Influence of soil nutrients on reproduction and pathogenicity of Rotylenchulus reniformis on cotton

Greenhouse  and  field  studies  were  conducted  to  evaluate  the  effect  of  soil  nutrients  on  reniform nematode ( Rotylenchulus reniformis ) reproduction and pathogenicity on cotton ( Gossypium hirsutum ). Initial greenhouse studies examined phosphorus (P) and potassium (K) at very low (10 or 44 mg kg-1) and high (50 or 123 mg kg-1) levels, respectively. Phosphorus produced significant increases in plant height and shoot and root dry weights as well as significant reductions in numbers of nematodes in soil and eggs from roots. Subsequent greenhouse studies evaluated increasing levels of P (10, 20, 35, 60, and 73 mg kg-1), K (44, 70, 106, 123, and 153 mg kg-1), and sulfur (S) at 3, 12, 20, 40, and 50 mg kg-1on cotton growth and nematode reproduction. Phosphorus significantly increased plant height at 15 and 30 d and shoot and root weights at 60 d. Potassium and S had no effect on plant growth with the exception of the highest level of S, which significantly reduced plant height and shoot dry weights. Overall, as P level increased, reproduction of the reniform nematode decreased. Potassium and S, irrespective of level, had no effect on densities of eggs or soil stages of the nematode. Field trials with cotton included combinations of P at 44.8 or 112 kg ha-1and S at 5.6 or 22.4 kg ha-1with or without 1, 3-dichloropropene at 28.1 L ha-1. Nematicide application significantly reduced nematode population density at mid-season and 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 supplemental nutrients.