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Controlling Pests On Orchid Flowers – Tips On Managing Orchid Pests

Controlling Pests On Orchid Flowers – Tips On Managing Orchid Pests


By: Bonnie L. Grant, Certified Urban Agriculturist

Growing orchids can be an addictive experience. These lovely flowering plants can be a bit fussy about their conditions and care, but the effort is worth it when you see the astounding blooms. There are several orchid flower pests for which to watch for that can seriously diminish the plant’s health and ability to produce the flowers for which they are known. Pests on orchid flowers may be sap feeders or chewing insects, but the damage they do can reduce plant vigor and, in some cases, even kill the plant. Identifying the villains and providing orchid pest control in a timely manner could save your plant.

Types of Pests on Orchids

Orchid flower pests are a collector’s nightmare. There are any number of nasty insects who can wreck the appearance and health of your plant. Recognizing which insect is attacking your orchid is key to managing orchid pests. Once you know which insect is causing the damage, you can successfully fight back.

Pests on orchid flowers fall into two categories: sap sucking and chewing.

Sap sucking insects remove plant sap which is necessary for the plant to fuel itself causing general malaise and leaf, stem, and flower problems. These include:

  • Aphids are common on many types of plants. These soft-bodied insects can transmit disease and cause leaf, young shoot, and flower damage.
  • Scale is harder to see but is recognized as bumps on the stems and other parts of the plant. Severe infestations cause yellowing and leaf drop.
  • Mealybugs are fuzzy, cottony looking insects that usually hide in the leaf axils. Symptoms are similar to scale.
  • Thrips are almost impossible to see and deform leaves and blossoms, while whiteflies look as their name implies and attack all growth.
  • Spider mites are also tiny but you can see their webs on the plant. Their feeding behavior reduces chlorophyll.

Chewing insects of orchids usually prey on plants grown outdoors.

  • These might be snails and slugs, whose chewing behavior leaves holes and chunks out of leaves. These pests are primarily nocturnal and you may need to wait until dark to find them. The easiest method of orchid pest control with these mollusks is to hand pick them or the use of diatomaceous earth, which is non-toxic and effective.
  • Caterpillars make Swiss cheese out of leaves and even eat buds. Managing orchid pests like these requires applications of Bacillus thuringiensis, a natural pesticide.
  • In rare occasions, cockroaches or grasshoppers may invade outdoor plants. Use cockroach baits in the area and bait grasshoppers with molasses.

Orchid Pest Management

There are many non-toxic methods of control that can manage these pests. Sucking insects are often just washed off the plant. Pyrethrins or horticultural oil sprays are also effective.

Mites are most active when the conditions are hot and dry. Increase humidity and, if you can, move the plant where it is cooler.

Keep all leaf and other debris cleaned up so pests don’t have hiding places. Keep orchids away from host plants such as citrus, other flowering plants, eucalyptus, beans, and taro.

The best defense is a healthy plant. Healthy plants can withstand some pest activity without significant loss of vigor. Another tip about orchid pests and management is to inspect plants daily. The sooner management begins, the better the outcome and the less damage the orchid will sustain.

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Insect Treatments for Orchids

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Nothing destroys the unadulterated beauty of an orchid more than a pest infestation. Insects such as scales, mites and mealy bugs can leave your orchid's foliage with unsightly spots. It makes sense that orchids grown outdoors are susceptible to pests, but insects can also plague your indoor orchids. You can use insect treatments to get rid of the little critters and to help keep your orchids pest-free and healthy.


Orchid Pest Management: Treating Common Orchid Flower Pests - garden

In recent years, orchids have become increasingly popular as houseplants, popping up for sale everywhere from smaller garden centers to big chain stores. Many of us have taken these plants home, given them plenty of TLC, only to be let down when they begin to suffer from wilting and discolored leaves. This has led to a common misconception that orchids are hard to take care of, requiring a special kind of green thumb. In reality, these plants are quite easy to care for once you understand their particular needs. In fact, it has been said that they thrive on negligence.

Most orchids we know as houseplants are epiphytes (like mistletoe and Christmas cactus), meaning they do not root into soil but have specialized roots that attach to other plants or rocks and absorb moisture from rainfall, humidity and dew. They typically come from tropical environments where water is abundantly present in places other than the soil profile. Therefore, they require slightly different care than your typical houseplant.

Since their roots have adapted to absorb water quickly when it’s present, they cannot handle extended periods of saturation, which often results in root rot and mortality. Overwatering is probably the most common cause of death for orchids kept as houseplants. This is hard for many to hear as they assume that their watering efforts, diligently performed with love, were beneficial to the plant.

