Each month V.D. Kaviraj will answer questions about plants and plant problems. Kaviraj is one of the foremost pioneers of Agro-homeopathy and author of the book, Homeopathy for Farm and Garden.
Send your questions with sufficient detail and pictures when possible (JPG or GIF format) to [email protected] with the subject “Plant Doctor”.
Note: When I refer to treating plants with homeopathic remedies, this is the standard dosing procedure: Put 20 drops of a 6X potency in a litre of water. Succuss the bottle 50 times. Put this litre in the watering can, fill it up with 19 litres of tap water and stir. If the watering can is smaller, the amount of remedy put in must be proportionally smaller. Thus a 10 litre can needs only ½ litre and just 10 drops of the remedy. Apply the contents of the watering can to the roots of the plants to be treated.
Hello Dr. Kaviraj,
I have a small lemon tree in my yard that has not grown an inch since I bought it 4 years ago. It always had only 2 leaves. It may not like the soil. We live 5km from the sea and I think the place I am living was covered by sea water in ancient times.
What can I do to make it grow?
First of all, you may want to have a soil analysis done. If the soil was once under water – sea water at that – it may have a high salt-content. Depending how long ago – if over 50 years then you have little to worry, unless it is lower than sea-level. In that case, Natrum mur may do the trick in neutralising the effects of salt water. If on the other hand it is well above sea level, the best solution seems to me to give it a dose of Carbo veg. That should settle it nicely. Please keep us posted about the progress.
Since permethrin (main ingredient in tick killer for animals) comes
from the marigold, is there some way to make a salve, cream etc. from
this plant, so the animals are protected but safe from the poison.
Hi Mike, you can also make a wash with Calendula tincture, about 100 drops on a litre. Wash the dog with it on a regular basis and that should keep the ticks off. If you use a cream or salve, you will stick the hairs in the pelt together and they will lose their isolation property and possibly make your dig catch a severe cold.
Our evergreen tree seems to be losing needles. We’re in the N.E. part of the U.S. and the soil the tree is living in is somewhat acid. Do you have any thoughts o this?
Pine trees love acidic soils. They are pioneer plants on acidic soils and the pH will therefore have little to do with it. I suspect a borer under the bark or another parasite, good at hiding in cracks. After you inspect the tree – bring a magnifying glass because many pests are extremely small – you may find a pest and this can be combated with Thuja. Alternatively, it could be a fungus and then you look for spores or hyphen – small, extremely thin web-like threads that infest the places where the needles have gone. In that case, use Salicylic acid to combat it.
It pays to read this month’s article on fungal diseases (below), because it will enable you to identify many fungal diseases with greater ease.
Function of Fungi
Fungi may be beneficial or detrimental to plants, depending upon the type, and what they use as a food source. In general, fungi are composed of microscopic cells that usually grow as long threads called hyphae, pushing their way between soil particles, roots and rocks. Hyphae are usually only several thousandths of an inch thick. A single hypha can span in length of a few cells to many yards. A few fungi, such as yeast, are single cells.
Hyphae sometimes group into masses called mycelium or thick, cord-like “rhizomorphs” that look like roots. Fungal fruiting structures (mushrooms) are made of hyphal strands, spores, and some special structures like gills on which spores form. A single fungus can include many fruiting bodies scattered across an area as large as a baseball diamond.
Fungi perform important services related to water dynamics, nutrient cycling, and disease suppression. Along with bacteria, fungi are important as decomposers in the soil food web. They convert hard to digest organic material into forms that other organisms can use. Fungal hyphae physically bind soil particles together, creating stable aggregates that help increase water infiltration and soil water-holding capacity.
Soil fungi can be grouped into three general groups based on how they get their energy. Decomposersâ€”saprophytic fungiâ€”convert dead organic material into fungal biomass, carbon dioxide, and small molecules, such as organic acids. These fungi generally use complex substrates, such as the cellulose and lignin in wood, and are essential in decomposing the carbon ring structures in some pollutants. A few fungi are called “sugar fungi” because they break down the same substances as do many bacteria. Like bacteria, these fungi are important for immobilizing, or retaining, nutrients in the soil.
Mutualistsâ€”the mycorrhizal fungiâ€”colonize plant roots. In exchange for carbon from the plant, mycorrhizal fungi help make soluble phosphorus and bring soil nutrients (phosphorus, nitrogen, micronutrients, and perhaps water) to the plant. One major group of mycorrhizae, the ectomycorrhizae, grow on the surface layers of roots and are commonly associated with trees. The second major group of mycorrhizae are the endomycorrhizae, that grow within the root cells and are commonly associated with grasses, row crops, vegetables, and shrubs.
