Q: My apple tree has little green fruit, flowers, new leaves, and dying leaves – all at once. It’s late October. What is going on?
Your tree is confused. This frequently happens when a high-chill variety is planted in a low-chill environment. Some people who grew up in colder areas of the country, such as the mid-Atlantic or New England, have fond memories of certain apple varieties that they grew up with. Some of these cold-climate (high-chill) varieties include MacIntosh, Cortland, and Red Delicious. (Although hard to believe, the original Red Delicious is a very good apple when eaten fresh from the tree.) These cultivars need an extended period of cold in order to bear fruit and thrive. I’ve seen these trees for sale occasionally in Southern California, probably due to customer requests. They may grow acceptably well the first year or two, but they will either fail to flower and/or set fruit, or flower and fruit at random times during the growing season. Eventually, they will decline and die. Sadly, this is probably what is happening to your tree.
You can grow apples in Southern California, but you must select low-chill varieties. Trees should be labeled with the chill requirements on the tag. Research before buying, since many apples may also require a pollen source to bear fruit.
Q: What is the difference between summer oil and winter oil (horticultural oil)? Are they considered safe?
Horticultural oil is a safe, effective remedy for certain stubborn pests, including scale, mites, and aphids. The oil will suffocate the insects (or arthropods) without causing harm to non-target organisms. You may have seen different types of horticultural oils – dormant oil, summer oil, and neem oil.
Dormant oil can be applied when the plant is dormant (generally in the winter). It is heavier and tends to stick around longer. It is especially effective against hard body scales, which like to overwinter and cause problems in the spring. It may harm non-dormant plants, so it should only be applied in the winter months.
Summer oil is lighter and can be used on healthy plants that are not dormant. It’s especially useful against the hordes of aphids that appear in the early spring. Keep in mind that these oils are only effective when used in direct contact with pests – they will not repel newcomers. Never apply oil to a plant that is water-stressed, and do not use when outdoor temperatures are above 90 degrees.
Neem oil is a plant-based miticide, insecticide, and fungicide. It is effective against a wide variety of pest insects, but is toxic to honeybees. When using, avoid application during daylight hours when bees are active, and avoid over-spraying onto neighboring flowering plants.
Los Angeles County
mglosangeleshelpline@ucdavis.edu; 626-586-1988; http://celosangeles.ucanr.edu/UC_Master_Gardener_Program/
Orange County
ucceocmghotline@ucanr.edu; http://mgorange.ucanr.edu/
Riverside County
anrmgriverside@ucanr.edu; 951-955-0170; https://ucanr.edu/sites/RiversideMG/
San Bernardino County
mgsanbern@ucanr.edu; 909-387-2182; http://mgsb.ucanr.edu