The tree gets adequate water. This problem was first noticed last year and now is occurring again. The tree appears to be healthy otherwise and fruit production is not affected. The symptoms do not appear to be those of fire blight, so we will rule it out first. That is good.
Fire blight is a bacterial disease which is difficult to manage.
A common problem observed in trees in New Mexico each spring is blackening of leaves of pear, cottonwood, and many other trees. This can be due to slight frost damage or by wind damage. Young leaves in the spring are often very tender and subject to damage from the winds which develop during our warm desert days. Temperatures can rise from very pleasant temperatures to rather warm mid-day temperatures. These warm days following cool nights, when combined with our frequent spring winds, can cause rapid desiccation of the leaves.