- Fruits: berries (strawberries)
- Crop Production: organic fertilizers
- Education and Training: extension, farmer to farmer, on-farm/ranch research, participatory research
- Pest Management: biological control, cultural control, economic threshold, field monitoring/scouting, integrated pest management, trap crops, mulching - vegetative
An on-farm experiment conducted in 2007 at a conventional strawberry ranch in Monterey County under direct management by the farmer cooperator tested the efficacy of insecticide-treated alfalfa trap crops for the reduction of lygus bug (Lygus hesperus Knight) damage in associated, untreated strawberries. This method of lygus bug control was transferred from an earlier successful demonstration of the technique in organic strawberries under management with tractor-mounted vacuums by the same farmer cooperator (Swezey et. al. 2007). Lygus bug abundance was significantly reduced in insecticide-treated trap crops when compared with untreated control trap crops, and damage in adjacent untreated strawberry rows was only slightly increased. Cutting the trap crops for height control and spray penetration was also tested. Cutting for height control was associated with significantly greater lygus bug control in the trap crop and reduction of damage in neighboring strawberries in 2007.
California produced over 86% of all strawberries grown in the United States in 2007. California strawberry production is a major state industry, ranking 8th among all state agricultural commodities in 2007 with an estimated farm gate sales value of over $1.3 billion on 34,600 planted acres (CDFA 2008). However, the California strawberry industry faces potential environmental, economic, and social sustainability problems with the use of insecticides in local watersheds of Santa Cruz and Monterey Counties, where over 40% of the strawberries are grown. In 2007, over 120,000 lbs of active ingredient neurotoxic organophosphate (malathion, dibrom, chlorpyrifos, diazinon) and carbamate (methomyl, naled, carbaryl) insecticides (in addition to nearly 2,000 lbs of active ingredient of the synthetic pyrethroid insecticides bifenthrin and fenpropathrin) were applied for insect control, principally to control the damage of one insect: the western tarnished plant bug (WTPB) or lygus bug, Lygus hesperus Knight, the key economic fruit pest of strawberries in the central coast counties. To attain high production volume, California strawberry growers are responsible for disproportionately high pesticide use rates. California strawberry production used an average of 282 lbs. of active ingredient (AI) pesticides per acre of production in 2007, far exceeding averages for any other California crop (CDPR 2008). In the Pest Management Strategic Plan for Strawberry Production in California (CMCC/CSC 2003), new materials and techniques for controlling lygus bugs were explicitly identified as one of the most critical research needs “to sustain the viability of the California strawberry industry.” Lygus bugs are also explicitly mentioned as a primary pest in the Crop Profile for Strawberries in California (NSF-CIPM 1999).
The feeding of lygus bug nymphs and adults causes distortion of strawberry fruit, which renders the berries unacceptable for fresh market sale. During feeding, lygus bugs destroy developing embryos in achenes (seeds) during early fruit development, thereby preventing growth of fruit tissue beneath and surrounding the damaged achene (Handley and Pollard 1993). Economic thresholds are exceeded at very low lygus bug densities. Unacceptable levels of damage occur at densities of one or two lygus bugs per 20 strawberry plants sampled (Strand 1994). The damage caused by lygus bug feeding on the strawberry fruit is often referred to as “cat-facing” and results in an undersized, cosmetically degraded fruit unacceptable in fresh marketing. Typical control programs can entail 6-8 applications of insecticide per season, often at biweekly calendar intervals (June-September). The cholinesterase-inhibiting OP and carbamate neurotoxins represent a known direct human health hazard to applicators and workers exposed in the fields. Detectable residues of some of these water-soluble insecticides, including diazinon and chlorpyrifos, have been implicated as causes of toxicity to freshwater aquatic organisms in ambient tests of agricultural drainage water in Monterey County.
To protect environmental and human health and reduce or eliminate the use and cost of toxic pest control materials, alternative approaches, such as certified organic production, must be validated and information about these approaches disseminated. For example, in 2007, California organic strawberry growers declared a farm gate sales value of $43.5 million on over 1700 acres. This comprised 5% of California’s total strawberry acreage. From 1999 to 2007, the declared value of California organic strawberries has increased 500% (from $8.7 million declared in 1999), and registered planted acres increased by over 120% ( http://www.cdfa.ca.gov/is/i_&_c/organic.html.). This growth has been in response to increasing demand for organic strawberries in California. During this time, we have worked closely with a cooperating organic strawberry farmer, Larry Eddings, Grower/President of Pacific Gold Farms, to develop organically compliant methods of lygus bug control. With a 2002 Western SARE-funded research project entitled : “Control of western tarnished plant bug (WTPB) Lygus hesperus Knight in organic strawberry production systems using trap crops and tractor-mounted vacuums” (SW02-035), our research team demonstrated that lygus bugs were attracted to in-field alfalfa trap crops more than to adjacent strawberry rows, and that a tractor-mounted vacuum treated trap crop significantly reduced damage due to lygus bug feeding in associated strawberry rows compared with a whole field vacuuming program and an untreated control (no trap crop). This was a unique and economically important result for the cooperating grower, because trap crop vacuuming constitutes a 75% reduction in machine energy/effort usually expended by organic strawberry growers in whole-field vacuuming programs (Swezey et al. 2007). Larry Eddings now profitably uses the trap crop technique on over 80 organic acres at Pacific Gold Farms, with ranches located in the drainages of the Monterey Bay National Marine Sanctuary. While these organic farms represent low pesticide residue environments for workers and the environment, there has been a tremendous regional effort on the part of NRCS to reduce agricultural runoff from conventional strawberries by integrating alternative methods of pest control. As a professional + strawberry producer team, we were motivated to demonstrate the efficacy of trap crops on Pacific Gold’s remaining 800 conventional acres. The economic and environmental benefits that could be achieved by reducing the use of lygus-directed insecticides are far-reaching: improved environmental health of the slough and sanctuary, improved water quality, savings to farmers by cutting chemical, energy and labor costs, and increased protection of worker health and safety.
Based on our previous collaboration, our research team composed of entomologist Sean L. Swezey and staff research associates Janet Bryer and Diego Nieto conducted research on a conventional strawberry ranch managed by Larry Eddings to test if using trap crop-directed insecticide applications on managed trap crops could decrease the need for insecticides in associated strawberries for lygus bug control. This project was distinctive in that it was attempting to inform the conventional industry (95% of CA acreage) as to the broad applicability of observations first made with a previous Western SARE research grant on organic acreage. This was a creative joining of the two production approaches for potential industry-wide benefit.