10 FAQs on Garden Problems
by Bob Chapman
After 55 years experience as a professional gardener, garden writer and a columnist for a major metropolitan newspaper answering garden questions, you note a repetition of certain gardening problems or FAQ's. Here's a sampling of them that come to mind. Reading the topics may reveal answers to problems that you may have experienced in your garden. You may want to download them and keep them, just in case you suddenly find a problem in your garden.
1. Squash plants eaten by little white flies
Whiteflies can do a lot of damage to the leaves of squash plants. They hide underneath the leaves out of sight of predators and humans until the population grows so large that the adults are seen flying around. Whiteflies are difficult to kill. At one stage of their life cycle they are immune to ANY insecticide. The eggs and pupa can be killed, but the nymphs that emerge from the eggs cannot be killed by insecticides. The adults do not feed. They are attracted to the yellow sticky paper sold for this purpose. Many counties, in cooperation with the state, have purchased and introduced a tiny wasp (the size of the head of a pin) that lays its eggs inside the whitefly eggs, thus killing them. Check with your University Cooperative Extension agent to find out if the wasps have been introduced. If so, do NOT spray, as you will kill the wasps, the only thing that will control the whitefly
2. Mushrooms suddenly appearing in lawns
Mushrooms will grow almost anywhere and at all times of the year, but they are most visible in lawns during spring and fall. The mushroom itself is the visible fruiting body of underground strands of fungi. Their function is to release millions of spores to the air to float along until they land hopefully on a spot suitable for their growth, thus spreading the species. A few of the thousands of varieties are edible and a few are very poisonous to humans and a few will attack susceptible plants. You can't kill the underground portions but you can take the backside of a steel garden rake and knock them over. They soon melt or are eaten by slugs and snails.
3. Black mold appearing on citrus leaves
The black residue found on the leaves and fruits is a common black mold. It is caused by a fungus that grows on the sugary material left on plants by sucking insects such as aphids, mealybugs, scales, and whiteflies. These insects are unable to digest all the sugar in the sap they suck from the leaves and the excess is secreted as "honeydew" and falls on the leaves and fruit below. A sooty fungus (sooty mold) grows on the honeydew. It is unsightly but harmless, as it does not attack the leaf or fruit. It can cause leaves to become pale as it shuts off light and prevents the leaf from producing food.
Sooty mold is usually washed off by rains. There is no way to rid the leaves of the discoloration but citrus fruits can be wiped off when picked.
Watch for ants getting into the tree. They will protect the sap-sucking insects such as scale, mealybugs or aphids from predator attacks. They use the sweet exudate from these insects as food.
Deny the ants access to the tree by applying "Tanglefoot" to the trunk of the tree near the base. Ants will use anything to gain access to the upper portions of the tree where the insects are located. Any branches or leaves that touch fences, buildings or other trees or shrubs will serve as a "bridge", allowing the ants to cross over to your tree. Prune off these branches or leaves, leaving a gap between them.
Most sucking insects are controlled by their predators. Keeping the ants away allows the predators to do their work and often no spraying is needed to control the sucking insects.
4. Baby's Tears invading gardens
This low growing invasive plant is difficult to control. As powerful an herbicide as Roundup is it won't faze baby's tears. Finale, another effective herbicide, will kill baby's tears. Finale can be purchased online at Biconet.com if not available locally.
A word of caution: Finale will harm all desirable vegetation so protect against spray drift when spraying by placing a barrier of cardboard or plywood between the desired plants and the baby's tears. Do your spraying in the morning to lessen the chance of spray drift.
An inexpensive way to kill baby's tears is by mixing sulfate of ammonia and water in a two-gallon sprinkler can with an attached nozzle and sprinkling this solution on the leaves. Sulfate of ammonia is an inexpensive (about $3), quick-acting source of nitrogen and is sold in twenty-pound bags.
Remove by hand, trowel or hula hoe any baby's tears adjacent to the stems of hardy perennials or shrubs. Put two or three trowels full of sulfate of ammonia in the bottom of a sprinkling can that has a nozzle and add just enough water to dissolve the crystals. Sprinkle the solution on the baby's tears. It will desiccate the leaves of anything the solution touches, so keep it from contacting desirable foliage. In hot weather the baby's tears will turn black in a few hours. After this, water the areas covered to get the sulfate of ammonia into the soil where it becomes a plant food.
Baby's tears are pretty but they tend to come back from even the smallest remnant. Complete eradication will take time and effort but it can be done.
5. Tomatoes with one end rotting
The condition is known as blossom-end rot and can occur at any stage of fruit development. It is not a disease caused by a fungus or virus. It is a physiological condition usually caused by any sudden changes in soil moisture, usually drying out, as opposed to drowning. It is most serious when the tomatoes are rapidly growing with high soil moisture and a hot spell occurs or the temperatures get above 90 degrees F. Sometimes a lack of calcium in the soil will trigger the disease. Although the blackened end looks odd the fruit is still edible. Simply cut off the bottom part of the tomato and enjoy a great taste.
Mulch with black plastic to keep the soil cool and help conserve moisture. To do this, cut open a garbage bag, cut a slit in it and spread it under the tomato vine with the slit around the stem. Stake it down or put something on top to keep the plastic from blowing around. Or mulch with organic material (compost) to reduce any fluctuations in soil moisture and soil temperature. Do not plant tomatoes in poorly draining soil. Keep the soil uniformly moist and do not feed with a high nitrogen fertilizer. Later in the season the vines may produce fruit that does not have blossom end rot.
Monterey Lawn and Garden Products sells a product called "Foli-Cal". When sprayed on the tomato plant it gives the plant a quick dose of calcium. It is available online at www.montereylawngarden.com.
