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This publication covers chemical weed control and weed response to a variety of crops.
This guide for growers, updated annually, provides information on production and pest management practices applicable to growing flue-cured tobacco in North Carolina.
Tobacco plants that are B deficient are stunted very early on in production when compared to healthy plants. Initial symptoms involve a noticeable distortion at the growing point. The youngest leaves will develop kinks and other unusual growth patterns. Additionally, the upper leaves will be very thick and brittle to the touch. It has a very distinct “ridged” feeling compared to healthy plants. Symptoms can progress very quickly once initial symptoms are observed. The distorted terminal bud will quickly become necrotic and may abscise from the plant. The older foliage will often become darker green in coloration and will also become distorted. The leaves will begin to curl downward and will take on a crinkled appearance.
By far, nitrogen (N) is the most widely applied nutrient for plant growth. It should come as no surprise, that symptoms of nitrogen deficiency readily develop with tobacco plants.
Calcium (Ca) is essential for proper plant development and leaf expansion. A calcium deficiency will first manifest in the youngest foliage because Ca is an immobile element within the plant. As calcium deficiency progresses, the developmental damages will also advance. The integral role of Ca in leaf development makes its early diagnosis vital to tobacco production.
Potassium (K) is one of the three core macronutrients, and consequently, deficiency symptoms manifest relatively quickly in tobacco. Potassium is a mobile element, which means it will translocate from mature tissues to the younger tissues where it is needed. This movement of K from older to younger foliage is what causes deficiency symptoms to develop first on the lower foliage.
Sulfur (S) deficiency can easily be mistaken for nitrogen (N) deficiency in tobacco. The ability to distinguish between the two is very important to determining a corrective measure.
Tobacco that is deficient in magnesium (Mg) will initially develop symptoms on the lower or older foliage. These symptoms occur as an interveinal chlorosis that begins on the leaf margin, typically toward the leaf tip. Mg is mobile within plant tissues and will readily translocated from older leaves to the young developing tissues during limited Mg conditions.
Phosphorus (P) deficiency in tobacco begins as a noticeable stunting when compared to a plant with a sufficient supply of P. Additionally, a P deficient tobacco plant may develop a darker green coloration of the upper foliage. Lower leaves will become chlorotic with a mottling of olive green leaf spots. The initial symptoms appearing on the lower foliage may be attributed to the fact that P is mobile within plant tissues and is translocated from these older leaves to the young developing tissues under periods of low P.
This publication, chapter 3 of the 2018 Flue-Cured Tobacco Information handbook, discusses tobacco varieties and variety testing.
This publication, chapter 7 of the 2018 Flue-Cured Tobacco Information handbook, provides information on topping tobacco and using ethephon, the only chemical approved for yellowing tobacco in the field.
Boron (B) is an essential element that frequently exhibits deficiency symptoms if it is in limited supply. Growers often apply additional B to avoid deficiencies, but if too much B is applied, there is the risk of B toxicity symptoms developing. Boron toxicities initially appear on the lower, older leaves. Early symptoms of boron toxicity will appear as wrinkling of the lower leaves and interveinal chlorosis along the leaf margin. The wrinkling is most likely caused by the lack of cell expansion when toxic levels of B are present. This wrinkling will develop across the leaf’s surface resulting in leaf deformation. Over time the interveinal chlorosis will move inward and develop over most of the leaf. Cells will rapidly die when excess B is supplied, resulting in necrotic spotting. With advanced symptomology, chlorosis and necrosis will progress up the plant to other leaves.
Manganese (Mn) deficiency begins as an interveinal chlorosis on the upper leaves. As the symptoms progress, the interveinal chlorosis takes on a white netting type appearance. With advanced symptoms, small white spots develop and over time the spots enlarge into larger white spots.
Copper (Cu) deficiency is extremely rare, consequently it is not normally seen in field conditions. To help with the diagnosis and treatment of Cu deficiency, we induced Cu stress under controlled greenhouse studies. In NC State University trials, symptoms first developed in the middle part of the plant. The middle region of the leaf developed brown veins, which quickly turned black. The tissue surrounding the veins became chlorotic. Symptoms progress up the plant to the younger leaves.
This publication, chapter 5 of the 2018 Flue-Cured Tobacco Information handbook, offers information of managing nutrients in tobacco production.
Zinc (Zn) deficiency has not been reported under field conditions. Most of the time, the soil will have enough micros to supplement any gaps in the chosen fertilizer plan. To present a more robust set of data, we induced Zn deficiency under controlled greenhouse studies for accurate diagnosis if the problem should arise. In NC State University trials, ornamental tobacco developed a silver cast to the leaves as the initial symptom of zinc deficiency.
Iron (Fe) deficiency does not readily occur under field conditions. To better catalog this deficiency, we induced Fe stress under a controlled greenhouse study. In NC State University trials, interveinal chlorosis (yellowing) developed on the youngest leaves. Over time the chlorotic areas became more pronounced.
Molybdenum (Mo) deficiency has not been reported under field conditions. (Descriptions based on the book, Hunger Signs of Crops, 3rd Edition, edited by H.B. Sprague.) Under controlled greenhouse conditions, tobacco plants are slightly stunted when Mo is limited. The lower foliage of the plant develops a chlorosis, initially as a pale green, then the spots progress to a necrosis. The leaves may be crinkled and become bent or twisted.
This publication, chapter 4 of the 2018 Flue-Cured Tobacco Information handbook, discusses tobacco management practices that improve stands and promote uniform growth.