The third group of fungi, pathogens or parasites, cause reduced production or death when they colonize roots and other organisms. Root-pathogenic fungi cause major economic losses in agriculture each year.
Saprophytic fungi are commonly active around woody plant residue. Fungal hyphae have advantages over bacteria in some soil environments. Under dry conditions, fungi can bridge gaps between pockets of moisture with their tube-like hyphae, and continue to survive and grow. In arid rangeland systems, fungi pipe scarce water and nutrients to plants. Fungi are able to use nitrogen from the soil, allowing them to decompose surface residue, which is often low in nitrogen.
Soil fungi are aerobic organisms. Soil that becomes anaerobic for significant periods generally loses its fungal component. Anaerobic conditions often occur in waterlogged soil and in compacted soil.
Four separate assays that help determine the types of fungi in soil and their extent of colonization are included in the next section. They may be performed concurrently or at separate times.
Seeing Soil Fungi
Fungi participate in a wide variety of soil processes. Some are mycorrhizal, increasing the capacity of plant roots to absorb nutrients. Fungi also secrete chemical compounds that dissolve minerals, making nutrients available to other organisms. Basidiomycetes are also associated with the ability of a soil to suppress plant disease. Some actinomycetes produce compounds that act as antibiotics. Streptomycetes sp. was the original source of streptomycin. As a group, fungi also help bind together soil particles, creating the fluffy “tilth” that is very desirable for root growth.
We often think of fungi as the “mushrooms” that are visible above ground. These are only reproductive structures, analogous to apples. The actually body of a fungus is a mass of microscopic threadlike filaments called a mycelium. Each thread is called a hypha (pl. hyphae). The everyday functions of fungi, secreting enzymes and absorbing nutrients, are carried out by the hyphae. In some fungi, a segment of hypha may contain several nuclei, so a section of hypha is not quite the same as a cell. Forest soils from the PNW often contain hundreds or thousands of meters of hyphae!
In general, the more fungal hyphae found in a soil sample, the healthier the soil, and the more able to support plant life. Mycorrhizal fungi increase the capacity for plant roots to absorb nutrients, as they secrete chemical compounds that dissolve minerals, making nutrients available. Basidiomycetes are associated with the ability of a soil to suppress plant disease. Some actinomycetes produce compounds that act as antibiotics. As a group, fungi also bind together soil particles, creating fluffy “tilth” that is very desirable for root growth.
Types of Fungi Present in Soil
Wear a latex glove for this assay, so fungi from fingers don’t contaminate the sample. Place a thin slice of potato in a petri dish that has been lined with a moistened paper towel. Place a sample (a pinch) of site soil in the center of the potato slice, spreading it into a circle about 1 cm in diameter. Repeat this for 2 more potato slices, each in its own petri dish. Leave the petri dishes in a dark place, and do not disturb for 2-10 days. After that time, examine the potatoes for fungal growth. Four general appearances are listed below, along with the type of fungi most commonly associated with each:
Gray & fuzzy growth – disease-causing fungi
Solid white growth – beneficial fungi
Solid brown growth – mostly basidiomycetes
Crinkly appearance – actinomycetes
If a diverse fungal community is present in the soil, different types of fungi may be present on the three potato slices. More than one type may be present on a single slice. In an unhealthy soil, disease-causing fungi will predominate on the slices. These fungi cause the familiar symptoms of rots, blights, and damping-off (a disease in which seedlings shrivel up at the soil surface and die).
If basidiomycetes are the dominant form on the slices, the soil is likely to be very healthy. These fungi form the classic “mushroom” as a reproductive structure. They are primarily decomposers of wood.
Actinomycetes are really filamentous bacteria. They give soil its “earthy” smell. If they are present in great numbers, the soil may be considered less than healthy. Some actinomycetes can produce compounds that inhibit the growth of arbuscular mycorrhizal (AM) fungi, so a predominance of actinomycetes may reduce the growth and vigour of grasses and garden vegetables, which are colonized by AM fungi.
