The following articles were compiled during the last 7 days by members of the Extension, Nursery, Landscape, Turf (ENLT) team to benefit those who are managing a commercial nursery, garden center, or landscape business or someone who just wants to keep their yard looking good all summer. Access the BYGL website for additional information on other seasonal topics at: http://bygl.osu.edu
For more pictures and information, click on the article titles. To contact the authors, click on their names.
Published on August 17, 2018
I’m seeing damage on ripening tomatoes in southwest Ohio caused by Brown Marmorated Stink Bug (BMSB) (Halyomorpha halys) nymphs. I first saw damage from both the adults and nymphs on my own tomatoes in 2015. At that time, we didn’t know which direction BMSB populations would take in the southwest part of the state. Would they become apocalyptic like in the Mid-Atlantic States or would they settle into becoming a “background” problem?
Thankfully, BMSB has followed a more moderate population trajectory in southwest Ohio compared to elsewhere with high populations confined to localized “hot spots” rather than being widespread. However, that doesn’t mean BMSB can’t present a challenge to both backyard gardeners as well as commercial growers. Even low populations can produce noticeable damage making tomatoes unsalable or not usable as table fare by home gardeners.
Both nymphs and adults use their piercing-sucking mouthparts to puncture the epidermis and extract plant juices. On green tomatoes, the damage may appear as whitish spots with indistinct borders. Although the spots may only measure 1/16 – 1/2″ in diameter, they can merge to affect large areas of the fruit.
On ripe tomatoes, the damage appears as hazy golden yellow spots. Stink bug damage may be superficial with little impact on the tomato flesh. While damaged tomatoes are still edible, their unsightly appearance reduces their marketability. However, heavy feeding may produce areas with whitish, spongy tissue, and feeding sites can initiate infections that enhance the “eww yuck” factor.
BMSB management on tomatoes is a challenge owing to the often sudden appearance of damage to ripening tomatoes. Heavy damage can occur before gardeners realize they have a significant bug problem.
There’s also a challenge with a limited number of insecticides labeled for use on ripening tomatoes. You must always read and follow label directions paying particular attention to the time between the application and the harvest of vegetables called the “harvest interval.” Unfortunately, this may preclude the use of many common insecticides if tomatoes and other targeted vegetable plants have ripened fruit that you’re planning to harvest.
Do not use traps thinking they will protect the tomatoes. Research conducted by the University of Maryland showed they do the opposite: they actually invite more bugs to the tomato party. Likewise, if you’re growing patio tomatoes, keep the outside lights turned off at night. They serve as “eat here” signs.
Finally, if you only have a few plants, the bugs can be managed by close inspections and digital control for the nymphs (use gloves!), or by using the “knock off and stomp” method for the adults. I love the smell of stink bug in the morning! Of course, you may want to leave your shoes outside.
Published on August 17, 2018
This is the time of the year in Ohio when female spiders of many web spinning species reach maturity. They become most evident when their gossamer creations are illuminated by early morning sunlight reflecting off a heavy dew.
I was lucky to experience this magical but fleeting light effect during an early morning hike around my neighborhood a few days ago. I was amazed by the sheer number of spider living near at hand.
There are over 600 species of spiders found in Ohio and most feed almost exclusively on insects. The spiders that are currently dominating (draping over?) landscapes are the Sheetweb Weavers (family Linyphiidae); the Funnel Weavers (family Agelenidae); and the Orb Weavers (family Araneidae).
As their common name describes, orb weavers produce flat, circular (orb) webs. The webs are intricate structures involving both sticky and non-sticky silk.
Non-sticky silk is used for “radial threads” which radiate from a central point like spokes on a bicycle wheel. The non-sticky silk is also used for “frame threads” which encircle the web like a bicycle wheel to hold the radial threads in place and to attach the web to supports such as plant stems. “Spiral threads” are composed of sticky silk arranged in a spiral pattern emanating from the center of the web; it’s the sticky silk that captures the spider’s prey.
A “stabilimentum” is a vertical pattern off dense silk centered in the web that is produced by many orb weavers. The stabilimentum produced by the large, showy Black and Yellow Garden Spider (Argiope aurantia) usually has a zigzag pattern giving rise to the alternate common name of “Zigzag Spider.” The dense webbing reflects ultraviolet light which attracts insects to their doom.
The closely related and similarly sized Banded Garden Spider (A. trifasciata) produces exactly the same type of orb web. This spider is also native to Ohio; however, it’s not as common as its black and yellow cousin.
Look closely between the branch tips of shrubs and you may spot the diminutive Trashline Spider (Cyclosa spp.). The silk in their stabilimentum enshrouds the drained bodies of previous victims; the morbid structure is responsible for the “trashline” common name.
