Although orchids are typically trouble-free plants, if you’re an orchid grower, you’ll inevitably run into issues with plant maintenance from time to time.
Knowing how to prevent orchid pests from invading your plant, spot problems with your orchid if it does show signs of pests, and know how to quickly and effectively get rid of those pests that do take up residence in your plant are essential skills for anyone who wants to grow orchids successfully and successfully throughout the year.
Knowing how to handle pest problems will enable you to care for and maintain your plant back to health in any situation.
Let’s look at orchid pests and how to spot, avoid, and get rid of them from your orchid.
Common Orchid Pests
Scale on Orchids
Symptoms: Scale is sucking insects that feed on rhizomes, pseudobulbs, the underside of leaves, and the axils of leaves. Frequently, they are concealed by old leaves and pseudobulb sheaths. When a plant is severely infested, chlorotic areas start to appear on the leaves and plant surfaces. These areas will yellow and possibly darken, and they may even cause the leaf to drop off too soon
When growing orchids, there are two types of scale that you may run into: The first one targets Phalaenopsis in particular, but it can also spread to most other soft-leaved plants. Look for these hard, brown, limpet-like creatures on the underside of the leaves, and if you find any, wipe them off with a cloth dipped in methylated spirits. You can also use the systemic insecticide regime mentioned above; systemic insecticides work by being absorbed
The other is called the Boisduval scale, which can be quite nasty. It prefers Cattleyas and their relatives but can also eat other orchids like Vandas. These flat, round scales on the underside of the leaves, which, if ignored, will eventually produce a large shipment of what initially appears to be a white fungus or mealybug—in reality, these are the nymphs by the thousands, and they are about to desiccate the rest of your collection—have a very fancy name for a real horror.
The problem we have is that it is a tropical insect, so many of our pesticides do not address the issue. Recently, we have found Doff to be useful; you may need to look around to find it; it is very effective against this type of scale and many other pests. You will likely need to give the plant a thorough cleaning after a few weeks or so for aesthetic reasons. Before beginning treatment, gently scrub the majority of the adults out of the pseudobulbs with an old toothbrush dipped in methylated spirits after removing any old sheaths (papery coverings from around the pseudobulbs).
Treatment: To physically remove the scale if there are only a few, use a Q-tip dipped in isopropyl alcohol or a toothbrush dipped in a pesticide like Malathion, Orthene, or Safer Soap (used in accordance with label instructions). Apply the pesticide at the crawler stage and repeat the application two weeks later for more severe infestations. Spray all plant surfaces, paying special attention to the leaf axils and undersides. To prevent scales from hiding and to make an inspection easier, remove old leaf sheaths and flower petals. Before adding new plants to the growing area, carefully inspect them.
To prevent scales from hiding and to make an inspection easier, remove old leaf sheaths and flower petals. Before adding new plants to the growing area, carefully inspect them.
Mealybugs on Orchids
Mealybugs on Orchids are sucking insects that can attack any part of the orchid plant, but they prefer to hide out at the point where the leaf and stem meet. Severe infestations result in chlorotic areas on the leaves, which may darken and cause the leaf to prematurely turn yellow.
Treatment: To physically remove the mealybugs if there are only a few of them, use a Q tip dipped in isopropyl alcohol or a toothbrush dipped in a pesticide like Malathion, Orthene, or Safer Soap (used in accordance with label instructions). Apply the pesticide and follow up two weeks later if the infestation is more severe. Spray all plant surfaces, paying special attention to the leaf axils and undersides.
Removal of outdated flower and leaf sheaths will remove hiding places and facilitate easy inspection. Before adding new plants to the growing area, carefully inspect them.
Aphids on orchids
The sucking insects known as aphids attack buds, flowers, and new growths in plants and spread disease between them. It’s possible for buds and flowers to not open, and leaves could have a sticky deposit.
Use a water jet to wash aphids off the plant as a treatment. Pesticides like Malathion, Orthene, or Safer Soap can be sprayed on plants when used in accordance with the directions on the label.
Other: The honeydew produced by aphids and other sucking insects attracts ants and makes a perfect environment for sooty mold. Check the plants for aphids, mealybugs, scale, and mites when sooty mold is present.
