Herein is disclosed the use of acicular wollastonite grains for killing grubs and method of making the grains. The method includes applying acicular wollastonite grains having an aspect ratio of at least about 5:1 to the ground at an area density of about 0.5 to about 6 mt per acre, with higher amounts in this range chosen for very bad grub infestations. The method of producing the acicular wollastonite grains having an aspect ratio of at least about 5:1, includes feeding wollastonite feedstock into a milling apparatus in conjunction with a screen mechanism. The milling apparatus and screen mechanism have parameters selected to produce acicular wollastonite grains having an aspect ratio of at least about 5:1, which can optionally then be fed to a cyclone where the acicular wollastonite grains are collected.
