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- Author or Editor: Marvin P. Pritts x
This LISA project involves four state universities and the USDA, and has the objective of developing and evaluating non-conventional production and pest management strategies for raspberries and strawberries. Production goals are divided between cropping systems and pest management. The evaluation of trellising systems for cropping efficiency, ease of harvest, and spray distribution is an example of a production related objective. Groundcover management systems for strawberries are being evaluated for their effects on both the pest complex and production system. Biological control strategies for root diseases are also being studied. Evaluations involve field performance, economics, and impacts on pesticide use. In addition, grower attitudes towards adoption of non-traditional production practices have been assessed. The project supports the publication of a newsletter that is distributed to 450 growers. The major goal of our work has been to improve production efficiency and provide growers with economical, dependable tools that can be used to prevent pest problems before chemical intervention is required.
Non-chemical methods for weed management are becoming important as fewer herbicides are labelled for use and as the market demands pesticide-free produce. We have studied the use of interplanted cover crops in strawberry plantings as an alternative/supplement to chemical weed management. Several different cover crops (tall fescue, marigold and sudangrass) were seeded between rows of newly planted strawberries in late June as runnering was commencing. An additional seeding of sudangrass was made in late July. For comparison, untreated plots and diphenamid treated plots were included in the experimental design. Measurements were taken throughout the season of soil moisture, light levels, crop nutrient concentrations, nematode numbers in soil and crop roots, runner biomass, and weed composition and biomass. Cover crops were incorporated in late fall and the planting was mulched. The following spring, crop nutrient concentrations, nematode numbers in soil and crop roots, weed composition and biomass, yield, individual fruit size, and aboveground strawberry biomass was assessed. The marigolds were too competitive for moisture to be an effective companion cover crop. The early planting of sudangrass was too tall, and fescue was too competitive for nutrients. The untreated plots contained many more weeds than other treatments, nematode levels were higher in the strawberry roots in these plots, and harvesting fruit was very difficult. The late seeding of sudangrass, however, provided significant weed control while not reducing yield relative to herbicide-treated plots.
Manipulating light, temperature, moisture, and nutrients to favor plant growth and productivity is an important component of horticulture. The technology required to achieve such manipulation ranges from inexpensive, basic practices to elaborate, costly approaches involving the latest engineering advances. For example, pruning and mulching are relatively low-tech methods for improving light interception and soil moisture status in small fruit plantings. At the opposite extreme are glass houses with supplemental lighting, CO2 enrichment, and nutrient film hydroponic systems Of greatest value to small fruit growers, however, is technology that ran be applied in field situations, such as the use of overhead irrigation for maintaining soil moisture status, frost protection, and evaporative cooling. One of the greatest challenges to small fruit growers and rcsearchers is integrating new technology into production systems. The introduction of a new technique for environmental modification usually has indirect effects on other aspects of management, which may require additional technology to compensate for adverse changes while maintaining the favorable change. In addition, unique macro- and microclimates demand and market opportunities, specific solutions, and the result is a dynamic, diverse collage of production systems used by growers throughout the world.
Strawberry (Fragaria ×ananassa) is a perennial plant with a compressed woody crown that responds to the environment in a similar way as other temperate fruit crops. Nutrient management practices are also similar, with a few exceptions. Levels of preplant amendments are determined based on soil test results, and are used to increase nutrient availability and modify pH as needed. Once plants are established, soil tests, coupled with foliar tissue analysis and observations of plant growth, are the best indicators of plant nutrient status and limitations. Drip irrigation is more efficient than granular applications for supplying soluble nutrients such as nitrogen (N). While most temperate fruit crops respond well to N in spring when growth resumes after winter, applications of spring N in strawberry can cause excessive vegetative growth, reduce fruit quality, and have only a marginal impact on yield. N is most efficiently taken up by plants when conditions favor root growth, and N applied in summer or fall is more effective at increasing yield the following spring, assuming that the carbohydrate status of the plant is good. However, if carbohydrate status is poor, supplemental N late in the season can reduce yield by requiring additional carbon (C) for N uptake. Many questions remain to better understand how to manage nutrients optimally in perennial strawberry.
A course was developed at Cornell University for the purpose of attracting nonmajors from across the university, instilling in them an appreciation for horticulture and then encouraging them to take additional horticulture and plant science courses. The course incorporates many engaging and interesting horticultural activities, with scientific concepts and horticultural techniques conveyed almost exclusively through hands-on instruction using the campus as a laboratory. Experiential learning and culinary experiences are key components of the course. Student evaluations are very high (5-year average of 4.94/5.00 with five representing “excellent”), and the class fills to capacity each spring semester with diverse students from across campus. Enrollment in other horticulture classes has increased since the course has been offered. Forty-three percent of students who took Hands-On Horticulture as a freshman, sophomore, or junior subsequently enrolled in at least one other plant science course. Participating horticulture faculty also find the class to be fertile ground for recruiting research and field assistants. Students report an increase in well-being and reduction in stress while taking the course, and write about how their worldview has changed after the course experience. This class has allowed students to discover or rediscover their role and connection to nature while simultaneously providing them horticultural skills and understanding of scientific principles.
