Garden Q&A: What kind of bees are these in my garden?

Q: I have some small bees visiting my pollinator garden but they rarely seem to land on the actual flowers. Am I not planting the right things for them — are they specialists? Sometimes they just hover near the plants, which is odd, like they’re trying to decide what they want.

A: There are a variety of bee and wasp look-alikes in the insect world. How better to avoid being attacked and eaten than to look like an insect whose sisters will enact vengeance? That's admittedly personifying things, but this type of deception is a good way to make a predator think twice, giving the vulnerable insect time to react and escape.

Flower flies, also known as syrphid flies, are one group using such mimicry. Many species have body colors, patterns, and shapes that resemble those of bees or wasps, though there are subtle ways to tell them apart. For example, true flies only have two wings, whereas bees and wasps will have four, though this is sometimes hard to see since wasps might pleat their wings into several layers when landed to make them less bulky. Flower fly antennae are very short, with a stubby base and a hair-like wispy tip, while bee and wasp antennae will be much more obvious and about as long as their legs, if not longer. Flower flies also have the habit, as you have noticed, of hovering near other plants without necessarily being interested in the flowers themselves. This gives the group their other common name, hover flies.

While syrphid flies can be pollinators, they mainly benefit gardeners by eating pest insects. Hovering adults are checking out the plant's suitability for egg laying. One larva could potentially consume several hundred aphids before it matures into an adult. Leaf litter underneath the plant is important for pupation and overwintering shelter.

Flower fly, looking very convincingly like a bee or wasp. (Miri Talabac/Handout)

Syrphids are an important part of the typical quartet of nature's little helpers (with lady beetle larvae, lacewing larvae, and tiny parasitoid wasps) useful in knocking-down an aphid outbreak. When you find a colony of aphids, before you reach for a pesticide or even a jet of water to knock them off, see how many among them are already being stalked by these predators. You won't have many predators visiting your plantings for future pest control if you deplete their food source, and several kinds of insect pests (like aphids) might look alarming when abundant, but don't actually cause much plant damage.

Q: Last season my tomato transplants developed some leaf spotting fairly early in the season. Is there anything I can do to avoid that again this year? I can't crop-rotate into a new spot to grow them, but I did pick varieties that said they were disease-resistant.

A: You’ve already taken a great first step — selecting varieties resistant to or tolerant of infection — but few of them have good resistance to fungal leaf spot diseases. Still, a few other simple approaches can be helpful to reduce the risk of a severe outbreak.

Your leaf spots were likely due to septoria or early blight, both quite common tomato diseases. If symptoms appear on lower foliage again early this summer, remove any leaves that are heavily infected before they contribute to disease spread. Using a thick organic (biodegradable) mulch around plants, plus avoiding overhead watering, will also help suppress infection.

How so? Many fungal and bacterial spores have an easier time infecting plants if the leaf surface is wet for long periods of time. Some spores reside on the soil surface (or atop dead, fallen foliage not cleared away) and splash onto live lower leaves during heavy rains or blow onto plants during storms. If you irrigate in such a way that wets the plant's leaves, like with a hose spray or a sprinkler, this creates conditions that can lead to greater infection.

While you can't do anything about the weather, you can avoid rampant disease by only watering the soil surface and by not crowding plants into dense groups. Proper spacing allows good air circulation to dry the leaf surfaces faster after rain or dew, reducing their vulnerability. It's also helpful to remove the lowest three to four lateral leaf branches once plants are well-established and beginning to form fruits.

If you discover symptoms you don't recognize, explore our key to common problems of tomatoes web page for images and information about typical tomato pests and diseases and how to manage them. We have similar pages for cucumbers and squash. As you might expect, most problems are easiest to address when caught early.

University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click "Ask Extension" to send questions and photos.