A:  The first step should always be to try to break the life cycle, because killing only the biting adults with typical mosquito sprays won’t get you good control in the long run. Look for breeding habitat: Mosquito larvae require water to live in, and they can use surprisingly tiny volumes to mature successfully — as little as one teaspoon. Eliminate any sources of standing water, or modify them, to discourage egg-laying and larval survival.

For garden water fountains or ponds, that could mean adding movement to the water surface, to disrupt egg laying and the ability of mosquito larvae to breathe. Ripples from dripping water or devices that vibrate enough to keep the water surface moving can help.

If water basins can’t be emptied often (or at all), see if they are suitable for treatment with Bti, a naturally occurring soil-dwelling bacterium whose toxins kill certain fly larvae without directly harming other types of wildlife. Otherwise, empty and refill them regularly as an alternative or supplement to movement or Bti treatment, since mosquito larvae can develop to adulthood in a short period. Not only will doing this potentially flush the larvae out, but it can dilute or remove their food source, which is bacteria living in the water along with algae and organic detritus.

A mosquito problem is harder to solve if you can’t access breeding sites like a poorly-draining roof gutter, for instance, or ponding in a natural area, or if a neighbor has standing water they won’t or can’t address. Use long-sleeved clothing and/or mosquito repellent to help evade bites when you can’t effectively suppress the mosquitoes themselves. If you’re sitting outdoors, use a fan pointed in your direction for a steady breeze to make it harder for mosquitoes to fly close enough to bite.

I strongly discourage spraying for adult mosquitoes. No matter what chemical is used, organic or otherwise, it is not selective for mosquitoes and may harm various other insects or wildlife. Spraying is only a very short-term solution: adult mosquitoes will fly in again from other areas.

For the long term, increase the diversity of flowering plant species in the yard or in your neighborhood, if there are common areas that can be converted from turf to other plantings. This buffet of alternative food and shelter will attract and support predatory insects and other animals that consume mosquito adults and/or larvae – a natural means of population suppression that is self-sustaining.

Explore our Controlling Mosquitoes web page for more tips and information about the impacts of pesticide use. The page also links to a UMD Maryland Grows blog post about mosquito control, which includes tips for a homemade trap for Asian tiger mosquitoes.

Q: The leaves on my pole beans are turning pale. Is this a disease?

A: Spider mites are a common hot-weather vegetable garden pest. Mite feeding damage is called stippling, which is the fine flecking causing leaves to turn light yellow or greenish-white. High populations of spider mites will also create visible silken webbing between leaves and where the leaf joins the stem.

In the hot weather that spider mites thrive in, using an insecticidal soap or horticultural oil spray to smother the mites on contact can injure plant tissue and cause even more damage.

Instead, try spraying the upper and lower surfaces of the leaves with a strong jet of plain water from a garden hose to knock off most of the mites. Keep plants well-watered, and don’t over-fertilize, which can increase mite populations.

Spider mite outbreaks tend to favor areas with heat buildup, where reduced air circulation stresses plants, such as planting beds close to a wall, solid fence, or heat-reflecting and heat-absorbing pavement or stone. Try to avoid growing mite-prone plants in such areas, or just be aware that those are the areas to check first when conditions favor a mite population rise and plant stress.

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.

A:  You can’t intervene much if you want to let the plants support wildlife. Insecticides would not be recommended (even organic options could harm pollinators) and a physical barrier like a cover of insect netting would, of course, prevent any pollinator access.

A wide variety of insects in midsummer can chew petals (and foliage), which include many species of beetles, grasshoppers, crickets, katydids, earwigs, and caterpillars. Some of the caterpillars that can eat coneflower (Echinacea) blossoms are camouflage loopers, which chew petals, certain inchworms that tuck into the crevices and are hard to find, and the sunflower moth, whose caterpillar bores into the flower head.

None of these insects damages the plant enough to worry about. In many cases, the true flowers in the center cone of the flower are still perfectly functional for pollinators. If pollinated flowers produce seeds, they are also valuable to birds like goldfinches. As with all daisy-style aster family plants, the petals surrounding the cone are the ray flowers, which are usually sterile. While ray flowers help to catch the eye of pollinators from afar, they are not providing any of the floral food, so if they go missing or are damaged, it’s not a great loss. Many gardeners plant these perennials for the benefit of wildlife, so we have to expect that wildlife will actually make use of them in ways we might not appreciate.

