- Author: Ben Faber
- Author: Craig Kallsen
- Author: Akif Eskalen
Dry Root Rot is a pretty fantastic disease symptom that is usually seen in lemon, but can be seen in orange, as well.
Craig Kallsen, UCCE Citrus Advisor in Kern Co. comments on a disease sample:
I have seen a lot of dry root rot over the years. It usually is something that damages or weakens the root system which allows a Fusarium species to colonize the rootstock. It is very common in older lemon groves that froze at some point in their past. Also common in groves that suffered a lot of gopher damage or where the wraps got too hot in the sun burning the bark and cambium. I have also seen it in cases of fertilizer or other soil-applied chemical burn. I have no doubt that graft incompatibility could do it too.
Akif Eskalen, UCCE Plant Pathology Specialist chimes in on a disease sample submitted:
As you can see from the attached picture there is a weird callus formation and symptoms of incompatibility at the graft union which I think is the primary cause of decline. We didn't observe any discoloration in the scion, however rootstock was completely discolored where we isolated Fusarium solani the causal fungus of Dry Root Rot. Dry root rot caused by either Fusarium solani and/or Fusarium spp. When there is a disconnection at the graft union, the phloem can not transfer enough carbohydrate to the rootstock to feed feeder roots. Fusarium fungal species are present in the soil and they can attack and easily colonize on starch depleted roots and cause DRR.
We still don't know what is causing the graft incompatibility on these plants. That needs to be investigated.
It's still not clear how and why citrus becomes affected.
- Author: Ben Faber
The UC IPM Green Bulletin is a very useful guide to many things pest, weed and disease management. The latest edition is now out.
Check it out. www.ipm.ucdavis.edu/greenbulletin
WHAT'S INSIDE…
Pest Note Updates | Page 2
Understanding Neem- | Page 3
based Pesticides
The Good Side of | Page 4
Pruning
Ask the Expert! | Page 6
SIGN UP…for a free subscription to the Green Bulletin at http://ucanr.edu/subscribegreenbulletin
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/span>- Author: Ben Faber
- Author: Ben Faber
With the proliferation of pests and disease that might appear in mulch used in orchards, it might appear that the practice will become more limited unless the material can be guaranteed to be safe. Polyphagous Shot Hole Borer and Asian citrus Psyllid are just two examples of pests that might appear in a mulch from an unknown origin. There are many other examples, though, and new threats keep coming. Composting is a process that can insure a quality product, but composts tend to be too expensive to be used as a mulch. There is a new solar processing technique that is being evaluated in the Central Valley that might produce a product that could be used as a mulch.
The proliferation of low-cost, high-efficiency and durable solar panels makes it possible to set up solar-powered composting systems that reduce reliance on alternative forms of power and avoid very expensive grid hook-up costs.
This type of technology lends itself to a more stable site layout, which can then utilise conveyors for material movement, further reducing reliance on diesel-powered equipment. A potato piler, a standard piece of equipment in the potato storage industry, is an ideal prototype for compost conveyors.
Static piles can easily be watered using simple irrigation systems that save water and further reduce diesel reliance. When combined with the already proven technology of a compost cap, reductions of VOCs and greenhouse gases can be substantial.
- Author: Ben Faber
A recent visit with Spanish researchers and packers was of interest. Virtually the whole industry uses a snapping method to harvest fruit. It is faster and often leads to fewer fruit rots than with clipping. In a past article by Reuben Hofshi in the CA Avocado Commission's AvoResearch is a review of the practices and results in various countries. It was well worth rereading:
http://www.avocadosource.com/Journals/AvoResearch/avoresearch_02_02_2002_Hofshi_Snap.pdf