By Rebecca Jepsen
for the Mercury News
April 3, 2009
Fertilize citrus with nitrogen. A 1-year-old tree needs about one-tenth of a pound, a 5-year-old tree will need 1 to 1½ pounds. It's best to divide feedings into three applications during April, June and August. Be sure to water well.
Citrus leaf drop is normal. Some varieties can lose thousands of leaves per day during peak leaf drop. Excessive drop can be caused by lack of water. Another cause might be an infestation of spider mites which will show up as brown spots on the leaves; treat by washing them off with a strong blast of water from the hose.
Codling moths can cause a great deal of damage to apples, pears, plums and walnuts by penetrating the fruit and boring into the core. On apples, look for brown-colored holes. If trees have low to moderate infestation, you can try nonchemical control such as picking up dropped fruit promptly, hang multiple traps, mass trapping or enclosing the young fruit in paper bags. With heavy infestations, you may need to resort to insecticides such as Spinosad of Carbaryl.
Powdery mildew is a common problem on many roses, dahlias, chrysanthemums, peas and squash. It produces a white powdery appearance on leaves; some roses are so susceptible that it may be easier to remove the plant and pick a disease-resistant variety. A homemade spray of baking soda, water and salad oil can be an effective, nontoxic treatment.
Syrphid flies are beneficial insects that do a great job of devouring aphids. In the adult form they look like a fly with the yellow and black striping of a honey bee. In the larval stage, they are a green slug-like worm with a white stripe down the back.
For more April gardening tips, click on www.mastergardeners.org/tips/april.html
What to plant now
Transplants: arugula, basil, beets, broccoli, chard, lettuce, mustard, peppers, potatoes, radishes, spinach. Local nurseries should have a good supply of most of these.
Seeds: arugula, basil, beets, chard, eggplant, lettuce, peppers, tomatoes.
To find a list of warm-season vegetables that do well in Santa Clara County, go to http://mastergardeners.org/picks/warm.html.