There should be enough blooms unscathed by these flower munchers that you can still enjoy the plants, if not this season, then in a future year at least. This is one reason why planting a given species in groups, if feasible, can reduce the visual impact of some imperfections or damage that would be more prominent on a lone plant or two.

If you want to use the blooms as cut flowers, you can bag a portion of them to exclude these nuisance pests: use an organza, tulle, or mesh bag with a cinch-tie to cover the buds so they open intact. (Mesh maintains airflow to reduce the risk of fungal growth.)

Q:  My iris leaves look diseased. Can that be treated?

A:  Possibly, but it shouldn’t be necessary. The fungus (Cladosporium) that causes leaf spot infections on iris doesn’t infect the belowground parts, but if plants are weakened by heavy infection, they won’t be able to store as much energy for future blooms. Since the fungal spores overwinter in dead foliage and infect new growth in the spring, then spread further as rain splashes spores around, sanitation is essential. A thorough clean-up at the end of the season is the main approach to discourage recurring outbreaks.

During the growing season, you could cut off all infected foliage tips and dispose of the debris. After the growing season, remove all frost-killed leaves and dead flower stalks. Like many fungal pathogens, this one thrives in mild, damp weather conditions, so grow iris where they get good air circulation (not too crowded or close to a wall or solid fence) to help wet foliage dry off faster. Full sun exposure promotes good flowering and helps dry leaves off after rain, dew, or irrigation.

If you need to water the plants during dry spells, either avoid wetting the leaves entirely (only water the root zone), or water early enough in the day so that the foliage can dry by nightfall. Many species of iris rarely need routine watering because they are sufficiently drought-tolerant, but plants that have been cut back may benefit from occasional irrigation during dry spells to help them regrow.

Fungicide can’t cure existing infections, and while it might successfully protect uninfected growth, I don’t encourage its use. As a last resort (other than just replacing plants repeatedly plagued with leaf spot), you could try a product with the active ingredient chlorothalonil, following all label directions.

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.

A:  No, they’re harmless. This is a widespread but not often seen millipede named Apheloria virginiensis, and it grows to about 2 inches long. (This species doesn’t have a widely-used common name; some sources call it the Kentucky flat millipede or the black-and-gold flat millipede.) Avoid handling them, as this and other species can produce defensive cyanide-containing secretions if they feel threatened by predators.

Millipedes might eat live plant tissues on rare occasions, but they don’t damage garden plants and generally help to decay already-dead plant matter. They also might scavenge dead invertebrates if the opportunity presents itself. As nutrient recyclers, they are valued members of the ecosystem and beneficial in gardens for breaking down leaf litter and other debris.

Millipedes might become more visible as they roam around during rainy weather, or if saturated conditions temporarily force them out of the soil. Otherwise, you’ll typically find them under or within moist rotting logs, stumps, and leaf litter. A few dozen species of millipedes occur in Maryland, with our largest reaching over twice this length, but it isn’t as colorful as the Apheloria.

Q:  How can I support fireflies in my yard?

A:  Preserving habitat is key, so they have the food, shelter, and environmental conditions needed to reproduce. As larvae (juveniles), these insects feed on a variety of pests, including slugs, snails, and caterpillars, plus earthworms and other soft-bodied invertebrates. They roam the ground, including exploring mossy areas or under rotting logs or leaf litter, to search for prey, and require moist or humid conditions to thrive. Some species spend a couple of years in this life stage before maturing into adulthood, which is comparatively short-lived, so suitable conditions for the larvae are critical.

As with some other beetles, firefly adults will sometimes visit flowers. Growing a diverse array of native plants can support fireflies by attracting the species they prey on as larvae and potentially feeding the adults if they seek nectar or pollen. If your landscape has the room, leave fallen logs to decay at their own pace, and welcome mats of moss at the edge of a lawn. (If moss is taking over areas of lawn, the grass was struggling to begin with, so the moss is not to blame for its decline.)

Outdoor lighting interferes with adult firefly behavior and makes it harder for them to find mates, since the light distracts from or drowns out their flashing. Turn off what lights you can, or switch them to motion-activated sensors or timers so they aren’t on all night.

Reduce or eliminate pesticide use. This spares the fireflies themselves from direct exposure and harm (especially from broad-spectrum ingredients like those used for mosquito and lawn treatments) and preserves their food source. Water quality is another concern regarding habitat degradation, and some pesticides could contaminate surface water in settings with leaching or erosion.

