Thanks, Jerry. The variety that I have is Arapaho, a thornless one.

Typical UV damage from sunlight. The segments actually do color and fill out just fine. Whitening occurs mostly during red phase; often those segments then weep juice and deflate, eventually drying out. Segments facing the sun are damaged much more often than other segments. The whole cycle can occur in 24 hours.

The actual process of the syndrome is unknown.

Yes, sun scald. Those segments look brown to me (not white) which means they will not fill in. Some varieties are more resistant than others. I had a lot of this on my apache blackberries, but less so on arapaho. This can be limited by protecting them from full sun on hot days, but that is a big pain to accomplish.

-Brett

Google up 'white drupelet disorder'.

Thanks, lucky_p, googling "white drupelet disorder" brought up a wealth of information. That is definitely the correct diagnosis of the problem. Trouble is, there doesn't seem to be much agreement on what causes white drupelet disorder. I have to doubt that it occurs as a result of too much light exposure, or sun scald, because my current planting of Arapaho has considerably less sun exposure than a previous planting a few miles away here in Colorado, which had no white drupelet symptoms at all. That previous planting received full sun all day long. My google search yielded a fairly persuasive argument by a long-time grower of blackberries in Georgia who says that it's caused by an iron deficiency in the soil, and that he solved the problem by adding some iron to his soil every five years or so.

Thanks to all who have responded with offers of helpful information on this topic.

I grow only Kiowa... which is noted for being affected - and it often is, especially when we get into the full heat of July. But...in pies, jelly, or jam... You'll not notice any evidence of white or light drupelets.... so I don't let it bother me.

Yes iron deficiency in the soil and happen on top most drupe-lets on berry, but you careful they get heavier turn after size up it also happen in side bush where shaded to when low iron. It happen on new planting more often its new planting for three to five years.

A good way to soil apply iron out sprayer straight stream along side plants, better than broad cast to soil iron can cause problems as broad cast.

Soil apply iron in sprayer at five teaspoons to gallon water apply walking speed. This to high rate for foliage one teaspoon to gallon foliage application.

You have plenty time to soil apply iron it work on next years crop, I go on both side row after harvest and remove spend canes apply feed grade liquid iron.

The good well stock garden center have liquid iron in small bottle that do most small planting. I bought mind feed store in 5 gallon bucket, because rate by acre is up to too to fours quarts acre, this last 3 years per application thereafter. You can wait until druplet disorder comes back before next application if comes back be slow showing up.

A soil sample do no good for this disorder its plant take up problem.

Thanks gator_rider6, I'm going to try the iron. I'll let you know next year if it works.

I would also give them a very close inspection. Make sure there are no bugs or eggs.