Biological Control Practices for High-Tunnel Crop Production
In 2003, the trend towards production in high tunnels has excellerated. Falling somewhere in between field crop production and greenhouse production, high tunnels offer growers many of the benefits of costly greenhouses without the high technological and financial investments. Research and grower adoption has proved the use of bio-control’s, (or natural enemies) to control pest populations in greenhouses to be effective in decreasing and or eliminating the use of chemical pesticides. No-where is this more evident than in Northern Europe, where widespread greenhouse production has forced growers to employ imported and released pollinators. These pollinators are extremely sensitive to pesticide use, thus prompting producers to seek out suitable alternatives for pest management. Prior to the commencement of our project, no research has been conducted on the use of natural enemies in the high tunnel environment where both beneficial and pest insects have ample opportunity to move in and out of the environment via ventilation, less controlled and constant temperatures and overwintering withint a temperate climate (essentially setting the pest/predator populations back to 'zero' each year).
The goal of our project is to evaluate the use of natural enemies for pest control in the high tunnel environment by taking extensive research data at the High Tunnel Research and Education Facility (HTREF) in Rock Springs, PA and conducting on-farm research in conjunction with our two grower cooperators in the southeastern and northwestern part of Pennsylvania. Information will be disseminated at presentations given at PASA (Pennsylvania Association of Sustainable Agriculture) , PVGA (Pennsylvania Vegetable Growers Association), HTREF (High Tunnel Research and Education Facility) field days and Extension In-Service Training Days as well as at our grower cooperators farm locations (at their request). At the end of the project, all of our data will be coordinated and published in a free informative pamphlet and distributed to those surveyed at the above events, advertised on our web site and distributed via the Penn State Department of Horticulture channels.
In year two of our project, scouting procedures were refined from experienced gleaned from the first year of data collection. In year two, another season of data was collected at the HTREF as well as at our grower cooperator sites in Holtwood, PA and Brookville, PA. Several releases of Encarsia formosa were made at Cedar Meadow Farm in Holtwood where student interns participated in much of the scouting and communication with the SARE Field Project Coordinator. Because of previous spider mite infestation, releases of natural enemies were also made independently of our project which focuses exclusively on the management of aphid and whitefly. Although a good level of whitefly control was believed to be achieved, our grower cooperator felt it was urgent to spray a broad scale insecticide to control an unusual stink-bug infestation (This pest is not normally a significant problem in Tomato crops in our region, however 2003 witnessed several outbreaks in the Southeastern part of PA). Despite weekly communication with our grower, This was done without prior consultation: due to the damaging effect of the insecticide, the study was terminated in early September. No releases were required at our Brookville grower’s site; they have a history of not spraying insecticides and believed that they actually achieved sufficient control of pests via the native natural enemies conserved on their farm. We are excited to see if this ‘pest free’ trend continues this growing season as the extreme importance of conservation and encouragement of native natural enemies (via not using insecticides in years past) may be at work here. It has also become apparent that in order to quantify and qualify the existence of native natural enemies, more frequent visits must be made to this site throughout the growing season to aid the growers with scouting and observation of the less obvious natural enemies. As is common (and we experienced the same trend at the HTREF) a population of whitefly began to build towards the late end of the growing season (Mid September) at the Brookville farm. Because of the lateness and declining temperatures, this pest was not treated with a natural enemy release. Observation visits were made to each farm to check in on scouting procedures and overall study success. Weekly communication via email or phone continued throughout the growing season. Scouting reports were submitted by the growers to the HTREF to evaluate need for releases weekly.
Outside of the incorporation of grower cooperators in year 2, we also held one PASA sponsored field day and two Extension-In service training events where our project was high-lighted. Sessions were devoted at each event to detail the research we were conducting here and also provide a forum for interested growers to ask questions and experienced growers to share knowledge. Similarly, although the requirement to give presentations at regional events was not to be met until year 3, presentations are to be given in February at the PASA Conference in University Park, PA as well as at the PVGA Conference in Hershey, PA. These sessions will be devoted exclusively to the use of biological pest management in high tunnels and will serve as a forum to disseminate information gleaned from the first two years of our study. (Highlights from these meetings will be reported in 2004). Finally, our 2003 High Tunnel Production Manual was published this year, within which is a very detailed chapter on IPM and Biological Control. While this chapter does not incorporate information learned from this study, it does provide an extensive overview of biological control and its application in high tunnel production.
