Expert: C.L. Fornari - 3/14/2010

Question
QUESTION: I have been taking geranium and fuchsia cuttings now for 30 plus years and never come across my problem this year. All my cuttings and older plants are getting black tips on all the new shoots and subsequently dying back and retarding growth. I keep pinching the black shoots out but this doesnt seem to improve the plants.  In fact 2 or 3 of the older plants lost their leaves rapidly and look like they have died having no more shoots coming thru.
Could they all be suffering from some kind os disease?. I overwinter these plants in a heated greenhouse each year.
Can you help please. Many thanks Vilma Neale

ANSWER: Vilma,
My initial thought would be Botrytis blight, the most common geranium disease in a greenhouse. You'd see gray fuzzy growth on the blackened tips if it's botrytis. Pinching the black growth would just spread the problem unless you're washing your hands/tools after each pinch. Is the greenhouse very humid, or did you recently have a string of cloudy days before this problem happened? That would argue for Botrytis because it spreads in high humidity and poor air circulation or slow drying of plants. I've had the worst Botrytis problems in a greenhouse after a stretch of cloudy weather.

Black tips also happen if fertilizer is too strong - but I doubt that you'd be fertilizing cuttings, right?  Is there time-release fertilizer in your potting mix that might be combining with a liquid fertilizer to create fertilizer burn?  

If the established plants are getting the same thing as the cuttings, that argues for disease not fertilizer burn, or drying of the plants/cuttings. The established plants have bigger root systems so would be less effected.

Check out the picture of Botrytis here: http://pubs.caes.uga.edu/caespubs/pubcd/C863.htm and read about other geranium diseases.

Increasing the air flow in the greenhouse might help (fans) and always water in the morning, and don't water on cloudy days.  Dispose of any effected parts of the plants, and any spotted/yellowed/blackened leaves.

I hope this helps!
C.L.

---------- FOLLOW-UP ----------

QUESTION: Thank you very much for your quick response. I have looked in several gardening books and thought that it may be Botrytis although it is not nearly so advanced as in your pictures.After reading your answer I am sure it maybe caused by the humidity in the greenhouse and not enough air-flow with slow drying of plants. This seems to fit my case. Can`t think it is any of the other possibilities. I have since sprayed the geraniums with Systhane Fungus Fighter this afternoon hoping that it will help Should this help? Also my fuchsias have the same problem but on the directions of the Systane Fungus Fighter it says not to spray Fuchsias! Can you recommend any other spray that would help the fuchsias too?
Many thanks  Vilma
?

Answer
Vilma,
I'm not familiar with Systane, so don't know if it's effective with Botrytis or not. Does it say it's for treating Botrytis on the label? If not, you may want to try another product. Since I'm not crazy about using hard-hitting fungicides in a home greenhouse, I'd recommend you try either Neem Oil or Bacillus subtillus, which is sold under the product name Serenade.  You'd be able to use Serenade on the fuchsia too. Then add a fan that's on a timer, and water as I discussed before, and you should be able to get control of this.

all the best,
C.L. Fornari
www.WholeLifeGardening.com