The Plant Doctor is in!|
Identifying the problem with a plant can be difficult and is often best done by a professional trained in symptom identification. Often what may be ailing a plant and what truly is wrong can be deceiving. Knowing the habit of a plant and the proper environment for it's healthy growth will aid you in diagnosis. We will attempt to aid you in some of the more general diagnosis for common ailing conditions and remedies.
Here is a simple list of common problems.
Identifying Diseases - click link for photo
A horticulturalist will identify the simple list first to eliminate them as possibilities. Next look at the soil. Push back a bit of the top dirt to see the top of the roots. Look for any mold or fungus. This may appear as film of white, pail green, yellow or orange. Mold will have a fibrous look. Molds can do damage to the roots. They actually feed on the plant root itself. Usually caused by water molds which are a result of water standing in air pockets in the soil. This is usually due to over watering or poor drainage. Molds can be killed with Copper Sulfate or a fungicide. An easy way is to turn or till the topsoil, tamp to eliminate air pockets and allow the area to dry out. Lack of water is instant death to mold.
Texas Root Rot , is a most damaging fungus. The plant or tree will quickly wilt without warning, and not drop it's leaves. Usually found during dry summers. Unfortunately by the time it is discovered over half of the root system is already destroyed. Seen in the Valley often on Pittosporum & Japanese boxwood shrubs. One branch will brown, and then another and another. It is best to replace the tree or plant. The good part is, all that is needed to end the condition is some compost and water. The bacteria quickly eat up the fungus. You can plant again right away without fear of infecting the new plant. Well hydrated humus with compost or mulch will never have the Rot.
Oak Root fungus is one to watch for on your trees. It is generally below the ground at the base. Just beneath the bark you will find a mat of whitish fungus. In the cool moist fall mushrooms will form at the base of the tree. If not remedied it can girdle the entire trunk and gradually choke off life support to the leaves. A little surgery is required. You must remove the soil around the outermost roots and expose all of the infection. Cut away all material that is infected and leave it exposed to the air. If the infection is not too serious you may save the patient.
Leaf Spot Fungus (red, brown, yellow or black spots) appear on the leaves. Some plants are affected and some are not. Almost all plants if in an unhealthy condition will show Leaf Spot. This is many different types of fungi. Spores that cause the disease are airborne or waterborne. Infected plants provide a good source of contagion. Pruning out infected leaves and good garden clean-up are important. Infected leaf litter lying on the ground can cause the problem. Infestation can be sprayed with Captan, Benomyl, Folpet or Maneb. Plants in a healthy condition will resist infection.
Powdery Mildew first appears as gray-white patches on plant tissue. It quickly spreads powdery fungus filaments. The powder is spores. You will find it commonly on roses, dahlias, mums, peas, beans and squash. Infected leaves will become crumpled and deformed. The spores of powdery mildew do not need water to germinate. Warm days, cool nights and a little humidity is all it takes. Many fungicides are labeled for powdery mildew but due to the many strains, spray and check the next day to see results. If it was not effective switch from say Benomyl to Folpet or Maneb.
Rust - a notorious plaque on roses, devastating to snapdragons but the type of rust you find on one plant won't affect another. The type on roses, won't affect snaps and vice versa. Usually in late spring, it appears as pustules on the underside of leaves. Brown, yellow and even purple the infection advances till there is a large mass of powdery spores under the leaf. The leaf eventually yellows and drops off. This fungus requires water to germinate. It takes 4 hours of wet to germinate the spore. Watering in the early morning, with the sun soon drying up the moisture from the leaves, can prevent this fungus. Spores can survive through the winter in leaf piles. Clean up fall droppings and remove them. If infected you can spray with a fungicide or dry out the garden.
Verticillium wilt invades roots and stems and prevents water and nutrients from reaching the leaves. The symptom is the wilting of one side of the plant. Cool moist soil promotes the fungus, but the condition will not be seen till the leaves are stressed by the sun. The fungus can survive in the soil for years. Eliminating it is difficult. Fumigation or solorization are required. Fumigation requires chloropicrin (tear gas). This only works on the surface soil and will not aid deep rooting trees and shrubs. Solorization requires covering the ground with plastic to elevate the temperature thereby pasteurizing the soil. If your planting is not commercial, or agricultural, you should plant a resistant variety of plant.
