Thrips (Thysanoptera) can cause serious damage to roses. Instead of the usual bright-colored blooms, your roses suddenly develop brownish petals and distorted buds, and the leaves have ugly pale spots. The deformed, rusted leaves start falling off, and the buds only open partially or not.
Thrips have a small, elongated body measuring about 1/16 inches. Depending on the species, they have fringed wings and appear yellowish, brownish, or orange. To get rid of thrips, cut and dispose of the damaged parts and treat the remaining plant parts with neem oil.
What are thrips? (Identification)
Thrips, scientifically called order Thysanoptera, are small insects of over 5000 species, some of which feed on plants while others prey on animals. The most common plant thrips on roses are flower thrips and western flower thrips.
According to North Carolina State University, thrips have small, elongated bodies of 0.5mm to 14mm long, depending on the species. However, plant thrips that frequent roses are 1mm or 1/16 inch long. Their tiny bodies make it difficult to see thrips with the naked eye, even at close examination.
Most thrips that invade roses have yellowish, brownish, or orange bodies. They also have fringed or hairy wings.
Life cycle and reproduction
Thrips have three stages in their life cycle, taking anywhere from two to three weeks.
They undergo asexual reproduction in a process called parthenogenesis, where a female thrip lays unfertilized an egg on surfaces of leaves, flowers, or buds. The egg hatches into larvae and later into a pupa before becoming an adult.
How do you know you’re dealing with thrips on your roses?
If you suspect your roses of thrips, quickly pluck one blossom and examine it. Remove the outer petals and smack them against a white paper, cloth, or tray.
The presence of yellowish or orange tiny insects of 1/16 inches long signifies thrips. Alternatively, blow air into the flower and observe tiny moving insects of yellowish or orange color.
Another way to confirm thrips on roses is to examine the plant parts carefully. Flecking and distorted buds, brownish leaves, and discolored petals signify thrips.
Signs of thrip damage on roses
Apart from just identifying the thrips, you also want to check the signs and be sure you’re dealing with an infestation.
Here are the signs of thrip damage on roses:
- Discolored flowers or petals– Bright-colored or white roses affected by thrips develop dark or brownish petals due to color break, which occurs when thrips feed on the petal tissues before the flower opens.
- Distorted buds that fail to open– Thrips in roses penetrate the buds and hide inside them, making them open partially or not in the blooming period. In addition, the buds distort and fall prematurely from the plant.
- Stunted growth– Thrips aggressively feed on the pollen grains and suck the cell sap from tissues. Because they feed on cell sap that the plant should use for growth, thrips-infested roses grow slower than normal plants.
- Flecked, distorted leaves– Thrips on rose cause flecks or pale spots on the surface of leaves near the affected buds. The spots result from thrips feeding on the leaves’ tissues before they open. In addition, the leaves appear distorted or deformed and drop off prematurely from the plant.
- Silvery plant tissues – Thrips use their mandibles to penetrate cells to suck sap, leaving silvery marks on the pricked parts.
- Black feces and distortion marks – Thrips often leave black droppings on the infested leaves. You’ll also notice white marks of distortion on the leaves of your roses.
How to Get Rid of Thrips on Roses
Although they have small bodies and cannot be easily seen, thrips aggressively feed on roses and destroy them fast. Their mandibles prick the outer layer tissues and suck the fluids from the cells. Infested rose flowers change their bright color to brown. At the same time, damaged buds, leaves, and flowers are unsightly.
Here’s how to get rid of thrips on roses:
Cut and dispose of damaged parts
Damaged parts don’t recover; thus, remove them to allow for fresh growth. Identify brownish-discolored flowers, distorted buds, dotted leaves and other damaged plant parts and cut them off your rose bushes and plants.
Dispose of the cut parts by placing them in a plastic bag and transfer them to the waste bin.
Spray the thrips with water, neem oil, or insecticidal soap
Thrips on roses hide at the base of the flower and in the closed buds. After removing the damaged rose parts, deal with the live thrips hiding.
Fill a spray bottle with neem oil, horticultural oil, or insecticidal soap and spray all over the plant to remove live thrips. Soak the infested plant parts until they’re dripping wet. Spray again after 6-8 days and repeat the cycle four times until the thrips are gone.
