ABSTRACT
Screening or microscreening greenhouse openings, such as vents and sidewalls, can inhibit the entry of winged insects into greenhouses (Figure 5.1), which will reduce the number of pesticide applications needed during the growing season. The hole or pore size (mesh) of the screening (Figure 5.2) will help decide the appropriate material to select, which will be contingent on the insect pests to be excluded. Screen size depends on the insect, whether it be aphids (340 μm or 0.013 in.), leafminers (640 μm or 0.025 in.), thrips (192 μm or 0.0075 in.), or whiteflies (462 μm or 0.018 in.). Select and install insect screening based on the smallest insect pest to be excluded. The installation of insect screening may decrease the incidence of viral diseases, such as the impatiens necrotic spot and tomato spotted wilt viruses that are vectored by the western flower thrips, because the screening material, depending on the mesh size, may exclude the insect pest from entering the greenhouse. Furthermore, screening greenhouse vents can exclude larger insects such as aphids, beetles, and moths from entering the greenhouse, some of which are capable of transmitting diseases. Screening will also prevent weed seeds from entering the greenhouse, which will alleviate potential problems with weed seeds establishing and
subsequently developing in flats or containers with growing medium (Figure 5.3).
