FAQ - Pesticides


Question: If plants are treated by the grower with a toxic substance, would a plant that I purchase remain toxic to pets and if so, for how long. I have cats and would like to know if they could get sick if they should nibble a leaf from a plant that was treated.

Answer: There isn't any firm rule on how long a toxic substance might last... it depends on the substance. There are a number of pesticides that are described as having "systemic properties", meaning that the chemical is still effective for several weeks after the application. "Systemic insecticides" are often slow-release materials added to the potting mix that can last several months. If the cats just take a nibble, it is unlikely that there would be an immediate problem. If cats were to eat violets (treated with systemic insecticides) over a long period of time, a common kind of insecticide (organophosphates) could build up in their system to a toxic level and cause a problem. The symptoms of this poisoning are tearing, incontinence, and salivating ... essentially a sudden onset of the body releasing water in every possible way, causing death by dehydration. Generally the organophosphates would only be used by professionals who used proper protection while home growers are more likely to use safer chemicals that pose little to no risk. But the only way to know the danger is to find out exactly what had been used and what the long-term danger is. Most of the time, there will be no danger at all. Happy Growing! Joyce Stork

Question: Is there a safe systematic insecticide for African violets? I found thrips on some of my collection. I removed all flowers and buds from the affected plants, but I would like to treat all of the plants with something on a regular basis to help keep the thrips down, as well as to guard against soil gnats and mealy bugs. I also have a number of other houseplants, from scented geraniums to ferns - I don't want bug problems! I also would like to know how it is that one is supposed to spray a violet down with a spray insecticide when we all know that you shouldn't get the leaves wet? Is that not harmful in and of itself?

Answer: Generally the systemic insecticides are not effective on thrips. This is because the molecule of the chemical is too large to pass through the ducts in the peduncles and pedicels (blossom stems). The systemic will kill thrips feeding on the foliage, but the blossoms remain quite safe for them to eat. Probably the chemical that is most effective at this time is Conserve SC. It has a longer term effect, and in fact you should only use it three or four times a year. It is quite expensive for the average home grower. Neem oil (much less expensive) is also reasonably effective on insects including thrips, but it works more slowly since it doesn't kill the thrips but rather prevents the thrips from reproducing. Both are safe to use to spray violets and will not spot if you use a fine mist and distilled water. Just getting the leaves wet will not harm a violet. It can be harmful to have a pool of water in the center of the crown, and wet leaves and sunshine will result in desiccated spots. The minerals in tap water may leave water spots that are hard to remove. Many show grower wash their violets before the show, but they carefully blot the excess moisture off and allow them to dry before putting them back in the light. Happy Growing! Joyce Stork

Question: There are little white/gray bugs in the bottom of the wick watered African violet plants. The bugs move pretty fast. They are so small they could be on other plants? I checked FAQ but I'm still not sure. Also a lot of plant have the leaves curling back around itself and also the leaves are reaching up. I haven't relocated anything and they've been fine for 5+ years. My collection is 100+. Any help would be greatly appreciated.

Answer: These critters are called spring tails, and as you might guess it is their unusual tail that allows them to move so quickly. They live in, lay eggs in, and feed on decayed matter in the potting mix and thrive where there is standing water. They depend on high humidity and constant dampness. They do not cause damage to the violets unless you happen to be a hybridizer who might have some tiny little seedlings sprouting. Spring tails are mostly just unsightly. They are fairly easy to control but you need to be thorough when you do it. Begin by removing all of the plants to another area. Wipe off all nearby surfaces including the plant stand and the outside of pots with a soapy cloth. Empty all of the wicking reservoirs and wash them well before refilling them with fresh water. Apply an appropriate insecticidal granular to the top of the soil or drench the pot with an insecticide (or insecticidal soap) designed for this use. Be sure to apply all around the top of the soil and not just on one side of the pot. Look for "spring tails" on the label as one of the insects that is controlled by the product, and be sure it is safe for use on African violets. The unruly leaves are not related to the spring tails. This often happens when plants are overcrowded or when they are not rotated. Sometimes they will position themselves better, once the cultural problem is corrected, but sometimes the only solution is to groom away the errant leaf. The leaves that are reaching up may indicate that there is not quite enough light. This can be a varietal preference, so look to see if it is all the plants reaching up, or just one or two varieties that would prefer a brighter location. Happy Growing! Joyce Stork

Question: Proudly, I have grown many African violets from leaves stuck in small beer bottles until ready for potting or thrusting upon friends. Alas now have tiny little jumping insects in the soil. I have washed the pots and dishes but not replaced the soil. What should I do now please, there are so many of them?

Answer: Those little jumpers are probably spring tails. They move fast and love moist soil conditions. I would try drenching the soil with a solution of Safer Insecticidal soap three times over a period of three weeks, following package directions. Neem oil, used according to package directions would also be helpful. They are not harming the plants, but you will be happy to have them gone, I'm sure! Happy Growing! Joyce Stork 

Question: I have black bugs that look like gnats. How can I get rid of these pests?