Smart tip: For best results, treat the roses with neem oil when there’s no wind, preferably early in the morning or evening. The temperature should be below 35°F. After four successful sprays, all the thrips will be gone.
Can you kill thrips when roses are flowering?
You can kill thrips when roses are flowering by spraying them with neem oil. Neem oil is safe and won’t damage the blooms or other parts of the roses when applied.
Keep in mind that roses attract bees. I recommend avoiding contact insecticides when roses are blooming since bees can easily trap and transfer the chemical particles to other plants in the garden, which is detrimental to the ecosystem.
Thrips are challenging to control once they infest your roses. The best measure is to prevent them by creating an environment that makes them uncomfortable.
Here are the best ways to prevent thrips on roses:
Thrips that feed on plants invade grasses and weeds that grow near the rose – especially in summer and spring. These insects find their way into nearby rose bushes and settle on them. Regularly cut nearby weeds and grasses and those at the base of the roses to ensure they have nowhere to live.
In addition, plant thrip-resistant trees or plants nearby so thrips don’t live on them and spread to your roses.
Grow your roses in a conducive environment
Roses thrive in rich, well-draining soil and under full sunlight for at least six hours of daily exposure. When planted in unfavorable conditions, roses suffer and become susceptible to diseases, weeds, and pests. That’s where thrips take advantage and invade roses since they aren’t rigorous or competitive.
To prevent thrips invasion, water the plant regularly and place the pot in full sun for at least six hours. The soil must be well-draining and fertilized regularly to make the plant flourish and thus leave no chance for thrips infestation.
Use row covers
Row covers, also called cages, prevent thrips and other tiny insects from penetrating and living in the roses. Thrips mostly migrate in large groups from nearby weeds and grasses to gardens and landscapes in summer and early spring.
Row covers have a tiny wire mesh that allows air and light penetration into the plants. However, they effectively block thrips when the rose plant is young and when they are highly susceptible to pests and insects. If your roses are young and thrips-free, add a layer or row covers to prevent thrips from penetrating. After the roses mature, remove the raw covers to allow more room for growth.
Reduce the use of nitrogen-rich fertilizers on the roses
The University of North Carolina Agriculture & Natural Resources reports that excessive use of nitrogen fertilizers promotes thrips in roses. This is because nitrogen-rich fertilizers soften the roses’ tissues, making them an easy target for thrips to prick and suck their cell sap for survival.
To prevent thrips on roses, reduce the number of synthetic nitrogen fertilizers you apply. Low-nitrogen fertilizers such as organic no-frills rock dust and prime garden fertilizer are ideal. Alternatively, apply composted manure that contains low nitrogen.
While insecticides can control thrips, using them is not advisable unless with strict restrictions. These insects are unnoticeable due to their small bodies. You’ll only realize them when flowers discolor and fall off the plant.
By then, they shall have developed into adults and be flown to a new location. Worse, chemicals don’t treat damaged parts unless they disappear or new growth emerges.
Therefore, the chemical control of thrips can only be successful when combined with the other physical and cultural control methods we discussed earlier.
Here are the precautions when using chemicals to control thrips.
- Use non-toxic contact chemicals that leave no residue on plant parts– contact chemicals are ideal for killing thrips on open plant parts. However, the chemical should be non-toxic to people, pets, and other plants and leave no residue after treatment. Spinosad is a non-toxic contact insecticide that kills thrips effectively.
Meanwhile, avoid using systemic organophosphate acephate insecticide since it’s toxic to natural pollinators such as bees.
- Reapply the insecticides until all the thrips are killed– To kill thrips from your rose plants completely, reapply the insecticide weekly until all the thrips are gone.
- Avoid using chemicals when the roses bloom– Roses bloom in late spring and early fall. The chemical particles can fall on the flowers, which bees can feed on or stick on their bodies, as reported by this article from Michigan State University. Bees feeding on and transferring harmful chemical particles to other plants is detrimental to the ecosystem.
Remove them immediately
You know you have thrips on your roses if you notice small, elongated insects with fringed wings that appear orange or yellowish. Therefore, remove them immediately.,
Cut and dispose of the damaged parts and spray insecticidal soap, water, or neem oil to eliminate the remaining live thrips. After successful removal, prevent future invasions following the methods we’ve discussed.
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