- Vegetables: tomatoes
- Crop Production: high tunnels or hoop houses, shade cloth
Insect pressure is one of the major challenges of vegetable production in the deep south. Heavy and repeated applications of pesticides are not only expensive and time consuming to the farmer, but is also much less desirable by the end consumers and the environment. Fresh market produce is expected to be visually blemish free with insect damaged produce fetching a lower price or not selling at all. This is a challenge to growers in the Gulf Coastal South where bug pressure starts early in the Spring and persists late into the Fall because of warm weather and plentiful moisture - many insects have another entire life cycle along the Gulf coast than those just a few hours inland.
Seeking an alternative to repeated pesticide applications, this project sought a method of mechanical exclusion of insects inside of an existing high tunnel. After researching net houses and screen houses, it was deemed that most bug screens available were limited in that there was a major reduction in airflow inside of the structure because of the fine mesh of the bug screens. Heat and humidity buildup inside of these structures was a major issue, and often led to disease, fungus, and mold outbreaks. Realizing that for the crops that our farm produces were mainly affected by larger body insects including moth caterpillars, stink bugs, leaf-footed bugs, and the various cucumber beetles and other beetles - we sought a material for screening that would exclude the larger body insects but still allow for adequate airflow and passive ventilation.
The idea for using woven shade cloth as a bug screen started to seem possible. We had noticed the effectiveness of the shade cloth as a bug screen on one of our tunnels by accident. We had an oversized piece of shade cloth with the extra portion hanging along the west wall of the high tunnel (adjacent to the roll up side walls). We noticed leaf footed bugs piling up on the outside of the shade cloth trying to get to the crops inside. The idea of a hybird high tunnel was born. We used our existing high tunnel and fitted a 50% woven shade cloth to the endwalls and sidewalls between the base boards and the hip boards of the structure.
For this study we proposed growing Spring season tomatoes on the inside of the structure versus a control crop of tomatoes grown on the outside of the structure. For the Fall season we used sugar snap peas as our test crop.
Project objectives from proposal:
-Difference was immediately noticeable, inside tunnel we were losing only 10%-20% of big tomatoes to bugs – outside tunnel we were losing 80%-100% in June and July
-Does get hot in tomato house, over 100 degrees some days
-Pollination does not seem to be affected – have had some blight issues
-Biggest difference came about a month after installing screen (late June) – 135 caterpillars on one outside row of tomatoes, 3 caterpillars on one row inside tomatoes
- Cherry tomatoes in field had less loss 30%-40% loss versus less than 10% inside tunnels (numbers were based on weight of marketable fruit harvested)
-Squash bugs infiltrated and started breeding inside -they remained inside of screen tunnel, we had to kill several generations inside of the tunnel.
-For the Fall crops the difference was less marked - We planted sugar snap peas on the outside of the tunnel and a control crop in the field. We had some armyworm problems on sugar snap peas when they were young, but an early cold spell in October seemed to have eliminated most of the caterpillar pressure in the fields. No fall caterpillars made it inside of the structure.
- The 50% shade cloth was effective against cucumber beetles as well, although these showed up on field (control) crops after majority of damage had been done by caterpillars. We found several in the field crops but none were present inside of structure.
-We were late to install screen on high tunnel (early June) some bugs got in already - leaf footed bugs began breeding inside of structure later in the season and the structure kept them trapped inside of the screen - this was a real problem - they had to be removed primarily by hand. Timing is critical.
-Moths laying eggs all over screen – young caterpillars can fall inside of screen and get to plants – Dr. A noted this same issue in his net house study
-Exclusion of good bugs (ladybugs, lacewings, mantis) but dragonflys still get in- somehow
-Small bugs still get inside and are hard to control (flea beetle especially) - Aphids were also present on some plants inside of structure
-Screen is expensive +/- $1000 to install screen on 30’x100’ tunnel
-Have to customize design to particular tunnel design - our end walls that were ordered did not quite fit right and we had to improvise screening at the bottom of the panels. There are no ready made kits for this.
-Although ventilation is good – airflow still restricted, need fans and misters to get proper airflow and cooling on hot still days