Tool sanitizing/sterilizing

This is relevant in other parts of the forum as well but posting here cuz Rashaan's mention of it in his post on perennial canker on apple, but please feel free to recategorize the post, Michael.

What are the best practices for insuring that we don't pass disease (viral, bacterial, fungal) from one tree to the next ? While grafting a few weeks ago, I wiped my knives and clippers with 91% isopropyl alcohol whenever switching varieties. I can't help but feel that this is not enough. I'd be grateful if others would share their guidelines for limiting disease transmission in pruning and grafting.

Josh Klatt
Ohio River Valley
Zone 6b

Yes, this is a very useful topic, and I would also like to know what others are doing on that respect. Through the years, I have used bleach - but this will make the tools rust badly, alcohol, and Lysol which supposedly eliminates 99.9% of bacteria. The problem is that we have no mean to know for sure how efficient the sanitizer we use really is efficient - that is until we actually have a problem, and then it is too late!
Claude

Jolicoeur Orchard
Zone 4 in Quebec

Fungal spores are not moved from one tree to another by a pruning shears. And thus this post does not belong in the fungal disease category but rather pruning in general .

Viral transmission by pruning certainly has relevance ... but this is uncommon. Plum pox comes foremost to mind. Infected trees should be outright destroyed rather than pruned. Grafting infected scionwood can introduce apple mosaic virus ... but then again the result is a sick tree needing to be removed that isn't a danger in the projected interim to other trees in your orchard.

And bacteria? They are. Right now. Out there. But why care? There's no opportunity in the here and now of dormant time. I stopped the practice of sterilizing my pruning tools in late winter / early spring once I understood new infections aren't going to happen while it's still relatively cool.

Think this question through from the perspective of the organisms. Fire blight bacteria overwinter in cankers on host trees. Once the weather truly warms, the bacteria multiply very quickly, oozing from the surfaces of infections from the previous season. These get situated "benignly" in bark crevices and bud scales -- think staging grounds -- all on their ownsome, whether we're pruning or not. Soon, rainfall, high relative humidity and/or dew allow the bacteria to travel the moisture highway into the stigma of flowers and and thus into the vascular system of the tree. Blossom infections often lead to shoot infections in that month following petal fall. Now each pruning cut indeed represents a parallel opportunity for infection if conditions warrant. Paul Steiner's notion of the ugly stub as a means to limit fire blight permeating deeper into the tree speaks to this. It's during "fire blight infection season" that tree-to-tree sanitation makes perfectly good sense.

Lost Nation Orchard
Zone 4b in New Hampshire



Edited 3 time(s). Last edit at 04/16/2013 12:07AM by Michael Phillips.

That makes sense... My biggest fear was to transmit something viral that couldn't be remedied later down the line, but that seems to be an unwarranted concern. Thanks for the detailed response !

Josh Klatt
Ohio River Valley
Zone 6b