Edible Gardening Series: Question of the Week – aphids
By Carol Wyatt-Evens and Sarah Bostick
Gardening in Florida can be incredibly rewarding and incredibly frustrating, at the same time. If you are new to the region, you soon learn that gardening in the Sunshine State can quickly become a full-time job. While our subtropical climate is perfect for growing an abundance of different vegetables, fruits, and herbs, it also can present some overwhelming challenges.
We can help!
UF/IFAS Extension Sarasota County agents and staff have created an online edible gardening resource center. The website features short videos from our 25-episode “Edible Gardening Series” webinars, along with blog posts and resources list for episodes. Get help on an array of topics that befuddle many gardeners.
Each blog post in the Question of the Week blog series is associated with a specific EGS episode, but they are written for everyone to enjoy!
Question of the Week:
Why are there so many aphids on my plants?
Aphids are prolific pest insects with a very interesting lifecycle. They are one of the most abundant sap-sucking insects in the garden and the landscape. Aphids are soft-bodied insects in the order Homoptera, the same order that includes whitefly, mealybug, and scale. There are over 250 species of aphids and they come in a wide range of colors including green, black, yellow, orange, and pink.
Some aphid species are monophagous, which means they will only feed on a single plant variety. Others are very good eaters and not at all picky. The green peach aphid, an extremely common pest here in Florida, happens to be the latter and recorded to feed on hundreds of plants across many different plant families.
Besides the devastation this insect can inflict by the sheer numbers of hungry bodies feeding on our plants, aphids can vector plant viruses to many of our garden plants. So, the tiny aphid can cause some big problems for us and our plants.
So, why are there so many aphids on your plants? The answer to the question lies in the aphid’s reproductive strategy.
Aphids have two forms of reproduction- asexual and sexual reproduction. In the spring, when food is plentiful and the temperatures are high, aphids reproduce through parthenogenesis. That is, the females give birth to live young through asexual reproduction. In short, there’s no need to mate to create.
Female aphids can birth up to 12 young per day – all are female and the immatures are clones of their mother. In as little as 7 days, they will go through four molts (shedding their skin) before reaching full maturity. At this point, the female aphids can immediately begin birthing new female aphid nymphs. This allows aphids to have 30 or more generations in a season. And this is why aphid populations seem to double or triple in size overnight.
In autumn when plants start to decline and food becomes scarce, the female aphids will begin to produce both female and male offspring. Once these immatures reach maturity, the adult aphids will reproduce through sexual reproduction. The adult aphid’s sole purpose is reproduction. They don’t even feed since they lack mouthparts. They will lay hearty, viable eggs that will give rise to the females that will start the spring cycle all over again.
In all, female aphids live up to 45 days and can produce between 50 to 100 offspring during their lifespan.
Although the aphid may hold the gold medal for the production of offspring – it also holds the top spot for being the favorite food of natural enemies!
Aphids are the candy of the insect world. There are many natural enemies of aphids that are commonly found in the urban landscape and will help keep aphid numbers in check. A few examples of nature’s biological control are:
- Ladybeetles – both the adult and the larval (immature) stages feed on aphids
- Syrphid fly larvae (aka flower fly, hover fly)
- Green lacewing larvae
- brown lacewing larvae
- parasitic wasps
Since aphids tend to feed at the terminal growing points of the plant where they are exposed, their natural enemies have a fairly easy job of keeping them controlled.
How to Help the ‘good bugs’
As responsible gardeners, our job is to support beneficial insects and biological control agents. Conserving natural enemies requires creating and maintaining a healthy environment for the insects. this can be accomplished by:
- Planting flowers for the natural enemies whose adult stages are nectar feeders such as the syrphid fly.
- Increasing the plant diversity in your yard. This will increase the diversity of insects as well as wildlife in the yard. this also provides habitat necessary for overwintering.
- If the pest insect requires chemical-intervention, opt for biorational products (horticulture oils and insecticidal soaps) that are less toxic to people, the environment, and beneficial insects. Spot treatments only, and apply early morning or late afternoon to lessen the chance of coming in contact with beneficial insects.
Aphids may have a great reproductive strategy, but they are no match for nature’s best pest control. However, the natural enemies require our patience. The natural enemies will take care of the aphids, but they need time to do it. Be patient and let nature do its job.
Factsheets and resources for gardening in Florida
Aphid biology and control:
- Green Peach Aphid, Myzus persicae (Sulzer) (Insecta: Hemiptera: Aphididae)
- Insect Management in the Home Garden
Photo credits: Potato Aphid- J. Castner, UF; Oak aphid, green peach aphid – L. Buss, UF; Melon aphid –F. Santana; Natural enemies -M.Hanak, Sarasota County; Tabacco aphids – M.Gulesci, Bugwood.org