saskafarian
05-12-2006, 06:47 AM
Cannabis is afflicted by over 100 diseases caused by fungi, bacteria, viruses, nematodes, plants, and abiotic challenges (genetics, nutrients, stress and pollutants) but only about a dozen cause serious problems.
With the exception of striping virus, the most common diseases of hemp (i.e., Hypochnus solani and Pythium sp.) can be controlled by treatment of the seeds with Clorox (25% sodium hypochlorite) diluted with an equal volume of water and adjusted to pH 9. Soak the seeds for 10 minutes, then rinse thoroughly with fresh water. (24, 25)
Cannabis' resistance to diseases and pests can be strengthened by the judicious use of methyl salicylate, which is a major component of wintergreen oil. Aspirin (acetyl salicylic acid) also is effective. Dissolve two tablets in a quart of water and apply the solution as a foliar spray.
Fungi & Bacteria --- More than 90 species of fungi attack Cannabis. Seedlings can be infected by damping-off fungi; the flowers and leaves are vulnerable to grey mold, yellow, brown and olive leaf spots, mildew and brown blight, pink rot, and viruses. The stalk and stems are susceptible to attack by grey mold, hemp canker, Fusarium oxysporum canker and wilt, stem nema, charcoal rot, anthracnose, and striatura ulcerosa. The roots can be diseased by Fusarium, rhizoc, sclerotium root rot, and nematodes. Alternaria alternata Keissler, a common fungal pathogen of many plants, can destroy up to 45% of hempseed in a crop.
K. Roder investigated hemp diseases, and isolated 7 strains of Sphaerella cann., 13 strains of Phoma or Phyllosticta, and 13 forms of Phomopsis, Coniothyrium, Vermicularia, Fusarium, and Cylindrocarpon. None of these species can infect the roots of hemp directly, unless the roots are weak or injured.
Gray mold (Botrytis cinerea) and hemp canker (Sclerotina sclerotiorum) can severely damage a hemp crop in wet years. In temperate regions with high humidity and low temperatures, botrytis can completely destroy a hemp crop within a week. Botrytis and hemp canker can be controlled by spraying alternately with the fungicides vinchlozolin (0.5 kg/ha) and iprodion (0.5 kg/ha) at two-week intervals from June through August. Tetramethylthiuran disulfide also is effective. Van der Werf, et al., however, found from three years of field experiments that one or two applications did not increase actual stem yield. They concluded that, "although fungal diseases may severely reduce hemp yield in the Netherlands, the use of fungicides is not worthwhile". They recommended breeding cultivars less susceptible to B. cinerea in particular. Botrytis can be controlled by applications of sulfur followed by "AQ-10", a microbial product. Bentonite clay also can control botrytis; it is better to use California calcium-bentonite rather than the more common sodium variety. Potassium bicarbonate ("Kali-Green") also kills botrytis. (26)
Botrytis appears as "damping-off" (moldy germination) on seedlings; it can be prevented by aeration of the soil, by hydrogen peroxide, or by the Burgundy Formula. Dissolve 1 lb of calcium sulfate and 1 lb of washing-soda crystals in 10 gallons of water. Soak the seeds in this solution, then rinse with fresh water.
The Chestnut Formula also prevents damping-off. Mix 2 parts copper sulfate and 11 parts ammonium carbonate in a glass jar. Dissolve 1 oz in 2 gallons of water. Soak the seeds in this solution, then rinse them with fresh water.
Botrytis is a stem disease in fiber cultivars, arising as a gray-brown mycelial mat, later covered with conidia. The stem becomes chlorotic along the edge of the mat, then reduces to soft, shredded cankers; the plant often snaps at that point, or wilts above it. The mature floral bracts of female drug cultivars are most susceptible to infestation. Leaflets turn yellow, then wilt, and pistils become brown. Mycelia envelope the infloresences, which dissolve into gray-brown slime.
Infection by Botrytis is directly affected by the level of calicum in the plant; the higher the amount of Ca, the lower the incidence of Botrytis. Sprays of Ca-silicate (2,000 ppm) and Ca-formate (2,000 ppm) provide effective control of fungi and are safe alternatives to highly toxic fungicides.