Such problems can be solved with a good layer of the right dung and/or some liming and the fungi become less dominant, since the soil acidity has been changed. Fungi are therefore a sign of the grade of acidity of the soil, coupled with the amount of organic matter present. If the soil is bare, one sees the gray and fuzzy growth, while in healthy soil the basidomycetes are predominant and solid white growth is often also seen, next to each other.
‘Fungi and bacteria can cause a wide variety of problems. Bacteria are minute plants, which can cause rotting, wilting, and the forming of galls.’ Bacteria do not fall under plant classification – this is simply nonsense. Bacteria are micro-organisms, which also live in our gut and the guts of all animals. Their function is digestion or decomposition and when there is enough organic matter available, they will not cause any problems in the garden. They are not even visible to the naked eye.
‘Fungi, which are usually visible to the naked eye, cause rust, spots, mildew, and damping-off. Both are generally encouraged by moisture, warmth, and humidity.
‘Control these problems with the proper fungicide or by removing and destroying diseased plants. Purchase disease-free or treated seeds and plants. Crop rotation, staking, mulching, and adequate soil drainage are also important.’
That is all they have to offer – purchase treated seed or use fungicides. We have the systemic option – treat the plant and solve the problem in the soil by adding humus, compost or manure. We do not advocate such measures because they are but a wild goose chase. Fungi are soil borne and their function is decomposition of plant litter, humus, manure or compost. If none of these are present the fungus will go for the living plant.
Hence we must make sure first that the fungus is kept busy – make nature work for you! Next we must use the appropriate remedy which will change the situation underground to the extent that the fungus no longer likes the plant and is checked in its further development; exactly what would happen in a natural setting, where other entities in the habitat cooperate with our crop to maintain an optimum balance.
Fusarium wilt – brassicaceae, Cucurbitaceae, Leguminosae, Solanaceae.
Fusarium wilt is a common problem amongst beans, peas, cabbage, sweet potatoes, tomatoes, and watermelon. The disease, which is caused by fungi, will at first cause the lower leaves to curl downwards. Latter, the leaves will yellow and the plant will become stunted. A cross section of the lower stem will reveal dark brown streaks running lengthwise.
Purchase wilt-resistant varieties of seeds and plants. Do not plant in a soil that has been infected by the disease. Crop rotation will naturally help.
Verticillium wilt – Solanaceae
Verticillium wilt is a fungus disease which affects tomatoes, potatoes, and eggplants. Initially the lower, older leaves yellow and droop. These lower leaves will fall off and the disease will spread to the rest of the plant. Often only the leaves at the tips of the plant remain. Of course this causes stunted growth of the plant and its fruit. In the case of tomatoes the fruit will remain small and undesirable.
Since this disease is soil-born, tomatoes, potatoes, and eggplants should not be planted where these same plants have been grown before. Remove any infected plants from the garden immediately and destroy them.
‘Fungi and bacteria can cause a wide variety of problems. Bacteria are minute plants, which can cause rotting, wilting, and the forming of galls.’ Bacteria do not fall under plant classification – this is simply nonsense. Bacteria are micro-organisms, which also live in our gut and the guts of all animals. Their function is digestion or decomposition and when there is enough organic matter available, they will not cause any problems in the garden.
‘Fungi, which are usually visible to the naked eye, cause rust, spots, mildew, and damping-off. Both are generally encouraged by moisture, warmth, and humidity.
‘Control these problems with the proper fungicide or by removing and destroying diseased plants. Purchase disease-free or treated seeds and plants. Crop rotation, staking, mulching, and adequate soil drainage are also important.
This list provides an international account of crop diseases. It begins with the causes of diseases. In addition to carrots and celery, diseases of parsnip, cumin, coriander, parsley, caraway, and cilantro are included.
The list describes infectious diseases caused by fungi, bacteria, nematodes, viruses, and phytoplasmas as well as noninfectious disorders caused by air pollution, allelopathy, mineral deficiencies and toxicities, pesticide-related injury, and many others. The description of each disease includes symptoms, causal organism or agent, disease cycle and epidemiology, control, and selected references. Control measures stress homoeopathic principles and cultural practices that apply to most growing areas.
This approach is ideal for plant pathologists, crop production specialists, growers, diagnostic clinicians, students, regulatory agents, crop consultants, educators, researchers, extension personnel, and others interested in the diagnosis or management of diseases of crops throughout the world.
Internal black spot
This disease is one of many affecting potatoes. Prevent this problem by not overfertilizing the plant with nitrogen.
