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Types of Nursery diseases
Noninfectious Disease
Infectious Disease
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.
Fungus or Infectious Diseases
✓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.
Common types of damping-off:
Pre emergence
Post emergence
– 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
– 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
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%
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.
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
ungerminated and newly germinated seeds are infected and rotten before appearing above the ground.
Pre-emergence damping-off –
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