6. Petunia flowers mysteriously disappearing
Petunias, geraniums, and other plants are often attacked by the tobacco budworm. They make your petunias and geraniums their personal restaurant. These worms are the larvas of a brown moth. The moth emerges in the summer, lays its eggs on your petunias and geraniums. The eggs hatch into tiny worms hardly big enough to see.
These worms are clever, hiding in the daytime from prying eyes and hungry birds. They prefer the young, tender petunia blossoms and, like the geraniums, will start eating the leaves when the blossoms are gone. Often the first sign of an invasion of the worms is when the petunias have a small hole in the middle of the blossom. And very soon all the blossom is eaten and your petunias have the appearance of having no blooms at all. The worms are voracious eaters. They eat almost constantly when they get to the size that you can see them.
In addition to the sudden failure to bloom and the holes in the buds or leaves of geraniums, look for the brown or black pellet-like droppings of the worm on the leaves. This is a sign that the budworm is present on your geraniums or petunias.
You can control the budworm by a weekly spraying of the unopened geranium buds, nearby stems and leaves with Orthene, a systemic insecticide. When spraying petunias cover the entire plant. The spray will protect a plant for about two weeks.
If you prefer a natural method, spray the geraniums or petunias thoroughly with Bt (Bacillus thuringiensis), a bacteria that attacks the worm. As soon as the worm eats the flower, leaf or bud sprayed with Bt it stops eating, but it takes a few days for it to die. Be aware that Bt has little residual effect and must be used frequently and regularly to control the worms. You have to keep looking for the young worms and spray the plant immediately.
7. Ficus leaves suddenly falling off
Ficus benjamina, the Weeping Fig, a popular houseplant, takes offense at being moved, placed in a draft, in a cool room, watered with cold water, a home with low humidity or a poorly lighted spot and will suddenly drop most of its leaves in protest.
So give the temperamental Ficus water at room temperature, set it on a two-inch high dish of gravel filled with water to increase the humidity, and talk to it every morning and never, ever use water from a water softener.
Give the Ficus a drink of water when the top inch or so of the soil dries out. Ficus doesn't like soggy soil. Ficus doesn't like to get his feet completely dry, either. Test the soil moisture by sticking your finger in the top and, if it's moist when pulled out don't add water. Refrain from watering on a strict schedule, use the above method and your Ficus will love you.
Feed your Ficus monthly (or follow directions on the houseplant food container) when new leaves appear, but when it is dormant and no new leaves are being sent out don't feed it. Your Ficus will soon send out a new set of leaves, so just be patient and you will again be rewarded with new pretty leaves.
8. Leaf curl on peaches
Peach leaf curl is found on both peaches and nectarines. Other plants and trees attacked by this disease are alder, apricot, azalea, birch, camellia, fruiting and flowering cherries, elm, ferns, maple, nectarine, oak, plum, poplar, rhododendron and willow.
Peach leaf curl can only be prevented by spraying the trees in the fall after the leaves have fallen and again in the spring before the buds begin to swell and before they open. There is no "cure" for peach leaf curl once the buds on the trees have opened.
The only really effective spray is a copper-based fungicide. Lilly-Miller Microcop, with Sta-Stuk, is one product readily available. Microcop is the fungicide, Sta-Stuk is an adjuvant that makes the spray cling to the surface of the bare shoots.
To understand why there is no cure you have to understand how the disease organism infects the tree. The disease is caused by a fungus, Taphrina deformans, which attacks both peaches and nectarines. Infection of the tree occurs as soon as the buds begin to swell in the spring. Fungal spores are carried by wind or splashed from the bark to the buds by rains. Later, the infected leaves develop a grayish-white covering of spores that are then blown onto the bark and lie there waiting until next spring to invade the host plant, your peach tree. Once inside the infected leaf there is no way to kill the fungus.
The infestation can be severe enough to cause leaves to drop. Fruiting may be poor and those that develop may be covered with raised, irregular or wrinkled lesions. Infected trees are greatly weakened by the premature loss of leaves, as these are the food producing parts of the tree. The disease is worse when we have a wet spring.
Many trees over the years will overcome a severe infestation when a spraying program was initiated in the fall following an outbreak and then spraying before bud break in the spring. These trees rebound and produce fine crops in the summer.
9. Zucchini has lots of flowers, but no squash
Few or no fruits are produced on squash, pumpkins or cucumbers because of poor pollination. There are two kinds of flowers produced, male and female. The male flower is the first to bloom and the female flowers shortly thereafter. Sometimes they get out of synchronization and the pollen from the male flower never gets to the female flower.
When the male flower's pollen never reaches the female flower the female flower produces a swelling resembling a small fruit. As it is not pollinated the fruit does not grow to maturity and it dies.
It is usually not too late to have a crop of zucchini. You'll just have to be patient and wait for the proper pollination to occur.
10. Tomato plants leaves withering and dying
Tomatoes are attacked by soil-inhabiting fungi, either Verticillium wilt or Fusarium blight. These enter the tomato plant through the roots. They cause the leaves to dry, wilt, curl up and/or turn yellow and die, usually starting from the bottom and working their way up. These fungi are persistent in the soil, lasting for years and there is no way to kill or control the disease. Do not replant tomatoes in the same place in your yard. Destroy severely infested plants by tossing them in the garbage. Do not compost them. Usually any fruit that is produced by infected plants is small, deformed and tasteless.
When purchasing tomato plants make sure that the tag on the plant states that the variety is "VFN Resistant". VF stands for Verticillium or Fusarium Wilt resistance, the diseases that are attacking your tomato, the N stands for nematodes.
Leaves turning yellow and falling off can also be caused by the russet mite, a microscopic insect. Control the mites by spraying the plant with wettable sulfur, making sure that the undersides of the leaves are thoroughly covered.