This fungus-causing disease affects potatoes, peppers, eggplants, and particularly tomatoes. It first appears as dark brown or black spots with rings similar to a “target” design. The disease first strikes the lower leaves and then may spread to the upper leaves. The infected leaves will wilt, yellow, and often die. Sometimes the problem will spread to the stems and fruit. We recommend Aconite and/or Silicea to control this fungus.
Crop rotation is important, as the disease can remain in the ground for about three years. Use seed that has been hot water treated. Treat your own seed with Thiram. Early blight is encouraged by moisture, warmth, and humidity; so provide adequate drainage and ventilation. Control outbreaks of the disease with a fungicide, such as chlorothalonil or Maneb. An organic approach would be to simply remove and destroy infected plants to prevent spread of the disease. Also, avoid working the garden after watering to reduce the chance of spreading diseases. Water early in the morning, to give the plants time to dry off.
Late blight is a fungus causing diseases which affects potatoes and tomatoes. It most often occurs in long wet periods of weather. The disease first manifests itself as dark green or black water-soaked spots. Occasionally the affected leaves will have a white powdery mildew on the underside of the leaves. Leaves will droop and appear as though they have been scalded or frost bitten. Fruit will develop rot and decay. Use of the proper fungicide is helpful, but infected plants are usually removed to prevent spread of the disease. Preplan by selecting certified, disease-free seed and plants.
Like the preceding, it girdles stems at ground level when the plants are young. On older plants, cream-coloured dots enlarge to dark brown or black-zoned patches. Spraying with Aconite or Belladonna at the beginning of the growing season will control it. It occurs largely on outdoor snaps.
This is a disease which affects carrots. Crop rotation can be helpful to inhibit spread of the disease. Also, purchasing hot-water treated seeds is recommended.
Here is another “classic” disease which causes tremendous damage, especially to azaleas. Several plant pathologists worked on it, but it was not until Dr. Cynthia Westcott discovered, in 1945, that Dithane-D-14 was a specific control, that it could be kept in check. Azalea petal blight is mentioned here because the resting stage survives on the soil under the plants. Here it can be killed by calcium cyanamide. Unfortunately, this is of little value except in protected, isolated gardens where a single plant is infected. The spores float for miles to infect blossoms, which turn a watery brown.
This disease is the bane of many plants, including some types of lilies; it often kills L. candidum (Madonna lily) bulbs in the soil. It is, however, spread above ground and comes within the scope of this soil disease discussion only because it moves down the stem and under the soil. Other lilies are less drastically affected. Spots are at first small purplish or brownish, fading to yellow. Leaf may finally collapse. Spraying with Bordeaux mixture is the old-time remedy. When tulips are infected with Botrytis Blight (tulip fire), small yellow or brown dots enlarge and cover the entire plant, flower and all. Leaves and petals look as though scorched by fire. Infected bulbs may carry the disease. Imported Dutch bulbs are reasonably clean.
Leaf spot diseases are caused by fungi and bacteria. Infected leaves have spots which appear as dead tissue. These spots can be yellow-green, tan, or black. The problem is particularly noticed on plants whose leaves are to be consumed, such as turnip greens. The spots will sometimes first appear as dark green water soaked spots. The spots are generally 1/16 to 1 inch in diameter. Remove infected leaves promptly and follow up with an application of fungicide, such as Maneb or chlorothalonil. Also, crop rotation can be a good preventative measure.
Lettuce rot is caused by the lower leaves coming in contact with the soil. The rotting of the lower leaves will often spread to the rest of the plant.
Prevent this problem by applying a layer of sand around the base of the plant. This will improve drainage and keep the leaves from laying on the moist soil which encourages rotting.
Mildew is a fungus. The term mildew includes powdery mildews, which are true mildews, and downy mildews, which are false mildews. True mildews lie on the surface of the affected plant and feeds on the plant through tiny suckers. False mildews are living on the internal fibers of a plant and appear on the surface of the plant. Mildews come in a variety of colours, but true mildews are generally white in colour and occasionally black.
Prevent mildew by planting in a sunny, well-drained area. Plenty of air flow and ventilation will also discourage the growth of mildew.
Downy mildew is not actually a true mildew at all. Unlike true mildews which grow on the surface of leaves, downy mildews originate from within the tissues of the affected plants. Downy mildew appears as yellow, white, gray, or purplish patches on mainly the underside of leaves. The patches are actually the spores of the fungi affecting the plant. Downy mildew can also be seen on stems and fruit. Lima beans, for instance, will develop a white downy mildew on the pods and eventually turn into black patches of mildew. This is a particular problem during long wet periods. Affected leaves will often not develop properly and fall off the plant.
