white druplets on Marionberries
Marionberries are a type of blackberry, or caneberry. Here is information from UC IPM about white drupelets. Compare photos and descriptions to see if this is what your sister is dealing with. http://ipm.ucanr.edu/PMG/r71800111.html
Hi Jacki D. yes, I think that answers our question... so perhaps she can water her berries a bit more in the hot weather to see if that makes a difference.
thanks very much for your help!