Long-term effect of Tylenchulus semipenetrans on citrus tree quality in reclaimed land of Egypt

Abstract

Citrus fruit yield is considered a short-term response to the citrus nematode,Tylenchulus semipenetrans damage and therefore this study addressed parametersmeasuring overall appearance of the sampled trees. Soil and roots from 20 trees ineach of three mature: 'banzaheer' lemon, 'Baladi' mandarin, and ‘Navel’ orange andone immature: ‘Navel’ orange orchards, all grafted on sour orange rootstock, inEgypt were sampled for the citrus nematode, T. semipenetrans, in February 2011 toinvestigate their correlations with tree parameters (tree height and vigor, canopydiameter, and trunk circumference) that reflect long-term nematode damage of thesampled trees. The correlation between pairs of these four parameters were alwayspositive and generally with high significant levels. Each of the four parameters wasnot significantly correlated with fruit yield of the mature trees but each of tree heightand vigor, and canopy diameter was correlated with fruit yield of the immature Navelorange. The relationships between pairs of these biotic parameters and T.semipenetrans population density in fibrous roots and soil were not consistent.Eleven edaphic factors in mandarin and mature orange orchards were measuredand compared. Both soils were dominated by rough grainy particles of sand. Levelsof potassium, calcium, phosphorus, ammonium and nitrate as well as soil solutionpH, organic matter content and electric conductivity in the soil samples weresignificantly (P ≤ 0.01) different between the mandarin and orange orchards. Toachieve better economic revenue of citriculture, local tackling of T. semipenetransproblem in newly reclaimed areas of Egypt was discussed.