ABSTRACT
This chapter presents some problems of physiological disorders. Mal secco seems to be yet “the” disease problem of citriculture and particularly of lemon groves. The great need of citrus protection from these diseases creates a lot of new ideas in a control program leading to their prevention, as it is clear that in many cases control measures are coinciding. The most significant thoughts on this subject were the evidences that new citrus threats are “ante portas” in the Mediterranean basin. Insect-transmitted viruses or other diseases are the most dangerous ones among disease agents, as insect vectors are able to destroy the phytosanitary control measures taken for citrus protection. The increasing communication among the countries has greatly increased the danger of transferring unknown disease in new areas, which probably will be still more virulent enemies in crops than in their native environment, as there were the cases of Downy mildew on grape vines or Hemileia vastatrix on Brazilian coffee.
