Investigate the response of a named Australian plant to a named pathogen
Investigate the response of a named Australian plant to a named pathogen through practical and/or secondary-sourced investigation, for example:
- Fungal pathogens
- Viral pathogens
Phytophthora dieback
- Causative Pathogen:
- Phytophthora cinnamomi
- Host Range:
- Food crop: Avocado, pineapple
- Other woody/ornamental trees: Fraser firs, shortleaf pines, loblolly pines, azaleas, camellia, boxwood
- Symptoms:
- Rot of fine feeder roots
- Root cankers in some species, leading to dieback and death of host plants.
- Wilt, stem cankers (with sudden death of tree)
- Decline in yield
- Decreased fruit size
- Gum exudation
- Collar rot (if infected through grafts near soil level)
- Control:
- Cultural control:
- Alleviation of high soil moisture levels and improving aeration by increasing drainage, and attention to mineral nutrition.
- The use of mulches rich in cellulose will often reduce populations of P. cinnamomi.
- Chitosan also inhibits fungal growth of P. cinnamomi. Gypsum amended soil reduced root rot of avocado seedlings. In hydroponic conditions, increased copper, sand filtration and reduced oxygen significantly reduced disease. Soil solarization, in isolation and with cover crops, significantly reduced P. cinnamomi populations in avocado orchards and sunlight exposure reduced heart rot of pineapple.
- Biological control:
- There are numerous microorganisms which inhibit P. cinnamomi via parasitism, antibiosis and competition. Although none of these microorganisms has yet provided economical control, there is increasing evidence that these organisms play an important role in the natural suppression of P. cinnamomi in certain soils.
- Bioenhanced mulches and repeated applications of the bacterium Pseudomonas putida suppressed P. cinnamomi infection on avocado roots.
- Earthworms were shown to transport biocontrol agents in potted soil which helped to alleviate avocado root rot.
- In vitro inhibition of P. cinnamomi was obtained with Byssochlamys nivea isolated from saline mud in western Australia.
- Chemical Control:
- Fumigating and certain phosphonate fungistats. A tactic that may be effective, dependent on spores, would be fumigating before planting. However, this would not be effective for eradicating chlamydospores since they are present deeper down in the soil, so fumigation may not reach them.
- Some experts do not recommend fumigation as P. cinnamomi is often able to re-invade fumigated soil and could cause worse damage since the competing microorganisms in the soil microbial community may be reduced by fumigation.
- Phosphonate fungistats can improve the ability of a tree to tolerate, resist, or recover from disease by Phytophthora cinnamomi.
- Phosphite has been used to limit the disease with some success and has been recognized as a major strategy for disease prevention. Phosphite is administered to plants through direct foliage sprays, aerial application by aircraft or through direct injection.
- Cultural control:
- Prevention:
- SPS measures
- Hygienic precautions can be applied to exclude P. cinnamomi from a place of production. Unsterilized soil or growing medium, or farm machinery, should not be brought in.
- Introduced plants should be kept apart until their phytosanitary status has been checked and all propagation should be done from healthy plants or seed.
- Cultural measures should be taken to reduce the risk of spread in case of introduction.
- If land does become infested, incidence of P. cinnamomi can be reduced, if not necessarily eliminated, by leaving the land under non-susceptible crops for at least 4 years, and by applying various control measures.
- Public awareness
- A standard dieback signage system is used in Western Australia to indicate the dieback status of an area to help prevent the spread of propagules by humans.
- SPS measures
Turnip Mosaic Virus
- Causative pathogen:
- Turnip Mosaic Virus (TuMV), a potyvirus belonging to the family Potyviridae.
- Host Range:
- Almost all Brassica species and other plants including:
- B. oleracea
- B. campestris
- B. juncea
- B. pekinensis
- Latuca sativa
- Nasturtium officinale
- Raphanus sativus
- Almost all Brassica species and other plants including:
- Symptoms:
- Chlorotic spots on inoculated leaves
- Mottling followed by systemic vein clearing
- Mosaic and/or necrosis
- Leaf distortion
- Stunting
- Management:
- Exclusion or avoidance – quarantine, growing crops in regions where the virus seldom occurs or during periods when the virus or its vector are at a low activity level and using virus-free seedling transplants.
- Reduction in virus spreading sources – controlling weeds and other virus hosts and insect vectors, destroying old crops promptly, separating new crops from maturing crops, and avoiding overlapping crops, particularly year-round cropping.
- Protection of the host plant – planting virus-resistant varieties, using barrier crops to reduce insect vector activity in the crop, using insecticides to protect plants, and using highly reflective mulches and oil sprays to deter insects.
Reference:
Extract from HSC Biology Stage 6 Syllabus. © 2017 Board of Studies NSW.
