Pore size requirements for mesh crop covers to protect potatoes from aphids

ABSTRACT Crop covers made from polymer meshes have proved successful in protecting potatoes from tomato potato psyllid in New Zealand. However recent field trials indicated that aphids could penetrate these mesh covers resulting in high levels of aphid plant infestation. The current study used a laboratory assay to examine the mesh pore dimensions required to prevent penetration by apterous adults of two species of aphids commonly found on potatoes. Of the 22 commercial meshes tested, Myzus persicae managed to pass through 20 and Aphis gossypii managed to pass through 21. Logistic regression analysis indicated that the maximum allowable pore dimensions to exclude (99% of) aphids were approximately 0.06 mm in length, 0.15 mm diagonal and an area of 0.012 mm2. None of the meshes tested met any of these criteria, and if crop covers are to be used to protect crops from both TPP and aphids then meshes with smaller pore sizes would be required.