Identifying Insect Pest damage
Close visual inspection will often reveal the culprit, though not always. Cutworms do their damage close to the ground, under the grass or mulch. Some insects are obvious large bugs and big eaters taking big chunks out of the leaves and stems. Others are tiny and hard to see, eating the underside of leaves or even inside the leaf as with leaf miner.
Look for leaf or stem damage. Look under the leaf to find bottom eaters. Leaf miners leave squiggly lines that are visible from the top of the leaf or even on the surface of fruit.
Control of insects is either done with pesticides or organic measures. Avoid pesticides unless populations are out of control. Predator insects in the proper balance will control most other insect populations. Pesticides kill predator insects as well as the damaging pests. Organic control is to introduce predators such as lacewings, lady bugs, midges, wasps and lizards. Available standing water such as a pond, will attract these insects and encourage them to stay. There are times when organic measures will not be sufficient. Times of high rainfall and warm humid conditions can promote populations into imbalance. And of course there are some insects that do not have sufficient predators to control their numbers.
Use of a pest management program is the most common approach. This allows the use of pesticides in a controlled calculated manner. In pest management programs, you exhaust all possible organic measures. When all else fails pesticides are used at a minimum application to significantly reduce the damaging pest population. We will not discuss the organic measures of insect control in this article. Many organic measures are complicated and require specific details on nest destruction, trapping, distracting, preditor introduction etc. We will rather describe the insects that are common problems in the south. Since most insects are killed with general pesticides such as Diazinon, Dursban, or Sevin, be sure the product you use is labeled to kill the specific insect you are trying to kill. Consult with a nurseryman and decide on a good plan of control with the proper pesticide mixed in proper proportions. Many pesticides are slow to bio-degrade. Overuse contaminates ground water only to reappear down stream. Unless we are the highest on the mountain, we are down stream from someone.
1. Accept minor damage
2. Use non-chemical alternatives
3. Use Chemicals prudently
Aphids - Tiny 1/8" oval pinhead green, pink or black bug. They huddle together on new shoots buds and leaves.
Cutworms - Large hairless larvae 3/4" to 1 1/2" green, white, brown, can be striped. Nests in ground burrows. Surfaces at night or on cloudy days. Eats surface roots or new sprouts. Will climb low branches to get young leaves.
Carpenter Ants - Small 1/8" to 1/4" red and black ant. Nests in corners and pockets of wood joints or tree crevasses. Larva of the ant is a wood eater. Can core and kill trees and shrubs. Can damage wooden structures.
Earwigs - Long dark brown or black bug 3/4" to 1 1/2". Has two horned tail. Works at night eating any soft fleshy tissue, stems buds, shoots, flower petals.
Grasshoppers - Small to large 1/2" to 3". Young nymphs eat voraciously. This is when they are most susceptible to pesticides. If a heavy infestation is noticed in the spring, that is the time to begin control. After they become mature adults they are hard to control.
Leaf Cutter Ants - Large 1/4" to 1/2" red ant. Nests in self constructed tunnels in the ground. A large colony can destroy a shrub or small tree overnight. Nest must be destroyed. Digging up and burying the nest repetitively over several days. Nest can have multiple entries and cavities. Linked colonies can run for miles. The photo shows the nest.
Leaf Rollers - (Caterpillar & moth) Rolls up leaves to hide during the day and to pupate. Young caterpillar eats continuously. It finally emerges as a moth to lay clusters of eggs on leaves and seals them in waterproof cement.
Mealy Bugs - Tiny 1/16" white flat oval slow crawler. They suck the plants juices causing stunting. A black mold grows on the dew excreted by the bug. Common on house plants.
Mites - Tiny. To the naked eye mites look like specs of red, yellow or green. They are relatives to the spider and are often called spider mites. They have eight legs. Small webs will be seen on the under side of leaves.
Moths - Many varieties of moths and the caterpillar that accompany them are prevalent. Watch for crawlers. Also called army worms.
Root Weevils - More than a dozen different kinds up to 1/2" in size. Gray or black adult eats notches out of leaves. Eggs hatch into larvae that are pink or white. They burrow into the soil and eat roots.
Scale - Soft or hard body scale has a waxy shell. It attaches in a stationary manner and sucks on the plant. Eggs hatch under the shell and crawl out to find their own location. Pesticides are effective only when the young crawler in moving out from the parents shell.
