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Sweat Bees and Syrphid Flies, Rust on Hollyhocks, and That sticky mess under trees
By John Fulton

[July 29, 2014]  Sweat Bees and Syrphid Flies - Everyone seems to be having troubles with “sweat bees” these days. Or are they sweat bees? Sweat bees are about a quarter of an inch long, and are usually a metallic green in color.

The yellow and black insects commonly called sweat bees are actually flies. Syrphid flies to be correct. When in doubt, count the wings (I know – easier said than done). Bees will have two wings per side, while flies have one.

Syrphid fly is a generic name given to an entire group of flies. There are some differences in appearance and color, but the yellow and black color is the major one in our area. The other names for syrphid flies are hover flies or flower flies. They tend to hover around your arms and face when you have been perspiring, and land to lap up the sweat. They are also commonly found on flowers, hence the flower fly name, and do a good job of pollinating.

Syrphid flies are actually beneficial insects. They help pollinate, larvae feed on dead organic matter, and the larvae are predators of aphids. They cannot sting, but their mouthparts can usually be felt when lapping up sweat from sensitive areas. You may feel a slight pinch which makes you feel like you’ve been stung or bitten.
 

Rust on Hollyhocks

Hollyhocks are one of the traditional, old-fashioned flowers often grown in our area. This year, they are definitely interesting – that is if yours survived the winter. Most area hollyhocks are infected with rust. Rust is usually a spring and fall disease problem, when it occurs. This year it has kept going with the type of weather we have experienced.

Rust first shows up on the bottom of the lower leaves, and the top side of the leaves has some rather striking bright yellow to orange spots develop. Rust can attack all plant parts including leaves, stems, and leaf petioles. The rust disease spends the winter in old plant parts on the ground. Removal of the plant material will help reduce infection possibilities. Increasing air flow and reducing humidity will also help. Control is best accomplished by removing infected leaves at the first sign of the rust (on the bottom of the leaves). Chemical control may needed, and sprays containing sulfur are effective.

 That sticky mess under trees

People are once again complaining about leaking sap coming from trees. What happens is a fine mist of sap coats things beneath a tree. This is actually called “honeydew,” which is a secretion of sucking insects such as aphids and lacebugs. What makes matters worse is a fungus begins growing in the honeydew, making it turn black.

There are two ways to deal with the problem. The first way is to spray the entire tree with a product, such as malathion, to kill the insects. The second way is to move anything portable from under the tree. If you opt for the first option, you need to make sure you can spray the entire tree. The presence of the syrphid flies this early indicates there is a food source available – such as the aphids causing the honeydew secretions.

[By JOHN FULTON, COUNTY EXTENSION DIRECTOR SERVING LOGAN, MENARD, AND SANGAMON COUNTIES]