Thrips on Orchids
Thrips on Orchids, which feed on flowers and occasionally leaves and can spread disease from plant to plant, are incredibly tiny sucking insects. Infected buds might not open, and infected flowers might have deformed petals with wet spots. The appearance of leaves can be pitted, stippled, silvery, or bleached.
Treatment: According to label instructions, plants and flowers can be sprayed with a pesticide like Orthene, Malathion, or Safer Soap. Because thrips remain concealed on the plant or can re-infest the plant from other flowers in the landscape, repeated applications will be necessary.
Control: Maintaining good hygiene and keeping plant hosts (such as flowers, citrus, gardenias, eucalyptus, etc.) apart from your orchids will help prevent infestation.
Whiteflies, which resemble small moths, attack buds, flowers, and new growth. When a plant with whiteflies is moved or disturbed, a cloud of tiny white insects rises from the affected area.
Following the directions on the label, plants can be treated by spraying with Malathion, Orthene, or Safer Soap. Continue making applications every four days until there are no longer any whiteflies.
Control: Keeping your orchids separate from their plant hosts will help prevent infestation, as will maintaining good hygiene and getting rid of weeds.
Arachnids, not insects, are the family that includes mites, which are known for their symptoms. The majority of the time, mites are small, reddish-to-brown pests that feed on the underside of the leaves. To see them, you might need a handheld lens. Webbing and brown splotches caused by mite excrement may appear on the undersides of leaves. A damaged leaf’s upper surface might initially have a silvery sheen that eventually sinks and turns brown. Due to a lack of chlorophyll, leaves may be spotted, stippled, or streaked.
Treatment: Plants can be treated by spraying them with a miticide like Kelthane in accordance with the instructions on the label, being especially careful to cover the undersides of all the leaves. Repeat applications—possibly three applications spaced out over a four-day period—will be necessary during warm weather when new generations mature every six days.
Prevention: Warm, dry weather is when mites are most active. Infestations can be avoided by raising the humidity, moistening the leaves, and, if at all possible, lowering the temperature.
Slugs and snails
Symptoms: These mollusks will eat away at the growing tips and leave holes and notches in the roots of flowers and leaves. On buds, chewed areas can also be seen. The slime trail left behind by these nocturnal pests serves as proof of their presence.
Chemical baits may be positioned in the growing area as a treatment. Water will render ash and diatomaceous earth ineffective when applied to horizontal surfaces to form barriers. Pests that have drowned can be removed the following day by spreading beer in shallow tins throughout the growing area. The controls will need to be applied regularly because watering will disperse them.
Caterpillars are the larval stages of butterflies and moths. Although uncommon, they are voracious feeders that can quickly cause significant harm to flowers and leaves.
Treatment: Look for caterpillars on the underside of leaves or physically remove them from the plant and destroy them. Following the directions on the label, Bacillus thuringiensis, also known as Bt, is a naturally occurring bacteria of insects that can be sprayed in the growing area.
Maintaining a clean growing area will help prevent insect pests and their eggs from hiding in fallen leaves and other debris. Keep caterpillars away from the landscape.
Grasshoppers and Cockroaches
Symptoms: By consuming flowers, roots, and new growth, grasshoppers and cockroaches harm plants.
You can use cockroach baits in the growing area, or you can spread a paste made of boric acid, sugar, flour, and water in every crack and crevice you can find. Never apply any of the substances directly to the plants. Another strategy is to fill the pot with water, followed by a mixture of liquid Sevin (1 tsp/gal).
Deter the grasshoppers by crushing them with a brick, shoe, etc. The following day, remove drowned victims from molasses and water-filled jars that have been partially buried.
Symptoms: Tiny, wet spots that are frequently encircled by yellow haloes appear on the leaves. If the infection is left untreated, it will quickly rot the leaves and roots and more gradually spread to the rhizomes or pseudobulbs. This wet rot may smell bad and appears to be covered in water. The disease in Phalaenopsis spreads so quickly that plants may completely rot in just two to three days. The bacteria can enter through wounds because they are opportunistic organisms. Dendrobium leaves start out looking yellow and wet, then turn black and sag.