Infected plants and diseased leaves which fall off the plant should be removed and destroyed. Crop rotation and adequate water drainage are also helpful. One control of the downy mildew is the chemical zineb. An organic solution to the problem is dusting with lime, flour, or sulphur.
Powdery mildew is a true mildew and appears as a powdery or felty white growth on the surface of affected plants. The problem most often occurs during periods of high humidity. This mildew feeds on the plant by means of tiny suckers, draining the plant of important nutrients.
Preventative measures of controlling mildew includes providing adequate ventilation and drainage. Applications of sulphur can help to control the problem on beans and peas. Benomyl, karathane, and chlorothalonil may be applied to vine crops, such as melons and squash.
Powdery mildew is the common name for the disease caused by several different fungi which produce a whitish, powdery growth on the surface of infected plants. A wide range of plants can be affected by powdery mildew, however each individual fungal species has a somewhat limited host range.
In general, powdery mildew fungi are favored by high humidity in the plant canopy (but are inhibited by water on the leaf surface) and warm temperatures. Cultural practices which increase air flow around plants, thus reducing the humidity in the plant canopy can help control powdery mildew. Additionally, protective fungicides are available for most plants, however timing of application is important in effective control.
A. Ornamental Diseases Caused By Fungi (examples):
Powdery Mildew of Rose
Powdery mildew of rose, caused by Sphaerotheca pannosa, is extremely common worldwide. The fungus attacks young, succulent foliage. The symptoms begin as slightly raised, blister-like, red areas on leaves. Eventually all infected above ground plant parts will develop a white powdery fungal growth.
S. pannosa overwinters in infected canes or buds and in fallen leaves. In spring, new shoots become infected from old mycelium from conidia (asexual spores) or from ascospores (sexual spores). Conidia and ascospores are disseminated to other susceptible hosts by air currents. The conidia and ascospores germinate and directly penetrate the plant. The disease is favored by night temperatures between 58-62°F and day temperatures between 65-78°F. The fungal spores cannot germinate in free water, but germinate readily when the relative humidity in the plant canopy is high (97-99% at night and 40-70% during the day).
Powdery mildew is managed with good sanitation practices. Prune out all infected canes, remove fallen leaves, and destroy all infected plant material. Protective fungicide sprays can be used when weather conditions favor disease development. Plants already infected with the fungus can be treated with systemic fungicides which should help to reduce the spread and activity of the fungus. Be sure to check for registered materials and read and follow the label directions very carefully. When powdery mildew is known to be a severe problem, it is best to plant tolerant varieties.
b. Other common ornamental hosts of powdery mildew fungi: Euonymus, Photinia, Lilac, Pecan, Verbena, Crepe-Myrtle, Sunflower, Catalpa, Cotoneaster, Holly, Locust, Mesquite, Mulberry, Privet, Apple, Pear, Phlox, Zinnia, and Stone Fruits.
A serious disease of narcissus: it is encouraged by nematodes that open a path for a Fusarium fungus. Buying bulbs from a reliable source is about the home gardener’s only control.
This rotting of onions is bred in moist soil. You can help to prevent this problem by planting bulbs in a well-drained soil.
The rotting of the necks of onion plants will be less likely a problem with the stronger flavoured onions than the milder ones.
This disease of potatoes is easily spread by garden tools that have come into contact with infected plants. Thoroughly clean garden tools to keep this from happening.
The fungus which causes this disease will first appear as red or reddish-brown areas on the lower stem and roots of infected plants. These discoloured areas eventually spread to the entire stem and root system. Plants infected by this disease may turn yellow, droop, or die. Stunted growth and pod development are also some of the symptoms.
Control this disease through crop rotation and by purchasing treated seed. Additional control methods for rot are as follows. Provide adequate drainage, as too much moisture encourages rot. Keep the proper balance of pH and fertilizers. Use a fungicide, such as Capan, or a soil fumigant, such as Vapam. Use a nitrogen-rich fertilizer, but be cautious. Peas produce their own nitrogen and too much nitrogen could cause the plant to produce nothing but vine. Moreover, nitrogen in excess is carcinogenic.
