Anthurium blight

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Steve:
 
Anthurium blight has been with us forever and affects a wide range of aroid genera. Breeders, including me, often select for plants that show apparent tolerance to it but generally have learned to live with it lurking in the wings. I am not sure that there are any Anthurium spp. nor hybrids that are truly 100% blight-resistant, although the riparians antioquiense and amnicola are known to transmit their tolerance to andraeanum hybrid (the so-called andraecolas) offspring. Conversely, there are a number of old andraeanum and crystallinum hybrids and quite a few montane spp. that are exquisitely susceptible to blight. Whether or not we are seeing more aggressive strains emerging in the trade is another matter entirely; I have not imported stock from the 'States since 2006 so would not be the right individual to address this possibility. It would be interesting to hear from Denis Rotolante, who would certainly know whether they are seeing new antibiotic-resistant strains, and with whom I exchanged info on Xanthomonas management in greenhouses in 2000-2001.
 
I completely disagree with the notion that small scale growers cannot effectively control this blight and should not be buying anthuriums now because of it (!!!). While the last time I actually had a lab make a positive pathogen determination for me was almost 10 years back, I think many of us know it when we see it, and I certainly no longer have the dread that I used to have for it when I first started growing anthurium in the late 90s. I suffered a number of severe outbreaks stemming from imported plants early in the last decade but, frankly, I have not had a serious problem with it for years in spite of growing more than "just a few" plants for cut flower ('Tropic Fire' and my own hoffmannii based hybrids) and 0000s of foliage-type collector goodies.
 
Basically, what makes anthurium blight control especially difficult for commercial growers is that the pathogen is rapidly spread, not only by mechanical means such as non-disinfected cutting tools, employees' hands, clothes, etc. - DR mentioned once that Cuban treefrogs clambering from plant to plant in his greenhouses were a suspected vector! -  but also by splashing water and leaves banging against each other (this is a bad thing generally for all anthuriums!). Anyone who has this problem should be extremely careful to avoid "hard" overhead watering or exposure to rain. While this seems counterintuitive to a tropical aroid fan, bestest and fastest control is gained when foliage is kept dry, well-ventilated but nearly motionless in order to minimize mechanical damage to the leaves that facilitates entry for the bacteria.
 
- My frontline treatment for foliar infection is Agrimycin (streptomycin sulfate 17%) AFTER removing all visibly infected plant tissue to a point well beyond the classic yellow halo line circumscribing necrotic tissue. I would need to check my notes to see at what concentrations I usually apply, but I do seem to recall that I make three apps about 5-8 days apart. I often rotate or follow-up with copper-based ag-chem although it is contra-indicated in the literature...some have recommended systemic copper but I have found it unnecessary, expensive and quite phytotoxic.
 
- While I occasionally use concentrated quat ammonium dips for disinfecting my pruners (at least three in the greenhouse, used in rotation), I definitely favor flaming tools between cuts to all my plants to red hot. If you do not consistently disinfect tools between plants, IMO, you will never gain good blight control once it is firmly established in your collection. 
 
- It is VERY important to remove infected leaves once they are visibly blighted to avoid the blight becoming systemic. I will say that my experience has been that if one permits a severe blight to extend from the lamina down the petiole (which will often mush at the geniculum and the base) to the main stem, the plant is generally going to hand in its lunch pail in very short order. If this occurs, toss these critters asap.
 
- It seems that many growers-gardeners love to fondle their plants when they're in their grow spaces. I cannot emphasize enough that any handling of aroids that are known or suspected of being blighted should be kept to an absolute minimum, and hands disinfected between this kind of manipulation.
 
Note: IME, Agrimycin will invariably burn/disfigure leaves of Anthurium veitchii and its hybrids, usually quite severely, as well as some old andraeanum primary hybrids and few others. It can also be extremely hard on seedlings.
 
J
 

 

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Date: Mon, 11 Jan 2010 13:54:00 -0600
From: S*@exoticrainforest.com
To: aroid-l@gizmoworks.com
Subject: [Aroid-l] Anthurium blight

A warning from our friend Leland Miyano from information originating from botanist David Scherberich.

There is now a very bad Anthurium blight which may be spreading.  At least two gardens in France have had to deal with this one which has no cure.  The one that is really bad is Xanthomonas campestris pv. dieffenbachiae which causes the leaf margins to turn yellow and all the leaves to drop.  I would suggest you be very careful about buying new Anthurium right now!  This has the potential to kill an entire collection. 

Some species appear resistant but others spread it quickly.  Some commercial growers in Hawaii lost almost entire crops of ornamental Anthurium (the kind you buy in the store) so be very careful about buying any Anthurium in a local nursery or discount store!

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1392979/

Any of you that are knowledgeable about this blight please pass along what you know.


Steve
www.ExoticRainforest.com

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