| 1573168 |
Foliage |
Air pollution injury (weather fleck) on tobacco. May 1997 |
| 1573165 |
Foliage |
Air pollution injury (weather fleck) on tobacco. May 1997 |
| 1573166 |
Foliage |
Air pollution injury (weather fleck) on tobacco. May 1997 |
| 1573164 |
Foliage |
Air pollution injury (weather fleck) on tobacco. May 1997 |
| 1402062 |
Damage |
Soon after exposure to high levels of atmospheric pollutants, leaves may develop dark green water-soaked spots about 1/10 inch in diameter. Within hours, the spots turn dark brown, sometimes remain brown, but often turn white within 48 hours. Symptoms occur most often in low areas of fields. Plants are most sensitive when growing rapidly (plant bed and 4-6 weeks after transplanting), but symptoms may appear at any stage of growth. In the plant bed or on very sensitive varieties, spots appear over the entire leaf surface but are usually confined to the leaf tips of less sensitive varieties. Occasionally spots coalesce, or a central spot may be surrounded by smaller ones. Weather fleck is often confused with other flecks caused by chemicals, diseases, or nutritional disorders. |
| 1524179 |
Symptoms |
|
| 1402061 |
Damage |
Soon after exposure to high levels of atmospheric pollutants, leaves may develop dark green water-soaked spots about 1/10 inch in diameter. Within hours, the spots turn dark brown, sometimes remain brown, but often turn white within 48 hours. Symptoms occur most often in low areas of fields. Plants are most sensitive when growing rapidly (plant bed and 4-6 weeks after transplanting), but symptoms may appear at any stage of growth. In the plant bed or on very sensitive varieties, spots appear over the entire leaf surface but are usually confined to the leaf tips of less sensitive varieties. Occasionally spots coalesce, or a central spot may be surrounded by smaller ones. Weather fleck is often confused with other flecks caused by chemicals, diseases, or nutritional disorders. |
| 1402004 |
Damage |
on seedlings is often confused with anthracnose |
| 1440063 |
Damage |
Exposure to high levels of atmospheric pollutants such as ozone may cause tobacco leaves to develop small dark green water-soaked spots. Within 48 hours, the lesions change to a brown color then to grey or white and appear as sunken necrotic areas bordered by chlorotic tissue. Lower leaf surfaces may show no evidence of damage in the early stages. Symptoms may occur at any stage of growth, but most commonly occur during periods of rapid growth. Older leaves are more susceptible. Lesions may coalesce causing the lamina to become necrotic and fall out. |
| 1440062 |
Damage |
Exposure to high levels of atmospheric pollutants such as ozone may cause tobacco leaves to develop small dark green water-soaked spots. Within 48 hours, the lesions change to a brown color then to grey or white and appear as sunken necrotic areas bordered by chlorotic tissue. Lower leaf surfaces may show no evidence of damage in the early stages. Symptoms may occur at any stage of growth, but most commonly occur during periods of rapid growth. Older leaves are more susceptible. Lesions may coalesce causing the lamina to become necrotic and fall out. |
| 5368861 |
Symptoms |
Dark tobacco. Note "ring spot" on the leaves. This “ring spot” (also known as "star and crescent spot") which has the form of a necrotic spot encircled by alternating rings of healthy and injured tissue, with the necrotic rings being partial rings or broken lines, is described in an Agronomy Journal of 1971 as physiological in cause (not being caused by a pathogen, air pollutant, nutrient, or chemical). The book "Diseases of Tobacco" 3rd edition, puts this "ring spot" and the reference that says it is not caused by an air pollutant, under the category of weather flecking.We have sent similar samples in the past to a private laboratory for a tobacco virus screen and they have always come back with negative results. |
| 5368862 |
Symptoms |
Dark tobacco. Note "ring spot" on the leaves. This “ring spot” (also known as "star and crescent spot") which has the form of a necrotic spot encircled by alternating rings of healthy and injured tissue, with the necrotic rings being partial rings or broken lines, is described in an Agronomy Journal of 1971 as physiological in cause (not being caused by a pathogen, air pollutant, nutrient, or chemical). The book "Diseases of Tobacco" 3rd edition, puts this "ring spot" and the reference that says it is not caused by an air pollutant, under the category of weather flecking.We have sent similar samples in the past to a private laboratory for a tobacco virus screen and they have always come back with negative results. |
