棉花病害
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CHAPTER FIVE: COTTON DISEASE
§5-1 Seedling Diseases
1.SYMPTOM
Seedling diseases include the decay of seeds in the soil, death of seedlings before they emerge from the soil (preemergent damping off), death of seedlings after they emerge from the soil (post-emergent damping off) and lesions on the roots and lower stems of young plants.
DISEASE CYCLE
Seedling diseases are more common under cool (temperatures below 65°F,18°C), wet conditions, but they may occur under any conditions that retard（延迟、阻碍） germination and early seedling growth.
The most obvious results of seedling disease include skips in the planting row caused by seed rot or death of seedlings.
SYMPTOM
Infected seedlings may be stunted and yellow. Dark, necrotic lesions on the stem may occur on one side of the stem, or as “wirestem” if they encircle the entire stem.
小结
发生概况：分布？ 危害？ 病害识别：为害部位？发病时期？症状特点？
病原：Rhizoctonia solani Pythium spp. Fusarium spp.
病害发生发展规律：越冬、传播、入侵、发病及其 影响因素(气象、棉种质量、栽培措施、棉花品种、 栽培管理)?
综合防治：精选棉种；种子处理；农业防治；化学 防治
disease called black root rot, is more common in other areas of the Cotton Belt, but it has recently been identified in Louisiana.
DISEASE CYCLE
Exact identification of the causal agent often requires isolation and laboratory identification. Except for T. basicola, these fungi are common in most cotton fields.
Symptoms caused by Verticillium generally appear after first flower. Symptoms on younger plants may be caued by Fusarium.
SYMPROMS
Young plants infected with Verticillium wilt show yellow leaves and stunting, and often die.wk.baidu.com
CONTROL
Virtually all cottonseed that is purchased in Louisiana is commercially treated with a combination of fungicides to control seedling diseases.
Rhizoctonia solani Pythium spp. Fusarium spp. are the primary organisms associated with seedling
disease in Louisiana. Thielaviopsis basicola, which causes a seedling
SYMPTOM
Black root rot causes the outer layer of the root to be black, but the inner tissue remains white.
Root and stem lesions that result in postemergent damping off are visible as dead, shriveled seedling in the planting row. Infected seedlings may survive, but are less vigorous, prone to（趋于） drought stress and may produce lower yields.
Avoid compacted and crusted soils. Plant at the proper depth based on soil and moisture conditions and on raised seedbeds that adequately drain water.
Hopper-box materials are generally not as effective as in-furrow fungicides. These fungicides often contain more than one active ingredient to control both Rhizoctinia and Pythium.
In addition, infurrow or hopper-box fungicides may be applied at planting. These materials are recommended in situations where seedling diseases are likely to occur.
3.CONTROL
Management starts with the planting of high quality seed treated with fungicides.
Delaying planting until soils are 65°F or higher and favorable weather is forecast after planting will reduce the incidence of seedling diseases.
The composition of fungi involved in the seedling disease complex are affected by soil temperature and moisture. Rhizoctonia solani and Fusarium spp. are more common under higher (75-90°F, 24-32°C) temperatures. Pythium spp. and T. basicola are more common in cool (59-68°F, 15-20°C), wet conditions.
The application of in-furrow or hopper-box fungicides is used to supplement seed treatment fungicides and is recommended in situations where seedling diseases are expected.
Nonlethal root and lower stem injury contribute to losses by reducing seedling growth and delaying plant development.
2.DISEASE CYCLE
Seedling diseases are caused by a complex of fungi acting either independently or together.
On some seedlings, the tap root（直根、主根） may be killed, causing a condition referred to as “nub-root” that results in a proliferation（增殖） of secondary roots above the point where the tap root is killed .
CONTROL
Apply herbicides and fertilizers properly, and control early season insects and nematodes.
All of these practices will encourage rapid germination and seedling growth and allow the seedlings to escape infection.
Poor seed quality, soil compaction（板结）, herbicide injury and early season insect and nematode feeding all retard early season growth and increase seedling diseases.
SYMPROMS
Often a single branch shows symptoms in the early stages of disease.
§5-2 Cotton Verticillium Wilt
1.SYMPROMS
Leaves wilt and show interveinal yellowing before becoming necrotic. Light to dark brown vascular discoloration is prominent in the stem and branches. Defoliation and death of plants may occur.
Older plants exhibit a chlorotic mottling on the leaf margins and between the major veins.
Plants attacked during later stages of growth display a mottling on the lower leaves first, later progressing toward the top of the plant as the season progresses.
SYMPTOM
Severe stand losses can result in yield losses directly or in losses imposed by replanting and delay in crop development.
Minor stand losses reduce the uniformity of the stand and result in problems associated with crop development, weeds and insect management.
