- Author: Surendra K. Dara
Biostimulants are beneficial microorganisms or substances that can be used in crop production to improve plants' immune responses and their ability to perform well under biotic and abiotic stresses. Biostimulants induce plant resistance to stress factors through systemic acquired resistance or induced systemic resistance. When plants are exposed to virulent and avirulent pathogens, non-pathogenic microorganisms, and some chemicals, the systemic acquired resistance mechanism is activated through the salicylic acid pathway triggering the production of pathogenesis-related proteins. On the other hand, when plants are exposed to beneficial microbes, the induced systemic resistance mechanism is activated through the jasmonic acid and ethylene pathways. The jasmonic acid pathway also leads to pathogenesis-related protein production in plants. In other words, when plants are exposed to pathogens, non-pathogens, or other compounds, various defense genes are activated through two major immune responses, helping plants fight the real infection or prepare them for potential infection. Beneficial microbes and non-microbial biostimulants are like vaccines that prepare plants for potential health problems.
Earlier studies in tomato (Dara and Lewis, 2018; Dara, 2019a) and strawberry (Dara and Peck, 2018; Dara, 2019b) demonstrated varying levels of benefits to crop health and yield improvements from a variety of botanical, microbial, or mineral biostimulants and other supplements. Some of the evaluated products resulted in significant yield improvement in both tomatoes and strawberries compared to the grower standard practices. There are several biostimulant products in the market with a variety of active ingredients, and some also have major plant nutrients such as nitrogen, phosphorus, and potassium. Depending on the crop, growing conditions, potential risk of pests and diseases, and other factors, growers can use one or more of these products. A study was conducted to evaluate the impact of various biostimulants on the yield, quality, and shelf life of strawberries.
Strawberry cultivar San Andreas was planted late November 2018 and treatments were administered at the time of planting or soon after, depending on the protocol. Each treatment had a 290' long strawberry bed where 10' of the bed at each end was left out as a buffer. Then, six 30' long plots, each representing a replication, were marked within each bed with an 18' buffer between the plots. Since the test products needed to be applied through the drip system, an entire bed was allocated for each treatment, except for the standard program that had one bed on either side of the experimental block, and plots were marked within each bed for data collection. The following treatment regimens were used in the study:
1. Standard Program (SP): Major nutrients were provided in the form of Urea Ammonium Nitrate Solution 32-0-0, Ammonium Polyphosphate Solution, and Potassium Thiosulfate (KTS 0-0-25). Nitrogen, phosphorus, and potassium were applied before planting in November 2018 at 170, 60, and 130 lb/acre, respectively. From 15 January to 9 May 2019, a total of 26 lb of nitrogen, 13 lb of phosphorus, and 26 lb of potassium were applied through 13 periodic applications.
2. SP + Terramera Program: Formulation labeled as Experimental A (cold-pressed neem 70%) was applied at 1.2% vol/vol immediately after planting. Additional applications were made starting from 2 weeks after planting once every two weeks until the end of February (six times), followed by 13 weekly applications from the beginning of March.
3. SP + Locus Low Rate Program: This program contained Rhizolizer soil amendment (Trichoderma harzianum 1X108 CFU/ml and Bacillus amyloliquefaciens 1X109 CFU/ml) at 3 fl oz/acre, humic acid at 13.5 fl oz/acre, and kelp at 6.8 fl oz/acre. The first application was made within 15 days and at 30 days after planting followed by once in February, March, and April 2019.
4. SP + Locus High Rate Program: This program contained Rhizolizer soil amendment (Trichoderma harzianum 1X108 CFU/ml and Bacillus amyloliquefaciens 1X109 CFU/ml) at 6 fl oz/acre, humic acid at 13.5 fl oz/acre, and kelp at 6.8 fl oz/acre. The first application was made within 15 days and at 30 days after planting followed by once in February, March, and April 2019.
