Garden Help Desk: Fall and spring options for eliminating aphids
- Even after hosing aphids off a plant, a few will remain, and others will arrive. Repeated hosing or other management treatments are required to manage the pests.
- The winged aphids can accumulate in such high numbers that they will form thick mats of insects at the base of the tree’s trunk.
- Winged aphids leave their summer hosts in late summer through early fall to find elms or zelkovas where they can lay their eggs. The eggs will overwinter and hatch in the spring.
- As stinkhorns mature, the tops of the stalks develop a slimy, foul-smelling cap that attracts flies that feed on the slime and can pick up spores on their bodies that will be carried to other sites.
- Stinkhorn mushrooms begin as an egg-shaped structure near the surface of the soil. The stinkhorn stalk and top will grow upward from the egg.
Two related questions today: I planted a Frontier elm in the southeast corner of my yard in Provo. I noticed the other day it was completely covered with these tiny bugs. I sprayed them off with a hose, but they are everywhere — along the trunk, the branches and piled at the base of the tree. Can you tell me what it could be and how to resolve?
I have zelkova trees that have become infested in the last week. Please let me know if you can identify the bug and how to get rid of them. I’ve looked online, but nothing matches.
Zelkova trees and elm trees are both members of the Ulmaceae (elm) family and closely related. Plants that are in the same family and closely related are susceptible to many of the same pests and diseases. Your trees are good examples of this.
These are aphids. Leaf feeding by aphids generally doesn’t affect the health of trees, but it can affect their appearance.
Like many aphid species on woody plants, your aphids spent the spring and very early summer on their host tree species (elms and zelkovas), then migrated to their summer host species in a different location. With the winter approaching, the aphids have produced a winged generation to migrate back to their winter/spring hosts and lay eggs. The eggs will overwinter on the trees and hatch in the spring.
This week’s wet weather may help to solve the problem for you, but you can also just keep using strong sprays of water to knock off aphids. They are fragile and most don’t survive. There will always be some left behind, though, so you need to repeat the sprays if you see more aphids this fall. It’s a little inconvenient, but it can help.
Make sure you also do a delayed dormant 2% oil spray to suffocate aphid eggs next year when the buds begin to swell. Thorough tree coverage is needed. It won’t get rid of all the aphid eggs, but it will reduce the population to a more manageable level.
Another option involves an application of a conventional systemic insecticide with the active ingredient imidacloprid. It is applied as a soil drench, poured slowly at the base of the tree’s trunk when the buds begin to swell. The chemical is taken up through the roots and moved out into the leaves.
The soil drench is a once-a-year application, usually done in the early spring. Imidacloprid is the active ingredient in several tree and shrub insect control products that you should be able to find at nurseries and garden centers. The product label will tell you how to measure your trees and determine the amount of product you’ll need per gallon (or 2 gallons) of water.
We’ve been having trouble with this strange fungus. This is a dead tree which we kept for a swing. We’re just wondering if you know what these are, if there’s something that could get rid of them? Thank you for your time.
These look like some kind of stinkhorn, a type of mushroom in the Phallaceae family of fungi. The fungal organism is down in the soil and is almost certainly feeding on the dead roots of the nearby tree and other dead organic matter.
The stinkhorns that you’re seeing are the fruiting bodies (reproductive structures) of the fungal organisms in the soil. The nearby egg-like structure at the soil’s surface is a developing stinkhorn that will soon send up another stalk. Late summer and fall, with our cooler weather and abundant soil moisture, provide the fungi with the best conditions for producing stinkhorns.
The stinkhorns are a sign that the decomposer fungi are doing well and breaking down dead organic matter as they should. They aren’t poisonous and don’t affect the health of nearby plants. There is no spray or other treatment that will get rid of them. They usually disappear on their own pretty quickly and will stop showing up each season once the dead roots and other organic matter are broken down well enough. Just pick them off and discard them.