Damping off is caused by other several fungi, mostly by the Protoctistan oomycetes Pythium aphanidermatum and P. ultimum. Other causative fungi include Fusarium solani, F. oxysporum, F. avenaceum, F. graminearum, and F. sulpurem, Rhizoctonia solani, and Macrophomina phaseolina.
The severity of infection by facultative parasites is affected by the levels of nitrogen and potassium; low N and high K provide resistance; high N and low K invite parasites.
Wilt is caused by Fusarium oxysporum f. sp. cannabis Nov. & Snyd. It first appears on 3-month old plants as a yellowish-green color and small dark spots on the lower leaves, which die but remain hanging. The plant may bend to the side of the stem that is affected.
In 1999, Ag/Bio Con, a Montana company, offered the world a mutant strain of Fusarium oxysporum as a mycoherbicide against cannabis --- an utterly insane promotion that has instigated lawsuits to cease and desist. Fusarium mutates very easily and spreads to other crops. It is an environmental disaster.
Verticillium wilt is caused by Verticillium(two species); Macrophomina phaseolina causes premature wilt (also known as charcoal rot).
Hemp twig blight is caused by Botryosphaeria maronii (Cav.) Charles & Jenkins. The leaves quickly wilt and droop and turn brown, but remain attached. The symptoms first appear on the tips of branches. The lower parts become bleached.
Two species of Colletotrichum cause anthracnose in cannabis.
Hemp canker, caused by Sclerotinia sclerotiorumi, is one of the most important diseases of cannabis. It appears as wet lesions on the branches of plants as they mature; the lesions become dark cankers. The pith fills with white mycelia. Black sclerotia then develop in the stem and in the pith. The plants wilt and collapse. The optimal temperature range for its growth and maturation of is 24-33o C. Sclerotinia can be controlled somewhat by proper drainage of the fields.
Yellow leaf spot is caused by two species of Septoria; brown leaf spot is caused by species of Phoma and Ascochyta; Phomopsis ganjae causes white leaf spot.
Severe leaf infections also are caused by strains of Sphaerella (stem browning), Phyllosticta, Cercospora, Microdiplodia, Macrosporium cann., and Pseudoperonospora (olive leaf spot), and Didymella arcuata. (32)
Didymella arcuata is found in association with the fungus Ascochyta cann. Lasch. The optimal temperature for the germination and growth of D. arcuata is 19-26o C. Its sporulation is promoted by light; its vegetative development is stimulated by darkness. (33)
Leaf spots caused by Cercospora cannabis Hara & Fukui are yellow-tan or brown. They are circular at first but become irregular and distinct.
Trichothecium roseum causes pink rot on cannabis drug cultivars in greenhouses.
Hemp rust (Melampsora cannabina) appears as orange patches on the leaves. It can be controlled by spraying with thiocarbamate.
Bacteriosis (stripe disease) is caused by Pseudomonas cannabina Sutic & Dows. var. italica Dows. Scattered reddish-violet spots (under 2 mm), surrounded by a pale yellow halo, appear on leaf blades, followed by rapid shedding. Small necrotic elongate cavities, filled with bacteria, appear on the stems.
Some less common but nonetheless virulent diseases of cannabis are anthracnose (Colletotrichum atramentarium) and brown blight, which is caused by species of Alternaria and Stemphylium.
Many of the bacterial and fungal diseases of cannabis and other crops can be controlled by applications of Bacillus subtilis, which is available in several commercial products (i.e, Serenade, manufactured by Agraquest).
Several bacteria that are pathogenic to humans have been found on Cannabis, including: Salmonella muenchen, Klebsiella pneumoniae, Euterobacter cloacae, E. agglomerans, Streptococcus (Group D), Thermoactinomyces candidus, T. vulgaris, Micropolyspora faeni, Aspergillus fumigatus, A. niger, A. flavus, A. tamarri, A. sulphureus, A. repens, Penicillium chrysogenum, P. italicum, Rhizopus stolonifer, Alternaria alternata, Curvularia lunata, and Histoplasmus capsulatum. Aspergillus can be killed by baking cannabis at 150o C for 15 minutes, but only about 15% is destroyed by smoking through a waterpipe. Microbial pathogens and toxins, however, are not destroyed by heating or other methods of sterilization.
