The Heartbreak of Botrytis

Decay at the terminal portion of the flowering stem of
poinsettia, due to infection by Botrytis cinerea

Dark blotches are bract
infections by B. cinerea

On Monday, December 16th, we received a sample of poinsettias that for all commercial purposes had been ruined by Botrytis blight. Botrytis cinerea is a pernicious and ubiquitous fungus that particularly infects wounded or senescent tissue such as old flowers. From this foothold it can spread to other plant parts. When the fungus sporulates, the colors of the black conidiophores (spore-bearing threads) and white conidia (spores) combine to give the appearance of a gray mold. The spores are easily carried around on air currents.

Botrytis cinerea can wreak havoc with many different host species, even causing canker on rose canes and fruit rot on plants such as strawberry. More specialized species of Botyrtis also exist. One is Botrytis elliptica, which affects primarily lilies. Botrytis tulipae causes a disease called "fire" on - you guessed it - tulip.

Closeup of conidiophores and conidia of Botrytis cinerea,
growing on cyathia (true flowers) of poinsettia. Black bar = 1mm.

The Achilles heel of Botrytis is its need for abundant moisture. In greenhouses, care must be taken to ventilate, even for a while after sunset, in order to keep the relative humidity down. Watching watering practices (timing, drainage) is also important. Fungicides are sometimes needed. Another essential element in Botrytis management is prompt removal of dead plant material from the house. For more information on Botrytis in greenhouses, see our blog from May 18, 2012.

Pansy bed at NCSU in early 2012. Botrytis blight.

Be on the look out for Botrytis blight on pansies in the landscape, especially in the late winter and early spring. To prevent problems, avoid overhead watering if possible, and make sure the plant spacing and surrounding shrubbery allow for good airflow. For more information on Botrytis in the landscape, see the May 31, 2013 blog.

Light colored dead blotches on flowers, spreading to leaves,
are a hint that you might have Botrytis blight in your pansies.

Just a reminder to check our holiday closing schedule. We look forward to seeing you in 2014!

Mike Munster and Kelly Ivors

Songs of the Season, with a Twist

Are you tired of nonstop carols yet? While not as popular as Santa, plants star in many songs of the season – and some of them have special associations for us here at the PDIC. Number one on the list must be “The Christmas Song,” aka Chestnuts Roasting on an Open Fire. This song reminds us of the blight that devastated the Eastern forests in the last century, leaving us with no chestnuts to roast. “Oh, Christmas Tree” (Oh, Tannenbaum) makes us think of North Carolina’s beautiful Fraser firs and the root rot they must escape before they can end up in our living rooms. Mistletoe figures prominently in “I’ll be Home for Christmas” and holly pops up in “Have a Holly Jolly Christmas” and “The Holly and the Ivy.”

But here’s a song that puts me in the holiday spirit even though the subject and the tune have nothing to do with snow, presents, Santa and all the rest. That’s because for many years, NCSU Plant Pathologists sang it lustily at every gathering, including the annual holiday party. I promise you have never heard it on the radio. Enjoy!

Photo by David Langston, Univ. Georgia

For a nice write up about managing root-knot nematodes, check out this article by Pender County Agent Charlotte Glen.

THE NEMA SONG

(To be sung with gusto to the tune of “The Battle Hymn of the Republic”)

A nematode was chewing on a young tobacco root.

Her keen and piercing stylet was protruding from her snoot.

Her salivary glands were squirting out the poison juice.

The galls keep hanging on.

(Chorus)

We must fight the nasty nema,

We must fight the nasty nema,

We must fight the nasty nema,

Rotate crops and pray.

A cotton plant must suffer on a hot and sunny day.

It transpires too much water when its roots are chewed away.

If we don’t lick the nema we will really have to pay.

The galls keep hanging on.

(Chorus)

Meloidogyne incognita,

Meloidogyne incognita,

Meloidogyne incognita,

Fumigate and pray.

The cortex cells are swelling to a giant size to stay.

The female’s sac’s protruding in a morbid sort of way.

The blind roots now are forming and the root knot’s on the way.

The galls keep hanging on.

(Chorus)

We must fight the nasty nema,

We must fight the nasty nema,

We must fight the nasty nema,

Rotate crops and pray.

Lyrics by Dr. G. B. Lucas