FOLIAR-FERTILIZER THERAPY - A CONCEPT IN INTEGRATED PEST-MANAGEMENT

Heavy agricultural use of fertilizers has been implicated in degradati on of the environmental quality of lakes, rivers and aquifers. There i s also widespread public concern about the use of pesticides, includin g fungicides, on farms and their potential effect on our environment a nd food. However, it is certain that the use of fungicides as part of intensive agriculture has stabilized our food supply and permitted mil lions of people to live longer lives. Data from our laboratory and oth ers have indicated that foliar sprays of phosphate and potassium salts can induce systemic protection against foliar pathogens in various cr ops such as cucumber, maize, rose, grapevine, apple, mango and nectari ne. Expression of disease tolerance is dependent on a number of factor s including use of fertilizers and pesticides. Therefore, the possible dual role of NPK fertilizers in activation of the mechanism(s) which induce plant protection against pathogens was studied. Data from the a pplication of this concept to Various host-pathogen interactions are p resented in the present review. A single phosphate spray of 0.1 M solu tion induced a systemic protection against powdery mildew in cucumber caused by Sphaerotheca fuliginea and against common rust in maize caus ed by Puccinia sorghi, and northern leaf blight (NLB) caused by Exsero hilum turcicum. This systemic protection against powdery mildew in cuc umber, common rust or NLB in maize was obtained on upper leaves after NPK fertilizer application on the lower leaves. In both the latter hos t-pathogens interactions, growth increase was also observed in maize p lants as a result of one foliar spray of phosphates. In addition, it w as evident throughout all the experiments that a single application of phosphates was effective in suppressing the lesions of powdery mildew on the diseased foliage of cucumber, greenhouse-grown roses, field gr own mango, nectarine and grapevine. This phenomenon was investigated i n combination with fungicides. (C) 1998 Elsevier Science Ltd. All righ ts reserved.