Where possible, leave leaf litter in place in the autumn instead of blowing it away or chopping it up. Natural mulches like leaf litter insulate the ground and provide hiding and foraging spots for wildlife. Like the measures above, this will broadly support local biodiversity.

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.

A:  Unfortunately, they want conditions we might not be able to provide in our gardens, but I have a fondness for this plant, too. In our region, you’ll find fringed bleeding-heart (Dicentra eximia) in the mountain habitat in West Virginia. For example, they grow in the Dolly Sods Wilderness, which ranges in elevation from roughly 2,500 to 4,000 feet, creating an environment akin to southern Canada and very different from where most Marylanders garden in the piedmont or coastal plain.

Fringed bleeding-heart is quite rare in Maryland, only growing wild in Allegany and Garrett counties, despite being sold around the state at native plant sales and nurseries. Much of its native range centers around the Allegheny and Blue Ridge Mountains, where West Virginia meets Virginia and Tennessee meets North Carolina. The emphasis there is mountain; despite the range being south of us, the higher elevation habitat makes most of Maryland hotter than the plant prefers.

Often growing in rocky ground with acidic soil in the wild, this species doesn’t go summer-dormant the way the popular non-native bleeding-hearts do (Dicentra/Lamprocapnos spectabilis), but heat may hamper growth and pause flowering. Some references say the plant will tolerate a near-neutral soil pH, and it prefers a rich soil (with lots of organic matter).

I’ve seen it growing alongside abundant reindeer lichen and heath family plants (blueberry, huckleberry, mountain-laurel, rhododendron, azalea, and wintergreen), on the edges of mixed hardwood-spruce forest. In a garden setting, growth is probably best in afternoon shade or dappled summer light (more sun would be fine in evenly moist, cool environments), in a soil that doesn’t get dry but also drains well.

If you are shopping for the plant, make sure the tag says Dicentra eximia if you want the Eastern native species. Dicentra formosa is the West Coast native analog, and sometimes it’s mislabeled as D. eximia, or a cultivar (like ‘Luxuriant’) is a hybrid between the two.

Q:  The lower leaves on my tomato are getting spotted. Will that kill the plant, or can I treat it?

A:  It’s likely a fungal leaf spot infection like Septoria or early blight, which are quite common in summer. Leaf surfaces that remain wet for long periods, from rainy weather, heavy dew, or running a sprinkler, are more vulnerable to infection. Fungal spores infect lower leaves first and spread upwards.

To discourage infection, try to keep the leaves dry. You can’t avoid wet weather, of course, but when watering the plants, only moisten the soil if possible (don’t shower the foliage in the process). Water early in the day so that the foliage can dry by nightfall, which will also help the plant stay hydrated through the heat of the day. Covering bare soil between plants with mulch will reduce the risk of infection. Removing three to four of the lowermost branches, once plants have established and fruits appear, will improve air circulation and reduce disease risks.

You can learn more disease prevention techniques and explore typical tomato problems on our Key to Common Problems of Tomatoes web page.

As a last resort, you could try to suppress the spread of infection by using a copper-based fungicide, but keep in mind that it can’t cure existing disease, it might not always work completely to prevent new infections, and spray residues might be harmful to pollinators or other organisms. As with any pesticide, always follow label directions carefully, and make sure the chosen product is labeled for the insect pest or disease you need to treat and for use on edible plants.

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.

A:  This sounds like feeding damage from a population of chrysanthemum lace bugs. Despite their name, they feed on several plants in the aster/daisy family, especially asters and goldenrods.

Named for their mostly clear, lacy-patterned wings, lace bug adults are fairly small, at about 4mm long. Don’t confuse them with the similarly-named, unrelated, larger and clear-winged lacewings, which are beneficial predators. Over a dozen lace bug species can be found in Maryland, their hosts ranging from azalea or rhododendron to oak, walnut, fringetree, linden, eggplant, and even grasses.

Like other “true bugs,” lace bugs have mouthparts that pierce and suck, which they jab into leaf cells to suck out the contents. This gradual removal of the leaf’s chlorophyll causes the pale, bleaching symptom. When large areas of feeding damage coalesce, they make whole sections of the plant look pale and stressed. I have seen leaf-edge browning and drying associated with these lace bugs, even though the roots have enough moisture.