Competition from weeds and an interplanted sudangrass [Sorghum bicolor (L.) Moensch, formerly S. sudanense (Piper) Stapf.] cover crop was allowed to occur in newly-planted strawberries (Fragaria ×ananassa Duch.) for varying lengths of time, and at different times during the growing season. Newly planted strawberries were most susceptible to weed and cover crop competition during the first 2 months after planting, as both runnering (stolon formation) and subsequent yield were impacted. In 1994-95, 1 month of weed competition in June reduced yield by 20%, whereas 2 months of weed competition reduced yield by 65%. However, 1 month of uncontrolled weed growth later in the growing season had little to no impact on yield, although weed biomass was much less then. Herbicide (napropamide) use alone was insufficient to prevent weed competition and yield reduction. In our study, yield was reduced 0.67 t·ha-1 or 5.5% for each 100 g·m-2 of weed biomass. The data suggest that it is critical for growers to minimize weed competition early in the planting year when weed growth is greatest. Since an interplanted sudangrass cover crop displaced a portion of the weeds, it could be seeded later in the year to provide some weed suppression without a negative impact on yield. Chemical names used: N, N, Diethyl-2-(1-naphthalenyloxy)-propionamide (napropamide); N-(phosphonomethyl)glycine (glyphosate).
Various levels of weed competition were implemented in a second-year well-established strawberry (Fragaria ×ananassa `Jewel') planting by cultivating and hand weed removal for defined periods of time over 3 years. The impact of weeds on subsequent productivity was then determined. Sixteen treatments were established where weeds were allowed to grow for defined periods (0, 1, 2, 3, 4, or 5 months) throughout the growing season. Treatments were maintained in the plots for 3 consecutive years. Spring weed biomass in 1997 had no impact on yield that same year. Weed biomass in 1997 was negatively associated with yield in 1998, although the trend was nonsignificant. However, several individual contrasts were significant. For example, the weed-free control treatment had the highest average yield, while season-long weed competition reduced yield by 14%. The inverse relationship between weed biomass and fruit yield became significant in 1999. For every 100 g·m-2 increase in weed biomass in 1998, fruit yield was reduced by 6% in 1999. Season-long uncontrolled weed growth reduced productivity by 51%. However, several plots with a limited amount of weed competition had higher yields than the continuously weeded control. These data indicate that yields from a well-established strawberry planting may not be vulnerable to a limited amount of weed competition for at least 2 years. Furthermore, data suggest that hand weeding and cultivation on a monthly basis for multiple years may be damaging as well. Growers should direct a majority of their efforts and resources toward controlling weeds in the planting year. Once the planting is well-established, growers may limit the number of times they hand weed to two or three per season.
Strawberry clipper is considered to be a major pest on matted-row strawberries in the northern U.S. and Canada. This pest is thought to be so threatening that even a single clipped bud indicates the potential for serious and rapid damage. Conventional wisdom states that fields should be treated for clipper during warm weather if they have a history of clipper damage—even if fields have not been scouted. Thresholds (fi ve clipped buds per meter) are based on the assumption that one clipped bud is equivalent to the loss of one average-sized berry. However, our data show no correlation between clipper damage and yield in field surveys, and our artificial clipping studies have found that strawberry plants have the ability to compensate for flower bud loss by increasing allocation to other fruits. For example, in plots of cv. Jewel, no significant difference was found in total yields between plots with no flower bud removal and plots with all primary flower buds removed (an average of 100 clipped buds per meter)—so long as the clipping happened early in the season. An increase in the size of secondary and tertiary fruit balanced the reduced fruit numbers. Similar trends were found with Kent. The ability to compensate for early flower bud loss also was assessed in a separate study with 10 strawberry cultivars. These studies suggest that our current threshold for clipper may be nearly two orders of magnitude too low, and that clipper may not be a true economic pest of strawberry.
Abstract
Longitudinally mowing rows to half their width and the V-trellis system were used to separate fruiting canes from primocanes in a raspberry (Rubus idaeus and R. neglectus) planting. The effects of these two systems on yield and its components were determined in 1985 and 1986 for the red raspberry ‘Titan’ and the purple raspberry ‘Royalty’. Both systems were compared to a standard I-trellis configuration, in which primocanes and floricanes grow together. Yields for both cultivars were significantly higher with the V-trellis than with the I-trellis system. Longitudinal mowing reduced yields in the V-trellis, but plots that were mowed outperformed the standard I-trellis. ‘Titan’ was more responsive to cane manipulation than ‘Royalty.’