Insects --- Several species of mites are injurious to stored hempseed: Tyroglyphidae (3 sp., especially T. farinae), Glycyphagidae (6 species, especially G. destructor), and predaceous Cheyletus eruditus. The maximum number of mites are found in July-August. T. farinae occurs constantly. Once introduced into storage, the mites can persist for several years. Tyrophagus can be controlled by treatment of the seed with fungitoxic preparations (i.e., Panogen and Aldogen). The mechanical damage of hempseed stimulates the breeding of mites. The miticide "Cinnamite" (cinnamaldehyde), produced by Mycogen, is very effective. (23)
Spider mites also plague hemp. Their effect is seen as minute white spots on the top of leaves. The mites appear as tiny black specks on the the underside of leaves. They can be controlled by introduction of another mite, Phytoseiulis persimilis.
The seedlings can be attacked by hemp flea beetles, cutworms and white grubs. The stalks and stems can be infested by European corn borers and hemp borers, weevils, and by modellid and longhorn grubs. The larva of the Death's Head moth (Acherontia atropos) occasionally bore into hemp stalks. Flea beetles, white root grubs, wireworms, fungus gnats, root maggots, termites and ants will attack the roots of cannabis.
The click beetle (Agriotes mancus), also known as wireworm in its juvenile form, infests the top six inches of soil and eats the roots of plants, including cannabis. Wireworm can be controlled by introduction of beneficial nematodes (Heterohabidis and Steinernema spp.).
Marijuana thrips (Oxythrips cannabensis Knechtel) is a sucking insect that is host-specific to hemp. Common thrips (Frankliniella occidentalis) eat the calyx of cannabis, causing deformation and affecting viability. Thrips can be controlled by the predators Amblysieus cucumeris, A. degenerens, and Orius tristicolor. The aphid Phorodon cannabis Pass. also is found on hemp.
The tarnished plant bug (Lygus spp.) has been found on hemp crops throughout Canada It feeds on the apical meristem, which appears malformed and stunted. Brown lesions are visible on the stem where the pest has been feeding. It can be controlled by the predatory Spined Soldier Bug (Podisus spp.).
The hemp flea beetle (Psylliode attenuata) hibernate in the soil until the temperature of the soil and air rises to 10o C (50o F). Then they emerge and feed on leaves and stems of seedlings. The pest can be controlled by planting
With the exception of striping virus, the most common diseases of hemp (i.e., Hypochnus solani and Pythium sp.) can be controlled by treatment of the seeds with Clorox (25% sodium hypochlorite) diluted with an equal volume of water and adjusted to pH 9. Soak the seeds for 10 minutes, then rinse thoroughly with fresh water. (24, 25)
Cannabis' resistance to diseases and pests can be strengthened by the judicious use of methyl salicylate, which is a major component of wintergreen oil. Aspirin (acetyl salicylic acid) also is effective. Dissolve two tablets in a quart of water and apply the solution as a foliar spray.
Fungi & Bacteria --- More than 90 species of fungi attack Cannabis. Seedlings can be infected by damping-off fungi; the flowers and leaves are vulnerable to grey mold, yellow, brown and olive leaf spots, mildew and brown blight, pink rot, and viruses. The stalk and stems are susceptible to attack by grey mold, hemp canker, Fusarium oxysporum canker and wilt, stem nema, charcoal rot, anthracnose, and striatura ulcerosa. The roots can be diseased by Fusarium, rhizoc, sclerotium root rot, and nematodes. Alternaria alternata Keissler, a common fungal pathogen of many plants, can destroy up to 45% of hempseed in a crop.
K. Roder investigated hemp diseases, and isolated 7 strains of Sphaerella cann., 13 strains of Phoma or Phyllosticta, and 13 forms of Phomopsis, Coniothyrium, Vermicularia, Fusarium, and Cylindrocarpon. None of these species can infect the roots of hemp directly, unless the roots are weak or injured.
