Snails and Slugs
Snails and slugs are at the top of most people's list as being one of the most revolting of all orchid pests. They have rasping mouth parts that scrape the surface of plant tissue. They can do extensive damage to the green tips of young orchid roots and stems and developing and maturing flowers. They usually come out at night so if you suspect them, take a flashlight in the evening to search for these culprits. Also, look on the bottom of the flowerpots; this is another favorite hiding place. They love cool, damp spots. If they travel across dry surfaces they will leave a telltale slime trail.
Snails and slugs attack at night and leave evidence of their damage on the young tender new leaf and roots growth and flower buds.
Other very unpopular beasts that vie with snails and slugs in the disgusting department are cockroaches. They also feed at night and enjoy munching on flowers and flower buds. I don't need to show you a picture of one of these guys because they are all too familiar. If you see one of them, they likely have many other brothers and sisters that aren't showing themselves. They have an amazing capacity to reproduce quickly, so treat at first signs of them or their damage. A sign of their existence is their black droppings and brown egg cases stuck on the bottom of pots or, in any spot that is dark.
These are cockroach egg cases and droppings. I know, this is gross!
More than once, to my great consternation, (actually my feelings were much stronger than this), upon inspecting my plants in the morning I discovered that mice had nibbled off the flower buds of some of my prized beauties right before they opened! Very frustrating!
Honeybees are Our Buddies
There has been a great deal of justifiable concern these days about the decline of the populations of honeybees and the threat that that poses to pollinating so many of our food crops, and one of the culprits is pesticides. One particular groups of insecticides are particularly toxic to honeybees and they are in the chemical group called neonicotinoid. The one that is most commonly available in this group is Imidacloprid, which goes under many different product or trade names. So read labels. and avoid insecticides with this chemical included.
Of course, the truth is that all insecticides will kill bees if they are sprayed on them so be careful when you spray. If you are spraying one of the stronger insecticides and are outdoors, do it in the morning or early evening when the bees are not working. As soon as the plant dries bring it inside.
Although bees and other pollinating insects do not cause any physical damage to orchids, if they land on the flowers and pollinate them, the flowers will very soon collapse. So, if you want your flowers to last their longest, keep the pollinating insects outside of your growing area.
Safe Pest Control Measures
It is a tricky thing to recommend chemical controls. All of them are poisons to some extent, so all require care. Just because the material is "natural' doesn't mean that it is not poisonous. That said, just use common sense. After all, aspirin, household cleaning agents, and many other materials found around the home are also poisonous if used improperly, but, they rarely are a threat to our health if we use them with caution.
One of the other problems, is that few pesticides are actually labelled for use with orchids. This does not mean not that they are unsafe to use with orchids, it's just that, relatively speaking, orchids are a very small "crop" compared to large scale ornamental and agronomic crops, so it doesn't pay for the manufacturer to go through all the expensive testing necessary to legally put "orchids" on the label.
The controls below are listed in their approximate order of safety, and are readily available.
There are many other products on the market, but I have limited these suggestions to ones that have worked well for me. Always start off with the first line of defense, which has the lowest toxicity. Some of the least toxic solutions must be applied more frequently since they kill on contact and are not residual. Most don't smell bad, an important feature for home grown plants. Some, like orange oil, also serve as pest repellents. The "heavier duty" materials, like Orthene (acephate), are ones that I sometimes use when the infestation is more severe or other controls haven't work. It is a reasonably priced, readily available, systemic material, which means it is absorbed into the plant sap, and is somewhat residual (it stays effective for several day or longer). Both of these features make it highly effective, but you must use more care with this material. It is good idea to wear rubber gloves and only apply this material outdoors with good air circulation.
Common orchid pests and their controls.
Below I have listed what I think are some of the most effective and least toxic controls for the most common pests. I have also included links to some of these products, since they can be difficult to find.
These insects are relatively easy to control. You just have to keep at it
First Line of Defense: Wash off with warm water and Insecticidal Soap.
You can totally control these insects with this method if you just keep at it for several days until there are no signs of any more of them.
Second Line of Defense: --Orange Oil - keeps and repellent aphids, shines the foliage and smells great.
Isopropyl alcohol on cotton swaps.
Caution: If aphids are on the flower buds of orchids try repeatedly washing them off with warm water. Using any chemical may damage the delicate developing buds or flowers.
More toxic solutions are rarely necessary.
Mealybugs are the bane of all orchid growers. Anyone who says they have never had them on their plants, is probably just not very observant! They are very damaging and require real diligence to eradicate them.
The first levels of control are all those mentioned above for aphids. Unfortunately, this pest is much more difficult to eradicate than aphids.
Use cotton swab drenched with Isopropyl alcohol.
Insecticidal Soap, http://www.domyownpestcontrol.com/bonide-insecticidal-soap-rtu-p-1667.html
Third, Final Line of Defense
Orthene (Acephate) for most severe infestations. Also, it is best to get this material in a dry form that can be mixed with water. This is a much more economical way to buy it and it is less likely to damage delicate foliage than the more commonly available form that is oil based (EC).
For orchids with mealybugs on their roots it is most effective to remove the orchid from the pot, soak the roots in a solution of insecticidal soap for a few hours, then re-pot in a clean new pot with new potting material.
Don't get discouraged with all these problems. They are actually not common if you keep your operation clean. However, it is important to act quickly when you do see a problem. It's a good idea to buy your arsenal of pest controls before you have a problem, and then store them somewhere dry and safe from freezing so they are ready to use when needed.
The next article will deal with more specific pests and their controls.