Pear tree problems - with images

[William Grote]

Tree Doctor Help Request - part 2 

I planted four perry pear trees this spring ( from Fedco )

All are in a field by themselves, completely separate from my apple trees by at least 250 meters and thick woods, and they just started to kick in with new growth shoots, but now all the older leaves as well as some of the fresh new ones have dark brown, almost black necrosis  that starts at the tip and works its way back ( see attached photos ) as well as dark spots, the color of these is far darke than that of the brown spots that some of my apple trees have in another location

Japanese beetles have been pretty bad this year, but other than that and aphids and the occasional tent caterpillar I have not seen many insects on them- 

Any ideas?  

[CiderSupply.com]

Hi William looking at your photos and from your description it is very indicative of what's called bacterial Leaf scorch. It is caused by the bacteria Xylella fastidiosa. It is spread by certain insects and either was brought into your area from surrounding trees that are infected, or it came in as infected pear trees. Some pear scionwood that was distributed by the USDA out of Oregon for nurseries for a number of years starting about 10 years ago test positive for this bacteria. The full scale of infected pear trees across the country is still unknown but they are actively trying to track it down. You can go to their website and they list all the cultivars that are known to be infected. DNA testing is the only way to determine it for sure and some years it's insignificant and other years it's catastrophic. There still is a chance that it may be fire blight, but I'm not sure where in the country you have your trees and if it's a fire blight area.

A dead giveaway for this Leaf scorch bacterial problem would be look in your area and see if you can find any oak trees that have limbs dying off and a similar leaf damage. We had all of our pear trees DNA tested for this bacterium and they tested clean. But if we had oak trees in the area that were infected with this bacterium, sooner or later our pear trees would become infected. According to the people that did the DNA testing and field sampling, this bacterium spreads to just about everything except apple trees so that's somewhat good news for cider makers. Unfortunately for wineries is especially devastating for grape crops.

Great info at Oregon State Department of Agriculture under the alert section.

Or just search Google for this PDF:

XylellaFastidiosaBrochure.pdf

Best regards

Chris Rylands

[William Grote]

Hi Chris

Thanks for the info, I am in northern New Hampshire

Ill take samples and send them in to UNH for testing, 

Will spraying with Captan help this?

[CiderSupply.com]

Hi William, no Captan wont work.

Xylella fastidiosa bacterium is transmitted by leafhoppers and a few other leaf insects. The bacterium grows in the xylem of the plant and physically clogs the vessels. This in turn creates water stress and leaf dying from the edges inward.

Control is still very much under study. But controlling the leaf hoppers probably is the best and establisging buffer zones. It is a growing National problem that has been spreading largely unchecked.

If you need to chat with the USDA lab that did our DNA testing just let me know. We were lucky, ours tested negative.

Best regards

Chris Rylands