EasyBio > Infectious Disease > Responses to Pathogens > Investigate the response of a named Australian plant to a named pathogen
Investigate the response of a named Australian plant to a named pathogen through practical and/or secondary-sourced investigation, for example:
- fungal pathogens
- viral pathogens
Phytophthora dieback
- Causative Pathogen:
- Phytophthora cinnamomi
- Host Range:
- Food crop: Avocado, pineapple
- Other woody/ornamental trees: Fraser firs, shortleaf pines, loblolly pines, azaleas, camellia, boxwood
- Symptoms:
- Rot of fine feeder roots
- Root cankers in some species, leading to dieback and death of host plants.
- Wilt, stem cankers (with sudden death of tree)
- Decline in yield
- Decreased fruit size
- Gum exudation
- Collar rot (if infected through grafts near soil level)
- Control:
- Cultural control:
- Alleviation of high soil moisture levels and improving aeration by increasing drainage, and attention to mineral nutrition.
- The use of mulches rich in cellulose will often reduce populations of P. cinnamomi.
- Chitosan also inhibits fungal growth of P. cinnamomi. Gypsum amended soil reduced root rot of avocado seedlings. In hydroponic conditions, increased copper, sand filtration and reduced oxygen significantly reduced disease. Soil solarization, in isolation and with cover crops, significantly reduced P. cinnamomi populations in avocado orchards and sunlight exposure reduced heart rot of pineapple.
- Biological control:
- There are numerous microorganisms which inhibit P. cinnamomi via parasitism, antibiosis and competition. Although none of these microorganisms has yet provided economical control, there is increasing evidence that these organisms play an important role in the natural suppression of P. cinnamomi in certain soils.
- Bioenhanced mulches and repeated applications of the bacterium Pseudomonas putida suppressed P. cinnamomi infection on avocado roots.
- Earthworms were shown to transport biocontrol agents in potted soil which helped to alleviate avocado root rot.
- In vitro inhibition of P. cinnamomi was obtained with Byssochlamys nivea isolated from saline mud in western Australia.
- Chemical Control:
- Fumigating and certain phosphonate fungistats. A tactic that may be effective, dependent on spores, would be fumigating before planting. However, this would not be effective for eradicating chlamydospores since they are present deeper down in the soil, so fumigation may not reach them.
- Some experts do not recommend fumigation as P. cinnamomi is often able to re-invade fumigated soil and could cause worse damage since the competing microorganisms in the soil microbial community may be reduced by fumigation.
- Phosphonate fungistats can improve the ability of a tree to tolerate, resist, or recover from disease by Phytophthora cinnamomi.
- Phosphite has been used to limit the disease with some success and has been recognized as a major strategy for disease prevention. Phosphite is administered to plants through direct foliage sprays, aerial application by aircraft or through direct injection.
- Cultural control:
- Prevention:
- SPS measures
- Hygienic precautions can be applied to exclude P. cinnamomi from a place of production. Unsterilized soil or growing medium, or farm machinery, should not be brought in.
- Introduced plants should be kept apart until their phytosanitary status has been checked and all propagation should be done from healthy plants or seed.
- Cultural measures should be taken to reduce the risk of spread in case of introduction.
- If land does become infested, incidence of P. cinnamomi can be reduced, if not necessarily eliminated, by leaving the land under non-susceptible crops for at least 4 years, and by applying various control measures.
- Public awareness
- A standard dieback signage system is used in Western Australia to indicate the dieback status of an area to help prevent the spread of propagules by humans. More information can be found in Project Dieback (Natural Resource Management Western Australia, 2013).
- SPS measures
Turnip Mosaic Virus
- Causative pathogen:
- Turnip Mosaic Virus (TuMV), a potyvirus belonging to the family Potyviridae.
- Host Range:
- Almost all Brassica species and other plants including:
- B. oleracea
- B. campestris
- B. juncea
- B. pekinensis
- Latuca sativa
- Nasturtium officinale
- Raphanus sativus
- Almost all Brassica species and other plants including:
- Symptoms:
- Chlorotic spots on inoculated leaves
- Mottling followed by systemic vein clearing
- Mosaic and/or necrosis
- Leaf distortion
- Stunting
- Management:
- Exclusion or avoidance – quarantine, growing crops in regions where the virus seldom occurs or during periods when the virus or its vector are at a low activity level and using virus-free seedling transplants.
- Reduction in virus spreading sources – controlling weeds and other virus hosts and insect vectors, destroying old crops promptly, separating new crops from maturing crops, and avoiding overlapping crops, particularly year-round cropping.
- Protection of the host plant – planting virus-resistant varieties, using barrier crops to reduce insect vector activity in the crop, using insecticides to protect plants, and using highly reflective mulches and oil sprays to deter insects.
Extract from HSC Biology Stage 6 Syllabus. © 2017 Board of Studies NSW.