5. SP + BioGro Program: Transplants were treated with Premium Plant BB (Beauveria bassiana 1.1%) by spraying 2 fl oz/acre (1.29 ml in 850 ml of water). About 7 weeks after planting, 30 gpa of Plant-X Rhizo-Pro (botanical extracts), 2 gpa of CHB Premium 21 (humic acid blend), 3 gpa of CHB Premium 6 (3% humic acids), and 5 gpa of NUE Flourish 4-12-0 were applied. Starting from mid-February 2019, 15 gpa of Plant-X Rhizo-Pro, 1 gpa of CHB Premium 21, and 2 gpa of CHB Premium 6 were applied four times every 2 weeks until the end of March. Starting from 5 April 2019, 8 weekly applications of 10 gpa of Plant-X Rhizo-Pro, 1 gpa of CHB Premium 21, 2 gpa of Premium 6, and 4 gpa of NUE Flourish 4-12-0 were made until 26 May 2019.
6. SP + Actagro Program: Structure 7-21-0 at 3 gpa and Liquid Humus 0-0-4 with 22% organic acids at 1 gpa were first applied within 1 week of planting and then three more times every 2 weeks until the end of December 2018. Additional monthly applications were made from the end of January to the end of April 2019.
All the fertilizers and treatment materials were applied through the drip system using the Dosatron (Model D14MZ2) equipment. The following parameters were measured during the experimental period from January to May 2019.
Canopy: The size of the plant canopy was determined on 21 January and again on 17 February 2019 by measuring the spread of the canopy across and along the length of the bed from 16 random plants within each plot, and calculating the area.
Initial flowering and fruiting: When flowering initiated, the number of flowers and developing fruits was counted from 16 random plants within each plot on 1 and 16 February 2019.
Fruit yield: Fruit was harvested weekly from every plant within each plot from 3 March to 26 May 2019 on 11 dates and the number and weight of the marketable and unmarketable fruit was determined. Due to a technical error, some of the yield data from an additional date (29 March) were lost and excluded from the analysis.
Fruit firmness: The firmness of two marketable fruit from each of five random plants per plot was measured using a penetrometer on 5 April, and 16 and 26 May 2019.
Fruit sugar content: The sugar content from one marketable fruit from each of 10 plants per plot was measured using a refractometer on 5 April and 26 May 2019.
Leaf chlorophyll content: On 11 March and 31 May 2019, the chlorophyll content of one mature leaf from each of five random plants per plot was measured using a chlorophyll meter.
Postharvest disease: Marketable fruit harvested on 21 and 28 April, and 5 and 26 May 2019 was kept at the room temperature in perforated plastic containers (clamshells) and the growth of gray mold (Botrytis cinerea) or Rhizopus fruit rot fungus (Rhizopus spp.) was measured on a scale of 0 to 4 (where 0=no fungus, 1=1-25%, 2=26-50%, 3=51-75%, and 4=76-100% fungal growth) 3 and 5 days after each harvest.
Data were analyzed using analysis of variance in Statistix software and significant means were separated using the Least Significant Difference means separation test.
Results and Discussion
Statistically significant differences among treatments were seen for the seasonal total number of unmarketable berries (P = 0.0172), the initial flower and fruit numbers on 1 February (P < 0.0014), the leaf chlorophyll content on 31 May (P = 0.0144), and the disease rating 3 days after the 28 April harvest (P = 0.0065).
Treatments did not differ (P > 0.05) in any other measured parameters of the plant, fruit quality, or yield. However, the total seasonal fruit yield was 13 to 31% higher and the total marketable fruit yield was 10 to 36% higher in various treatment programs compared to the standard program. The seasonal total of unmarketable fruit yield was also 4 to 25% higher in treatment programs than the standard program except that there were nearly 12% fewer unmarketable berries in the Actagro program compared to the standard program.
While treatments did not statistically differ for many of the measured parameters, numerical differences in marketable fruit yield could be helpful for some understanding of the potential of these biostimulants. Additional studies with larger treatment plots would be useful for generating additional data.