The spiders rest in the middle of their trashline. Their small size and mottled coloration makes them very difficult to see among their similarly sized and colored bundles of trash. Indeed, research has shown that the trash bundles serve to confuse predators, such as birds and wasps, intent on making a meal of the spider, and the greater the number of bundles, the greater the confusion.
Funnel weavers produce large, flat, sheet-like webs spun across grass, under rocks or boards, or over the branches of shrubs such as yews and junipers. The webs slope gently towards a narrow funnel or tube where the spider resides, awaiting its next victim.
The spiders are medium-sized and resemble small wolf spiders. Funnel webs may measure more than 1′ across and can become very evident with dew, or when they snare dust during droughty conditions.
Sheetweb weavers construct several types of webs depending upon the spider species. Some species spin flat or slightly curved webs that overlay vegetation and rival the sizes of webs spun by funnel weavers. However, there is no funnel in the web. The spiders hide beneath one edge of the web, or in plant foliage along the edge of the web, to await their prey.
One of the more interesting sheetweb weavers is the bowl and doily weaver (Frontinella communis). This is one of the few spider species with males capable of producing webs; however, females still dominate web weaving.
The spider constructs a complex web structure consisting of distinctly bowl-shaped webbing suspended from plant stems by a crisscrossing array of silk threads; this is the “bowl” in the common name. The bowl is anchored below by a horizontal array of interwoven silk threads; the “doily.” Flying insects drop into the web-bowl after bouncing in pin-ball fashion off the interlacing silk threads used to suspend the web. Of course, when they drop into the web-bowl, they fall into the “arms” (and fangs!) of the awaiting spider!
Preserve; Don’t Kill
Spiders eat insects and research has consistently shown they remove a significant number of pests that we would have to deal with otherwise. Of course, numerous arachnid engineered insect traps draped over low growing shrubs can look like Halloween decorations.
Continually removing the webs will eventually cause the spiders to take a hint and relocate elsewhere. If you see the spider on the web, just shoo it off before destroying their web so you don’t accidently commit and arachnicidal act.
Authors Erik Draper
Published on August 15, 2018
I was asked to help a vegetable grower figure out what was going on with something wreaking havoc and eating his ripening sweet corn. Typically, when someone mentions sweet corn and problems, the first demon that comes to mind are those little masked, sweet-toothed bandits, known as raccoons! When I arrived out in the field, I was surprised to see the corn stalks standing tall in nice rows. The masked marauders climb up the cornstalk to the get to the ripest, uppermost ear of corn; consequently, the corn stalks are most often snapped off or pushed over down to the ground from the plump little pilferers! It wouldn’t be so bad if they would munch the whole ear of corn, but nooo way! They’ll take a couple of bites out of the ear, move on to the next sweet smelling corn stalk and the climb for corn continues through the night. One hungry raccoon can damage numerous cornstalks and destroy 2-4 dozen ears of ripening sweet corn in a single night!
I digress, so as I walked out into the field there wasn’t a single corn stalk tipped over and I thought, “what in the heck is the problem… the corn is all upright!” I then looked more closely at the actual ears of corn and saw the damage.
It was consistently about 18 inches to 2 feet off the ground and not a single ear had been bent down or torn off or ripped open. The damage was more prevalent on the outside rows of sweet corn and was always on the side of the ear of corn and through the husks covering the ear.
The damage began as an elliptical area or opening and progressed up the ear until the husks split open to reveal the upper part of the ear. Everything was neat and tidy and no half-munched kernels were on the ground or scattered around the base of the stalks.
The damaged ear continued to dry out and secondary pathogens then began to invade the open wounds and ruin the entire ear of corn.
Did you figure out the problem? It baffled me until I found some damage near a huge mud puddle that held some tracks, then it fit together and all made perfect sense.
And now it will all make sense to you when you see the culprit…
I can image that this culprit will be invited to dinner for this year’s Thanksgiving day meal because it is already stuffed full with sweet corn!! Should be quite tasty!
Published on August 15, 2018
My wife loves mandevilla (Mandevilla spp.). The deep green foliage and showy flowers of these tropical or subtropical vines provide a nice trellised accent on our front porch. So, when she told me one of our vines was under attack by hordes of sap-sucking aphids, I acted quickly … in the interest of domestic bliss.
As with any pest management effort, it’s important to identify the pest. I was surprised to discover the aphids adorning the mandevilla stems were Oleander Aphids (Aphis nerii). These bright yellow aphids are easy to identify with legs that look like they were dipped in black ink and black cornicles (siphuncules) which are the two “stovepipes” on the top of the back end of their abdomens.
