1. Describe the incidence of strawberry pests under low tunnels with a focus on arthropods, pathogens, and weeds. There is currently little research devoted to pest surveys of protected culture crops although this production system is increasing in popularity among growers in the Northeast. By surveying common strawberry pests under low tunnels compared to other production systems, this objective aims to develop new information on pest barriers and challenges of low tunnel systems. Surveys will be conducted on low tunnel, conventional, and organically grown strawberries in central New York, both in research plots and at commercial strawberry farms. We predict that several pests of strawberry respond positively under plastic tunnels such that they reach higher densities on low tunnel strawberry. Past observations indicate that spider mites, slugs, tarnished plant bugs, long-necked seed bugs, creeping perennials, and some pathogens establish well under low tunnels, thus a special focus will be made on these particular pests. Weeds are likely less of an issue, though some species may present specific challenges. Dr. Kerik Cox, an associate professor in plant pathology at Cornell, has agreed to provide guidance on identifying disease incidence and severity as a collaborator on this project.
2. Develop biological control recommendations for two-spotted spider mite (TSSM) that are tailored for low tunnel strawberry systems. A major concern of strawberry growers is the effect low tunnels have on TSSM, as this species is pesticide resistant and reproduces well under plastic tunnels. A promising alternative for control of TSSM is biological control. Objective 2 is intended to develop specific biocontrol recommendations for TSSM using commercially available predatory mites. Several predatory mite species will be tested on multiple strawberry cultivars under varying plastic types to determine which combination of predatory mite species, strawberry cultivar, and plastic type optimizes TSSM control. Further experiments will be conducted to describe the physical and chemical characteristics of strawberry cultivars to help explain the possible variation in TSSM control.
3. Optimize control of tarnished plant bug (Lygus lineolaris)(TPB) using the entomopathogen, Beauveria bassiana on low tunnel strawberry. To date, control of TPB by this fungus has been unsuccessful on field grown strawberry. Factors limiting its success include exposure to low relative humidity and harmful ultraviolet radiation in the open field, both of which reduce spore germination and pathogenicity of Beauveria bassiana. A major goal of this objective is to determine if plastic low tunnels provide a better environment for applying B. bassiana, by reducing exposure to UV and maintaining higher a higher humidity, to increase the success of this entomopathogen against TPB on strawberry.
Results generated from the above objectives will be presented at grower meetings, published in peer-reviewed journals and extension bulletins, and will be developed into instructional YouTube videos to broadly disseminate our findings.
Many growers in the Northeast are interested in low tunnel systems to maximize strawberry yields. However, tunnel systems are relatively new to the region and information on pest management is lacking. The purpose of this project is to identify the dominant pests of low tunnel strawberries and to develop tunnel-specific biological control recommendations for the two-spotted spider mite (Tetranychus urticae)(TSSM) which is often problematic under low tunnels.
TSSM is a serious pest of strawberry worldwide and is becoming increasingly resistant to chemical control. In addition, this pest appears to reach especially high densities on protected culture strawberry compared to those grown in the open field. This is likely due the hospitable environment created by the low tunnels, but the specific benefit of the plastic (e.g., maintaining warmer temperatures and a higher humidity, or the plastic’s UV blocking capabilities) that positively impacts TSSM is unknown. Understanding why TSSM reaches higher densities under plastic is crucial for building an appropriate pest management plan. In addition, it is important to evaluate how low tunnels impact pest management practices, namely biological control. Furthermore, the effect these tunnels have on pathogens, weeds, and other arthropod pests is largely unknown and warrants investigation.
Many growers in the Northeast struggle in managing TPB on strawberry and many other crops. This bug is highly polyphagous, and can move into crops from nearby weeds. It is particularly devastating on strawberry because it deforms developing fruit during feeding, rendering fruit as “cattfaced” and unmarketable if present. Management of this pest is often difficult, and highly reliant on pesticides. Alternative tactics, including the use of biocontrols, is promising but has largely unsuccessful against TPB in the field. Beauveria bassiana is a great candidate for biocontrol of TPB, as it is effective on many greenhouse pests and is widely available in several formulated products. So far, its use has been mostly in greenhouses and its efficacy under low tunnels on strawberry is unknown.
Information on pest barriers and recommendations for management is needed by low tunnel strawberry growers. This project aims to address this by identifying common weeds, pathogens and arthropod pests that are likely to be targets of control under low tunnels, and by developing specific recommendations for management of TSSM and TPB. Results generated from this study is intended to provide a foundation on which to build management programs and to promote sustainable agriculture.
A day neutral strawberry planting (var. ‘Albion’) was established that included both low tunnel production and open production in the field during 2018 and 2019 (Fig. 1). Arthropod pests, pathogens, and weeds were monitored throughout the season with a specific emphasis placed on species commonly found on strawberry. A combination of pitfall traps, sticky cards, vacuuming were conducted to describe general arthropod pest abundance while targeted sampling was conducted to monitor for specific strawberry pests. This included baited slug traps, flower tapping (for tarnished plant bug monitoring), and incubating ripe fruit to determine infestation rates of spotted wing drosophila or other fruit pests. Weeds were harvested every two weeks to determine relative weed abundance between open-field and low tunnel grown strawberries, and visual surveys in both systems were conducted to describe pathogen incidence. This effort was extended in 2019 to monitor for pest at two grower sites, and one additional research site across central NY.