Use a garden hose and aim a strong spray of water at the leaves, both tops and undersides. Adults can fly and might return, but the juveniles cannot fly. Or, just give the plant a good, vigorous shake and see who falls off. This approach isn’t perfect and won’t eradicate them all, but it doesn’t have to – the plant will live and regrow just fine next year.

Avoid using insecticides on plants as popular with pollinators as the aster family members are. If nothing else works and the lace bug population remains high, horticultural oil or insecticidal soap might suppress them enough to minimize their impacts, though it’s pointless to try if the plants are already heavily damaged. (In that case, spraying the foliage could worsen the damage by “burning” the injured leaves.) You’ll have to thoroughly coat both sides of the leaves with the spray. Even these low-toxicity options could endanger any caterpillars present.

Do not spray while temperatures are above 85 degrees, or you risk phytotoxicity (plant damage from chemical exposure), even on healthy leaves. Additionally, contact insecticides need re-applying roughly every 1 to 2 weeks for a few sessions to catch missed individuals, which can be a hassle.

Since treatment won’t reverse existing leaf damage, I typically wouldn’t bother with trying it, aside from the hose-off method. This is a native insect, and it’s part of the “ecosystem services” we’re striving to provide by planting native aster and goldenrod species. Everything feeds on something else: predatory insects, spiders, and other beneficial organisms will remove some of the lace bugs on their own.

Q:  Do flowers for attracting hummingbirds need to be red?

A:  While red is a popular color with Ruby-throated hummingbirds, they will just as eagerly visit blue, purple, pink, orange, yellow, and white flowers. A trait the most popular blooms share is a long, tubular, bell or trumpet shape, often hanging or drooping downwards, preventing other pollinators from easily landing on the flower petals to crawl inside.

Plants in the mint family (Lamiaceae) are frequently visited, such as sages (Salvia species, both cold-hardy and tender), the aptly-named hummingbird mint (Agastache species) and beebalm/bergamot (Monarda species). Also favored are our locally native perennials lobelia (not solely the red cardinal flower), butterfly weed (Asclepias tuberosa, orange), tall phlox (Phlox paniculata, white, pink, and other colors), and our annual jewelweed (Impatiens capensis, orange, and I. pallida, yellow).

Keep in mind that hummingbirds catch lots of insects, both to round out their own diet and to raise their nestlings. Therefore, you can grow an even wider variety of flowers that attract small insects that will help feed hummingbirds living near your garden, even if you can’t accommodate as many of their preferred flowers due to constraints of space or growing conditions.

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.

A:  Plant viruses and virus-like organisms (phytoplasmas) can cause weird symptoms, like distorted growth or yellowed patterns on the leaves. A more common cause of abnormal foliage in tomatoes, especially this time of year, is herbicide exposure.

Like other pesticides, herbicides fall into certain “modes of action” categories, based on how their ingredients function. Growth regulator herbicides that function similarly to plant growth hormones tend to be the culprits in this case, which is why they interfere with new growth. In comparison, chemicals that interfere with photosynthesis or the formation of chlorophyll can give young leaves a yellower or whiter bleached look.

If you didn’t use any weed killer, perhaps a neighbor, farm, or golf course upwind of you did. Applications on a warm or breezy day may volatilize, where the gaseous residues drift onto vulnerable plants. Tomatoes are sensitive to herbicide drift and will typically show exposure symptoms first.

If symptoms are mild and subtle, all you can do is wait to see if the plant outgrows the exposure, since nothing can remedy the damage. If herbicide is the culprit and the exposure was great enough, recovery will not be possible, and the plant should be replaced. Viral infections cannot be cured either, though not all plant viruses are fatal to the host, or even always symptomatic. Even so, remove plants believed to be infected with a virus so they don’t contribute to pathogen spread. Plant viruses need a living host to survive, so the debris of infected plants can usually be composted.

Q:  I used to put down grub control each year, but in my new yard, I’m not sure if it’s needed. What do you suggest?

A:  I would not apply any insecticide, especially routinely, unless a pest has been identified and is observed to be causing intolerable levels of damage. (Even in that situation, other management options often exist before resorting to pesticides.) Often, lawn browning, thinning, or a general lack of vigor is presumed to be grub-related when grubs are either absent or not abundant enough to cause symptoms.

Cool-season turfgrasses like tall fescue (the most common lawn type in Maryland) naturally go dormant for the height of summer, as heat and drier weather force them to pause growth. Dormancy can result in some browning or a lackluster appearance, so it’s not necessarily due to grub problems or disease. (That said, Brown Patch disease is one of our most common summer fungal issues for turfgrass, especially if it’s irrigated regularly. Even so, it does not require treatment.)