This rotting of horseradishes is controlled by keeping the garden area free of wild horseradishes
Crown rot or Southern stem blight is a fungus disease that attacks the plant on the stem at or just above the soil level. The problem my first be noticed as a white fungus growing at the base of the stem or on organic matter laying on the surface of the soil surrounding the plant. Eventually, sclerotia will develop in the mould. These are small seed-like bodies which are light tan to dark brown in colour. The leaves of affected plants will turn yellow and wilt. The plant, as well as surrounding plants, will die.
Crop rotation may be somewhat helpful, but removal of affected plants and the soil surrounding the plants is highly recommended. Soil removal is important, because the disease can remain in the soil for over a year. Making sure that all organic matter is plowed under will give the fungus less places to develop.
Damping-off disease is caused by fungi that live in the soil. The problem causes young seedlings to turn brown, wilt, and die. The fungi can attack the seedlings shortly before or shortly after emerging from the soil. This is a common problem when starting young plants in trays.
There are several ways to combat damping-off including the following. Purchase seed which have been treated for the disease. Either sterilize the soil or use a sterile growing media. One such fumigant is called Vapan. Vermiculite and sphagnum moss make an excellent sterile growing mixture. Also, provide adequate drainage for the seedlings as this encourages the problem. If growing the seedlings inside, keep the humidity down. High humidity is known to create a good environment for fungi. In the garden a well drained soil and crop rotation is important.
Many fungi that live in a soil on organic matter, such as saprophytes (living off dead matter), will turn parasitic when tender seedlings come in the 2-4 leaf stage.
“This is a confusing fungus because it has many forms, often called by different names in the perfect and imperfect stages. It is one of the major causes of damping-off of seedlings. Seeds may be attacked before they sprout. I have, for example, seen a row of mixed sweet peas’, in which Rhizoctonia killed off all white-seeded forms but left black-seeded varieties intact
”At other times, it kills the seedling after it has formed its first true leaves, rotting it off at the soil line.
”Best defense against Rhizoctonia is the use of a sterile growing medium, such as vermiculite, Perlite or sphagnum moss (florists often use steam-sterilized soil, but this is beyond the reach of most amateurs). Such treatment does not, however, completely avoid infection if tools and flats or pots are not sterilized or if they are set on dirty benches.
To prevent this problem from happening to your potatoes, plant the potato seed shallow in a thick bed of mulch. This will assist the plant in developing faster. Crop rotation is also a good preventative measure.
The rotting of fruit can occur through damage inflicted by insects, garden tools, or simply the fruit laying on a warm, moist soil. These conditions will give bacteria and fungi an opportunity to develop. Fruit may become discoloured, slimy, soft, and foul smelling. Over-mature fruit can also develop fruit rot.
A number of things can be done to discourage fruit rot including the following. Control pests to reduce injury to fruit and spread of diseases. Be careful when working the garden with garden tools. They can inadvertently create open wounds. Keep fruit up off of the soil by staking or mulching. Do not allow ripened fruit to remain on the vine. Crop rotation and proper drainage are also important. Control outbreaks of fungi-causing diseases with the proper fungicide. Better use Silicea as a control of fugal diseases.
Phymatotrichum Root Rot
Phymatotrichum root rot (also known as Texas root rot or cotton root rot) is caused by the soil-borne fungus Phymatotrichopsis omnivorum (PO). The fungus has an extremely wide host range affecting over 2,300 species of dicotyledonous plants (monocots are not affected, although the fungus has been found to grow and reproduce on some monocots without causing any disease). PO is limited geographically to parts of the United States (parts of Arizona, New Mexico, and Texas) and Mexico. Even within its geographical boundaries, the fungus is spotty in occurrence. The fungus is found in soils which are high in alkalinity and low in organic matter. Spread of the fungus is limited as it does not produce any viable spores, but spreads instead through root grafts between nearby plants.
Symptoms first appear during the summer when air and soil temperatures are high. The first evidence of the disease is a slight yellowing of the leaves. Quickly the leaves turn to a bronze colour and begin to wilt. Permanent wilting can occur very rapidly; as little as two weeks from the first expression of disease. Plants infected with PO die rapidly with the leaves remaining firmly attached. In some cases, the tree wilts so quickly that there is little colour change, though they become dry and brittle. A reddish lesion develops around the crown of trees killed by this fungus.