Answer: If they fly and appear also to be moving in the soil, then they probably are fungus gnats, shore flies, or fruit flies. Fruit flies are rather common in the fall when we tend to bring in garden produce to finish ripening on the counter top. They can be very hard to eradicate until a hard frost, unless you keep the tomatoes, etc. outside. All of these gnat pests depend on a moist place to nest and lay eggs, and decayed matter on which to feed. In most cases they do no harm, but they are a nuisance. Safer Insecticidal Soap may be helpful as a drench. the soapy substance dries the skin of the insect and causes death. The drench (soil drench of one to two tablespoons of concentrate in a quart of tepid water applied monthly) must be poured through the soil so that every part of the potting mix is in contact with the solution and the insects cannot move to a safer area in the soil to escape. In addition, be sure to wipe off the outside of the pots and the surfaces around the plant to get rid of any decayed matter (peat moss, dead leaves, etc.) If there is standing water anywhere in the area, it should be covered or removed. Household insecticidal sprays may be effective to eliminate a few flying pests, but will not kill the larvae in the soil. Neem oil may also be used as a drench although it may be messier than the Safer Soap. Happy Growing! Joyce Stork

Question: I have a problem with discoloration showing up on the tops of my African violet leaves. It looks something like leaf miners; the affected area of the leaf becomes flat and brown, though there are often islands of healthy green. There is damage on the tops of the leaves, but nothing underneath. The discolored areas are flat, as if someone had "let the air out of the leaf" in that area. I noticed this on one plant, only on one side of the plant. In the last few days it is moving from the outer to the inner leaves, but still mostly on one side of the plant. Tonight as I was removing that plant to quarantine I saw that the plant next to it, a different variety, is just starting to show the same symptoms. This would seem to indicate a pest problem, though examination under magnification showed nothing obvious. I would be happy to provide photos on request.

Answer: I cannot say for certain, but I would be most suspicious of foliar thrips which eat a path that is perhaps 1/16th of an inch wide across leaves. They have a flying stage which allows them to travel quite easily. Leaf miners are less common in violets, but not impossible. I would definitely recommend isolating the affected plants and treating them. One very safe product for home use is Neem oil (used three times 5-7 days apart) which prevents the insect from maturing into an egg-laying adult. Indoor garden sprays containing pyrethrin products (look for active ingredients ending in the word "thrin") will also provide some control. Keep the affected plants away from the rest of your collection for three months until you are absolutely certain that they are insect free. Happy Growing! Joyce Stork 

Question: I think a couple of my African violets have cyclamen mites. The center becomes stunted and greyish with flowers that did not fully bloom. I tried to find Kelthane in my area and could not. I have been informed that it is discontinued. What else can I use to get rid of the problem without throwing them away. They have been with me for at least 3 years but I do not want to risk spreading the mites to other plants. I have about 25 African violets at this time. I did separate the 2 from the others.

Answer: It does sound like cyclamen mites are a possibility. I would suggest that you discard the two affected plants. You could try putting down leaves, but keep them isolated until the babies are developing normally. You should treat the rest of your collection. Kelthane was effective but I wouldn’t recommend using it in a home setting. There are few chemicals out there that work as well. I have been told that Neem oil can be effective and it is one of the safer materials to use. It is a natural biological that works by not allowing the young to mature to an adult reproductive stage. You will want to treat at least three times, five days to a week apart. Make sure to get the solution down into the very center of the plant.... immersing works well although it is messy. It is also a good treatment for powdery mildew. Happy Growing! Joyce Stork

Question: I may have a mite problem. I was told at an African violet show that I should just start leaf cuttings and discard the plant. He said the mites only stay in the smallest crown leaves and I should be safe taking cuttings from the outer (older)leaves. Some of my plants are no longer in commerce. I would be sad to throw them out. I have about fifty plants and I do not want to lose all of them over a few problem plants. Suggestions?

Answer: You have my sympathy. Mites are only able to feed on the tenderest cells of the plant, which includes the new leaves in the center of the violet, the blossom stems, and sometimes slightly wilted older leaves when the plant is dry. You can treat the plants for mites, but if they are well established it will take at least a year for the violets to look nice again. Marathon and Neem Oil are two products that have been shown to be somewhat effective. Disposal is often the wiser choice and the one I recommend. You certainly can take leaves to propagate. When you do so, rinse them under a gentle stream of tepid water and then use the techniques described in the article on propagating leaves on this web site. While the leaf is rooting, it will be very turgid (and too hard to feed on) and any mites still present will starve before the new offspring are big enough to be a food source. Be sure to keep the leaves enclosed until the plantlets are large enough to transplant (about 6 months). You may want to treat and save the most precious hybrids for about a month until you are certain that the leaves are rooting, but then you should discard them to prevent re-infestation. Also be aware that geraniums, begonias and ivies (as well as other tender plants) are frequent hosts of cyclamen mites. If they are in the growing area, you would be wise to treat or discard them as well. Happy Growing! Joyce Stork

Question: I am still having problems with tight centers and poor plant condition generally with mites as the seemingly popular cause. My question is on Cyclamen mites in particular. Are these animals associated only with Cyclamen? I have never seen Cyclamen on the island, and as I am on a rural section, there can't be any (even if they exist) within half mile of my plants at least. Are there any other plants that the Cyclamen mites inhabit ,or are they just a general pest?

Answer: They are just a general pest that is common to cyclamen but definitely infest other plants as well. African violets are most often damaged by cyclamen mites. I found a web site http://ipm.ncsu.edu/AG136/mite3.html that lists the following as hosts: ivy, snapdragon, chrysanthemum, larkspur, geranium, fuchsia, begonia, petunia, daisy, and azalea. You might find the same web site interesting for more information about cyclamen mites, including a way to kill them using hot water. This technique has been used by violets growers with reported success. Happy Growing! Joyce Stork

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