deck_16772353 Flashcards
(45 cards)
Question
Answer
Powdery mildew
Oidium citri (fungus)
Apple scab
Venturia inaequalis (fungus)
Chilli blight
Phytophthora capsici Fungi
Early blight
*Alternaria solani *Fungus
Gray leaf spot (GLS)
Cercospora zeae-maydis (FUNGI)
Crop: Maize
named as Chaskarpa for genotype ICAV305 (Entry No. 38) and Shafangma Ashom for genotype S03TLYQ AB05 (Entry No. 35
Yangtsepa, Khangma Ashom 1 and Khangma Ashom 2.
Late blight
Phytophthora infestans
Rice blast
Pyricularia oryzae (FUNGUS)
Blast can affect leaf blades, stem nodes, panicle and grains. Leaf blast attacks especially between the seedling stage and tillering stage. Early leaf lesions are rounded, white to grey-green with darker green borders. Older lesions become spindle-shaped with grey centre and brown margin. At heading stage blast again increases attacking nodes and panicles. Infected nodes start rotting and eventually the culm can break at the node. Nodal blast can also result in barren panicles (white heads). In early Neck Blast, lesions at the neck appear greyish-green and later turn black. Infected necks can rot and break. Early Neck Blast leads to chaffy grains while late Neck Blast gives partly filled grains with kernels that are chalky, brittle and often useless
(Tricyclazole),.
- Adopt cultural practices to reduce blast occurrence in all stages by:
a. Using disease-free seed or fungicide-treated seeds for prevention of seedling b
b. Avoiding high-density planting
c. Planting within recommended planting period
d. Apply nitrogen fertilizer in splits as nitrogen fertilizer promotes excessive vegetative growth leading to high humidity that favors disease development
Rice sheath blight
Thanatephorus cucumeris (or Rhizoctonia solani)
This fungus can kill rice plants, or result in greatly reduced yields. Patches of dying rice can be very noticeable. However, the disease normally does not spread fast, and at present it is not a cause for concern.
Turcicum leaf blight (TLB)
Exserohilum turcicum
Maize
This was the most important disease of maize, causing significant yield losses. However, the release of tolerant varieties means that it is now relatively easily managed.
Chaskarpa
Shafangma Ashom
Khangma Ashom 2.
Yangtsepa, Khangma Ashom 1
Huanglongbing (HLB)
Candidatus Liberibacter asiaticus
What is Huanglongbing (HLB)?
Devastating citrus disease globally; No known cure; Entered Bhutan in the 1960s; Major threat to citrus production.
Why is Huanglongbing (HLB) a serious problem?
Reduces yields; Poor fruit quality; Premature tree death; Increases production costs.
Where is HLB a problem in Bhutan?
Present in almost all citrus-growing Dzongkhags; High incidence below 1200 masl; Detected in mandarins above 1200 masl.
What are the symptoms of HLB in citrus trees?
Yellow shoots among green shoots; Blotchy mottle on leaves; Shoot dieback across whole tree; Mottled, yellow, leathery leaves; Corky veins; Small, upright leaves; Zinc deficiency symptoms; Colour inversion in fruits; Lop-sided fruit with aborted seeds.
What problems can HLB symptoms be confused with?
Phytophthora root/trunk rot; Trunk borer; Powdery mildew; Zinc deficiency (symmetrical chlorosis vs blotchy mottle).
What causes HLB in Bhutan?
Candidatus Liberibacter asiaticus, a phloem-limited bacterium; Spread by Asiatic citrus psyllid; Symptoms appear in 1-3 years.
How is HLB transmitted?
Natural transmission via Asiatic citrus psyllid; Spread by grafting with diseased budwood; Not seed transmitted.
When can HLB damage be expected?
Areas with Asiatic citrus psyllid below 1200 masl; Rate of spread increases with psyllid density.
What plants can host HLB?
Several citrus species and hybrids; Non-citrus hosts: periwinkle/vinca, dodder (Cuscuta spp.).
How is HLB managed in citrus orchards below 1200 masl?
Progressive removal of infected trees; Replant with pathogen and psyllid-free materials; Stump treatment with glyphosate; Area-wide vector management; Remove alternative hosts (e.g., curry leaf, Murraya spp.).
How is HLB managed in orchards above 1200 masl?
Use varieties suited to high altitudes (1200-1700 masl); Strict quarantine measures; Regularly inspect and rogue out diseased plants.
Is there any chemical management for HLB?
No chemicals to control HLB; Insecticides used to suppress Asiatic citrus psyllids below 1200 masl.
What non-chemical management strategies are used?
National quarantine: Use pathogen-free nursery stock; Avoid collecting wild germplasm; Destroy HLB-affected stock; Farmers should not share se
