Spread factor, penetration depth and stain height of drops of aqueous pesticide mixes on Kromekote® cards
Abstract Spreading behaviour of water‐based pesticide drops ranging from 50 to 450 μm in diameter was studied on Kromekote® cards (K‐cards), using spray mixes of five chemical insecticides, and three commercial formulations of Bacillus thuringiensis var. kurstaki (BTK). Spread factors (SF, the ratio of the stain diameter ‘D’ of a drop on the card to the spherical diameter ‘d’ of the drop making the stain) ranged from 1.0 to 4.5. The investigation on the role of drop size on SF, hp (the penetration depth) and hE (the stain height), showed that drops of the chemical insecticides underwent complete spreading and penetration into the card with no hE above the card surface, and that both SF and hp increased with drop size. The mixes of BTK underwent only partial spreading. The smaller drops (50 to 150 μm) of Dipel® 6AF and Thuricide® 48LV, were spherical, but the medium, ones (150 to 300 μm) provided spherical segments, and the larger drops (300 to 450 μm) formed flattened cylinders. All BTK drops showed hE bu...