Treatments of predatory mites were applied to low tunnel and open-field grown plots and monitored for their relative efficacy in controlling TSSM. In addition to collecting leaflets from plants to determine TSSM presence and severity, ripe fruit was collected each week to determine any secondary effects of predatory mite treatments on strawberry yield. No pesticides were applied during the above monitoring.
Experiments were conducted in the lab to determine if plastics mitigate exposure of B. bassiana to UV . and how this may impact biocontrol against TPB. First, agar plates inoculated with conidia of two strains of B. bassiana (GHA and ANT-03) at a concentration of 1 X 106 conidia mL−1 and covered with either one of three plastic treatments (Warps Flex-O-Glass, Tufflite IV, and Dubois) ranging in UV transmission from low to high or a control (saran wrap or aluminum foil to serve as positive and negative controls, respectively). Plates were then exposed to a UV-B dose 40.3 kJ m−2 in an UV chamber and incubated for 16 hours to determine percent spore germination. This experiment was repeated again on live TPB adults. After UV exposure, bugs were placed in growth chambers and monitored every two days to determine time of death. Once dead, cadavers were moved onto moist paper towels to monitor for sporulation by B. bassiana.
Analysis of 2019 data is just getting under way as the final week for data collection was the week of November 5th. Results in 2018 suggest that most arthropod pests reached higher densities under low tunnels as compared to open plots (Fig. 1). The single exception was aphids, which reached higher densities on open field strawberries. This effect was particularly strong for TSSM and predatory mites. Tarnished plant bug counts (not pictured) reached above threshold densities in both low tunnel and open field systems. Tunnels appeared to repress common leaf spot prevalence on strawberry leaves, while there was more insect damage on low tunnel strawberries and no effect on leaf blight infestation (Fig. 2). Weeds appeared to increase in biomass overall under low tunnels, but this was not consistent across weed species (Fig 15).
Comparison of TSSM control by beneficial mite treatments (1) N. fallacis, 2) P. persimilis, 3) N. fallacis + P. persimilis combined, and 4) no mites) revealed a little difference between the predator species (Fig. 4; p = 0.58 indicated by a generalized mixed-effects model), although treatment 1 and 3 resulted in the lowest TSSM density. In addition, of predatory mites retrieved from the field, > 95% of them were N. fallacis. This suggests that this species may be the best option for long-term management of TSSM on low tunnel strawberries. However, there was no effect of beneficial mite treatment on strawberry yield (Fig. 5).
Plastics had a significant effect on B. bassiana sporulation and pathogeneicity against TPB when exposed to UV. Saran wrap and UV-transparent plastics resulted in the lowest proportion of germinated spores (Fig 6 and 7), and this also translated to increased longevity of inoculated insects (Fig 8). This suggests that UV-blocking plastics can be used to optimize B. bassiana efficacy and improve biocontrol of TPB on strawberry.
Future efforts will be conducted to determine the impact of strawberry cultivar and plastic type on TSSM population dynamics and predatory retention/efficacy. In addition, we plan to test B. bassiana treatments against conventional pest management practices under different plastics in the field to determine relative efficacy in controlling TPB.
Education & Outreach Activities and Participation Summary
This research was presented at the 2018 Great Lakes Fruit Workers Meeting in Ithaca, NY, the 2018 annual Entomological Society of America meeting in Vancouver, BC, the 2019 AgriTech annual symposium, and the 2019 Entomological Society of America meeting in St. Louis, MO. This research was also a topic for an extension educator workshop organized by Esther Kibbe on berry pest management (see attachment for handout). This workshop took place in October 2019.
Results of this project will proved needed information on pest incidence and severity on protected culture strawberry, an important crop in NY and across the Northeast. This information contributes to sustainability by providing the foundation on which management programs can be built from. Growers will know which pests to prepare for, and thus can plan accordingly. By limiting pest control efforts to a few target pests, growers can save resources and better protect their investment in low tunnel production systems. In addition, a major goal of this project is to develop recommendations for biological control of TSSM, a devastating pest of protected culture strawberry. Alternative options for management of TSSM are needed, especially it becomes increasingly resistant to pesticides; however, current options for biological control have variable success. By tailoring current options in biocontrol to low tunnel strawberry, this project hopes to reduce the variability of biocontrol success and reduce grower reliance on pesticide use.
We have learned a great deal about sustainable production of strawberries in the Northeastern U.S. while conducting research for this project. We have specifically come to realize the great difficulty in conducting biological control experiments in the field with small pest targets, such as herbivorous mites. We hypothesize that the lack of success of predatory mites in controlling TSSM in the field was the high rate of predator dispersal from our strawberry plants, thus we will conduct further experiments to address this.
High predator retention is a crucial component of successful biological control. There are many factors influencing predator retention in the field, and for predatory mites, host plants appear to have a strong effect. Thus, we will conduct similar experiments as in 2018 but on several strawberry cultivars in the field during 2019. In addition, we will also test the effect of plastic type commonly used for low tunnels on TSSM population dynamics and predator retention.
Finally, we have become increasingly appreciative of the efforts growers and researchers make to better improve sustainable agricultural practices. After conducting pest surveys in the field to describe pest incidence on strawberry, we are now more aware of the immense pest pressure that occurs when pesticides are not used in a management program. Thus, we are even more motivated to solve this issue by further developing management practices that promote sustainability and responsible pest management.