Last May/June during a hot period and soon after fruit set, avocado growers and PCAs in the Oxnard/Camarillo area were calling in about young fruit about he size of a quarter showing up with white spots.  Cutting into the fruit there might only be a small black spot just below the injury.  Because that's what it is, a wound response on the part of the fruit to a physical damage.  This occurred on several orchards also in the San Luis Obispo area and it seemed to happen in orchards that had recently been sprayed for avocado thrips.  No piercing-sucking  insects were found at any of these sites. Insects that would feed by feeding on the fruit and causing damage and malformed fruit. Insects that could typically make probing inspections of fruit prior to laying eggs. No eggs or larvae were found in the fruit. Nothing like lygus bug, BMSB, Bagrada bug or other stink bugs was found.

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=15198

Did it have anything to do with the spray? With the hot weather? With the hot weather and the spray? With the hot weather and the insects that came with it?  Did it have anything to do with the hot weather?  Did it have anything to do with insects?

And then late June, the calls stopped.  No more damaged  fruit was being found. And then a lone call from Cayucos.  Damage was found on young and older fruit.  New damage seemed to be occurring on the fruit that normally sets later in that northern area.  The grower walked the orchard and didn't find any bugs.  The PCA swept the grove for insects.  A yellow sticky card was put out. 

So far, no insect has been found on the fruit. So what caused and "is" causing the damage to the fruit?  It's not clear.  Fruit that was damaged in Oxnard back in late May was tagged to see if it recovered.  Ten fruit were flagged and two months later, those tagged fruit were still on the trees.  So either the fruit that was attacked fell off with the initial damage or the fruit observed later had healed itself.  Fruit have this capacity when they are actively growing to cover over damage.  Often it is malformed.  In most of cases with this fruit, the damage was very superficial.  Occasionally, there deeper pits, but we didn't see any burrowing or tunneling.

If anyone else saw similar damage and has more to offer about this happening, I would be glad to hear about it.

Photos:  Damaged fruit that was flagged and observed 2 months later.