Gray mold (Botrytis cinerea) and hemp canker (Sclerotina sclerotiorum) can severely damage a hemp crop in wet years. In temperate regions with high humidity and low temperatures, botrytis can completely destroy a hemp crop within a week. Botrytis and hemp canker can be controlled by spraying alternately with the fungicides vinchlozolin (0.5 kg/ha) and iprodion (0.5 kg/ha) at two-week intervals from June through August. Tetramethylthiuran disulfide also is effective. Van der Werf, et al., however, found from three years of field experiments that one or two applications did not increase actual stem yield. They concluded that, "although fungal diseases may severely reduce hemp yield in the Netherlands, the use of fungicides is not worthwhile". They recommended breeding cultivars less susceptible to B. cinerea in particular. Botrytis can be controlled by applications of sulfur followed by "AQ-10", a microbial product. Bentonite clay also can control botrytis; it is better to use California calcium-bentonite rather than the more common sodium variety. Potassium bicarbonate ("Kali-Green") also kills botrytis. (26)
Botrytis appears as "damping-off" (moldy germination) on seedlings; it can be prevented by aeration of the soil, by hydrogen peroxide, or by the Burgundy Formula. Dissolve 1 lb of calcium sulfate and 1 lb of washing-soda crystals in 10 gallons of water. Soak the seeds in this solution, then rinse with fresh water.
The Chestnut Formula also prevents damping-off. Mix 2 parts copper sulfate and 11 parts ammonium carbonate in a glass jar. Dissolve 1 oz in 2 gallons of water. Soak the seeds in this solution, then rinse them with fresh water.
Botrytis is a stem disease in fiber cultivars, arising as a gray-brown mycelial mat, later covered with conidia. The stem becomes chlorotic along the edge of the mat, then reduces to soft, shredded cankers; the plant often snaps at that point, or wilts above it. The mature floral bracts of female drug cultivars are most susceptible to infestation. Leaflets turn yellow, then wilt, and pistils become brown. Mycelia envelope the infloresences, which dissolve into gray-brown slime.
Infection by Botrytis is directly affected by the level of calicum in the plant; the higher the amount of Ca, the lower the incidence of Botrytis. Sprays of Ca-silicate (2,000 ppm) and Ca-formate (2,000 ppm) provide effective control of fungi and are safe alternatives to highly toxic fungicides.
Damping off is caused by other several fungi, mostly by the Protoctistan oomycetes Pythium aphanidermatum and P. ultimum. Other causative fungi include Fusarium solani, F. oxysporum, F. avenaceum, F. graminearum, and F. sulpurem, Rhizoctonia solani, and Macrophomina phaseolina.
The severity of infection by facultative parasites is affected by the levels of nitrogen and potassium; low N and high K provide resistance; high N and low K invite parasites.
Wilt is caused by Fusarium oxysporum f. sp. cannabis Nov. & Snyd. It first appears on 3-month old plants as a yellowish-green color and small dark spots on the lower leaves, which die but remain hanging. The plant may bend to the side of the stem that is affected.
In 1999, Ag/Bio Con, a Montana company, offered the world a mutant strain of Fusarium oxysporum as a mycoherbicide against cannabis --- an utterly insane promotion that has instigated lawsuits to cease and desist. Fusarium mutates very easily and spreads to other crops. It is an environmental disaster.
Verticillium wilt is caused by Verticillium(two species); Macrophomina phaseolina causes premature wilt (also known as charcoal rot).
Hemp twig blight is caused by Botryosphaeria maronii (Cav.) Charles & Jenkins. The leaves quickly wilt and droop and turn brown, but remain attached. The symptoms first appear on the tips of branches. The lower parts become bleached.
Two species of Colletotrichum cause anthracnose in cannabis.
Hemp canker, caused by Sclerotinia sclerotiorumi, is one of the most important diseases of cannabis. It appears as wet lesions on the branches of plants as they mature; the lesions become dark cankers. The pith fills with white mycelia. Black sclerotia then develop in the stem and in the pith. The plants wilt and collapse. The optimal temperature range for its growth and maturation of is 24-33o C. Sclerotinia can be controlled somewhat by proper drainage of the fields.
Yellow leaf spot is caused by two species of Septoria; brown leaf spot is caused by species of Phoma and Ascochyta; Phomopsis ganjae causes white leaf spot.
Severe leaf infections also are caused by strains of Sphaerella (stem browning), Phyllosticta, Cercospora, Microdiplodia, Macrosporium cann., and Pseudoperonospora (olive leaf spot), and Didymella arcuata. (32)
Didymella arcuata is found in association with the fungus Ascochyta cann. Lasch. The optimal temperature for the germination and growth of D. arcuata is 19-26o C. Its sporulation is promoted by light; its vegetative development is stimulated by darkness. (33)
Leaf spots caused by Cercospora cannabis Hara & Fukui are yellow-tan or brown. They are circular at first but become irregular and distinct.
