What's up with Aphids and Ants?
8 Jun 2005
2005 ARS Award of Merit Certificate Winner
Someone to Watch Over Me…
by Brenda Landers-Smith
“I get by with a little help from my friends…”
John Lennon, 1967
You may not be aware of a friendship that has developed among your roses in the garden. It began with an innocent introduction. But after the “how do you do’s” and casual conversation something more intimate has developed.
This is not a story of romance, of chivalry and valor, but a dynamic chemistry between two high profile characters you meet year after year. Unfortunately, they are also your rose’s enemy…
Allow me to introduce the aphid and the ant…..
Aphids (Homoptera), also known as “plant lice” are one of the most common plant pest insects. They are pear shaped, soft bodied insects often only 1/8 inch in length with long legs and antennae. They have long thin mouthparts that resemble beaks which they spear into plants and suck the juices (sap) from the plant tissue. Some species of aphids are also responsible for spreading many different viral diseases. Aphids come in almost every color from green, yellow pink, brown, black and any shade in between. Take a look under a magnifier to confirm diagnosis. An aphid will have a tiny pair of cornicles which have been described as looking like “dual exhaust pipes” on their posterior. Aphids are the only insects that have them!
Aphids live in colonies and are usually found on tender developing buds and undersides. They over winter as eggs and show up as adults ready to feast in Southern California around the month of March. You may ask “Why so many and so fast?” The lifecycle of aphids is attributed to the fact that female aphids reproduce parthenogenically (without males). The females emerge from over wintering eggs as “stem mothers”; they do not need a mate to reproduce. They then give birth to live daughters that in turn give birth to live granddaughters. The fast growing population is the result of rapidly producing females. Aphids reach adulthood in one week. Later in the season they produce both sons and daughters…then finally mating occurs and eggs are layed to “over winter’ to begin the cycle again.
The attractive feature that brings ants into the romance is honeydew. Yes, honeydew, the sweet nectar of the aphid. With this attraction the ants become the knights in shining armor to aphids. In a survival of the fittest world, of enemy combatants such as spiders, ladybugs, lacewings and minute parasitoids, the aphid has an ally, the ant.
Aphid honeydew secreted from the cornicles is a sugary liquid waste that ants LOVE. While ants are tending and protecting their friends to ensure their supply of this nectar, ants use their legs to rub the aphids which stimulate them to produce the honeydew. This activity is known as "milking" the aphids.
Honeydew in itself poses an unsightly problem. The honeydew secreted from aphids sometimes falls like a fine rain on leaves below. A black fungus is then colonized, called “sooty mold”. Although the leaves are not directly hurt by the droplets, the sooty mold shades necessary sunlight.
Ants will also fend off aphid predators and rescue aphids by carrying them to safer territories. A less romantic way to describe this rescue is the ants “farm” the aphids like a Lilliputian cattle herd and protect them from harm. (They also have an affinity for cottony scales, mealybugs, soft-type scales, and whiteflies.) Ants also save the eggs in their nests over the winter and bring them out in the spring. Indeed a friendship of devotion and dedication.
But alas, our roses do not like the sap sucking aphid or the co-conspirator ant - so what can you do to keep them out of your rose garden?
- Grow companion plants such as white sweet clover, spearmint, sweet fennel, Queen Anne’s lace, goldenrod, hyssop, and sunflowers to attract ladybugs and other insects that feed on aphids.
- Buy ladybugs – release in garden.
- Garlic tea spray - 3 T. chopped garlic in a blender, sieve and add to 1 gallon water.
- A forceful spray of water will wash off aphids. Once knocked off they will not usually crawl back up but ants are known to pick up the aphids and carry their friends back.
- Aphids can be removed from stems by cleaning off with fingers or brushing a cotton swab dipped in water and alcohol.
- Wash with insecticidal soups to kill aphids on contact but spare beneficial insects.
- Spray horticultural oils.
- Slowly pour boiling water over ant nests.
- Attract worms and repel ants by applying a ring of coffee grounds around your plants. My favorite mocha stop, Starbucks, offers BIG free bags of coffee grounds in most participating stores. Bring a plastic garbage bag with you to protect the carpet/upholstery in your car…the moisture leaks from the bag - coffee stains!
- Grow spearmint and tansy to repel ants
- The National Wildlife Federation of San Diego County provides this
Ant Management recipe: Mix 1/3 cup granulated sugar with ONE teaspoon (no more!) boric acid powder (available at drug stores). Add 2 cups water. Mix very well. Keep this bait refrigerated. Pour the bait over a small piece of sponge which you have put in either a small glass jar (like a votive candle holder) or a small margarine container with a lid in which you have punched holes. Place outside where you see the ants. It takes about a week to get a high percentage of kill on the ants. Clean and refill jars twice weekly in hot weather, changing the sponge as necessary. The only mistake you can make with this system is not having the sponge inserted correctly into the jar. It needs to be full of bait and stick up slightly above the level of the bait in the jar. This forms a "bridge" that the ants can walk on to get above the bait and really load up with it to take it home to kill everyone! Dogs tend to ignore this bait but boric acid is toxic to cats, so if you have cats you need to use the margarine tub with a lid on it to keep the cats out of the bait.
Understanding the dynamics of these partners in crime may help observant rosarians combat the problems they cause. Funny, even the world of insects the saying “I’ll scratch your back, you scratch mine” applies.