Spring is a fantastic time to be in the garden – everything around you is waking up and signs of new life can be seen everywhere. On your rose bushes, you may also be able to spy signs of life: tiny aphids clinging to the stems and undersides of the leaves.
The invasion appears to have happened overnight – and there’s a very good reason for that as aphids can reproduce incredibly quickly. The rose aphid typically overwinters in its egg and females begin to hatch in early spring; they are able to reproduce immediately without the need for a male mate.
Aphid mothers are viviparous – they give birth to live young – and can reproduce through parthenogenesis. They essentially give birth to a tiny clone of themselves; and some adults can continue to reproduce parthenogenetically even during the winter if the climate is mild.
Each tiny female is able to reproduce in a matter of weeks, meaning that the aphid population currently residing in your rosebushes can increase exponentially over the summer without even a single male present. And over the course of a single growing season, if uncurbed, these little devils can literally suck the life right out of your rose garden.
While aphids can be many different colours, those that attack roses (Macrosiphum rosae or the “Rose aphid” and Macrosiphum euphorbiae, also known as the “Potato aphid”) are typically green or deep pink to reddish-brown.
Their antennae are dark, and sometimes the bend in their back legs and their head can be dark in colour as well. The adults of most rose aphids range in size from barely 1/16” to just over 1/8”; in fact, the largest aphid species are typically only ¼” long. Their tiny bodies and coloration provide excellent camouflage and help them blend in very well on most rose buses.
Most species are also equipped with a pair of cornicles or siphunculi – small upright rear-pointing tubes on their lower abdomen; on some species they are quite short and may even be mistaken for pores. The cornicles can exude a defensive fluid called cornicle wax, which can harden very quickly and, though experts aren’t sure of its purpose, is believed to draw predators away from the aphids.
Even though aphids have a very specific appearance and are easily recognizable, given their tiny stature and colouration, it’s usually only when the aphids moult, shedding their whitened outer skin as they mature, that they are fairly easy to spot.
For most of the year, aphids are wingless. But when large colonies get established and the aphids begin to compete for food, some aphids will begin to develop wings, allowing them to spread to other rose plants and sometimes to other areas of the garden.
The effects of aphids on roses
Aphids are small, soft-bodied insects that can survive in almost any climate zone. Because they multiply so quickly, many generations can occur in a single growing season and, if you’re not vigilant, they can wreak havoc in your rose garden.
These voracious little pests will bite into the stem of your burgeoning roses, sucking up the sap and producing a sweet, sticky substance called honeydew that will cling all over the undersides of the leaves and along the stems. This can lead to the growth of sooty mold which causes branches and leaves to blacken.
The most common effect of an aphid infestation is stunted growth – if you notice misshapen or yellowing leaves, check the undersides for tiny pests. Though a healthy rose bush can support a few aphids, large infestations will affect the blooms as stripping away so many of the nutrients transported in the rose sap can cause the flowers to become far less vibrant and vigorous – they may even begin to look deformed or distorted.
Also, some aphid species can transmit viruses between plants, or even attract other pests such as ladybugs – one of their top predators.
Aphids and ants
Another insect that appears in great numbers alongside aphids are ants. These two vastly different insect species share an odd symbiotic relationship – while the aphids are a food source for the larger insects – who can be seen actively herding their tiny livestock, the ants protect the aphids in a number of ways.
Though you would never typically consider these scavenging insects to be farmers, not only will they not harm the aphids in their care, they actively protect them from aphid lions, lacewings, ladybugs, and other predators. They also help the aphid colonies move from one feeding site to another.
Recently, researchers have determined that ants also protect “their” aphids from fungal outbreaks that would normally decimate the aphid population, by removing the bodies of any infected aphids.
Why do ants herd and protect aphids? For the honeydew, of course! The sticky resin is a favourite treat for the ants, who actually “milk” the aphids, stroking their abdomens and encouraging the production of honeydew, which the ants will also carry back to their colonies to feed to their own larvae. What’s more, farmed aphids supposedly produce larger drops of honeydew and more offspring than those without a protective company of ants.
In these cases, it appears that controlling the ant population will also decrease the aphid population.
How do you kill aphids on roses?
Though there are many commercial pesticides available that will eliminate the aphids from your rose bushes, these formulations are not species-specific and may even harm beneficial insects – such as aphid predators.
A key to controlling your aphid population is to eliminate the “head-start” these ravenous little insects have over their predators every spring, and even through the winter in mild climate zones.
While aphid predator species don’t begin to hatch until temperatures hit an average of 60°F every spring, the aphids can hatch at just 50°F and – with no need to mate before reproducing – their colonies can grow to a considerable size before their predators are even ready to mount an attack.
