April to-do list for gardeners

By Rebecca Jepsen
For the Mercury News
April 3, 2010

Fertilize citrus with nitrogen. A 1-year-old tree needs about 1/10 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 in well.

Citrus leaf drop is normal. Some varieties can lose thousands per day. 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 sanitation, mass trapping, trunk banding or fruit bagging. With heavy infestation you may have to resort to chemical control using insecticides such as Spinosad or 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 is 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 sluglike worm with a white, half-inch-long strip down the back.

For our complete list of April Gardening Tips, click on: www.mastergardeners.org/tips/april.html.

What to plant now

Transplants: arugula, basil, beans, beets, broccoli, chard, lettuce, mustard, peppers, potatoes, radishes, spinach. Local nurseries should have a good supply of most of these.

Seeds: arugula, basil, beets, carrots, chard, eggplant, lettuce, peppers, radishes, squash, tomatoes.