Master of Science (MS)
Plant Pathology and Crop Physiology
Among the variety of pathogens of cotton (Gossypium hirsutum), nematodes play a major role in reducing yield. Across the U.S. cotton belt, millions of dollars are lost annually due to nematode infestation. In the Mid-South and Southeast United States, root-knot nematode (Meloidogyne incognita) and reniform nematode (Rotylenchulus reniformis) are responsible for the highest percentage of damage. Crop rotation and nematicides are currently the most commonly used management strategies for nematode management. Soil fertility, which has a direct effect on plant growth, is also known to influence disease severity. Therefore, soil fertility would be an additional factor to consider for management of nematodes. The objectives of these studies were to evaluate the effects of soil nutrients on reniform nematode reproduction and pathogenicity on cotton. Four 60-day-duration greenhouse studies were conducted to evaluate the effect of different soil nutrients on reniform nematode pathogenicity and reproduction. Nutrients used in greenhouse studies were phosphorus (P), potassium (K) and sulfur (S). For the first study, P and K were used in high (112 kg ha-1) and low (0 kg ha-1) levels with a soil mixture of 70.1% sand, 25.4% silt, and 2.5% clay. Treatments for the second, third and fourth studies were five increasing levels of P (10, 20, 35, 60, and 73 mg kg-1), K (44, 70, 106, 123, and 153 mg kg-1), and S (3, 12, 20, 40, and 50 mg kg-1 ) mixed with soil comprised of 68% sand, 30% silt and 2% clay. Application of P produced a significant increase in plant shoot and root dry weights in studies one and two. Similarly, reproduction of reniform nematodes in these two studies were significantly influenced by levels of P. Studies three and four focused on K and S and did not show any effect on reproduction of reniform nematodes. Treatment with S had a significant negative influence on shoot height and dry weights. Under field conditions, nematicide application significantly reduced nematode population density at mid-season and at harvest in 2011 and at planting in 2012. In both 2011 and 2012, management of soil nutrients did not significantly influence nematode reproduction. In both years, seed cotton yield was significantly increased with nematicide, but not with nutrients.
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Kularathna, Herath Mudiyanselage Manjula Thaminda, "Influence of soil nutrients on reproduction and pathogenicity of Rotylenchulus reniformis on cotton" (2013). LSU Master's Theses. 3340.