Extension Report

Baldwin County Extension Office

302A Byrne Street

Bay Minette, AL  36507

Telephone (251) 937-7176 or

928-0860/943-5061 ext. 2222

FAX (251) 937-7285

Ayanava Majumdar

Extension Entomologist

& Sustainable Agriculture Research Program Coordinator

December 27, 2011

Emerging Technology: Net House for Backyard Vegetable Production

This article is based on original research with net houses done in Alabama over the last two years. A net house is based on the principle of physical exclusion of insects from host plants using insect netting (synthetic fabric). A number of physical exclusion techniques are already popular among commercial and backyard vegetable producers, for example, the use of row covers to keep away beetles from various crops and the use of soil collars to stop cutworms from climbing plants. A net house is different from other techniques since it allows a person to stand and work with equipment inside the unit. There is only one access door for a person and equipment to enter, but the rest of the unit is sealed on all sides to keep away insect pests. Published literature indicates that commercial net houses are being used in many countries in South America, Europe and Asia for production of egg plants, leafy greens, cabbage and tomatoes on large acreage; their use in the U.S. is restricted to a few acres in California and Florida. Alabama Extension constructed the first large net house, a 7000 square feet experimental structure, in Baldwin County using a 50-mesh insect net in 2010. That structure was 14 feet high on the sides and 17 feet in the center. Crops grown inside this large unit were tomatoes and bell peppers planted using traditional equipment with plastic and drip irrigation. All planting operations were completed a day before the unit was sealed leaving only a double-door on the short side for entry. A number of insect pheromone traps were used to compare the moth number or insect pressure inside and outside the large unit. This large net house was found to exclude 100% tomato hornworms and looper moths resulting in no outbreak of caterpillars in the absence of insecticide. Fall and beet armyworm moths were reduced 80-90% inside the 50-mesh net house providing a major cost saving on insecticides compared to armyworm outbreaks outside (read more at http://www.aces.edu/timelyinfo/entomology/2010/December/Dec_2010.pdf). We did observe aphid outbreak on bell peppers due to exclusion of natural enemies and high humidity conditions created by the 50-mesh fabric. Based on those experiences with a high cost net house, we are now tweaking this production technology for making low-cost net houses (see picture) using local resources readily available to a backyard vegetable gardener. In 2011, several small (80 square feet) net houses were built in various parts of Alabama using double-folded ¾ mesh Gard’N Net sold by Dalen Products, Inc. At each site, the soil was prepared first and then drip tape was installed before the small net house was built. The insect nets were double-folded and held in place with numerous small zip ties so that the effective hole size was about 0.25 square inch (goal was to intercept the large and medium sized moths to some extent). The insect net was mounted over 6-feet tall plastic stakes that were strong yet flexible and anchored to the ground using camping hooks. The side walls of the net house were stapled to the ground using garden staples. A nylon rope interconnected the plastic stakes so that the unit can withstand strong winds. A ‘door’ was cut on one side and kept closed using plastic ties that unzipped whenever needed. Tomato and bell pepper planting was done after construction was over. The entire structure can be made by investing $70 or less and such a net house can last two production seasons with good care. Results indicated almost 70% reduction in moth numbers for loopers, corn earworm and tomato hornworm in Fairhope, AL – region of unusually high insect activity. Control plots in Fairhope are typically destroyed completely by hornworms, but the net house technology may provide relief to gardeners. The reduction in moth numbers inside net houses resulted in less caterpillars per plant that were removed manually throughout the season. Using a net house, gardeners still have to scout the plants because even the few moths can lay a large number of eggs resulting in an outbreak if no control measures are taken. Due to the large mesh opening, stink bugs and grasshoppers entered the unit and a few insecticide applications were needed to manage them. Home owners can use any registered insecticide inside the net house but the number of applications can be reduced drastically if the structure is carefully built. Beneficial insects and pollinators were freely moving through the small net house due to large openings in side walls (a major benefit for organic producers!). Summarizing, the low-cost net house using Gard’N Net is not a silver bullet solution to all pest problems but we are going to continue research with a wide range of fabrics in future tests. I strongly recommend home gardeners and commercial producers to join the Alabama Vegetable IPM page on Facebook to see many photos of insect pests and research projects discussed herein. You can stay updated regarding pest problems throughout the season and interact with researchers as needed via Facebook and the IPM newsletter (email bugdoctor@auburn.edu for e-subscription). Net house crop production is still under research, but you can build similar units to try in your backyard and share results with us. Stay tuned for more research-based pest management information in future articles. Merry Christmas to all readers!

Alabama Fruit & Vegetable Conference Planned for February 10 & 11, 2012

There will be a statewide vegetable conference for fruit and vegetable producers at the Auburn University Hotel and Conference Center from February 10 to February 11, 2012. This is the major annual conference organized by Alabama Fruit and Vegetable Growers Association that is attended by over 250 producers, crop consultants, pesticide industry representatives, distributors, and media personnel. The 2012 event will start at 8:30 am each day. There will be various hands-on educational sessions on February 10th at the Ham Wilson Arena and Old Agronomy Farm at Auburn; training topics include small/beginner farmer education, sprayer calibration, irrigation systems and others. There will be day long educational sessions on February 11th related to vegetable production, seed technology, soil fumigation, insect, weed, nematode and disease management, invasive pests and fruit production issues by 30 expert speakers from various States. Special sessions for beginning farmers and immigration updates will be also available. This conference is a highly attended event every year and provides educational opportunities for a wide range of audiences. Exhibitors are encouraged to apply for a low cost display of their fine products. For more information, call me at 251-331-8416 or email bugdoctor@auburn.edu right away. See you in Auburn!

Email address: bugdoctor@auburn.edu

Phone: 937-7176 or 943-5061, ext. 2222

Baldwin County Extension Programs are supported by the Baldwin County Commission.

The Alabama Cooperative Extension System (Alabama A&M and Auburn Universities) in cooperation with the U.S. Department of Agriculture is an equal opportunity educator and employer.