Trials were established in Summer 2002 and 2003 to test the consequences of the application of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural predators (insects and arachnids) on pecan (Carya illinoinensis, cv. `Pawnee') trees. Film application started immediately after bud break and was repeated every 7-10 days for seven (2002) or nine (2003) times during the season. On both years, treated trees frequently showed lower leaf temperature (up to 4 °C) than untreated trees. Leaf net assimilation rate, stomatal conductance and stem water potential were not affected by film application. Nut size and quality did not differ between the two treatments. In 2003, shellout (percentage of nut consisting of kernel) was in fact 54.2% and 55.5% for treated and control trees, respectively. Moreover, the two treatments yielded similar percentage of kernel crop grading as fancy, choice, standard and damaged. Similar were also the percentages of kernels that showed damage caused by stink bugs. Only on one date the number of adult yellow pecan aphids (Monelliopsis pecanis) counted on film-treated leaves was lower than in control leaves. In general, the density of common natural predators (lady beetles, green lacewings, spiders) of pecan pests did not differ between the two treatments; however, the number of green lacewing eggs was frequently lower on film-treated leaves. In film-treated trees the number of nutlets damaged by pecan nut casebearer (Acrobasis nuxvorella) was significantly higher than that observed on trees treated with conventional insecticide (24.2% infested nutlets vs. 9.3%, respectively) and did not differ from trees that did not receive either product (29.9%).