§5-1 Seedling Diseases
1.SYMPTOM
Seedling diseases include the decay of seeds in the soil, death of seedlings before they emerge from the soil (preemergent damping off), death of seedlings after they emerge from the soil (post-emergent damping off) and lesions on the roots and lower stems of young plants.
DISEASE CYCLE
Seedling diseases are more common under cool (temperatures below 65°F,18°C), wet conditions, but they may occur under any conditions that retard（延迟、阻碍） germination and early seedling growth.
The most obvious results of seedling disease include skips in the planting row caused by seed rot or death of seedlings.
SYMPTOM
Infected seedlings may be stunted and yellow. Dark, necrotic lesions on the stem may occur on one side of the stem, or as “wirestem” if they encircle the entire stem.
小结
发生概况：分布？ 危害？ 病害识别：为害部位？发病时期？症状特点？
病原：Rhizoctonia solani Pythium spp. Fusarium spp.
病害发生发展规律：越冬、传播、入侵、发病及其 影响因素(气象、棉种质量、栽培措施、棉花品种、 栽培管理)?
综合防治：精选棉种；种子处理；农业防治；化学 防治
disease called black root rot, is more common in other areas of the Cotton Belt, but it has recently been identified in Louisiana.
DISEASE CYCLE
Exact identification of the causal agent often requires isolation and laboratory identification. Except for T. basicola, these fungi are common in most cotton fields.
Symptoms caused by Verticillium generally appear after first flower. Symptoms on younger plants may be caued by Fusarium.
SYMPROMS
Young plants infected with Verticillium wilt show yellow leaves and stunting, and often die.wk.baidu.com
CONTROL
Virtually all cottonseed that is purchased in Louisiana is commercially treated with a combination of fungicides to control seedling diseases.
Rhizoctonia solani Pythium spp. Fusarium spp. are the primary organisms associated with seedling
disease in Louisiana. Thielaviopsis basicola, which causes a seedling
SYMPTOM
Black root rot causes the outer layer of the root to be black, but the inner tissue remains white.
Root and stem lesions that result in postemergent damping off are visible as dead, shriveled seedling in the planting row. Infected seedlings may survive, but are less vigorous, prone to（趋于） drought stress and may produce lower yields.
Avoid compacted and crusted soils. Plant at the proper depth based on soil and moisture conditions and on raised seedbeds that adequately drain water.
Hopper-box materials are generally not as effective as in-furrow fungicides. These fungicides often contain more than one active ingredient to control both Rhizoctinia and Pythium.
In addition, infurrow or hopper-box fungicides may be applied at planting. These materials are recommended in situations where seedling diseases are likely to occur.
3.CONTROL
Management starts with the planting of high quality seed treated with fungicides.
Delaying planting until soils are 65°F or higher and favorable weather is forecast after planting will reduce the incidence of seedling diseases.
The composition of fungi involved in the seedling disease complex are affected by soil temperature and moisture. Rhizoctonia solani and Fusarium spp. are more common under higher (75-90°F, 24-32°C) temperatures. Pythium spp. and T. basicola are more common in cool (59-68°F, 15-20°C), wet conditions.
The application of in-furrow or hopper-box fungicides is used to supplement seed treatment fungicides and is recommended in situations where seedling diseases are expected.
Nonlethal root and lower stem injury contribute to losses by reducing seedling growth and delaying plant development.
2.DISEASE CYCLE
Seedling diseases are caused by a complex of fungi acting either independently or together.
On some seedlings, the tap root（直根、主根） may be killed, causing a condition referred to as “nub-root” that results in a proliferation（增殖） of secondary roots above the point where the tap root is killed .
CONTROL
Apply herbicides and fertilizers properly, and control early season insects and nematodes.
All of these practices will encourage rapid germination and seedling growth and allow the seedlings to escape infection.
Poor seed quality, soil compaction（板结）, herbicide injury and early season insect and nematode feeding all retard early season growth and increase seedling diseases.
SYMPROMS
Often a single branch shows symptoms in the early stages of disease.
§5-2 Cotton Verticillium Wilt
1.SYMPROMS
Leaves wilt and show interveinal yellowing before becoming necrotic. Light to dark brown vascular discoloration is prominent in the stem and branches. Defoliation and death of plants may occur.
Older plants exhibit a chlorotic mottling on the leaf margins and between the major veins.
Plants attacked during later stages of growth display a mottling on the lower leaves first, later progressing toward the top of the plant as the season progresses.
SYMPTOM
Severe stand losses can result in yield losses directly or in losses imposed by replanting and delay in crop development.
Minor stand losses reduce the uniformity of the stand and result in problems associated with crop development, weeds and insect management.