Orchid roots need to completely dry out between watering. That is why some “neglect” can go a long way. Orchids do require a more specialized potting mix that drains quickly and has ample pore space for air circulation. Many premade mixes are available, consisting of some combination of bark, peat moss, perlite or sand.

There is a pretty wide margin of error between just enough water and not enough to support the plant. However, saturated soil conditions can be detrimental. The easiest way to assure that you are not overwatering is to check the planting medium. If it still feels damp a few inches down, no need for water. Ensure it has dried out completely before watering again.

The amount of water an orchid needs may vary by season, especially if you move them to an outdoor location during the warmer months. In general, my orchids are not one of the houseplants I water every week, they are probably an every-other-week type schedule this time of year.

Although orchid roots cannot tolerate saturation for very long, orchid plants do love humidity. Many common houseplant species, such as Phalaenopsis orchids, thrive in 50-85% humidity, which is difficult, if not impossible, to maintain indoors in the wintertime without use of a humidifier. My home is consistently around only 20-30% humidity in winter, but we have a woodstove that greatly contributes to the dry air.

To provide additional humidity many home orchid growers place their plants on a tray of pebbles. Water can be added to the tray, not to exceed the height of the pebbles, and the plant’s pot can be placed on top. The specialized orchid roots are able to absorb humidity from the air, much like they would in their native tropical home.

Another factor that makes orchids ideal houseplants is that they do not require a lot of light. Too much light can lead to sunburn leaves or cause blooms to drop early. Many east facing or shaded west facing windows provide ample light. A bright south facing room, with indirect light on your plant can be optimal.

If you are interested in becoming an orchid enthusiast, please join the University of Illinois Plant Biology Greenhouses for their Spring Fling and Orchid Sale next Saturday, March 10 (10am-2pm) and Sunday, March 11th (1pm-3pm).

“Our sale focuses on the more uncommon orchid species,” says Debbie Black, the Plant Biology Greenhouse Manager. “We focus on smaller species that fit indoor spaces well, versus the more common everyday varieties”.

Black and other members of the Plant Biology Greenhouse staff, will be on hand to answer any questions about orchid care and help you select the perfect plant. In addition, The Conservatory and Plant Collections will be open for display. They offer a great local, tropical escape from the winter blues.


Aphids and Orchids

Aphids are small insects, ranging in size from 1-10 millimeters. They have soft bodies that can be green, black, brown, or even translucent. There are 4,400 different species of aphids. Fortunately, only 250 of those species are problematic for agriculture and gardening. Fewer than that are a problem for orchids. Aphids get their nourishment by sucking phloem sap from the plants they are inhabiting. In turn, they produce a sticky substance called honeydew. Ants often thrive on honeydew and in some situations will even farm aphids, protecting them from predators. Another aspect of aphids that makes them difficult to manage, is their ability to reproduce. Aphids can reproduce sexually or asexually and they can give birth to nymphs or lay eggs. This happens several times a year and several generations can reproduce within the same year. An aphid population can explode very quickly. When a plant becomes unfavorable to survival or overpopulated, an aphid can produce winged nymphs that will fly to colonize a new plant.


How to Use Alcohol on Orchids Indoors

Rubbing alcohol is an effective pest prevention and pest control method against aphids, mealybugs and, thankfully, soft scale insects. While it still might slightly dehydrate the houseplant, it’s safe to use on indoor orchids because it, unlike chemical insecticides, isn’t toxic.

Naturally, it’s not a good idea to apply alcohol directly to your orchid’s leaves. There are two ways to use isopropyl alcohol to get rid of orchid pests :

  • Alcohol on a Cotton Swab:

    Take a piece of cotton and soak it in alcohol ( 70% isopropyl alcohol ), then press it directly against the orchid pests. It works especially well for boisduval scale, spider mites, mealybugs and aphids.

    Press lightly several times on each insect you find to make sure that the alcohol dissolves its waxy covering.

    Apply the alcohol thoroughly on all parts of the orchid, especially leaf crevices, sheaths, midrib and leaf edges.
  • Orchid Alcohol Spray:

    Mix isopropyl (rubbing) alcohol with a few drops of soap. You can use either regular mild liquid soap or a specialised insecticidal soap. Put the mix in a misting bottle or a pump sprayer. Do not put more than a few drops of soap, however, to avoid damaging your orchid’s flowers and buds. Also refrain from using water in the mix, because mealybugs and soft scales have a water-repelling coating over their bodies.


