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Friday, June 2, 2017

Yellowing of Pear Might Be Fireblight Disease

Q. The pears started looking like this last week.  Any ideas on what I should do?

A. They look pretty rough. Because of their weaknesses in fireblight disease and this time of year I first think of fireblight disease. They are highly susceptible to this disease which is usually not a problem in the desert unless it is has been wet, windy and cool in the spring and early summer.

This disease can be transmitted from tree to tree on pruners that were not sanitized. One of the reasons I am so picky about sanitizing pruners. Disinfect with 10% bleach and oil equipment afterwards. The disease hits Asian pear the worst, then European pear like Bartlett not as bad and apples as well. Fuji, Pink Lady and Mutsu are susceptible apples. Also quince. It can spread very quickly.

The only remedy is pruning it out far below the infection and sanitizing shears between each cut (10% bleach). If the disease gets in the trunk the tree cannot be saved and should be removed from the property asap and with great care so the disease does not spread. Sanitize all hands, gloves, tools, etc. Very virulent disease.

University of California on fireblight

Other possibilities include planted too deep (move the trunk back and forth and see if moves in the soil a lot or dig to see where the roots are). This usually surfaces like this in hot weather. In cool weather the tree has more tolerance to the planting depth.

Poor drainage and collar rot or root rot. Get any wood mulch away from the trunk. Improve drainage. This can slowly choke tree turning leaves yellow first due to not taking up many nutrients, then leaf scorching because the roots cant take up enough water and eventually strangulation/death/drought due to root rot. Vertical mulch with four holes 18 inches from the tree to act as a sump. Posthole digger works well.

The leaves are yellow like iron shortage but I don’t think it is.

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