The fungus also produces signs on or near infected plants. Strands of fungal hyphae are produced on the surface of infected roots. These strands are usually visible with a good hand lens. When strands are viewed under a light microscope, cruciform (cross-shaped) hyphae unique to this fungus can be seen. Another sign is the formation of a white to tan coloured spore mat on the surface of the soil around infected plants. Spore mats develop during periods of high moisture and are not always produced in New Mexico. Spores produced in spore mats have never been germinated, and are considered to have no function in the survival or infection by this pathogen. Therefore, spore mats do not spread disease, but are merely evidence of the presence of the fungus.
This disease is very difficult to control. The fungus survives over 12 feet deep in the soil reducing the effectiveness of soil treatments, such as solarization and fumigation. The fungus can be kept inactive by altering the soil environment (reducing alkalinity and increasing organic matter). Kept in mind that the following treatment must be applied very quickly after the first sign of disease. Additionally, the treatment will need to be applied every year in order to prevent reoccurrence of the disease. This treatment is no guarantee of control and is expensive and labour intensive.
Steps to control PO
1. Heavily prune back infected trees or shrubs.
2. Loosen soil underneath the plant out to the drip line.
3. Cover ground with 2″ of composted manure.
4. Cover manure with ammonium sulphate (1 lb to 10 sq. ft.).
5. Cover ammonium sulphate with soil sulphur (l lb to 10 sq. ft.).
6. Soak area with water till water penetrates the soil to a depth of 3-4 ft.
7. Also treat any adjacent susceptible trees or shrubs even if there are no symptoms.
Avoiding areas known to be infested with the pathogen is the best control measure.
Again, so far the ‘experts’. With the homoeopathic remedies the entire thing is part of the whole and if we imitate the whole in a sufficient manner, we can keep such fungal diseases at bay. The solution may be in a remedy from the elemental group, or the companion plants, a remedy from the weed department could even be the solution to a fungal entity. It may also be a remedy that is not associated with the plant community we try to imitate. Belladonna likes to grow solitary on garbage heaps, but is an excellent remedy against rust. The remedies above mentioned by the experts can of course all be used in potency, without such labour intensive programs as to alter the soil’s pH.
This is a disease of tomato plants. Cultivating the soil will help.
This disease of cabbage is controlled by purchasing disease resistant varieties.
Rust fungi produces spores which appears as reddish-orange spots on the leaves of affected plants. These areas of orange are easily rubbed off when brushed. They can often cause great damage to some crops.
Control the disease by applying a fungicide, such as chlorothalonil or Zineb. An organic approach to the problem is dusting the leaves with lime. The best protection is the use of Belladonna and Aconite.
Caused by a Phytophthera organism, it girdles the stem at ground level, after which the plant wilts and dies. Rust can be controlled in greenhouse soils only by steam sterilization of the soil. Outdoors it is not too common, which is fortunate, for there is no practical control. The classic snapdragon rust does not invade the soil; it is best controlled by growing rust-resistant varieties.
Asparagus rust appears as reddish or brownish spots on the stems and leaves of Asparagus. The spots release a cloud of spores when brushed or rubbed. The disease will certainly cause poor quality shoots and often will kill the plant. The problem usually occurs in damp areas, because the spores need moisture to germinate. Plant resistant varieties, such as Mary Washington, in a well drained area to prevent the problem. Control the disease with applications of a fungicide, such as Zineb or chlorothalonil.
This disease occurs as wart-like growths on the foliage and fruit of infected plants. On the tubers of potato plants, the scab can appear as either indented or raised areas of growth.
Naturally, crop rotation can help in the control of this fungus disease. Keep the pH level low. Too much alkalinity will only encourage the growth of scab. For organic gardeners this means not to use wood ashes where scab has been a problem. Sulphur is said to be an effective control also.
Scurf, also known as soil rot or soil stain, is a disease afflicting sweet potatoes. The fungus, which can remain in the soil for several years, causes brown or brownish-black spots on the tubers. The disease causes the harvested potatoes to shrink in storage. This is particularly a problem in heavy soils.
Control scurf by planting seed potatoes which are certified disease-free. If heavy soil is a problem, adding sand to the soil will benefit soil texture. Also, keeping the soil pH below 5.5 is recommended.
Septoria leaf spot
Septoria leaf spot is a fungus disease which affects tomato plants mainly in the eastern and mid western states. The disease occurs during very wet periods. The fungus appears as water- soaked spots on the lower, older leaves. These circular spots, usually no more than 1/8 inch in size, eventually turn gray with dark edges. As the disease progresses it will spread to the upper foliage of the plant. All but the topmost leaves may fall off. Even if this does not kill the plant, the lack of foliage may cause the fruit to get sunscald or develop improperly. Advanced stages of the diseases may reveal tiny dark dots in the gray spots which are spores of the fungus.