Snails - Semi-circular shelled crawler from 1/8" to 1". Feeds at night or on a cloudy day. Hard to eliminate. Will always return. Controlled with bait. Hides at night. Placing a piece of plywood, elevated about an inch is an attractive hiding place. In the early morning turn over the board to discover and kill the snails.
Squash Bugs - 1/2" to 3/4 inch long. Daytime feeder. Hides at night. Placing a piece of plywood, elevated about an inch is an attractive hiding place. In the early morning turn over the board to discover and kill the squash bug.
Thrips - Nearly microscopic pest, rasps the soft leaf or flower tissue to drink the juice. In a heavy infestation the leaves or flowers fail to open, appearing twister and stuck together. Look for black fecal pellets dropped by the thrip.
Whiteflies - 1/32" to 1/16" tiny white fly found on the underside of leaf. Brushing the plant will scatter the fly in a large flurry. Progressing through four stages - egg, stationary pupae, nymphs, adult fly, it can only be killed as a nymph or adult. Pesticide control is expensive. Using a dilute soap solution every other day sickens the nymph and adult and prevents them from eating.
Rodent and other animal Damage
Rodent damage in the landscape can be frustrating in your attempt to institute a control. Some of the more common culprits are deer, birds, squirrels, moles, mice, gophers, rabbits, as well as dogs and cats.
Poisons and poison baits can kill your pets as well as pests and should be avoided unless a severe infestation is the problem, and then it should be done by a control professional. Often cage traps are the best. Avoid maiming traps such as mole gigs and snap traps. Pets and other beneficial animals will be caught and maimed as well as the pests. Cage traps can catch pets also, and the disposal or release of the rodent can be difficult and should be done by a professional. Detering the pest is the best control.
1. Accept minor damage.
2. Avoid poisons and poison baits.
3. Employ a professional pest manager.
Cats can be an excellent deterrent to birds, squirrels, moles, mice, gophers, and rabbits. Cats will dig in beds to bury feces, they will claw and scratch trees to manicure their claws, and they will lay in soft cool flower beds crushing the tender plants. A large cedar post with bark is an attraction to cats and one that they will seek out. Female cats are the most home bound and are the best hunters. Male cats wander and are prone to spraying in their area as a marker. More than one cat is usually required to control an area of a quarter acre. Maintaining the cats is also an involvement. Neutered cats are poor hunters, and maintaining the health and population of the cats is something that must be considered.
Dogs are a good deterrent to birds, squirrels, moles, gophers and rabbits and some species catch mice. Dogs and cats when raised together are good companions. Dogs in general will not kill deer, but will chase them away preventing them from eating your shrubs. Dogs will dig in beds chasing bugs and grubs and to expose the cool earth. They will then lay and sprawl in the area. They will sample most plants to investigate the flavor. They will urinate anywhere.
While looking for all the possible pests and diseases that can ail a plant or tree, the primary concern should be soil fertility. Healthy plants and trees can fight many of the problems they face by being in a good growing condition. A yellowing condition is often identified as iron deficiency (chlorosis) when in fact the pH (acidity or alkalinity) of the soil is out of balance preventing the elemental nutrients from being absorbed by the roots. Mulch and bacteria do much to neutralize pH. Plants and trees often tolerate a soil that is a little too acid but rarely tolerate even moderate alkalinity. As is well noted, there are many fertilizers that are labeled -"For Acid loving Plants"-, you will not see a label that says -"For Alkaline loving plants"-.
A neutral soil which has a pH of 7.0 will not harm growth. Well hydrated soils that are unfertilized will often show a neutral pH. Yet the complaint is that the garden does not grow well. The inclination is to fertilize by adding nitrogen and in fact the growth improves but, quickly stops and yellow returns. A correct diagnosis of the condition is not lack of nitrogen but rather no acidity. Especially in a soil that naturally tends to be alkaline, as in Valley soils, it is most difficult to keep the soil acid.
Solutions to the acid problem are most economically handled by adding phosphorus and sulfur. Small amounts of nitrogen rather than large will prevent the plant from growing fast and flaccid. The phosphorus in the form of phosphoric acid immediately swings the pH to the acid range while the sulfur continues in a slow conversion to maintain the acid pH. in the acid range. Care should be taken to apply the proper amount as labeled on the product. Measuring the pH of the soil with a simple pH test kit will verify the desired level has been attained.
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