There are people more expert than I on this....and particularly for your area and I hope they will answer...but a couple things as starters: 1. It would help if this year you could take some leaf samples in to a local State Extension agent that could tell you exactly what the problem is for your tree.....it sounds like you have two problems, one related to the tree and one related to the fruit.....no exacting identification makes advise on sprays problematic. 2. In the Northwest, many organic guys are finding some happiness with Spinosad (Entrust, Bullseye, etc. are trade names).....it is a fermenting bacteria......but again, this is only if you know you have worms in your fruit (you said "bugs" but we need to know more).....I think the odds are good that Spinosad would help and you need to learn more about it and how to apply it, in my opinion. Local nursery would help.

You are lucky to have had any cherries by now. Many people wait 4-5 yrs for their first fruit. If you remove the 3/1, you may have to wait yrs for any replacement to bloom. Keep the 3/1 and buy another tree. Bing is a very good pollinator for Rainier. It however is prone to split in rain, as is Rainier. A self fruitful variety like Sandra Rose, Sonata, Lapins, Skeena, or Sweetheart would be a good pollinator for Rainier, if they bloom together, and would not need another to pollinate itself. Bing and Rainier do bloom together. Sweetheart on a dwarfing rootstock like Giesla 5 blooms as fast as anything. It also matures later, which I think gets closer to your dry season. But it can overbear, giving small fruit of inferior guality. You solve that by severe pruning to remove fruit buds and force vegetative growth. The final size of your trees depends on how much you prune. The Fruitnut

You don't need 4 in 1 sweet cherries these days. You can grow Stella, Lapins, and a few other self pollinating varieties that should be hardy enough for your area. The biggest problem, as with anywhere in the east, is fruit that cracks from rain. A near ripe cherry will split with even a light rain. You can get a 4 in 1 if that is what you want, but you don't need it if all you want are sweet cherries.

A Bing cherry tree growing in southern California will do reasonably well the first several years, just enough to get your hopes up. After that, it will start dwindling away, more & more each year. And will eventually look so sad you'll remove it. If you want a tree that will grow and produce cherries, ask at your nearest independent garden center which cherry will do well where you live. Several will. But only if you obtain the correct kind. Ask when it/they will be available. (In SoCal, bareroot tree fruits are generally available during Jan. & Feb; sometimes in Dec.) As for the flowering cherries and other trees that require substantial amounts of chill -- total hours between 32 and 45 during Dec, Jan & Feb, but subtracting all hours above 65F -- will grow but will bloom erratically & will leaf out erratically. So save yourself a lot of grief and grow "low-chill" fruit tree(s) suited to your region. The large garden centers know which ones they are. But you need to ask. One big problem: Just because a garden center in your region sells a specific fruit tree doesn't mean it will thrive there. Jean, who gardened in Long Beach, CA, for 30-some years.