Thanks to Dr. Jenita Thinakaran for the assistance at the start of the study, Hamza Khairi for his technical assistance throughout the study, the field staff at the Shafter Research Station for the crop maintenance, NorCal Nursery for the strawberry transplants, and Actagro, BioGro, Locus, and Terramera for their collaboration and financial support
Dara, S. K. 2019a. Improving tomato yield with nutrient materials containing microbial and botanical biostimulants. eJournal of Entomology and Biologicals, 6 June 2019 https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=30448
Dara, S. K. 2019b. Evaluating the efficacy of anti-stress supplements on strawberry yield and quality. eJournal of Entomology and Biologicals, 10 August 2019 https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=31044
Dara, S. K. and D. Peck. 2018. Microbial and bioactive soil amendments for improving strawberry crop growth, health, and fruit yields: a 2017-2018 study eJournal of Entomology and Biologicals, 3 August 2018 https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=27891
Dara, S. K. and E. Lewis. 2018. Impact of nutrient and biostimulant materials on tomato crop health and yield. eJournal of Entomology and Biologicals, 9 January 2019 https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26054
- Author: Surendra K. Dara
The traditional Integrated Pest Management (IPM) model is focused on maintaining ecological balance in the cropping system with some attention to the economics of pest management related to the yield losses. The new model, recently published in the Journal of Integrated Pest Management, is more comprehensive covering the management, business, and sustainability aspects of pest management and discusses various components within (Dara, 2019). IPM, according to the new model, can be defined as an approach to managing pests in an economically viable, socially acceptable, and environmentally safe manner.
New IPM model from Dara, 2019
Based on the information generated by several studies in California and other reports, here is how the new IPM model can be adapted for producing strawberries sustainably.
1. MANAGEMENT ASPECT
A. Pest Management: The term “pest” includes arthropod pests, diseases, and weeds and the management includes the various practices used to suppress them.
- Select varieties that produce good yields while resisting biotic and abiotic stresses.
- Choosing the right mulch and good irrigation and nutrient management contribute to good plant growth and health. Micro-sprinklers save water and hold pest management benefits.
- Explore the potential of beneficial microbes and biostimulants to improve nutrient and water absorption and to maintain crop health. Inoculate the transplants with biostimulants to induce systemic resistance and periodically apply, especially after fumigation, to improve the beneficial microbial activity in the soil.
- Healthy plants resist pest problems and reduce the need for control options. Plant health can be maintained through good cultural practices (biostimulants, nutrients, irrigation, soil conditioning, etc.).
- Predatory mites effectively control twospotted and Lewis mites, but natural enemy populations may not be sufficient to control the western tarnished plant bug.
- Light traps can be useful for managing lepidopteran pests.
- Tractor-mounted vacuums can be a part of the IPM program for managing the western tarnished plant bug, but their pest control efficiency is not necessarily superior to other strategies and are not without some associated risks. For example, operation of vacuums requires fossil fuels and they are used at a much higher frequency than pesticide applications.
- Use botanical, microbial, and chemical pesticides in combination. Combinations can improve pest control efficacy and rotations reduce the risk of resistance development.
- Rotating strawberries with crops such as broccoli can reduce the severity of certain soilborne diseases.
B. Knowledge and Resources:
- Understand pest biology, vulnerable stages of the pest, and appropriate strategies for each pest, different life stages, season, and budget. For example, relying on natural enemies for the western tarnished plant bug control is not effective and can lead to higher pest damage.
- Accurately identify the issue through visual observation or laboratory diagnosis for proper corrective action.
- Try to explore modern technology to monitor crop health.
C. Planning and Organization:
- Regularly monitor crop health for early detection and prevention of potential pest problems. For example, thorough scouting to determine the level of western tarnished plant bug infestation is very important for making the treatment decision. Deformed fruit is not always an indicator for the treatment threshold as nearly 1/3 of the fruit deformity occurs from environmental and other causes not related to the western tarnished plant bug.