The insecticides in grub control products are applied to turf areas, but might be absorbed by the roots of nearby trees, shrubs, and perennials, including those grown for wildlife benefit. We don’t know the full impacts of those treatments on these other organisms, including whether soil applications risk harm to desirable invertebrates like fireflies (whose larvae hunt pests on the soil surface), centipedes (which also prey on pests), the solitary wasps that specifically hunt grubs to consume, and other species.

Grub control is sometimes mistakenly used to try to rid a lawn of mole activity, but these animals consume an array of other invertebrates, so the removal of grubs won’t necessarily get rid of them.

I would not automatically apply any pesticide (organic or otherwise) to the lawn in your situation. Use our Lawn Care and Maintenance recommendations to support good growth and resistance to most problems. If you can, replace sections of lawn not needed for its foot traffic tolerance or pathway delineation with other groundcovers or plantings. Fortunately, a mix of different species is resilient to issues like grub root feeding, so grubs are not likely to be a problem in lawn alternative plantings.

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.

A:  You probably ran into bacterial wilt, a common disease that affects cucumbers and their muskmelon and summer squash relatives. It is transmitted by an insect (cucumber beetles) and is incurable once the disease symptoms appear. Both striped and spotted cucumber beetles chew on their namesake plants, though the former is more likely to spread the pathogen.

As the name implies, the first symptoms are the wilting of individual leaves, followed by longer sections of stem, then entire plants. To verify the beginnings of wilt are not due to underwatering, feel the soil a few inches below the surface for moisture content. A plant that remains wilted when the roots are damp is either suffering from root rot due to overwatering or poor drainage, or should be suspected of contracting a wilt disease.

Bacterial growth clogs the water transport vessels, which is why watering more won’t resolve this wilt. Affected plants may initially recover at night, but will collapse again the next day as their water needs increase with sun and rising temperatures. Infected plants die within one or two weeks after the onset of symptoms. Remove and compost the debris (composting won’t risk spreading this particular pathogen).

Plants are most vulnerable between the seedling stage and flowering. Planting late (about mid-June) can also reduce the risk of exposure since the beetles tend to congregate less by that point.

The most reliable way to prevent infection is to deny cucumber beetles access to the plant. Even though only a fraction of them carry the pathogen in their bodies, all it takes is one successful transmission to doom a plant. Cover new transplants or seedlings promptly with floating row cover or insect mesh netting. (You’ll need to remove it for bee access when flowers open.)

Remove crop debris at the end of the season so it doesn’t harbor overwintering adults. Although tilling the soil in fall or spring can kill overwintering beetles, it damages soil structure and can increase weed germination.

You could remove beetles manually, knocking them into a container of soapy water, but that might allow some to start feeding and transmitting the bacteria before they’re found. They’re also skittish, quickly hiding or dropping off the plant when disturbed, so it can be hard to catch them all.

If all else fails, you could resort to an organic insecticide; active ingredient options include spinosad, pyrethrum, or neem oil. Make sure the product is labeled for use on vegetables. A kaolin clay spray is another option that acts as a feeding deterrent to coat the foliage and stems, and might suffice to make beetles bypass the plant.

Q:  Which trees and shrubs best support pollinators? I see plant lists focusing on small plants like perennials, but not many mentions of larger plants.

A:  Tomorrow begins National Pollinator Week, a great time to think about how our home landscapes support pollinators and other wildlife. The primary pollinators in our ecosystem are insects, and among them, several major groups are important for pollination: bees and wasps, beetles, butterflies and moths, and flies. Hummingbirds also pollinate certain flowers whose nectar few insects can reach.

There are too many good candidates to list here. With such a diverse range of flower traits that attract these different organisms, you can plant just about anything native that has showy flowers and it should support pollinators.

Pollinator garden lists often focus on attracting bees and butterflies, which is somewhat limiting. To accommodate more pollinators, grow several tree and shrub species, whose blooms can vary in color, shape, size, orientation (hanging, upright, etc.), scent, and what time of day they are open or fertile.

When selecting plants, always consider their compatibility with the existing site conditions: summer sun exposure, soil moisture and drainage, and any deer problems. Although trees and some shrubs eventually outgrow a deer’s browsing reach, you still may need to protect young trunks from antler rubbing. Make sure a plant’s expected mature size will fit where you want it, since growth-restricting pruning should be avoided.