Independently of the SARE project, we have established a ‘farm market’ that will be held on the PSU Campus each week whereby our high tunnel produced foods and flowers will be sold to employees and students. In 2004, we will be requesting that customers complete surveys, allowing us to gain a better understanding of customers knowledge of pesticide/food issues as well as what their interests are in foods produced under a Bio-Control production system (as discussed in the original proposal). We believe this to be a significant and important component to this study. In Europe, where biological control is overwhelmingly and successfully used, a critical component of its adoption is the marketing of an IPM (bio-control) label placed on foods that were grown under these pest management practices.
We achieved great success using biological controls in our study at the HTREF. Our results are quantified in a series of graphs that show our target pest populations staying well below the Economic Injury Level (EIL) for the specific crop, especially in the high tunnels where releases were made. In the other high tunnels where releases were not made, sufficient pest control was also achieved without the need for any pesticide use. In fact, not even one crop was treated with pesticide at the HTREF in 2003 (including crops in the 30 other high tunnels not involved in this study). Not only did released natural enemies make their expected impact on pest populations within the high tunnel that they were released within, but native predators and parasitizers were also noted to have played an important role in pest control as well (such as the Aphid Midge, Aphidoletes sp.) Similarly, species released in SARE tunnels migrated to other tunnels after achieving good control in the study tunnels. We are becoming increasingly confident that pest control can be successfully and economically maintained in the high tunnel environment via the use of biological control. Similarly, with detailed economic records kept, we are beginning to elucidate that biological control is comparable to the expense of chemical control and in some cases less expensive.
Impacts and Contributions/Outcomes
Much data was collected in year 2 and this data collection and analysis has helped us to further devise new and more effective ways to scout in the final year. We have established working relationships with our grower cooperators this year and look forward to another year of testing biological control tactics on farm. Our project was highlighted at numerous events and the specifics of the project will be discussed at well attended meetings later this winter.
Changes of Work
In year 1, the initial survey was eliminated. However, in year 2, a survey has been designed and will be distributed in a slightly different manner than was originally submitted. This survey will be made available to attendee’s of presentations at the PASA and PVGA conferences. They will also be available for distribution at general information tables that are hosted at these conferences. This will help us to better gage the need for our research and also provide us with contacts for future grower cooperator partnerships and even potential sites to host future field days.
We have had several contacts regarding grower interest in participating in our project. We are considering whether there is a way to widen the scope of our project by including more grower cooperators.
In year 2, after discussions with our panel, we made the decision to include a greater variety of natural enemies for more targeted control of our pests. Instead of using only Ladybird Beetles and Green Lacewings as originally proposed, this year we also released aphid and whitefly parasitoids. Including these parasitoid insects was an important decision and we believe greatly helped to control pests much better than with the original predatory species alone.
In year 3, we will also be incorporating new components into the project including banker and trap crops along with providing supplemental food to our predatory insects. Recognizing the great importance of encouraging a beneficial environment for our native predators and parasitoids to move into the high tunnels along with the augmentative release of these species, we have decided to include these important aspects into our system.
Finally, years 1 and 2 of the project have caused us to recognize the importance of not only quantitative data and analysis but also qualitative and empirical. In year 3, data will be collected as in the first two years of the study but a more qualitative and characterized analysis will also be made of each tunnel each week to give an overall and more subjective description of the state of pest management in each tunnel. This will help enable us to make some note of pests or predators that are encountered in the tunnel but are not located on the flagged (scouted) plants. It will also help to serve those growers who want to use bio-control but don’t necessarily have the time to spend doing the required scouting. It will allow our scouters to get a ‘feel’ for the 'state of health' of the high tunnel and make weekly observations of other non target pests, natural enemies, disease or nutrient deficiencies or toxicities, etc... This more 'holistic' characterization will not take place of the quantitative data that must also be collected for the purposes of this study.