As the sap begins to run and new growth begins to emerge, the aphids’ live young are able to feed and mature. The aphid population increases rapidly and will reach its peak in the early summer. As colonies grow, a generation of winged aphids will be born who will migrate to other nearby roses, decreasing the competition for food on each bush.
Therefore, it’s definitely best not to wait until your garden is full of insects, but rather to attempt to keep the aphid population in check until the beneficial insects can catch up.
While many home gardeners begin their counter-attacks with a heavy blast of water from the garden hose, hoping to dislodge the growing colony from the plants stems and leaves, we don’t recommended that approach when dealing with roses.
It’s a bit of a recipe for disaster: overwatered roses can retain too much moisture in the soil and around the plants, leading to the development of Powdery Mildew or Black Spot.
Rather than soaking the entire plant with water, many natural spray solutions exists. We recommend always testing a small area before trying any solution on your roses; watch the plants for a few days for any adverse reactions before a widespread application – after all, the “cure” might cause more damage than the aphids.
Neem oil or other horticultural oils can be quite effective against aphids; remember to follow the package directions when applying, as not all oils are created equal!
Insecticidal soaps may also help to curb the aphid population during the spring; however, you should discontinue their use as the temperatures rise to avoid harming other species. And always choose the purest forms of oils and soaps that you can find as many can contain harmful additives.
What home remedy kills aphids?
A simple way to prevent aphid booms is to avoid over-fertilizing your bushes in the early spring. Because they love to feed on plants with robust and rapid growth, wait until slightly later in the season – when the predators have begun to control the aphid population – to fertilize your roses.
One of the easiest solutions is, of course, to introduce and encourage natural aphid predators, such as green lacewings and ladybugs – which are also both quite lovely to look at – by planting dandelions, dill, fennel, mint or yarrow in your garden.
And if you are considering adding to your garden, think about putting in mustard or nasturtiums – which are also particularly appealing to aphids – at a safe distance from your roses as a diversion for the pests.
In addition to some insect species, aphids can also be a tasty treat for many species of birds, so encourage their visits with a bird house set high in a convenient tree or a feeder stocked with birdseed near your rose bushes.
There are several other natural methods to control the tiny pests with ingredients or supplies that you already have on hand. Vigilant gardening – inspecting your roses early and often for signs of an aphid infestation – will allow you to take appropriate control measure quickly.
Some gardeners recommend using orange and banana peels to repel aphids. Bury small pieces of banana peel 1-2” deep in the soil around your roses, or spear orange peels directly onto the stems.
These highly fragrant fruit peels contain d-Limonene, a natural chemical that will destroy the waxy coating on both aphids and any farmer ants, causing them to suffocate and die. Orange oil can also be an effective repellant.
Other home gardeners suggest dusting your roses with flour, believing that this constipates the aphids and prevents them from feasting on the sap.
Diatomaceous earth is a non-toxic and organic garden additive that kills aphids, though it should not be applied while your roses are in bloom, as it can also be harmful to pollinators.
To make a homemade insecticidal spray, you can use either isopropyl (rubbing) or ethyl (grain-based) alcohol. Simply mix equal parts of 70% (or 140-proof) alcohol and mist your roses lightly. You can also add alcohol to a soapy emulsion to make it more effective.
Does soapy water kill aphids on roses?
It’s believed that soap may also kill aphids by removing their waxy protective layer. And though regular dish soap won’t harm beneficial insects, commercial insecticidal soaps have been designed to maintain the plant’s waxy cuticle whereas dish soap may strip it away.
If you use a homemade soap spray, stick to liquid dish soap that is not scented or citrus-based, nor formulated for grease removal. You should use a teaspoon or two of soap mixed with water and spray the stems and undersides of the leaves, beginning at the bottom and working your way up the rose bush; you must wet the aphids thoroughly for the best results.
As always, test your solution in a small area; if the rose leaves appear dull after they’ve been rinsed and dried, the soap may be causing dehydration. If the spray helps, continue applying it every morning or evening until the aphid infestation clears up.
Some gardeners add a pinch of cayenne pepper and one teaspoon of dish soap to a quart of water to also discourage other garden pests from nibbling on the rose leaves.
Will vinegar kill aphids on roses?
Just like dishwashing soap, vinegar is lethal to insects; therefore it should only be using before appearance of aphid predators.
Apple cider vinegar is great at repelling the ants that may be protecting your aphid population as well as the pests themselves. Spraying equal parts water and apple cider vinegar wherever you see an ant trail will prevent them from returning to the area; spraying it directly onto the ants will kill them.
Many plants are sensitive to the acidic nature of vinegar, so we suggest diluting the apple cider vinegar further (1 part vinegar to 3 parts water) before spraying it onto your plants – testing a small area first. If your roses tolerate the vinegar, continue using it until the predator insects begin to appear.