Insects & Diseases
Insects and diseases are more than a nuisance on plants, if left untreated they can kill it and/or spread to other healthy ones. Treatment as soon as noticed is the best course of action. The following is a summary of products that work on insects and diseases that I and others that I know have used on their orchids with success.

Indoor growers should teat their plants outdoors and bring in after a few hours of airing out or wait until the next day if practical, i.e., winter time is not a practical time to do this. Everyone should buy liquids in smaller quantities to avoid degradation after opening, use liquid insecticides within 6 months after opening or buy a new batch.

Store powders and liquids out of sunlight and powders in a cool, dry place

Spray plants early in the morning so that they will dry off before the temperature gets to hot in greenhouse.

Aerosol bombs or smoke generator types should also be done early. The exhaust fans should be set for 85 F so that the little critters will wake up and get active while the insecticide is in the greenhouse. Aerosol bombs may be used in late afternoon, turn up the exhaust fans to 85 F when you know they will not come on again before nightfall and set off bomb.

Use the directions for application to roses to determine strength of the mixture to apply.

General Rules For Treating Plants:

Never spray a dry plant, spraying the day after watering is good, exposed roots should be watered 15-30 minutes before spraying, especially things mounted on slabs or in basket.

Mix up only what you will need, the chemicals lose potency after mixing.

Use a spreader sticker or a clear dish detergent(one with no lotion type additives, you can see through it), 2-3 drops per gallon of spray.


Foliar Spray - This is spraying the leaves top and bottom and getting only a minimum onto the roots and in the pot.

Drenching - This is more than spraying, it involves spraying the leaves(top and bottom) and getting some down into the pot. I use a hose end sprayer to do this function. If you have only a few plants, a pump up sprayer will do. Or spray the plant and pour some around/in the pot.

TBS - Tablespoon

Tsp or tsp - teaspoon

Never spray with the same insecticide twice in a row, alternate two or more to prevent the critters from developing a resistance to one. Mealybugs are some of the toughest insects to control. Drench at 7-10 day intervals with alternating insecticides 3 three times.

Enstar, Precor - these are growth regulators that prevent insects from reaching maturity, breaking the life cycle. May be used with other insecticides, improving the chances of control.

Diazinon - available in many concentrations, use at the rate recommended for roses, a contact spray, no systemic action. About $10 per quart. Also available as a microencapsulated form called Knox Out.

Dursban - same as Diazinon, microencapsulated form is called Duraguard $10-16/qt-$40/qt

Orthene WP - a systemic in powder form, kinda stinky but effective, 2 tsp/gal.

Liquid Sevin - same as Diazinon, keep off of exposed roots.

Talstar - a wettable powder with systemic action, 1 tsp/gal. $65/lb.

Gnatrol - a biological treatment for white fly and fungus gnats larvae, effective on grubs in mix only, drench mix to get to larvae, there is a residual action. Spray foliage with a contact spray or aerosol bomb to kill adults for full control. Gnatrol has a residual action against the larvae.

Aerosol bombs - total release bombs for greenhouses only. Many aerosol bombs are available for greenhouse use. They treat up to 3000 sq feet per bomb. All internal fans should be running while in use to disperse the chemical and dry off the leaves. Good ones are Attain, X-Clude, Knox Out, Orthene, Preclude(growth regulator) and others.

Attain - many insects and mites, see aerosol bombs.


Cleary's - available as a WP or liquid, a good broad spectrum systemic fungicide. About $40 -50 per quart/ bag.

Captan or Sulfur - two old favorites, no systemic action. We use it to wipe directly on leaf and rhizome cuts when removing diseased tissue or dividing plants. Available in 8 oz containers for $6-8 or 5 lb bags for $17-20.

Physan/Green Shield - any ammonia derivative that is good for removing algae, moss and has a fungal and antibacterial action. Use no more than once per month. Use at ? TBS/gal for spraying plants, 1 TBS/gal for walls, benches and floors.

Subdue/Resimyl - for root problems, may be used in conjunction with Cleary's for total treatment of fungal problems. Subdue has been priced out of sight by changing it to a 1 drop/gal strength. Resimyl is the same chemical and is about $55/qt. Use 4-7 drops / gal.

Strike/Bayleton - a powerful systemic that is to be used only as a last resort. Useful in controlling microfungus or unknown problems that seem unaffected by other fungicides.

Terrachlor 75%WP - a good general fungicide for root problems during repotting or transplanting and drenching newly unflasked plants when planting into compots.

Daconil - broad spectrum fungicide, no systemic action.

Dithane M45 WP - a good broad spectrum fungicide, one of the only ones that will stop many rots in monopodals(Vandaceous) plants.

Truban - another root rot type fungicide, use as a drench.

Benlate/Benamyl - a systemic fungicide used on orchids for years, mixed 50/50 with Truban its called Banrot. In the late 1980's the factory making Benlate DF did not adequately clean out its material handling system and some of the prior material being made at the plant was introduced into the batch of Benlate DF. Unfortunately the contaminant was a potent weed killer. Orchids and other plants died, lawsuits were filed and Benlate/Benamyl are no longer recommended for use on orchids. Use your own judgment.

Bacteria in orchids is probably the shortest route to death possible. An untreated plant can be dead in 2 days and the spores infecting others. A real problem in softer tissued plants. Cut out any dead or infected tissue and wipe with Kocide or Agri-Strep powder, blow or wipe off any extreme excess. Q-Tips or fingers are good for this. Prevention is the best cure.

Kocide - a copper compound that has an anti-fungal and anti-bacterial action, used mainly by Phal growers as a preventive for bacterial problems. Cheap $12-14 per 5 lb bag. Some people report problems if used on thin leaved orchids such as Miltonias, but I have never seen any problems. Do not used a spreader/sticker as some will interfere with the absorption of the copper, use a few drops of detergent. Keep away from the root zone. Use at ? TBS per gallon as a foliar spray.

Agri-Strep(Streptomycin) - a WP form of an anti-bacterial drug that my be used no more than 2x per year. More frequent use may cause a buildup of resistant strain of bacteria. About$8-10 per 2 oz or ? lb bag.

Snails and Slugs:

Qbane - A rock grit impregnated with Metaldehyde. Sprinkle a few grains in each pot, attracts them also.

Grandslam - (75% Measurol) 2 tsp/gal.

This may seem like a lot of stuff, but you will need to pick and choose sooner or later. Many are only available as multiple lifetime supplies for a bunch of dough. Split up those 5lb bags with friends or find someon who will sell a little that has been repackaged.
Revised on: Mon, Feb 27, 2012