Table 3. Synergy effect of polyoxin D and iminoctadine tris (albesilate) combination in cucumber inoculated with Botrytis cinerea.

	EC50 (ppm)
Polyoxin D zinc salt (A)	3.25
Iminoctadine tris (albesilate) (B)	11.3
AB mixture ((A: 25%(a), B: 75%(b))	3.04 (observed)

According to Gisi’s method,³⁰⁾ the following formula was used for calculation. EC₅₀(theoretical)=(a+b)/[(a/EC(A)50)+(b/EC(B)50)]=100/(25/3.25+75/11.3)=6.98 ppm. R=EC₅₀(theoretical)/EC₅₀(observed)=6.98/3.04=2.30. Criteria: R≦0.5; antagonism. 0.5<R<1.5; additive. R≧1.5; synergism.