Cultural Controls

Inspect your orchid daily for fungus gnats. You will probably notice the adults first. Look for them on the flowers, foliage, pot rim and soil. Delicate-looking adult fungus gnats are between 1/16 and 1/8 inch long and look somewhat like mosquitoes. The wings are clear to light gray and the legs are slender. The antennae are longer than the insect’s head and are segmented. You may see these pests hovering around the plant. Once you discover adults, there may already be eggs or larvae in the potting medium.

Repot the orchid in a well-draining medium that is slow to decay. The best soils contain slow-decaying organic materials such as coconut chunks or fiber and charcoal. Perlite is a good inorganic ingredient. Fungus gnat larvae feed on the fungi that grow in warm, fertile, overly moist soil. They also consume decaying organic matter, such as decomposing potting media and rotting plant roots. The older the potting media is, the more likely it is to be infested with gnat larvae.

Allow the top 1 inch of potting soil to dry out completely between waterings. Water your orchid only when necessary. Empty the saucer often and do not allow water to accumulate in it. Fungus gnat eggs and larvae require moist soil and soon die if they dry out.

Fertilize your orchid monthly with a 30-10-10 orchid food to keep it healthy. Do not over-feed the plant. Follow the packaging instructions.

Trim dying or dead vegetation off the orchid immediately to avoid attracting adult fungus gnats. Pay particular attention to areas of the plant near the soil line. Remove dropped or shed plant material and debris from the potting medium surface as soon as you notice it.


Bugs, pests & diseases

Keep pests away

Noticing bumps, bugs or spider webs on your orchid?
Here’s what you can do about them.

Common orchid pests

Frequently asked questions

Have you discovered white bumps on your orchid? Does it feel sticky? It’s likely your orchid has developed a scale infestation. Before you address this issue, be sure to move your infected orchid away from other plants to prevent the infestation from spreading.

Save your orchid save your aesthetic. Treating your orchid can be as easy as looking in your cupboards for some of these common items.

Rubbing alcohol

Combine one part rubbing alcohol with one part water, and apply the mixture to the plant with a cotton ball or spray bottle. Make sure to repeat two or three times every one to two weeks to keep the infestation at bay. Keep in mind that it takes time — a minimum of two to four months of regular and intensive control methods — to eliminate a scale infestation, and even then you may not be able to fully eradicate it.

Horticultural, neem or mineral oil

Mix equal parts oil and water and spray the entire plant. If you use this method, don’t spray your plant on hot days when the temperature is above 80 degrees. Also, move the plant to a shaded area until the solution has dried. The oil mixture will be less effective if it has been sitting for more than eight hours, so be sure to mix up a fresh batch of oil each time you’re going to spray.

Spray weekly or biweekly to control the infestation.

Sometimes all your plant needs is a little tender loving care in the form of a new home. Much like a hermit crab changes shells for protection, your plant might just need new soil and a new pot to eliminate its symptoms and prevent further infestation.

Insecticidal soap

You can either make your own insecticidal soap, or purchase a commercially made batch from a retailer. Simply spray your orchid and the infestation should be eliminated in one to two weeks.

Insecticide

This option should only be used for advanced case of scale. Choose a product that’s specially formulated for use on orchids or household plants.

A mealy bug infestation can make your orchid look like it’s been floating among the clouds thanks to an accumulation of white fluffy patches.

Like scale, mealybugs can easily crawl from plant to plant, so be sure to isolate your orchid if it has any neighbors.

A mealybug infestation can be solved by diluting either equal parts horticulture soap or rubbing alcohol with water and spray or wipe down your plant.

Seeing tiny webs around your orchid doesn’t mean it needs a dusting. Rather, you’re probably dealing with a spider mite infestation.

Control these pests with a light spray of horticultural oil or insecticidal soap diluted with equal parts water.

If you’ve noticed that your plant has spots on it and it doesn’t appear to be a hosting mites, it could be a fungal or bacterial infection. In this case, you can use your nose to help you determine the issue.

An orchid with a foul smell and discolored leaves is likely the victim of a bacterial infection.

If your orchid has a spotty appearance but smells fine, it’s likely a fungal infection.

How to treat bacterial or fungal orchid diseases:

First, move your orchid away from other plants. Then, remove the infected area with a sterile razor blade or pair of scissors and spray the plant with a fungicide. While fungicide won’t affect the bacteria, it should still be applied to a bacterial infection to prevent a fungal infection from forming.

If you’re dealing with a fungal infection, make sure your orchid is placed in an area where it will receive plenty of air circulation.


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