Spotted Wing Drosophila

Another TMG Winter School alert:  an invasive fruit fly

Warning:  this is so gross

Dr. Frank Hale from UT Extension told us about SWD.  Drosophila suzukii, the Spotted Wing Drosophila (SWD) is native to southeast Asia.  It was first spotted in California in 2008.  Since then, it has been detected in Washington, Florida, Utah, Michigan, Wisconsin, Kentucky, Louisiana and - in 2011 - in Unicoi County in Tennessee.  This nasty little critter lays eggs in fruit crops.  Strawberry, blueberry, grape, cherry, apple, fig, you name it.  

Females lay eggs under the skin of ripe fruit shortly before harvest. Larvae hatch and begin to feed within the fruit, causing softening in the area of feeding. There can be several larvae in a fruit, which hastens softening and fruit collapse. Holes the size of pin pricks are evident within the soft areas of infested fruit. These holes result from egg laying and are used as breathing holes by larvae. In addition, these holes provide entry points for diseases such as brown rot and botrytis.

Adult Female - note ovipositor

Adult Male - spotted wings

Egg-laying holes in blueberries

Pupae in blueberries

We told you this was gross.  We asked what the effect would be on a person who ate infected fruit and Dr. Hale said, "Additional protein."  He's funny.

We should warn our grower friends about this pest.  They should make traps and put them out at least 2 weeks before the fruit will be ripe.  Learn how to make a trap here.

SWD trap

Boxwood Blight - additional information

We posted a couple of weeks ago on Boxwood Blight.  Dr. Alan Windham from the University of Tennessee has provided us with the presentation he made at Winter School. Click here.

Downy Mildew on Impatiens

Impatiens are the go-to shade plant for color here in the Memphis area.  At the Tennessee Master Gardener Winter School this month, we were alerted to a disease that is making a comeback:  Downy Mildew.

Underside of leaf

Infected plant

Downy Mildew is caused by a fungus, Plasmopara Obducens.  It was first detected in the UK in 2003 and in Tennessee in 2004.  In 2011, however, widespread regional outbreaks were observed in the United States.  Growers are particularly concerned by an outbreak in Palm Beach County this fall and winter. 

Initially, leaves may look yellowish or speckled. As the disease progresses, whitish downy growth, which is the spores that spread the disease, will be visible on the undersides of leaves.   Chemical treatments such as Ortho Max Garden Disease Control can be applied to prevent the disease but are not effective for plants that already have it.  Remove infected plants and bag them. Check impatiens before buying. Don't buy any that have a powder-like substance on the leaves' undersides.

Downy Mildew attacks Impatiens walleriana, the most common species.  SunPatiens and New Guinea impatiens are not susceptible.  Also consider planting other flowering plants such as begonias, lobelia and osteospermum.



Begonia



Lobelia

Osteospermum

Boxwood Blight

At the Tennessee Master Gardener Winter School last week, we heard a presentation from Dr. Frank Hale and Dr. Alan Windham, of the University of Tennessee Institute of Agriculture, on some potential diseases/pests to be aware of for the upcoming growing season.  The first one we want to alert you to is Boxwood Blight.  The following discussion is abstracted from a paper written by North Carolina Extension Specialists Dr. Kelly Ivors, Dept. of Plant Pathology, and Dr. Anthony LeBude, Dept. of Horticultural Science, North Carolina State University, Mountain Horticultural Crops Research and Extension Center, Mills River, NC.  The entire paper can be found by clicking HERE.

Boxwood Blight (Cylindrocladium buxicola) is a fungus that first appeared in the UK in the mid-1990's.  It was recently discovered in a small region in North Carolina, forcing the grower to destroy more than 30,000 container plants!  You can see that it can have devastating economic effects.  It can be dispersed naturally through water (splashing rain, flood water, overhead irrigation, droplets carried by rain), by animals, on contaminated tools and equipment or through movement of contaminated nursery stock.

Once a plant is infected, death comes very quickly - often in less than an week.  The leaves have tan to brown spots on the top, with a white fungus on the bottom side.  Quickly the whole leaf turns brown, then all the leaves drop off. 



White Fungus



Brown leaves and denuted branches

 Infected stems can have dark brown or black lesions, either linear or diamond shaped.



Lesions on stems



Carefully inspect any boxwood plant before you purchase it.  Make sure that you or your landscape company sterilize any equipment before and after you prune your boxwoods.  At this point, to limit spread and movement of the pathogen, all infected plants should be destroyed. Infected plants should be burned to ash or sealed in heavy, black plastic trash bags and taken to an approved landfill. DO NOT RECYCLE PLANTS OR MEDIA. Containers should be sanitized before reuse.

Next:  Impatiens at risk!