Tuesday, August 28, 2012

Grub-Killing Wasps For Your Lawn

The large colorful hunting wasps, Scolia dubia (Order: Hymenoptera;  Family Scoliidae), may look intimidating, but are harmless to you unless you grab one and force it to sting in self defense.  Adults are most numerous late in summer (usually August) and are present now on flowers (see August 17 post for example) and hovering over lawns in search of food for their young.  Their larval food is actually grubs, primarily Green June beetle larvae, that feed on and damage grass roots in lawns.

The adult grub-wasps dig into the soil when they “smell” (anyone who has seen holes made by skunks digging for grubs in their lawn knows this is possible) a grub, sting it to paralyze it, then lay an egg on it.  The paralyzed grub is then helpless to defend against the hatched grub-wasp larva that will consume this fresh food supply until it is fully grown.  The grub-wasp larva then pupates in the soil, ready to emerge as an adult the following summer.  If there are enough of these wasps in your yard, they can help reduce the numbers of grubs in your lawn, providing natural control of pests.  Here's a video of a grub-wasp feeding on nectar:
For more information on the grub-killing wasp, Scolia dubia, please follow this link:

Friday, August 17, 2012

Native Plants for Beneficial Insects in the Southeast: 1. Aralia spinosa

Aralia spinosa, or Devils walking stick, has very large, dissected, tropical-looking leaves that give it almost a palm-like appearance.  Its range covers primarily the southeastern United States:
It produces very large clusters of small white flowers in mid to late summer in North Carolina (July – September).  These flowers are highly attractive to a variety of insects that can be considered beneficial:  bees (pollinators), predatory wasps (help with natural control of insect pests), and butterflies (aesthetically pleasing).  I especially like visiting the plant in the mid-afternoon because in full bloom it is often covered in large butterflies like tiger, black, and spicebush swallowtails as well as monarchs.  The photo below gives some idea of how this looks.
I like plants that perform more than one ecological function, and Aralia spinosa fits that bill.  Apart from feeding beneficial insects in the summer, the berries it produces in the fall are also a valuable food source for birds.  This perennial plant does have some downsides though, that may help to explain its limited horticultural use.  It is very spiny along both stems and leaves, so needs to be handled with care.  Also, it will spread some through rhizomes.  Unless they are cut back, individual plants can grow into small trees up to about 30 feet tall.  I deal with removal of unwanted specimens using gloves, long-handled loppers, and a separate brush pile for spiny plant material such as Aralia or blackberry.  I’ve found the best location for this plant is along a tree line or forest edge where it can be contained by mowing and forest shade.
Some Links For More Information:
Aralia spinosa Horticultural Information
Going Native - urban landscaping for wildlife with native plants