Vanda leaves develop translucent patches that later turn black and sunken. Small, round spots start out yellow and wet on paphiopedilum leaves and eventually turn reddish brown and sink. Before the leaf tip is impacted, the spot enlarges in all directions and may spread to the developing crown. If left unattended, the disease quickly takes over the entire plant and turns it into a shriveled, dark mass. The leaves of Grammatophyllum have water-soaked browning spots that eventually turn black and sink.
Physan or copper compounds should be sprayed on infected and nearby plants in accordance with label instructions (copper should not be used on dendrobiums or blooming plants). The growing area should then be cleaned with a 10% bleach solution. Both diseased plants and those close by should be treated. Avoid overhead watering if the disease is present because it spreads through water splashing. If an infection occurs, keep leaves dry, improve air circulation, and lower the temperature and humidity because the pathogen prefers hot, humid conditions (if possible). Infection can be avoided with regular copper-based preventive sprays, especially in hot, muggy weather.
Acidovorax (syn. Pseudomonas) (syn. Pseudomonas)
Symptoms: A small, soft, water-soaked blister may appear anywhere on the leaf. The infected area starts out looking dirty green, grows, coalesces, and eventually turns brown or black, dries out, and sinks. Particularly when the disease reaches the tip of the leaf, it oozes bacteria-filled liquid. The warmer months are when it happens most frequently.
Cattleya infections typically only affect older leaves and enter through wounds on older plants. It moves slowly and rarely results in death.
In Phalaenopsis, the blister-like spots could have a yellowish or light green halo surrounding them. Spots congregate, and the infection quickly spreads. The plant will die if the diseased area spreads to the crown.
Treatment: Immediately remove any infected tissue, then spray the plant as directed on the label with a bactericide like Physan or copper compounds. Use a 10% bleach solution to clean the growing area.
Prevention: The waterborne pathogen Pseudomonas cattleya prefers warm, moist environments. Eliminate overhead watering, lower humidity and temperature (if possible), and improve airflow.
Phytophthora and Pythium species
Symptoms: All plant parts are susceptible, but the infections typically start on the leaves, new growth, or roots. If not promptly treated, the disease spreads quickly and will kill the plant.
On the underside, small, irregular, watery brown spots that are the first signs of leaf disease quickly turn purplish brown or purplish black. There could be a yellowish advancing margin to the spots.
When pressed, the lesions may ooze water and enlarge with age. Old lesions can occasionally turn dry and black, which frequently makes the plant vulnerable to other diseases. When the temperature and humidity are high, the disease may spread quickly to the roots and rhizome.
Continued symptoms: New leads are easily pulled off because they have a purple or purple-brown area with a yellowish advancing margin.
Infections appear as a purplish-black, frequently clearly defined, the discolored area in the center of pseudobulbs, roots, or rhizomes. The plant wilts as a result of the infection, which frequently begins in the roots and can advance to the base of a pseudobulb or leaf.
A creamy yellow discoloration on one or both sides of the pseudobulbs is possible on Cattleyas. The discoloration eventually softens and turns black or brown, and the bulb rots as a result.
Treatment: The disease is highly contagious and will spread from plant to plant from splashing water, so the best course of action is to discard the plant unless it is valuable. If the plant is priceless, keep it separate from your other plants, use a sterile tool to remove any infected tissue, and then treat it with a suitable fungicide like Subdue or Banrot while adhering to the label’s instructions.
Prevention: The spread of the illness is aided by high temperatures and humidity. Consider using a preventative fungicide spray as directed on the label, especially during hot, humid weather.
Fusarium causes the phloem to become plugged and blocks moisture from moving through the plant’s vascular system. Yellow, thin, shriveled, wrinkled, or wilted leaves that have been infected eventually die.
A circle or band of purple or pinkish-purple discoloration on the rhizome’s outer layers, which is visible when the rhizome is cut, is the plant’s diagnostic symptom. The entire rhizome may turn purple if the disease is severe, and the pseudobulbs may also become discolored. The fungus spreads from plant to plant as a result of using non-sterile cutting tools, which is how the pathogen is spread through poor hygiene. While mildly infected plants gradually deteriorate over the course of about a year, severely infected plants may die in 3–9 weeks.
If the purple band is visible, discard the infected portions of the pseudobulb and rhizome. Repot only the portion of the plant that doesn’t have a purple hue. As directed on the label, soak sanitized plants in a thiophanate methyl solution (such as Cleary’s 3336). Be sure to thoroughly clean the growing area and the cutting equipment. Before making another cut after making contact with infected tissue, the cutting tool should be sterilized.
