivating hydrangeas and daisies. I began my gardening trip in my backyard and unswervingly contributed my efforts to these plants. I love these plants deeply, and at the same time, I also thank my family, my master, and friends for their understanding and support.