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Fertilize & Disease Control

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Fertilize & Disease Control

Insect pests can disfigure, weaken and possibly kill even some of our most drought-resistant trees and bushes. Examine foliage to look for juniper tip and cypress tip moths’ ¼” silver-white cocoons. If you find cocoons, shake the branch once a week and look for silver-tan moths. They tend to fly up and light back down similar to whiteflies. Spray Sevin mixed with diazinon, then reapply again in two weeks. When the eggs hatch in June or July, spray again with Ortho Isotox. For problems with juniper twig girdler, spray with 1 tablespoon of lindane to one gallon of water. If you apply in this month repeat again in May.

There are plenty of hungry caterpillars and worms out now. Spray with a product containing BT, such as Safer Caterpillar Killer, if you’re having a serious problem controlling them.

Birds and insects are spreading fuchsia mites which attack new growth, distort buds and foilage and turn the flowers red. Some varieties are resistant, but others such as jingle bells and marinka are more susceptible. They can usually be controlled with beneficials, but if the infestation is serious, cut out the infected parts and dispose of them in the trash. Spray with Sevin at least twice, two to three weeks apart. Mix it with a miticide to prevent killing all the beneficials.

Spider mites can damage and sometimes kill plants by sucking out the juices. They are tiny reddish or black spider-like insects and will leave a fine webbing over, around and under leaves and twigs. Sometimes fertilizing will overcome the mites without spraying. Use a miticide to combat heavy infestations. 

Follow all safety instructions when using any chemicals.

Some beneficial insects like ladybugs are available at nurseries now and can be a great help in controlling insect pests. Apply by small spoonfuls in the cool evening hours, especially on fuchsias. Look through a catalog and send away for lacewings, predatory mites and other beneficial insects. Birds and bats eat many insects that can harm your garden, so encourage them. Welcome spiders and hold back on chemicals.

Continue feeding flowers you planted in the fall for growth and bloom. Water in fertilizer pellets or granules every four to six weeks or use a liquid fertilizer every two weeks.

Alyssum, calendula, dwarf stock, Iceland poppy schizanthus, sweet William, viola, and wall flower do well in San Diego. Use a liquid fertilizer high in nitrogen, such as 20-20-20, to speed up the blooms. If you have sweet peas or linaria, use 0-10-10 if necessary; they don’t generally need nitrogen. Keep calendula, cineraria (tall varieties), Iceland poppies, linaria, snapdragon and stock blooms deadheaded or picked to promote blooming.

Don’t fertilize wildflowers unless you notice yellowing and weakness in the plants. Fertilizing will encourage growth, reduce the size of the flowers, and make them leggy. Protect these plants from snails and cutworms and keep them watered if the rains aren’t adequate.

Revive cyclamen by feeding them with a balanced fertilizer every two weeks. If you use too much nitrogen, you won’t get many flowers but you will have lots of leaves. Try to avoid watering the leaves and crown of the plant.


Watch for twisted and out of shape leaves which indicate cyclamen mites. Mites cause the leaves to twist and disfigure and become colorless. Since mites are not insects, they must be sprayed with a miticide rather than an insecticide. Check the package to make sure it can be used on your specific plant. The proper amount of fertilizer and light may offer some assistance in fighting off pests. Bait for snails and slugs.

When buds appear, change to a complete fertilizer. Use BT if caterpillars are a problem and bait for slugs and snails. Spider mites are also a potential problem now. Try washing the leaves with Safer soap or spray with a specific miticide. Making sure they get enough sun may give them enough strength to fight mites off by themselves.

After spring-flowering bulbs fade, continue to water and give them bulb food from Best or Whitney Farms to encourage blooming next year. Tie the leaves in knots until they are completely yellow, only then cut them off. Fertilize irises with a fertilizer low in nitrogen and high in phosphorus and potassium. Protect your plants from snails and slugs now.

Fertilizing water plants is a little more work than feeding other plants. It often means getting physically into the pond with the plants. Be sure to wear protective clothing and long rubber gloves. Some types of algae can be absorbed into the skin and produce allergic reactions. Water lilies should be fertilized every 4 to 6 weeks from April through August. You can find fertilizer pellets specifically for water lilies which are slow release. The rule of thumb is to use approximately between five and ten grams of a good fertilizer such as 10-20-10 for every gallon of soil.

