Fertilize citrus with nitrogen. A one 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 3 applications during April, June and August. Be sure to water in well.
Citrus leaf drop is normal. Some varieties can lose 1,000s 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.
Tomato seedlings should be planted after the soil temperature reaches 65°F (and nighttime temperatures stay above 55°F). Some kitchen thermometers will measure temperatures in this range. Tomatoes can be planted vertically into the ground, plant deeply – up to the top few leaves (remove all leaves that will be underground). Or, dig a trench, lay the plant horizontally with all but the upper few leaves buried (again remove all leaves that will be underground). Both methods provide for stronger plants by increasing the root system.
Poison Oak is a California native plant that provides shelter and food for many native birds and wildlife. However, approximately ¾ of our population have an allergic reaction to the oils in the plant. Plant removal should be done folks who are allergy-resistant, by digging up the plant and/or applying herbicides. Caution: poison oak should never be burned; the fumes can be highly toxic.
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 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 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, non-toxic 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 ½ long strip down the back.
For our complete list of April Gardening Tips, click on: http://www.mastergardeners.org/tips/april.html