Pollinated flowers produce seeds, which can spread the plant long distances, especially if you leave them for birds or wind to disperse. For this and many other reasons, try to use locally native species.

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.

A:  I advocate for welcoming harmless snakes into the garden. You ran across a Dekay’s Brownsnake, a small nonvenomous species and ally in the home landscape. They only grow about a foot long, and primarily eat slugs and earthworms.

I recommend shying away from garden clean-up regardless of timing because of the benefits that retaining leaf litter and other plant debris provides for wildlife. Not only will such snakes happily explore this resource and take shelter from weather and predators among fallen leaves, but so will their prey and a range of beneficial organisms and pollinators like ground-nesting bees.

If you need to remove or reduce debris buildup from certain planting beds, try to move it intact to another spot in the yard. A compromise for disposal would be to keep it on-site but shred it for faster composting, so you can reuse its nutrients in the landscape and reduce the risk of spreading invasive species by sending the material elsewhere. However, shredding could injure or kill any residents and will render the material of little use to the fauna that rely on leaf litter as food, shelter, and foraging space.

Snakes aside, leaf litter insulates and protects perennial plant crowns (the main growth points, where roots meet stems). Removing it, especially in winter or early spring, may increase the risk of cold damage, causing dieback or deformities of the expanding new growth. As with other mulch materials, the layer also slows evaporative moisture loss from the soil and discourages erosion and weed seed germination.

Q:  Last year, my apple tree had lots of small fruits on it after it flowered. This year, there are so few. Did I need to fertilize again?

A:  There could be several reasons why the crop is light this year. Although yearly fertilization can benefit fruit trees, use the results of a laboratory soil test to determine if any particular nutrients are deficient, aside from providing a nitrogen boost for overall growth. Poor fruiting a year following a glut of production is probably not directly due to nutrient deprivation.

A large harvest can trigger “alternate bearing” or biennial bearing cycles, where the tree fruits abundantly one year and minimally the next. This is a common phenomenon for apples and pears. Stone fruits (peach, plum, etc.) avoid some of this by self-thinning their fruit, shedding a portion of the crop while it’s still very young (called “June drop”), but they still can benefit from intervention. You can avoid biennial bearing if you manually thin the fruits on a tree that’s bearing heavily while the fruits are still small. Try this if your apple starts forming a heavy crop again next year.

Fruits result from pollinated flowers, so if pollination was poor due to cool or damp weather, too few pollinators in the area, or lack of a compatible companion tree (not all fruits require one), then there will be fewer fruits that year.

The development of next year’s flower buds overlaps with the ripening of this year’s fruits, and that creates a big resource burden on the tree. If too many fruits are ripening, the tree can’t form nearly as many flower buds, so the following year’s harvest potential shrinks. By removing some of the fruits of a bumper crop before they get too far along in their development, the tree can use some of those resources to grow flower buds.

In June, remove about a fifth to half of the fruits on apple, pear and plum trees. In a cluster of four plums, for example, remove two. (Any with damage take priority for removal.) For peaches and nectarines, remove what’s needed so you have a fist’s distance between the fruit.

Thinning provides the additional benefits of improving air circulation to discourage disease and avoiding branch breakage from heavy fruits once they ripen. After thinning, the size of remaining fruits can increase rapidly since they reap the benefits of more resource availability.

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.

A:  It sounds like you have asparagus beetles, a common and aptly-named insect pest for this crop. Adults overwinter in and around the asparagus bed, and, after mating, they lay eggs on the emerging spears. The larvae eat the foliage and chew on the stems that the unharvested spears produce. Heavy damage can reduce plant vigor, which impacts future harvests.

As you noted, covering the plants to prevent beetle access may be difficult, since the insects can have multiple generations per year, and asparagus plants get several feet high by summer. To avoid pesticides, it may be worth trying to use insect mesh netting to protect asparagus if the beetle populations are high. You’d need to use stakes or some sort of support system to drape the netting over the plants and down to the ground, though there may be a risk of trapping some of the emerging adults in spring inside the enclosure.

Make sure any plant debris is removed from the bed at the end of the season, so the adult beetles have less shelter for overwintering. They may hide in leaf litter or hollow-cut asparagus stems.