- Look for signs of pesticide resistance and use appropriate strategies to reduce the risk.
- Maintain records of pest occurrence, seasonal trends, strategies that worked, and all relevant information, to build institutional knowledge for future use.
- Take the right action at the right time.
- Regularly attend extension events and read research updates. Choose or design practices that are ideal for your farm based on the research updates.
- Periodically provide training to all individuals on the farm who directly or indirectly contribute to good agriculture practices.
- Share good management practices with each other for area-wide improvement of crop production and pest management.
- Try to educate the public so that they make better choices when purchasing produce. For example, good IPM practices can be more sustainable than organically approved practices and well-informed consumers can make a choice among conventional, organic, or sustainably produced grains, fruits, and vegetables. Public education can also help to eliminate otherwise good produce that is discarded because of minor imperfections. In strawberry, fruit deformity is caused due to the feeding of the western tarnished plant bug, genetic factors, poor pollination, or very low temperatures. Although most of the deformed strawberries, especially those from insect damage, have equal quality as marketable strawberries, they are discarded because of their shape. If the consumer market can accept deformed strawberries that still have good taste and nutritional quality, it can significantly reduce the wastage and the amount of pesticides sprayed to control the western tarnished plant bug.
2. BUSINESS ASPECT
- A strong IPM program can help growers produce sustainably while ensuring profitability.
- Consumer choices depend on their knowledge of sustainable agriculture. When they understand that produce with an IPM or Sustainably Produced label is safe for human and environmental health, it will have a major impact on food production systems.
3. SUSTAINABILITY ASPECT
- The current interpretation or perception of sustainability does not reflect true sustainability in terms of environmental health, profitability, food security, social equality, and other elements. A good IPM model can address all these issues to ensure farm productivity, food affordability, and environmental safety.
RESEARCH and OUTREACH
- Research and outreach component is the foundation of IPM to identify pest issues, develop appropriate knowledge for their management, and effectively disseminate the related information. Supporting research and outreach efforts of universities and other entities is essential for continuing IPM.
In addition to the below references, there are several articles in this eJournal on crop production and protection topics related to strawberry.
- Download “Biology and management of spider mites in strawberry” in English and Spanish at http://ucanr.edu/spidermiteguide or scan the QR code. Information about different species of spider mites and predatory mites is available in this guide.
- Efficacy of botanical, chemical, and microbial pesticides on twospotted spider mite and their impact on predatory mites http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=18553
- Entomopathogenic fungi can endophytically colonize strawberry plants when applied to the soil and negatively impact twospotted spider mite infestations http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16821
- How to detect resistance to miticides in twospotted spider mite populations and strategies to reduce the resistance development http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22097
- Comparison between the twospotted spider mite and the Lewis mite http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=5771
- An overview of lygus bug biology, damage, and management in strawberries http://cesantabarbara.ucanr.edu/files/75473.pdf
- Lygus biology, monitoring, and management videos http://ucanr.edu/SDYouTube
- Fruit deformity in strawberry from lygus bug and other factors http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19630
- Potential of a solar-powered UV light trap as a pest management option in strawberry http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=25307
- IPM tools for controlling western tarnished plant bug in strawberry https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19641
- Entomopathogens (pathogens of insects, mites, and ticks), their modes of infection, and how they can be used as a powerful tool in IPM http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=24119
- Biopesticides and IPM https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=25912
- Lygus bug and natural enemy populations in organic and conventional strawberries https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14030
- Microbial and bioactive soil amendments for improving strawberry health and yields (2017-2018 study) https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=27891
- Beneficial microbe-based products for strawberry health and yield (2016-2017 study)
- Beneficial microbes and entomopathogenic fungi for strawberry health and yield (2015-2016 study) https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22709
- Entomopathogenic fungi antagonizing Macrophomina phaseolina https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=28274
- Entomopathogenic fungi and other biologicals against Fusarium oxysporum
- Micro-sprinklers in strawberry https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19699