We are in the middle of mite season right now in the Central Valley. These small animals - smaller than a pinhead - are causing all kinds of damage to vegetables and fruit / nut trees alike. Like spiders - to which they are related - they make webs. In fact the webbing is one of the ways that you can spot them. Here's a couple of pictures of what the mites and the webs look like. But be warned, if you wait until the mites are this far along, you may not be able to control them. Even the best products will fail if there are too many mites around. The webbing, when it becomes too extensive intercepts whatever spray is directed their way and the mites wait beneath until the danger of being poisoned is past.
The first picture is of mite damage to almonds. I found in the same orchard a couple of trees that had lost all of their leaves because of the mites. The second picture is of grapes. The poor vineyard looked like it had been torched. If you live in an area with mites, it really pays to watch closely for the first signs of the mites. Around Fresno, we're watching through most of July. This year things got really bad about the third week of the month, but in varies depending on place and no two years are exactly alike.