I have a few aphids on some of my beautiful Shasta daisies (Leucanthemum ‘Becky‘), daisies that have flowered profusely throughout the summer. I know aphids can overtake and cause havoc in the bed of daisies but I needed to know how much of a problem I had.
Insects buzzed and circled around my head yesterday as I knelt to check out the aphids that traveled along stems beneath the blooms. These insects will suck the sap out of leaves, tender stems and the flowers, and they will transmit diseases like fungus and mold. I saw no signs of wilting leaves or buds. And I saw very few aphids. Now the question, “Should I treat these flowers with an insecticide?” That’s a question that every gardener faces when insect pests invade their gardens. Insecticides would certainly take care of the aphids, but….
… what damage would the insecticide do? The answer to that question comes by observing your garden. There is a small world of insects living there, good ones and pests. Insecticides will kill all insects, benign insects as well as insects that are the natural predators of pests such as ladybugs, praying mantis, assassin bugs, spiders and more. Let’s take a closer look at the small world around these daisies.
The hover fly is a common fly in our area. It gets its name from their ability to hover in midair, then dart here and there, sometimes backwards. The adult does not sting and feeds on pollen and nectar and they are important pollinators but their larvae are very important predators of aphids, thrips, and other caterpillars. These are excellent insects for the garden. Insecticides would eliminate them.
The green bottle fly (Lucilia sericata), also called a blowfly, is a scavenger of all things decomposing and will lay eggs in carrion, thus cleaning up what other animals cannot eat. Unless this fly invades your house or garbage and causes problems, it is not a threat to humans in the garden. It’s a natural pollinator attracted to the nectar of the daisy.
Almost too small to be identified as ants by my eyesight, the camera zoomed in on these miniature ants who are after food, too. These are benign insects that do no harm to the daisies and are food for other insects and birds.
This little butterfly could be the Yehl Skipper (Poanes yehl), a fairly uncommon skipper that is seen along the coast at this time of year, but I prefer my IDs to be confirmed by an expert. This fella would be done in by an insecticide.
This soldier beetle or Pennsylvania leatherwing beetle (Chauliognathus pensylvanicus) is a cousin to the lightning bug. They are common in the garden and beneficial as a pollinator and a predator of aphids and other small insects.
A variety of bees visited the daisies and we all know we need those pollinators. Although the sweat bee can be a nuisance when it seeks out the salt in our sweat, it is considered a benefit in the garden due to pollination.
These tiny insects were unknown to me. These winged insects were the size of pepper flakes to the naked eye. I watched them through the camera lens become the meal of a few hungry crab spiders that lived around the petals.
The answer to the original question about insecticides is IPM (Integrated Pest Management). IPM is a sustainable method of management using biological, cultural, physical and some chemicals to minimize environmental damage. Using a insecticide for the aphids indiscriminately will have a negative and damaging effect on all insects that depend on this small ecosystem for life. Because there is no sign of damage to the plants and the insects are a part of the food chain for predator insects, I will allow the aphids to live in the daisy bed and permit the natural system to work. But I will monitor the flowers for signs of disease or damage. If I must interfere, I will learn about the life cycle of the insect, how best to control it physically, such as picking off or pinching the colonies to kill them. My next step will be to spray soapy water beneath the blooms. And if all else fails, the very last attempt would be a careful use of pesticides, preferably the newer natural pesticides derived from botanicals.
It’s better to become familiar with IPM techniques and implement a regular monitoring program before using any biological controls. Read more about IPM here.
Ann Hohenberger, The Garden Club of Gloucester