Prevention: Maintaining good hygiene is a straightforward method of prevention. After each use, sterilize cutting tools, preferably using a flame.
Root rot has several symptoms, including medium breakdown, poor drainage, and/or overwatering of the plants. Rot quickly develops when roots are harmed by trauma, salt buildup from hard water, or excessive fertilization. Because of how quickly the disease spreads and how contagious it is, infected plants eventually die from brown root rot.
Although the symptoms of rhizoctonia can be seen on plant aerial parts, the disease primarily affects the plant’s roots. The leaves and pseudobulbs turn yellow, shrivel, thin, and twisted, and the size of the new growths gets smaller and smaller. Typically, brown rot and white or brown fungal growth are visible on the roots. The fungus encircles and kills the plant in cases of severe infections. Small seedlings’ lower leaves and rhizomes are quickly invaded by the infection.
Treatment: Use a sterile cutting tool to cut away infected roots and leaves. Then, according to label instructions, cover the remaining plant in a systemic fungicide like Subdue or thiophanate methyl to protect it. Use a 10% bleach solution to clean the growing area.
Preventative measures include using fresh potting soil and avoiding overwatering your plants. Unpot the plants, examine their roots, and repot as necessary when disease in other plants is suspected or when repotting is overdue. In areas with hard water, pots should be flushed at least once a month to prevent root damage. To do this, water deeply to dissolve the salts and then deeply again an hour later to remove them from the pot.
Glomerella spp. and Colletotrichum spp.
Symptoms: The aerial part of the plant is affected by this fungus disease. Most frequently, leaves are attacked. Beginning at the apex and moving toward the base, leaf tips turn brown.
Sometimes in the form of concentric rings or numerous dark bands across the leaf, dark brown or light gray patches also appear. Typically, the affected area is well-defined and somewhat sunken, while the rest of the leaf looks healthy. The infected area develops sporing bodies. On the underside of mature sepals and petals, flowers develop raised, watery, black or brown pustules. The blotches could converge and completely cover the flower.
Treatment: Thiophanate methyl-based systemic fungicides (like Cleary’s 3336) or protectant fungicides (like Mancozeb), as directed on the label. switch between using systemic and preventative fungicides.
Prevention: Good air circulation, regular sanitation, reduced temperatures (if at all possible), and more light may help stop the spread of this illness. When light levels are low and moisture levels are high, the pathogen is most active in warm weather.
Symptoms: A yellow spot on the underside of the leaf is the first sign of the infection. The yellow-green area on the top surface of the leaf may be seen shortly after infection takes place. The spots may eventually cover the entire leaf as they continue to grow in size in a circular or haphazard pattern. The spots darken and slightly sag with aging, turning purple-brown or purple-black. The expanding margin continues to be yellow.
Particularly when the infection started close to the base of the leaf, heavily infected leaves typically fall off the plant too soon. The spots become sunken, purplish brown to purplish black, and enlarge in erratic patterns. The leaf’s top surface first turns chlorotic, then necrotic.
Phyllosticta and Guignardia species
Guignardia infection first manifests as tiny, elongated, dark purple lesions on either leaf surface. These lesions extend into purple streaks or diamond-shaped areas as they run parallel to the veins.
Spots frequently combine to form significant irregular lesions that may cover a significant portion of the leaf. The lesion’s center becomes tan with advancing age. In the impacted area, raised, black sporing bodies form. primarily affects Ascocentrum, Vandas, and their hybrids, and may be an indication of inadequate lighting. The names Phyllosticta and this blight refer to two distinct sexual phases of the same fungus.
Phyllosticta symptoms include spots that can appear anywhere on the leaf or pseudobulb. Small, yellow, and slightly sunken, the lesions are. Particularly if the infection is on the leaves, they grow larger and change from being round to oval and more sunken. They age to become tan to dark brown, and their reddish to purple-black margin becomes slightly raised. In the center of the spots, tiny, raised, black spore structures eventually form. Each spot measures about 14 in across. Leaves with severe infections may fall off too soon. Its presence might be a sign of inadequate lighting. The names Guignardia and this blight refer to two distinct sexual phases of the same fungus.