Insect netting is a physical exclusion tactic for insect control that provides growers with many benefits.Around the world, nets or screens are commonly used for reducing excessive solar radiation and weather effects on high-value crops such as vegetables. A net house is a sealed structure made of high-quality fabric designed to keep insects away from the host plants.
Depending on the mesh size, insects excluded can range from small insects like thrips to large moths like tomato hornworms. InAlabama, a large 50-mesh net house was found to exclude nearly 100% of hornworm moths and 80% of armyworms on tomatoes in an outbreak year. (Armyworms are very adaptive and will exploit any structural weakness.)
This reduced the need for insecticides to negligible levels. (Open tomato fields were treated weekly.) To be successful, however, a net house has to be carefully constructed and plants grown inside must be insect and disease free to reduce chances of carryover. Aphids, introduced via infested tomato transplants, caused a major problem on tomatoes and peppers grown in the net house evaluated inAlabama.
Keep Pests Out Of High Tunnels
In a large net house, the major expense is the cost of insect netting and support structures. Since 2010, research on various low-cost fabrics and integrated systems has continued inAlabama. Today, some producers are utilizing the concept of insect exclusion using readily available or existing materials.
One such possibility is the integration of insect exclusion with high tunnels. Greenhouse producers are already familiar with the use of insect netting, but the large-scale use with a high tunnel is relatively unknown. Insect netting can be put on the longitudinal sides to prevent entry of insects when the sides are rolled up. Producers may use black shade cloth on the sides to cut back on the cost of material.
Click on the next page to read about considerations when using insect nets in high tunnels
Some important considerations for using insect nets or exclusion methods in high tunnels include:
Know what to control. Choose the fabric according to the target insect; do not aim for 100% reduction of all insects. In sustainable production systems, pest prevention or delayed infestation could be the goal.
Choose net or fabric with adequate pore size (mesh). Growers should aim to use fabric with the largest possible opening that will block the target insect but allow maximum air movement. Lack of air movement can cause serious disease outbreak in crops grown inside.
Exclude natural enemies (predator or parasitoids). Nets also keep beneficial insects out. So watch for any hot spot of insects and treat them to prevent their spread.
Release natural enemies inside the net house. Growers can utilize commercially available natural enemies and release them in high tunnels. Many have reported good activity of green lacewings that feed voraciously on aphids in high tunnels.
Fully extend the fabric. When using shade cloth with high tunnels, ensure that the fabric is fully extended, allowing greater air movement. A fully extended 40- or 50-mesh fabric could be sufficient and cost-effective for small growers.
When in doubt, contact the Extension service in your state and get the insect pest(s) identified. Next, think about the three-tiered sustainable insect control approach, which includes cultural controls, mechanical barriers, and the use of insecticides.