| 5368864 |
Symptoms |
Dark tobacco. Note "ring spot" on the leaves. This “ring spot” (also known as "star and crescent spot") which has the form of a necrotic spot encircled by alternating rings of healthy and injured tissue, with the necrotic rings being partial rings or broken lines, is described in an Agronomy Journal of 1971 as physiological in cause (not being caused by a pathogen, air pollutant, nutrient, or chemical). The book "Diseases of Tobacco" 3rd edition, puts this "ring spot" and the reference that says it is not caused by an air pollutant, under the category of weather flecking.We have sent similar samples in the past to a private laboratory for a tobacco virus screen and they have always come back with negative results. |
| 5368914 |
Symptoms |
The spots usually start as small dark green water-soaked areas. Within 48 hours, the lesions change to a brown color then to a gray or white and appear as sunken necrotic areas bordered by chlorotic tissue (on dark tobacco you usually do not see any yellow halo). The spots are often concentrated along the side of the midrib and large secondary veins but can be found anywhere on the leaf. On expanding leaves the spots appear near the tip. Lower leaf surfaces may show no evidence of damage in the early stages. Lesions may run together causing the leaf surface to become necrotic and fall out. Symptoms may occur at any growth stage, but most commonly occur during periods of rapid growth. Older leaves are more susceptible. Dark fired types usually show less injury than burley types when at the same growth stage and exposed to the same level of ozone. |
| 5368915 |
Symptoms |
The spots usually start as small dark green water-soaked areas. Within 48 hours, the lesions change to a brown color then to a gray or white and appear as sunken necrotic areas bordered by chlorotic tissue (on dark tobacco you usually do not see any yellow halo). The spots are often concentrated along the side of the midrib and large secondary veins but can be found anywhere on the leaf. On expanding leaves the spots appear near the tip. Lower leaf surfaces may show no evidence of damage in the early stages. Lesions may run together causing the leaf surface to become necrotic and fall out. Symptoms may occur at any growth stage, but most commonly occur during periods of rapid growth. Older leaves are more susceptible. Dark fired types usually show less injury than burley types when at the same growth stage and exposed to the same level of ozone. |
| 5368916 |
Symptoms |
The spots usually start as small dark green water-soaked areas. Within 48 hours, the lesions change to a brown color then to a gray or white and appear as sunken necrotic areas bordered by chlorotic tissue (on dark tobacco you usually do not see any yellow halo). The spots are often concentrated along the side of the midrib and large secondary veins but can be found anywhere on the leaf. On expanding leaves the spots appear near the tip. Lower leaf surfaces may show no evidence of damage in the early stages. Lesions may run together causing the leaf surface to become necrotic and fall out. Symptoms may occur at any growth stage, but most commonly occur during periods of rapid growth. Older leaves are more susceptible. Dark fired types usually show less injury than burley types when at the same growth stage and exposed to the same level of ozone. |
| 5368917 |
Symptoms |
The spots usually start as small dark green water-soaked areas. Within 48 hours, the lesions change to a brown color then to a gray or white and appear as sunken necrotic areas bordered by chlorotic tissue (on dark tobacco you usually do not see any yellow halo). The spots are often concentrated along the side of the midrib and large secondary veins but can be found anywhere on the leaf. On expanding leaves the spots appear near the tip. Lower leaf surfaces may show no evidence of damage in the early stages. Lesions may run together causing the leaf surface to become necrotic and fall out. Symptoms may occur at any growth stage, but most commonly occur during periods of rapid growth. Older leaves are more susceptible. Dark fired types usually show less injury than burley types when at the same growth stage and exposed to the same level of ozone. |
| 1497045 |
Symptoms |
Weather fleak on tobacco |