You can manually remove beetles and larvae by picking them off or knocking them into a container of soapy water, but this may get tedious for a large patch of asparagus plants. Be vigilant, as winged adults of each new generation can fly and disperse to other asparagus plants, so good control over one generation doesn’t necessarily mean the plants will remain pest-free if beetles from outside your garden find your patch.

If you need to resort to insecticides, options include naturally-derived ingredients like neem oil (a type of horticultural oil), pyrethrum, or spinosad. Find a product labeled for use on vegetables, and follow its directions for use.

Q:  When I find plant damage and soil disturbance, what’s the difference between moles and voles? How do I tell them apart when I can’t see the animal itself?

A: Distinguishing between moles and voles is easy: voles eat plant material, like bulbs, roots and stems, and moles prey on invertebrates (mainly insects and earthworms). One way to remember the difference is to use the first letter of their names: voles are vegetarian, moles eat meat. Although voles might occasionally take advantage of an easy insect meal, they are not a major part of a vole’s diet.

Both moles and voles use tunnels in the soil to forage and travel through the landscape, hidden from predators. Moles rarely come to the surface, while voles spend some time above ground. The location of tunnels will change based on soil moisture, food availability, and other environmental factors. Some animals, such as voles, shrews and mice, take advantage of unused mole tunnels.

The tracks most gardeners see are “runway” tunnels the animals use for foraging. Mole runways – used for finding prey – lie just beneath the surface of the soil. In lawns, vole runways are cut into the grass at the surface, and are especially visible after snowmelt. Signs of active runways could include clipped grass and piles of rice-sized greenish or brown droppings.

Moles burrow in deeper dens, usually about eight or more inches below the surface. They push soil up into a mound, several inches high on the surface, whereas voles do not create large soil mounds.

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.

A:  If the plant’s growth looks normal and vigorous, then it’s probably in the right conditions, and it’s just the ruderal trait of the plant you’re dealing with that’s causing the periodic vanishing act.

Ruderal plants are those that colonize disturbed habitats (think of “rubble,” the origin of the term in Latin). Examples of events promoting ruderal plant growth include wildfire, soil erosion or regrading, and clearings formed by storm-felled trees or deforestation for development. In garden settings, this can also include areas repeatedly disturbed by digging, like transplanting perennials or installing annuals.

Ruderal species tend to be short-lived. In the wild, ruderals germinate from the seed bank when conditions favor them and their colonization of a habitat that suddenly has less competition. Besides Cardinal Flower (Lobelia cardinalis), Columbine (Aquilegia), wild petunias (Ruellia, which isn’t a petunia relative), and blanket flower (Gaillardia) are other examples of ruderal species.

Ecologically, they fill an important niche, stabilizing soils to reduce erosion, supporting beneficial soil microbes and wildlife, and (when the ruderal species in question is native) competing with invasive species also vying to colonize available ground.

You may find that light soil disturbance every couple of years allows Cardinal Flower seeds already in the soil from prior generations to germinate. This can help perpetuate the planting without you having to buy more to refill their void in the garden. If you’d rather not depend on self-seeding (if plants pop up where you don’t want them), you can try collecting ripe seed and sowing it yourself so you can manage where the Lobelia grows once the seedlings are old enough to be planted out.

Q:  Do I need to do anything to my aging strawberry bed? The plants are looking tired and scraggly.

A:  Due to diseases and crowding from several seasons of growth, June-bearing strawberry cultivars typically decline after three to four years. You can start a new bed with fresh plants in a new location, or renovate the old bed. (Don’t move runners from an old bed if you had problems with insect pests and diseases, or else you’ll just contaminate that new planting.)

Our Growing Strawberries in a Home Garden web page guides this issue and includes a link to a video demonstration of bed renovation by the University of Maine. For novice strawberry growers, this technique may look brutal for the plants, but they rejuvenate well and the refreshing of growth is needed to keep them productive and vigorous.

After the end of the second-year harvest, mow or manually trim plants to a height of 2 to 3 inches, or just above the crowns. Apply fertilizer, then thin the “daughter” plants to 6 inches apart. Use a garden spade or other hand tool to turn under or remove runners that strayed beyond the 12- to 18-inch-wide growing bed, leaving a bed of mingled mother and daughter plants.

Repeat the third year: mow, fertilize, and thin daughter plants to 6 inches apart. In the fourth year, alter this process by turning under the mother plants and allow only the strongest daughter plants to form the 12- to 18-inch-wide beds. Plant new plants every three years if you’re growing strawberries in containers.

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.