VULNERABILITY TO CONTAMINATION WITH PLANT PATHOGENS AND PESTS IN SPECIFIC CROP ROTATIONS OF AGROFORESTRY HOLDINGS ON SANDY SOILS

Researches regarding contamination with plant pathogens and pests, in specific rotation of agroforestry holdings on sandy soils, revealed the biological material and the climatic conditions as vulnerable points to infection. Determinations on Cowpea aphid borne virus infection in 144 cowpea genotypes, showsed a negative correlation between production and plant resistance to this pathogen, at 3-4 true leaves and flowering stages (r = - 0.792 **, r = - 0.744 **). In peanut the presence of f fusarium wilt, produced by Fusarium oxysporum f.sp. vasinfectum, that caused sporadic drying plant, was signaled with a frequency of 2.25 to 22%, depending on the genotype. In maize symptoms of infection caused by Fusarium moniliforme, Ustilago maydis and attack produced by Rhopalosiphum maidis and Ostrinia nubilalis were signaled, the degree and frequency of attack being in relation to genotype. The climatic conditions of the years 2012 and 2013 have influenced in different ways the cowpea plants infection with Pseudomonas syringae pv. vignae (Da = 18.85 to 20.64%) and Uromyces appendiculatus (Da = 12.6 to 34.7%).