4.3. Experimental Design and Evaluation of Herbicidal Tests

The test compounds were applied as solutions in a mixture of isopropanol/water = 1:1 + 0.25% Tween 20 to arrays of two plant species (dandelions and thistle) that are susceptible to natural macrocidins. Plants were grown in 100 cm² pots with two individuals/pot and four replicates/treatment. Within each species there were three treatments: untreated control, the macrocidinoids (100 or 150 mM) and the commercial herbicide diflufenican (1.2 mM). Spraying was done with 0.4 mL/100 cm². Effects were assessed after 14 days and a second time after three to six weeks when mortality was fully developed. A mortality factor, i.e., the percentage of eventually dead plants, was calculated according to the Henderson-Tilton method [22] using the formula:

with T_b = number of plants before treatment (=8); T_a = number of vital, treated plants at the end of observation period; C_b = number of vital, untreated control plants at beginning (=8); C_a = number of vital, untreated control plants at the end of observation period.