We moved into a new home in 2015. We have a lemon, several other varieties, and a very sour, unknown orange. The previous owner said the tree was very sweet at first. People around us believe the sourness is because the bees are pollinating it from the lemon. How do we get the orange to sweeten up?
Pollination from a lemon or any other citrus will not cause the fruit or the plant to change any of its original characteristics. Instead, they pass the changes on to the next generation. You see the results of this in plants that germinate from the seeds in the fruit of the pollinated plant. This is basic plant genetics. Hence, the bees are not the answer to the sour fruit.
Cool summer temperatures or the lack of heat is one of the answers especially those oranges grown along the coast. But, I don't believe that this is the case here. Instead, I believe it is a varietal issue. Oranges don't necessarily ripen in one calendar year. It is common for a new crop of oranges to form with last year's crop still on the plant. Naval Oranges ripen December through March, while Valencia Oranges ripen April through June. I think you have a late ripening variety and if you sample the fruit today it would be sour.
My suggestion is to let the fruit continue to mature on the plant. Every three weeks going forward from the expected ripening date, I'd pick one and taste it. It should sweeten up as the year progress.
My two cherry trees were traumatized last spring and summer as they were heavily, hit with Black Cherry Aphids. I kept cutting off the affected leaves but the trees looked bad all summer long. In the past, I maintained control of the Aphids by putting a ring of the sticky stuff around the trunk. This year it didn't help at all. What can I do for an Aphid-free season this year?
Aphids are a problem on Cherry, Apple, and Plum trees.
It causes the leaves to curl up like one of those Italian cookies. Many gardeners confuse it with the curly leaf or Peach Leaf Curl found on Peaches and Nectarines. Hopefully, you had an opportunity to apply a dormant spray of Copper or Horticultural Oil. This cleans up any of the over-wintering insects on the bark and in the crevices of the trees but it doesn't prevent the Aphids from returning.
You control the Aphids by being diligent and checking the trees as the leaves are emerging for curly leaves. Once, you see the problem you pick the curly leaves off the trees and spray with Insecticidal Soap, making three applications a week apart.
I’d still apply the sticky stuff also know as Tanglefoot or Pest Barrier. Aphids are ferried around by ants, as they feed on off the clear sticky residue called 'Honey Dew.' Aphids are present year round but are only problematical in the spring.