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30 Cards in this Set
- Front
- Back
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Types of Nursery diseases |
Noninfectious Disease Infectious Disease |
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1. Noninfectious Disease |
✓Influence of nutrients on incidence of B. pine needle blight ✓Leaves and needles of vigorous plants are less susceptible to fungus infection. ✓Fertilizers may reduce the severity of leaf and needle disease. ✓Responses observed from the relationships between nutrient in soils and tissues and the incidence of needle blight on B. pine (causal org. Cercospora pini-densiflorae) ✓Positive correlation was noticed between the incidence of needle blight and soil and tissue parameters (K, Mg and OM in soil and Ca, Fe, Mu and Zn in the tissue). ✓Negative correlation was observed on needle blight in relation to Mn content in soil and N or P content in the tissue. ✓Low and high concentration of soil and tissue parameters increase the incidence of needle blight in terms of N, P, Ca, Fe and Zn content in soil and K content in the tissues. ✓Low and high concentration of an element decreased the activity of an organism of Mg content in tissues. ✓Influence of pot size and shade ✓shade reduces death of transplanted seedlings ✓survival of dipterocarp wildlings in virgin forest was high under heavy shade ✓height growth of seedlings was influenced by variation of pot diameter. |
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Fungus or Infectious Diseases
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✓Damping-off ✓diseasemost destructive disease of nursery planting stocks with more than 30 different fungi as the causal organisms. The most common genera are Fusarium, Phytophthora, Phythium, Rhizoctonia, Botrytis, Dilodia and Cuvularia. It affects both canifer and hardwood seedlings and both seeds and seedling of all kinds of vegetables, cereals, fruits and forest trees in the nursery are also affected. |
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Common types of damping-off: |
Pre emergence Post emergence |
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– seeds may fail to germinate or if the seed germinates, the developing radicle and cotyledons are attacked by the pathogen resulting in rotten seed sand non-emergence of seedlings. |
Pre-emergence |
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– occurs on seedlings that have already emerged above the ground. The fungus attacks the succulent tissue at the seedling base and spread rapidly particularly in the roots. At this stage of infection, the basal part of the seedlings becomes thinner to wilt completely or suddenly fall over before wilting. The characteristics falling over of the seedlings is no the normal type of wilting resulting from inadequate water supply. |
Post-emergence |
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Conditions favoring damping-off |
✓Overcrowding of seedlings, too much shade, high humidity and poor air circulation favors post-emergence damping-off. ✓Cool, wet and compacted soil that increase losses from the disease. ✓High soil temperatures for certain fungi and low temperatures for others. ✓A heavy and excessively wet soil, poor drainage, highly organic soil especially organic matter. ✓Certain fertilizers such as lime, wood ashes, and manure that is not well decomposed and tend to neutralize the acid should be avoided. ✓Dense of more than 75% may favor damping-off disease. ✓Pythium damping-off increase from a minimum at 13% to a maximum at 100% |
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Conditions favoring damping-off (Continuation) |
✓Unfavorable acidity. Increasing pH showed decreasing damage by damping-off causing organisms. ✓Pregerminated seedlings under intensive nursery conditions were damaged due to damping-off causin organisms. ✓Dubious origin. Seeds from other localities are often susceptible to damping-off disease. ✓Wrong timing of sowing. It varies with the locality because of factors such as soil temperature and moisture, season of sowing and the fungus involved. ✓Excessively deep planting predisposes seedlings to soil-borne pathogens and often favors pre-emergence disease. ✓Nitrogen fertilization promotes the attack of soil-borne pathogens. |
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Nursery Diseases and their Control in the PhilippinesClassification of Damping-off by Kobayashi* |
Pre emergence damping off Top rot Damping off Root rot Foot rot |
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ungerminated and newly germinated seeds are infected and rotten before appearing above the ground. |
Pre-emergence damping-off – |
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– the basal portion of germinated seedlings are infected; they become slender and fall down on the bed. As the disease occurs collectively and diseased seedlings disappear, patches without seedlings are observed on the seedbeds. Quite often, all seedlings disappear on the seedbed due to damping-off. |
Damping-off |
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– cotyledons of germinated seeds are affected after appearing above the ground. |
Top rot |
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The roots of the seedlings are affected. Very young seedlings die just after germinated due to root rot. As they grow, some affected seedlings survive but with suppressed growth. Oftentimes, then needles become reddish or purplish. Common in pines. |
Root rot – |
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the stem of the seedling is infected two to five centimeters above the ground level. Infection is caused by pathogens in the soil around the stem. As the stem is girdled, the upper part of the seedling gradually wilts. |
Foot rot – |
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Species and Causal organisms |
Benguet pine – Phizotonia spp, Fusarium spp and Pythium spp. Moluccan sau, Bagras, Agoho, G. ipil ipil and Mahogany Rhizoctonia solani, Fusarium spp. And Pythium spp. |
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Control Measures |
Soil disinfection before Soil burning was also recommended. Seed disinfection Soil disinfection after germination Improvement of environmental conditions – |
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seedling pots should be kept under well-drained conditions. Seedlings should be treated as soon as possible when they are transplanted. |
Improvement of environmental conditions – |
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drench the places where diseases occurred with a dilute solution of Tachigaren hydroxyisoxazol, (1,000 times, 3 liters/sq.m) |
Soil disinfection after germination – |
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dress the dry seeds thoroughly with Thiuram powder (0.1 to 3%) of seed weight) |
Seed disinfection |
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Cultural methods |
✓heavy or excessively wet soil should be avoided, beds should be kept well-ventilated. ✓Nurseries should be located on well-drained sites. ✓Dense sowing of seeds should be avoided in any method used whether by broadcast or by drill sowing. ✓Acidic soil is generally unfavorable to damping-off, thus application of lime or wood ash or any substance that may neutralize the acidic soil should not be used on seedbeds. ✓Avoid overshading, shade should not be more than 30% ✓Outplant healthy seedlings only. ✓Cultivate nursery soil before using and practice clean cultivation thereafter. |
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use of antagonistic organism to control pathogenic organisms (ex. Ectomycorrhizal fungi against damping-off causing fungi |
Biological Control |
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is generally unfavorable to damping-off, thus application of lime or wood ash or any substance that may neutralize the acidic soil should not be used on seedbeds. |
Acidic soil |
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should be located on well-drained sites. |
Nurseries |
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___ should be avoided, beds should be kept well-ventilated. |
heavy or excessively wet soil |
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should be avoided in any method used whether by broadcast or by drill sowing. |
Dense sowing of seeds |
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Avoid overshading, shade should not be more than ___ |
30% |
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promotes the attack of soil-borne pathogens. |
Nitrogen fertilization |
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Monogenic , host specific |
Vertical |
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Polygenic , more durable |
Horizontal |
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reduces death of transplanted seedlings |
shade |
