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Black and Yellow Flies and Rust in Lawns
By John Fulton

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[August 08, 2015]  Black and Yellow Flies - The appearance of the black and yellow flies we have become accustomed to probably means we have had a good year for flowers and also higher than normal aphid populations. . The yellow and black insects commonly called sweat bees are actually flies.

Syrphid flies to be correct. Sweat bees are about a quarter of an inch long, and are usually a metallic green in color 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 in Lawns

This past week or so, rust has paid us a return visit. The stress from higher temperatures, and lack of rain (for a short time), have slowed the growth of grass. As grass growth slows, rust is one of the lawn fungi we are dealing with. Rust appears as an orange or yellowish-orange powder (spores) on grass leaf blades, especially in late summer to early fall when the weather is dry. Rust typically develops on lawns growing very slowly. Higher temperatures may also contribute to slow growth. Overall, the turf may assume a yellow, red, or brown appearance. A close look will reveal the pustules, which easily rub off on your hand. Rust spores can easily be tracked into homes.

Low fertility (in particular nitrogen) and low water availability slow down turf growth, allowing rust to develop. Seasons with excess rain may have rust outbreaks due to loss of available nitrogen. Cool nights with heavy dew and light, frequent rainfall add to the ideal conditions for rust to develop. Warm, cloudy, humid weather followed by hot, sunny weather also favors rust development on lawns. Kentucky bluegrass, perennial ryegrass, and tall fescue are all affected, depending on cultivars. Rust spreads through air, water, shoes, equipment, and sod. Rust may weaken turf grasses and make them more susceptible to other problems.

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 Control rust through sound turf management. Begin by choosing a quality blend of turfgrass seed. Resistance to rust can vary according to the race of the disease present. Maintain lawns through sound watering, mowing, and fertilizing. If you are watering, water early in the day so the grass dries quickly. Manage problem thatch. Increase vigor with an early fall nitrogen application, but don't overdo it. Check soil phosphorus and potassium levels through soil testing. Also assure good airflow over the site, and provide light penetration by pruning trees and shrubs in the area near the lawn.

A change in the weather will make rust fade away. Early September is a key time for fertilization. Use something with an even analysis or a winterizing fertilizer. If conditions are dry, irrigation is also needed to increase the growth rate of the lawn. Fungicides are rarely suggested on home lawns for rust control, just focus on the listed cultural practices described above – and it is not recommended to mow the lawn in white tennis shoes, unless you are trying to determine if you have rust.

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

 

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