By: Kathleen McKie
Only 1/16″ of an inch long, the rose aphid is one of about 4,400 species of aphids, varying in color, size, and choice of diet! Rose aphids are usually green, pear shaped, soft bodied, and have long legs and antenna. They are sometimes found singly though usually in my garden they are found in dense colonies and clusters surrounding and feeding from the newest rose buds and stems! They almost form a cloak or wrap around the stem and bud and might be overlooked as they form such a soft-appearing jacket! They can be wiped off with your fingers and some will even fall to the ground when disturbed. They do not attempt to flee or move but you can see their feet moving in distress. They can communicate with other aphids by a chemical cloud that is emitted by cornicles located on the hindquarters of the aphid. Their call is like a dinner bell and the invitation seems to be accepted by multitudes of the little critters before the rose bush has even had time to fully put out its newest growth each season.
Aphids feed on new growth where the sap content is highest and the tissues are softest. The feeding tube attached to the aphid’s head is forced into the plant tissue and chemicals are injected into the plant to improve the flow of nutrients. A healthy plant will shunt nutrients away from the damaged area and will instead pump tannin into the area. The tannin slows the activity of the aphid, causing the aphids to cluster even closer and work even harder to continue pumping. Aphid infestations produce stunted shoots and withered buds. They produce sticky honeydew that attracts ants and causes the leaves to produce a sooty black mold fungus.
The aphid winters over near to the host plant. Eggs are deposited on the canes and as the first warm weather becomes more consistent, the eggs hatch producing female nymphs that begin to feed. The nymphs rapidly molt into adults. During most of the season rose-aphids reproduce asexually, with adult females giving birth to live nymphs (that are already pregnant!!!), as many as 12 per day, each ready to produce young of its own in 10 days. The aphid depends on sheer numbers and speedy reproduction for their survival. You can see that population control for these little guys needs to occur early in the season!
The management of this tiny but mighty pest varies in my garden during the growing season. I am very committed to judicious but regular spraying for insects. The desire to preserve the beneficial critters precludes the use of any constant random use of more toxic sprays. One would most love to depend only on natural predators such as ladybugs, of which there are literally thousands in my garden and it seems, hundreds in my house on occasion! However, it is almost always necessary to intercede, by gently wiping off the little green cloak of aphids or by use of a strong spray of water. These methods are certainly earth friendly, but a major infestation of aphids into a large garden requires a more frontal attack!! All the many ladybugs in my garden are not able to make dent in the aphid population, especially during the first spring birth.
For years, I have used Ferti-lome Rose Food with Insecticide on a monthly basis for the mainstay of my monthly feeding program. I noted that I rarely if ever had aphids during the active growing season of the year. That finding gave me an idea that led to a regimen that has made all the difference in aphid control for the past several years. As soon as I have completed my pruning, usually a month before I plan to apply Ferti-lome Rose Food with Insecticide, I apply according to the label a dose of DiSyston at the drip line of each bush. DiSyston is the insecticide disulfoton that is the active insecticidal ingredient in Ferti-lome Rose Food with Insecticide. In doing so I avoid the first wave of aphids that would be far out of control before I wanted to apply Ferti-lome.
Once all danger of frost is over and I begin my regular feeding program, the aphids are held in check by the disulfoton in Ferti-lome. Disulfoton is considered a toxic insecticide and should be used with caution and with complete attention to precautions listed on the label. I have an abundant supply of earthworms and ladybugs in my garden, and it is my hope and belief that such products, used carefully and judiciously are not unsafe in the environment.
Chemicals which are effective on aphids include Merit 75W (imidacloprid), a systemic insecticide (also found in Bayer Advanced Garden Rose and Flower Insect Killer), Orthene (acephate), and Talstar One, a multipurpose insecticide, effective against termites, aphids, cucumber beetles, and thrips.
Learning your garden and its problems and pests will better enable you to formulate care plans that will work for you. I love to be in touch with my garden and hope that it will make me a better caretaker of all the nature that has been entrusted to me. While I find the soft green body of the aphid another wonder of nature, I would prefer she work her wonders elsewhere!
This is a 2007 Award of Merit article
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