The Whiteflies, Aphids, and Mealy Bugs of Winter
by Maud Kane, Master Gardener
Cornell Cooperative Extension

Isn't it amazing; how many things exist in nature and yet we never notice them? Well, now that plants are indoors, the varmints who pester them are indoors too. I'm talking about whiteflies, aphids, and mealy bugs. Believe me, there are far more pleasant things that I would rather talk about. I bought a plant after being swept with emotion… seeing the way the plant swayed in a breeze. Tall, elegant, willowy (not me; the plant). It's a real keeper. Granted, it was in a greenhouse which I thought of as an especially protected environment. I was reassured by my "tour-guide" that this specimen was known to "bounce back" from damage even though it looked quite fragile. I should have taken that as a warning. Bounce back from what? Well, at the moment it's flies and mealies. I had tried to console myself with an end of season special. Rule #1: Don't sweat the small stuff; Rule #1a: Go shopping to ease pain. So, I bought a luscious looking Hibiscus on sale at a commercial greenhouse. A week later, the aphids made their appearance. Why me? I've never had these types of bugs on indoor plants in my life so what gives now?

Well, instead of whining, I guess I should just mention what I found out. So here goes. When I saw small shiny, glistening spots on the upper surface of leaves, that's not amore. That's honeydew, or more specifically, the life blood of your plant being sucked out by insidious parasites. For example, there are many varieties of aphids, but indoors the baddie is the green peach aphid and sure enough, they look really light in color compared to their outdoor cousins. They pierce the veins in the leaves and stems and drink the sap. Their excrement is left on the leaves, along with some of the sweet sap. Sooty mold can land on this residue and pose an added threat to the plant.

It's not bad enough that there are now holes in the plant, but ants love to feed on this sap too…. so much so that they adopt aphids. Unbelievable! This is so bizarre, but honestly, it says that in all the books I looked in. "The ants gather and feed on the secretions of aphids." One text goes so far as to give their narrative (which I could really live without reading) on how the ants gather up aphid eggs in the fall, "tenderly care for them over the winter," and then bring the little newborns/eggs up the stems to launch their attacks all over the plant's new growth. Isn't that gross? Can you imagine ants running a collective farm system on your houseplants? Just what this country needs: more biological terrorists.

What could be yuckier you say? You had to ask. Mealybugs. Picture a colony of fuzzy armadillos; the tiny little creeps hiding on the under side of leaves or right in the joint of a new shoot's armpit. Warm dry climates make them happy; just like the other scale insects in their family. So when the heat is on inside....you guessed it. Like aphids, they are digging in for a meal and their saliva includes a poisonous injection into the plant. But they are more covert, having hard-to-detect nymphs and sometimes constructing a waxy shell around themselves so that water beads off.

Well, look out for rubbing alcohol on a Q-tip 'cause I'm gunning for them now. That sounds like the most commonly advised solution to get through their barricade. Soap solutions are mentioned, and in the case of aphids, a particular home remedy is touted: Stinging Nettle and cold water extract, sprayed repeatedly at "full strength." (Recipe: 500g fresh nettle steeped in 1.3 gallons of water for 72 hours, then strained.) Let me just run out to my Martha Stewart-like backyard and gather some. But hey, all seriousness aside, there are some commercially prepared pesticides which may solve these problems. Just remember… you're the one breathing that indoor air-no dangerous chemicals allowed! The spray I was shown by a concerned co-worker is clearly labelled: "May be used indoors...in offices and schools year-round." I can't say "be careful" enough! Read the label.

Last but not least, that little cloud of minute Whiteflies. They just love greenhouses. Hey, wait a minute, my house is red! I thought my eyes were playing tricks. A plant with DANDRUFF! But no, they are scale relatives that also appear in the form of wedge-winged adults. They have a complicated lifecycle including some stages I won't go in to. Suffice to say…. they may be present in several forms before they are spotted. They have microscopic larvae and hide on the underside of leaves. So again, direct soap sprays may miss the mark.

Some nurseries, and probably some gardening catalogs, can equip you with the small yellow plastic tags coated with non-drying glue. These can be placed by windowsills or right in the pot. "All the better to catch your wings with my dear......" Apparently, traditional sprays are rarely successful and have to be applied early in the morning as the new winged crusaders emerge. Thanks, but no thanks. I have enough trouble in the morning getting myself to emerge. The only practical solution I found that sounds reasonable is to reduce the temperature and humidity.

Then there's the new chemical approach: "Resmethrin," which is a synthetic pyrethroid, whatever that means. Just one teaspoon of this stuff to a gallon of water is supposed to give "excellent control." Also mentioned in our reference library is a commercial aerosol product made especially for whiteflies. But indoors (and out) be particularly aware of what you spray or apply. It's deemed better to give up the fight and just throw the darn thing out than to keep dosing your air, your house, and your plants with compounds that are dangerous to humans!

So, if there's a moral here, it's to be careful what you buy and where you buy it, what you spray and who or what is in its path! Isolate new houseplants upon arrival to make sure they really are as healthy as they look. Always wash your tools really well after use if you have to trim a diseased or infested plant.

For all your lawn and garden questions call the Master Gardeners at the Cooperative Extension office 315-536-5123 leaving your name, question, phone number and a time we may return your call with the results of our research. If you are interested in becoming a Master Gardener, a new class will be forming in January. Call the Co-op Ext office for details.