Bee Balm Blues Courtesy of Fourlined plant bug, Poecilocapsus lineatus

 

Can you guess why they are called fourlined plant bugs?

 

Bee season has arrived and the flood of pollinators and other beneficial insects in my flower gardens is underway. My bee balms and other monardas are revving up their flower heads in preparation for another busy season serving nectar and pollen. While inspecting my perennials in anticipation of this event, I noticed several bee balms adorned with small necrotic spots and puckered leaves. This was the handiwork of the fourlined plant bug, a bodacious member of the Hemiptera clan infamous for distorting and disfiguring plant parts. Like other true bugs, this rascal has sucking mouthparts that pierce plant tissue and rupture delicate cells. Following the initial piercing by the beak, salivary enzymes are secreted into the plant to digest and liquefy plant tissues in preparation for the big suck. Inside the bug’s head is a tiny pump that is activated after insertion of its needlelike stylets into the plant. Rhythmic contractions of muscles create negative pressure, drawing nutrient rich cell contents into the digestive tract of the beast. One would think this insult was enough, but no, after the bug has removed its beak the lingering digestive action of these salivary enzymes, or pectinases, continue to degrade cell walls, leaving behind unsightly necrotic spots. In addition to leaf distortion and discoloration, dead tissue zones drop from leaves creating a lattice of small irregular holes.

A few weeks ago, tiny red nymphs of fourlined plant bugs hatched from overwintered eggs in plant litter. Their feeding distorts leaves and creates necrotic spots. A very pregnant female will soon deposit eggs in plant tissue. Digestive enzymes secreted into leaves produce dark lesions on leaves that remain long after adults scurry away.

Digestive enzymes injected into a leaf by fourlined plant bugs create long lasting necrotic lesions.

Besides pestering my herbaceous perennials, fourlined plant bug is known to attack more than 250 species of plants including many vegetables, trees, and shrubs. While this may sound like the 11th biblical plague, fourlined plant bugs do their dirty work early in the season and my bee balms and other perennials will surely outgrow these plant bug shenanigans and flower just fine. Most gardeners consider fourlined plant bug damage to be cosmetic and nothing more. To reduce damage caused by the bug, remove old plant debris from the garden in late autumn. Bugs overwinter as eggs in plant rubble so this will reduce the inoculum of colonists the following spring. If retribution is more your style, you can cup your hands around infested leaves, dislodge the bugs within, and simply crush their little bodies or deposit them into a cup of soapy water (their swimming skills are not well developed). Applications of horticultural oils or insecticidal soaps will also bring a swift end to their lives. If using soaps or oils, as with all insecticides, be sure to follow label directions and avoid applications when pollinators and other beneficial insects are present. Directed sprays of water with a garden hose may dislodge these bugs, sending them to the soil where the hungry jaws of ground beetles and other predators await. If bee balms and other pollinator-friendly plants abound in your beds, this week take a peek and look for the handiwork of foulined plant bugs.

Acknowledgements     

The great references “Fourlined Plant Bugs” by Jeffrey Hahn and Suzanne Wold-Burkness, and “Role of Saliva in the Highly Destructive Fourlined Plant Bug (Hemiptera: Miridae: Mirinae)” by Allen Carson Cohen and Alfred G. Wheeler Jr., were used in preparing this episode. 

Tigers along the Potomac: Bronzed Tiger Beetle, Cicindela repanda repanda

 

On the banks of the Potomac, beautiful bronzed tiger beetles search for their next meal.

 

Tigers, perhaps the most iconic and magnificent of all cats, remain in India, Nepal, Bhutan, Bangladesh, Myanmar, Russia, China, Thailand, Malaysia, Indonesia, Cambodia, Laos, and Vietnam according to the World Wildlife Fund. While the chance of spotting a tiger in the wild here in the DMV is nil, insect lovers and other naturalists can enjoy more than a dozen species of tiny six-legged tigers in forests, along the ocean and bay, and on riverbanks throughout our region. On a recent trip to the mighty Potomac River in Maryland, a budding seven-year-old naturalist discovered a gorgeous bronzed tiger beetle hunting prey in the sandy soil of a riverbank. We met the beautiful six-spotted green tiger beetle about this time last year along a bike trail not far away.

Tiger beetles are fierce predators as both juveniles (larvae) and as adults. Sabre-like mandibles impale soft-bodied insects and other invertebrates which make the riverbank their home. Most species of tiger beetle larvae spend their youth as sedentary hide-and-wait predators in galleries constructed in soil. When unsuspecting prey pass nearby, larvae pop out of their lair and spear their hapless victim. Larvae enlarge galleries as they grow and develop.

Bronzed tiger beetles dash about a sandy riverbank along the Potomac on a sunny afternoon. A curious tiger stares back at an iPhone before moving in for a closer look. Watch at full speed and then at 70% reduced speed as a bronzed tiger jets away from an annoying stick.

The strange tiger beetle larva lives in an underground lair and captures unsuspecting prey that stray too near.

Life along a riverbank is fraught with peril as rivers like the Potomac often flood and submerge adjacent land. For mobile adult beetles, as waters rise, flight or a mad dash can take them out of harm’s way. But what fate awaits soil dwelling beetle larvae when waters rise? Galleries submerged by floodwaters soon become severely oxygen poor and these tiny creatures need oxygen for survival. Scientists have discovered that some species of tiger beetles inhabiting water-logged soils switch their metabolic activity from oxygen-driven to anaerobic metabolism (oxygen not-needed) during times of immersion. In studies, different species of tiger beetles survived 60 to 120 hours of submersion. Yikes! Wish I could hold my breath that long. And when soils become a bit too soggy, guess what, larvae of at least one species of tiger beetle, the hairy tiger beetle, simply move out and find soils with lower moisture levels where they can survive and thrive. Unfortunately, as rivers are dammed and lakes form, riverbanks with just the right moisture levels may be harder to find for tiger beetles on the move. Scientists fear these river-dwelling species may fail in their attempts to relocate to less soggy soils. In several locations, subspecies of hairy tiger beetles have declined dramatically in recent years, likely due to human-made alterations of their habitat. In addition to dams that dramatically alter riparian ecosystems, soil compaction by human foot-traffic along river banks may contribute to the demise of tiger beetles along rivers and lakes. Tread lightly and carefully along riverbanks and try to stick to existing trails rather than blazing new ones, lest we further disrupt habitats of these tiny but magnificent tigers. 

Acknowledgements

Two excellent articles “Movement of Cicindela hirticollis Say Larvae in Response to Moisture and Flooding” by Mathew Louis Brust, William Wyatt Hoback, Kerri Farnsworth Skinner and Charles Barry Knisley, and “Hypoxia tolerance in adult and larval Cicindela tiger beetles varies by life history but not habitat association” by Mathew L. Brust and W. Wyatt Hoback were used to prepare this episode. Thanks to eagle-eyed Abby for spotting a pretty bronzed tiger beetle that provided the inspiration for this episode.

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