Most of the year these tree-dwelling plants are tucked away in the shade. Bring them into a semi-shady spot facing the same direction they are used to and you’ll start to see some exotic and beautiful blooms. Feed regularly with a balanced liquid fertilizer 8-8-8 or fish emulsion through the summer. Add a high bloom formula occasionally and keep watch for when they need water. If it is damp when you poke your finger down into the soil an inch or two don’t water them. Water only until you see it beginning to drain out of the container. If it’s rainy, don’t water at all. It’s best to use a drip system if possible. 

If your trees have light green leaves and dark green veins, they may be suffering from chlorosis. Apply a chealated iron and zinc product to the ground and around the tree to counter act it or spray the foliage with a product made specifically for this problem and apply when you fertilize.

Water deeply every two to three weeks. To avoid fungus disease (gumosis) be careful not to water the trunk. Let the hose run slowly on the ground about one-third of the way from the trunk to that far past the drip line.

Pests are becoming active now. Beware of aphids, mealy bugs, rust and silver mites and wooly whitefly. You may need a magnifying glass to see them and if necessary, consult a book about controlling citrus pests. Check for snails, they especially like orange trees. Remove them and clip off any leaves touching the ground.

Washing citrus trees can help prevent or rid them of pests. Use an insecticidal soap or 1–2 tablespoons of dishwashing liquid (not for the dishwasher) per gallon of water and apply with a hose-end sprayer The pressure helps by removing dust so beneficial insects can attack pests. The leaves can be hand-washed for extreme cases. Cut the tips of any branches that touch the ground to help prevent ants. Don’t cut too much, the trunk needs the branches to protect it from sunburn. Regular commercial spraying is best to get rid of ants.

Tip: putting a copper band around the tree trunk prevents snails from crawling up.


It’s time to fertilize the areas you prepared last month around bushes, ground covers, lawns and most ornamental trees. Heavy rains wash away nutrients, so use a granular fertilizer high in nitrogen. Water well or apply when rain is expected. Flowers such as azaleas, begonias, camellias, epiphyllums, ferns, fruit trees, fuchsias, roses and vegetables have special requirements, so follow directions carefully. Feed plants showing signs of slow or stunted growth, disease or yellow leaves. If your garden is overgrown, feeding will just make it flourish, so clean up the area first.

Nitrogen is the key word when fertilizing avocado trees. The amount of nitrogen needed is in direct relation to the age of the tree. A mature tree (8-10 years old) requires about two pounds of nitrogen per year, along with various amounts of other nutrients whereas a tree five years old needs half that amount. Consult a book or nursery for specific details. If you live on the coast, divide the amount needed by five and apply equal amounts once a month from February through June. In inland areas, divide by four and feed monthly March through June. If you use slow-release, half should have been applied in February and the second half half in June. Avocados require rich soil, excellent drainage and a thick layer of mulch over the roots.

All established warm- and cool-season lawns will benefit from a complete fertilizer now. The nitrogen will give results you can see – growth and green – while the potassium and phosphorous will last in the soil and feed the roots. After this complete feeding, use pure nitrogen once a month for the rest of the season. You’ll need ¾ to 1 pound of nitrogen per 1,000 sq. ft. of soil depending on the type of grass. Apply fertilizer to damp ground with dry grass then water deeply so it won’t burn. You can use a slow-release fertilizer on warm-season lawns which will last approximately three months. Keep cool-season grasses cut 1½” to 1¾” now. If there is little rain, water often and mow weekly.

Roses need lots of water now to strengthen the stalks and leaves for new blooms. Continue fertilizing roses this month. See Pat Welsh’s Southern California Gardening Book for details about method options. Feed again on the same date this month that you marked on the calendar last month. Fertilize just before a heavy rain or irrigation. If there isn’t enough rain, keep roses irrigated. 


Continue to control fungus with Bayer Rose and Flower or Fungicide Plus by Spectracide mid-month. Mix them both using the amount of water indicated for one of them if you’re showing roses. For each gallon, add a small amount of dishwashing liquid to help it adhere better. Either wash off aphids with a hose or control them with systemics such as Bayer Rose and Flower Care, Insect Concentrate or Ready-to-Use, which are safer than sprays if roses aren’t near food plants. Find a product with BT to help you control caterpillars which are becoming active now. Follow all safety instructions when using any chemicals.

Use a slug and snail product recommended for the vegetable garden to protect lettuce. You can also bait the perimeter and cut them off at the pass. Leaflhoppers carry disease and if necessary treat them with diatomaceous earth. Unfortunately this may kill the beneficial insects as well. By planting herbs and marigolds in with your vegetables you can confuse and cut down on insect pests. Consult a vegetable gardening book to see what herbs will work best in your vegetable garden. 

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