Frank, Z.R., The Institute of Plant Protection, Agricultural Research Organization (A.R.O.), The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel
Verhaegh, W.B., The Winand Staring Centre, P.O. Box 125, Wageningen, 6700 AC, Netherlands
Bakker, J.W., The Winand Staring Centre, P.O. Box 125, Wageningen, 6700 AC, Netherlands

A method to investigate the effect of moisture-dependent soil aeration on plant disease is presented. Constant volumetric moisture contents between 22 and 39% in a loam were employed, and corresponding soil aeration levels were attained, by applying constant water pressures between -400 and -5 cm to the soil via tensiometer ceramic cups. In the range of available water, small changes in matric soil water potential resulted in large changes in soil aeration. Young 'Moneymaker' tomato seedlings were inoculated with Fusarium oxysporum lycopersici either by transplanting to infested soil, or by injecting the inoculum into the soil through preinserted tubes and thus avoiding wounding of roots. Two to three weeks later the effects of treatment were obvious. From comparison of infected plants to their controls in each moisture treatment it was inferred that, in the range of small matric potentials (i.e. wet soil), soil aeration is the decisive factor. In badly aerated soil, inoculated plants succumbed to disease. The combination of a good aeration with plenty available water was optimal to disease endurance. In the soil used, aeration changed from bad to sufficient between -10 to -60 cm matric potential. © 1991 Kluwer Academic Publishers.