Kaolin (Surround®) was assayed to evaluate and quantify its effects on the foraging behaviour of blueberry maggot (Rhagoletis mendax) females. Host choices, total residence time, walking, cleaning and oviposition were quantified in choice-tests when females encountered kaolin-treated and untreated fruit of highbush and lowbush blueberries. Untreated blueberries were the first fruit visited in 71 and 79% of the assays for highbush and lowbush respectively. Total residence time, total walking time and length of walking bouts were significantly shorter on the two kaolin-treated host species fruit than on untreated host. Few oviposition attempts were observed on any species of fruit independently of the treatments. Foraging behaviour was impaired by the presence of kaolin on the fruit surface as it stuck on the fly’s body. However, recognition of the host did not seem to be affected by the presence of particle film.