Aphid control is a real concern of gardeners and several options have been proposed including yellow sticky traps. These can be yellow cards or yellow drinking cups, both coated in some sticky material.
The concept is simple. Aphids are attracted to the color yellow and head for the trap. once they get they become stuck and die. Problem solved.
You can buy these commercially, or make your own following many DIY online recipes. But do they work? Will they solve an aphid problem in the garden? Lets find out.
Yellow Sticky Cups for Aphid Control
This investigation started when someone posted a meme in our Garden Fundamental Facebook Group, which showed a yellow drinking cup like the one pictured above. It had been coated with Vaseline and the meme claimed that, ” it will save your plants from aphid damage.” A good way to control aphids would be a real benefit for gardeners.
You can easily make your own aphid yellow sticky cup: Instructions.
You can also buy commercial products to do the same thing. These are normally small cards which are coated with a sticky material. They don’t use Vaseline, so would a Vaseline cup work as well?
How Do Aphids Harm Plants?
From a gardeners perspective, their main harm is in damaging the tip of plants, especially flowers. They like to congregate near new growth and suck the juices right out of the plant. When a large number do this at the same time, the tip of the plant dies and more importantly for the gardener, the plant does not flower.
But the real danger from aphids is that they transmit viruses from plant to plant.
The Life Cycle of Aphids
We talk about aphids (also called plant lice) as being one pest, but there are 5,000 species and there is a fair amount of variability in their life cycle. If you have been gardening a while you probably know they come in many different colors, including green, black, blue and red.
The following is the life cycle of a typical aphid. In temperate climates they overwinter as an egg attached to a host plant. In spring, the eggs hatch to produce wingless females. They crawl around until they find a suitable feeding spot, usually on the plant where they hatched.
In warm climates they may skip the egg stage for most of the year.
Females then give live birth to more wingless females that are pregnant at birth. This unusual asexual reproduction produces more mothers without the need to waste time making males. “A newly born aphid becomes a reproducing adult within about a week and then can produce up to 5 offspring per day for up to 30 days!” As a result, the colony grows quickly. This is why plants seem to go from having no aphids to having hundreds in a few days.
At some point, the plant stops producing new growth, or things just get too crowded. No problem for aphids – they just start producing females with wings. These females leave the plant to find a new home and start producing more wingless females, to keep the cycle going.
In fall, it’s time to lay eggs and they need a male for fertilization. So the female gives birth to some males and winged females, they have sex all over your plant, and the female goes off to lay eggs on a suitable host plant.
Are Aphids Attracted to Yellow?
Yes they are, along with many other insects. You might think that these sticky traps are a new invention, but they were developed and researched as early as 1959. There is a “perfect” yellow, but just about any bright yellow will work.
Does Vaseline Trap Aphids?
Vaseline is a popular sticky material used by DIY promoters of these traps, probably because many homes have some Vaseline hanging around. I am sure some bugs get stuck on it, but it is not clear how it compares to a commercial product.
A better DIY product to use is Tanglefoot, which will certainly trap aphids.
Debunking Myths Can Be Easy – Sometimes
Aphids are attracted to yellow and they do get stuck on sticky stuff – so they work, right? Wrong.
First of all it is important to understand that yellow sticky traps were invented and are still used to “monitor” populations. The number of captured insects are counted at a regular interval. When the number suddenly spikes you know there is a pending problem and a pesticide is sprayed. When used as a monitoring and warning system they work quite well, but they don’t work as a control system.
But even if you did not know this, there is a more obvious issue.
Almost none of the aphids on a plant can fly. They are not going to leave a good food source, crawl down a plant, crawl across the ground, and up the stick holding a yellow cup. The cup might catch a flying aphid, but most of the aphids do not fly.
It certainly will not save a plant that has aphids because there is no way that the wingless aphids on your plant will get trapped.
The trap may prevent or reduce future infections on other plants, but not on the plant in question.
Catching Beneficial Insects
The other issue with the yellow sticky traps is that they also trap beneficial insects. Some claim that even birds can be affected when they try to eat the stuck insects.
How Do You Control Aphids?
The best approach for most gardeners is to do nothing. Nature will respond by providing beneficial insects like ladybugs or lacewings to control the problem.
Another good option is to run your fingers up the plant stem and squish the aphids. Or use a strong stream of water to knock them off the plant. Doing this a couple of days in a row usually solves the problem.
Insecticidal soap will also work, but don’t use dish soap, for the reasons explained in Is Dish Soap Safe for your Plants?