Control the problem by crop rotation, deep cultivation, and weeding of the garden area. Weeds belonging to the nightshade family should especially be destroyed. The best control is to use Ocymum basilicum or plant some basil in the vicinity.
This disease is the most common disease afflicting lima beans. The fungus first appears as reddish blotches on the pods of the bean. These blotches may completely cover the pods and cause the pods to drop off of the plant. Advanced stages of the disease will turn the reddish blotches to gray or brown. Red streaks in the veins of the underside of the leaves may appear, as well as reddish spots.
Control this disease by purchasing western grown seed or seed that has been hot-water treated. Crop rotation is very important also. Do not save seed affected by this problem, as the disease can be carried by the seed. Try not to work in the garden when it is wet. This is another way in which diseases are spread.
Yeast spots are recognized as grayish brown spots on the seed of lima beans. The yeast fungus enters the bean pods by puncture wounds made by stink bugs.
Control the disease by controlling the pest.
Corn smut is a fungus that creates massive numbers of black spores. Left unchecked the problem can wipe out an entire corn crop. It appears as a boil-like area on various parts of the corn plant including the tassels, stalks, and ears. The boils are usually greenish-white in colour. These will eventually burst, releasing numerous spores. The plants will become stunted and disfigured. The disease overwinters not only in the soil and on old infected corn stalks, but also on other grasses. Smut is a dangerous fungus and infected grains must be destroyed. Further on in this book, we have an extensive description of the dangers of smut.
Crop rotation can be helpful. Remove any boils before they burst and spread the disease. Infected plants should be removed and burned. Never use old infected stalks in your compost, as the disease can remain active for several years.
We see from these examples that the agronomist’s ideas are based on incomplete information. We do not only advocate avoidance of chemical fertilisers, but their replacement with proper compost or a bio-dynamic preparation such as B-500. We do not advocate the use of chemical sprays, no matter their other ‘advantages’, except perhaps in a homoeopathic potency, suitable to the case at hand.
The consideration that chemical fertilisers impoverish the soil is borne out by the facts. Poor soil also contains fungi, which really belong in the soil to break down organic matter. When these are not fed their normal diet, they will attack the living plants. Nowhere in nature do we find entire populations attacked by fungi, except when man has interfered.
Dieback in West Australia and elsewhere is the result of removing so many trees that the fungus has not enough to eat and will attack the remaining stands of trees. These stands are too small to maintain themselves and succumb under the onslaught of many fungi, which in the past had enormous amounts of dead plant material to feed on. Robbed of their usual food source, they will need to feed on the living trees, simply to guarantee their own survival.
That the solution lies in planting as many trees as possible, seems to the orthodox the opposite of what needs to be done. Their argument is that the fungus must be killed first and not fed more, lest it multiplies too rapidly. However, sufficient trees will produce sufficient debris and the fungus will be happily leaving the trees alone. When fed sufficiently, why would it go elsewhere?
Attacking living plants is more difficult than to eat their debris. Plants have their own defense mechanism, of which salicylic acid is but one component. Hence the solution is to fool nature into believing that everything is following the lines of proper spacing and mixed cultivars, giving the impression that no monoculture exists in that place.
Fungi are the largest group of plant pathogens. They can be thought of as plants which lack chlorophyll; but they are not plants, they are organisms in their own kingdom. Fungi obtain food from other living organisms or from decaying organic matter. They produce microscopic spores which can be compared to seeds of higher plants. The spores develop into threads (hyphae) which grow and branch into mycelium or other specialized structures (fruiting bodies).
Fungi enter plants through wounds, natural openings or by direct penetration through the surface of the plant. The fungal mycelium grows through the plant and eventually produces more spores. These spores can then spread the disease to other susceptible plants. Some fungi have complicated life cycles which require more than one type of spore and/or more than one type of host plant to complete the life cycle.
Fungi are disseminated (spread) by airborne spores (wind currents), soil, water (move in irrigation water or rain splashes), seed, or by vectors. Vectors are agents that transmit diseases from one plant to another. Examples of vectors are: man, other animals, insects, tools, other microorganisms (fungi, nematodes, etc.), etc.