Trichothecium roseum causes pink rot on cannabis drug cultivars in greenhouses.
Hemp rust (Melampsora cannabina) appears as orange patches on the leaves. It can be controlled by spraying with thiocarbamate.
Bacteriosis (stripe disease) is caused by Pseudomonas cannabina Sutic & Dows. var. italica Dows. Scattered reddish-violet spots (under 2 mm), surrounded by a pale yellow halo, appear on leaf blades, followed by rapid shedding. Small necrotic elongate cavities, filled with bacteria, appear on the stems.
Some less common but nonetheless virulent diseases of cannabis are anthracnose (Colletotrichum atramentarium) and brown blight, which is caused by species of Alternaria and Stemphylium.
Many of the bacterial and fungal diseases of cannabis and other crops can be controlled by applications of Bacillus subtilis, which is available in several commercial products (i.e, Serenade, manufactured by Agraquest).
Several bacteria that are pathogenic to humans have been found on Cannabis, including: Salmonella muenchen, Klebsiella pneumoniae, Euterobacter cloacae, E. agglomerans, Streptococcus (Group D), Thermoactinomyces candidus, T. vulgaris, Micropolyspora faeni, Aspergillus fumigatus, A. niger, A. flavus, A. tamarri, A. sulphureus, A. repens, Penicillium chrysogenum, P. italicum, Rhizopus stolonifer, Alternaria alternata, Curvularia lunata, and Histoplasmus capsulatum. Aspergillus can be killed by baking cannabis at 150o C for 15 minutes, but only about 15% is destroyed by smoking through a waterpipe. Microbial pathogens and toxins, however, are not destroyed by heating or other methods of sterilization.
Insects --- Several species of mites are injurious to stored hempseed: Tyroglyphidae (3 sp., especially T. farinae), Glycyphagidae (6 species, especially G. destructor), and predaceous Cheyletus eruditus. The maximum number of mites are found in July-August. T. farinae occurs constantly. Once introduced into storage, the mites can persist for several years. Tyrophagus can be controlled by treatment of the seed with fungitoxic preparations (i.e., Panogen and Aldogen). The mechanical damage of hempseed stimulates the breeding of mites. The miticide "Cinnamite" (cinnamaldehyde), produced by Mycogen, is very effective. (23)
Spider mites also plague hemp. Their effect is seen as minute white spots on the top of leaves. The mites appear as tiny black specks on the the underside of leaves. They can be controlled by introduction of another mite, Phytoseiulis persimilis.
The seedlings can be attacked by hemp flea beetles, cutworms and white grubs. The stalks and stems can be infested by European corn borers and hemp borers, weevils, and by modellid and longhorn grubs. The larva of the Death's Head moth (Acherontia atropos) occasionally bore into hemp stalks. Flea beetles, white root grubs, wireworms, fungus gnats, root maggots, termites and ants will attack the roots of cannabis.
The click beetle (Agriotes mancus), also known as wireworm in its juvenile form, infests the top six inches of soil and eats the roots of plants, including cannabis. Wireworm can be controlled by introduction of beneficial nematodes (Heterohabidis and Steinernema spp.).
Marijuana thrips (Oxythrips cannabensis Knechtel) is a sucking insect that is host-specific to hemp. Common thrips (Frankliniella occidentalis) eat the calyx of cannabis, causing deformation and affecting viability. Thrips can be controlled by the predators Amblysieus cucumeris, A. degenerens, and Orius tristicolor. The aphid Phorodon cannabis Pass. also is found on hemp.
The tarnished plant bug (Lygus spp.) has been found on hemp crops throughout Canada It feeds on the apical meristem, which appears malformed and stunted. Brown lesions are visible on the stem where the pest has been feeding. It can be controlled by the predatory Spined Soldier Bug (Podisus spp.).
The hemp flea beetle (Psylliode attenuata) hibernate in the soil until the temperature of the soil and air rises to 10o C (50o F). Then they emerge and feed on leaves and stems of seedlings. The pest can be controlled by planting