Readers who grow common milkweed (Asclepias syriaca) for monarchs (Danaus plexippus) and other colorful native insects are no doubt familiar with this non-native aphid. Indeed, it’s sometimes called the “milkweed aphid” for its preference for various members of the dogbane family (Apocynaceae); most notably plants in the genera Asclepias (milkweeds); Cynanchum (climbing milkweed, C. laeve), Vinca, and Nerium (oleander).
Of course, aficionados of plant taxonomy may be surprised that I was surprised to find oleander aphids on mandevilla. That’s because I didn’t know these vining plants also belong to the dogbane family; until the aphids taught me.
This is not the first time oleander aphids provided me with a plant ID and taxonomy lesson. I never knew there was such a thing as climbing milkweed until I stumbled across a vine in an Ohio woodlot festooned with these aphids. Plant pests can be very helpful with making a plant ID.
Oleander aphids are parthenogenetic meaning there are no males; all are females. This partially explains why this aphid can rapidly develop high population densities. They also seem to be resistant to high summer temperatures which is unlike many other aphid species that are most prolific during the cool temperatures of spring and fall.
As their common name implies, oleander aphids evolved with their namesake Mediterranean host and draw chemical protection from their host plants. The milky, sticky sap of oleander and milkweeds contains serious toxins called cardenolide glycosides. As with a number of other insects that feed on plants in the dogbane family, oleander aphids incorporate the glycosides into their flesh as protection against predators. It’s speculated that their bright yellow coloration warns predators against taking a taste.
On the other hand, some insects are unaffected by the aphid’s chemical shield. Although research has shown the aphid’s honeydew contains cardiac glycosides, the chemicals do not dissuade some ants from “tending” the aphids in exchange for a sweet treat.
There are also several predators that are not dissuaded by the aphid’s toxic flesh including syrphid (hover) fly larvae, lacewings, and even some lady beetle larvae and adults. Of course, some predators may be cowed by the ants.
A common nemesis of oleander aphids as well as a number of other aphids is the parasitoid wasp, Lysiphlebus testaceipes. The wasp lays eggs in the immature aphids; one egg per aphid. Parasitized aphids are called “aphid mummies” for their swollen, dark brown bodies enveloped in a dry, parchment-like exoskeleton
It’s important to preserve the aphid’s enemies. So, I blasted the mandevilla stems with a solid stream of water to send the aphids on a wild water ride while declaring, “I am Zeus!” I believe this impressed the Mediterranean aphids but may have surprised the neighbors. Unfortunately, forcefully dislodging the aphids with water may only provide a temporary reprieve depending on the overall aphid trajectory.
In case water-logged aphids return, I’m holding in reserve other management options that are also “gentle” on aphid predators and parasitoids. This includes using an insecticidal soap; purchased, not home-mixed. Remember that soaps and detergents produced as cleaning agents may also contain chemicals that are harmful to plants. Manufactures have no need to exclude these compounds because they are not producing products labeled for use on plants. Knocking the leaves off my wife’s mandevilla using a “do it yourself” soap mix would not be beneficial to domestic bliss.
Authors Erik Draper
Published on August 14, 2018
In the world of plants, most often our attention focuses on bloom color, size and timing of when blooms will make an impact in our landscape. Blooms are nice as a moving focal point during the growing season, but people become a little upset when plants don’t do what they are supposed to and only when they are supposed to do it. This is the time of year that concerned citizens call into the office wondering whether or not their magnolias or rhododendrons are going to die. When asked why they think that the plants are going to die, the response is always the same, “because they are blooming again and they already bloomed this year!”
The official term for this startling behavior of plants blooming twice in a year when that is not typical, is “remontant”. Therefore, remontant is another name for what we term “reblooming” plants. Reblooming plants will bloom in their expected season and bloom cycle time frame and suddenly an unexpected second set of flowers appears later in the season! In the landscape world, remontant plants are extremely desirable and this reblooming trait in new hybrid plants is intentionally selected for and sought out.
Remember that plants like magnolias, rhododendrons, forsythia and even crabapples, will set bloom for the next year, during our current growing season. It is the formation of those blooms for next year, which often contribute to remontant tendencies of certain plants. The blooms must be formed and ready to go by the time the plants shut down for winter. With this “ready to bloom” approach, some plants after a strong growth phase or pause or a significant stress, seem to determine “I’m not waiting any longer… IT’S BLOOM TIME” and emerge.
Although we can admire that out-of-season bloom, bear in mind that if that specific, individual flower blooms now, then that specific, individual flower will NOT bloom again during its typical bloom time the flowing year. A downside of remontant blooms is a slight reduction in overall flower numbers for next year’s floral display, depending on the number of flowers that actually bloomed out of season. Rarely will remontant plants be totally without any flowers during their typical bloom time. So get out there and enjoy that “crazy bloom”!