The diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae) is an important pest of broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, and other cruciferous crops. It exclusively feeds on cultivated and weedy crucifers and has a worldwide distribution. Larvae feed on foliage and growing parts of young plants or bore into the heads or flower buds resulting in skeletonization of leaves, stunting of the plants, or failure of head formation in some hosts. In warmer areas, the diamondback moth has up to 12 generations per year. While multiple species of parasitoids and predatory arthropods provide some level of natural control, insecticidal applications are a primary means of diamondback moth management. Although several synthetic and biological pesticides are effective against the diamondback moth, resistance to Bacillus thuringiensis (Ferré et al. 1991), abamectin (Pu et al. 2009), emamectin benzoate, indoxacarb, and spinosad (Zhao et al. 2006), pyrethroids and other pesticides (Leibee and Savage 1992; Endersby et al. 2011) has been well-known from around the world. Excessive use of any kind of pesticide leads to resistance problems (Dara 2020; also see a video presentation) to an individual pesticide or multiple pesticides. Integrated pest management (IPM) strategy encourages the use of various control options both for maintaining pest control efficacy and reducing the risk of resistance development (Dara 2019). Regularly monitoring the pest populations to make treatment decisions, rotating pesticides with different modes of action, exploring the potential of biocontrol agents, and other non-chemical control approaches such as mating disruption with pheromones are some of the IPM strategies for controlling the diamondback moth. While sex pheromones effectively used to manage several lepidopteran pests and are proven to be a critical IPM tool, mating disruption is not fully explored for controlling the diamondback moth. A study was conducted in Brussels sprouts to evaluate the efficacy of a sprayable pheromone against the diamondback moth and to enhance the current IPM strategies.
The study was conducted on a 10-acre Brussels sprouts field in Santa Maria. Cultivar Marte was planted in early July 2020 with expected harvesting in mid to late December. A typical diamondback control program includes monitoring diamondback moth populations with the help of sticky traps and lures and applying various combinations of biological and synthetic pesticides at regular intervals. This study evaluated the efficacy of adding CheckMate DBM-F to the grower standard practice of monitoring the diamondback moth populations with traps and lures and applying pesticides. Treatments included i) grower standard pesticide program (Table 1) and ii) grower standard pesticide program with two applications of 3.1 fl oz of CheckMate DBM-F on 9 August and 11 September. Treatment materials were applied by a tractor-mounted sprayer using a 100 gpa spray volume and necessary buffering agents and surfactants. Each treatment was 5 ac and divided into four quadrants representing four replications. In the middle of each quadrant, one Suterra Wing Trap was set up with a Trécé Pherocon Diamondback Moth Lure. Lures were replaced once a month in early September and early October. Sticky liners of the traps were replaced every week to count the number of moths trapped. Traps were placed on 1, 12, and 24 August, 1, 11, 18, and 27 September, and 6 October and the moth counts were taken from respective traps on 8 and 20 August, 1, 11, 18, and 27 September, 6 and 15 October. CheckMate DBM-F was applied at 3.1 fl oz/ac on 9 August and 11 September. The number of larvae and their feeding damage on a scale of 0 to 4 (where 0=no damage, 1=light damage, 2=moderate damage, 3=high damage, 4=extensive/irrecoverable) were recorded from 25 random plants within each replication on 30 August and 6 and 18 October. Data were subjected to analysis of variance using Statistix software and significant means were separated using Tukey's HSD test. The retail value of various pesticides was also obtained to compare the cost of treatments.
Table 1. Pesticides, buffering agents, and surfactants, their active ingredients, rates/ac (along with the IRAC mode of action groups), and retail pricing for those applied in the grower standard diamondback moth control program.
When CheckMate DBM-F [(Z)-11-Hexadecenal (3) , (Z) - 11 - Hexadecen-1-yl Acetate (1)] was applied the first time on 9 August, Dibrom 8 Emulsive was replaced with Warrior II, the buffering agent Quest was not used, and the surfactant Dyne-Amic was replaced with Induce (dimethylpolysiloxane) to avoid potential compatibility issues. The impact of this substitution is expected to be negligible within the scope of this study. The retail cost of 3.1 fl oz CheckMate DBM-F is $45.60. The cost of lures and traps would be about $4-8 per acre for a six-month crop like Brussels sprouts.
Results and Discussion
Moth populations: Traps in replication 4 in both treatments on 8 August and replication 1 in the grower standard were missing, probably knocked down by a tractor. The day before CheckMate DBM-F was first applied, the mean number of adult diamondback moths caught were 227 in the grower standard and 271 in the plots that would receive the pheromone application. There was a gradual decline in moth counts during the rest of the observation period in both treatments. However, the decline was higher in the plots that received CheckMate DBM-F. The number of moths per trap were about 19% higher in the pheromone-treated plots compared to the grower standard before the study but were nearly 98% lower by the end of the study. The reduction in moth populations from mating disruption was significant on 18 September (P =0.039) and 15 October (P = 0.006).
Larval populations: The mean number of larvae per 25 plants in a replication was zero on all observation dates except for 0.01 on 30 August in the plots that received CheckMate. Four insecticide applications by the time the study was initiated, and the remaining six applications effectively suppressed larval populations.
Damage ratings: Larval feeding damage ratings were consistently low (P < 0.0001) in the plants that did not receive CheckMate DBM-F. The damage was limited to the older leaves at the bottom of the plants and must have been from early feeding before the initiation of the study. The lack of larvae and the evidence of new feeding damage also confirm that the crop remained healthy and pest-free.
Since frequent pesticide applications effectively suppressed larval populations and prevented their feeding damage, the effectiveness of mating disruption in reducing yield losses could not be determined in this study. Since larval counts were not made weekly or between pesticide applications, those that were probably present between the pesticide applications could not be determined. Moths found in the traps probably developed from the larvae in the field or could have been those that flew in from other areas. However, lower moth populations in CheckMate DBM-F treatment demonstrated the overall influence of mating disruption and pest suppression.
It is common to make about 10-12 pesticide sprays during the 6-month crop cycle of Brussels sprouts. The cost of each application varied from about $73 to $192 depending on the materials used with an average cost of about $128 per application in this study. The cost of two CheckMate DBM-F applications is $91. If diamondback moth populations could be reduced with mating disruption, it is estimated that 2-3 pesticide applications could be eliminated. That results in $164 to $292 of saving for the pesticide costs and additional savings in the application costs per acre by investing $91 in the mating disruption. Since the diamondback moth can develop resistance to several chemical and natural pesticides, eliminating some applications as a result of mating disruption also contributes to resistance management along with potential negative impact of pesticides on the environment. Compared to other mating disruption strategies, a sprayable formulation compatible with other agricultural inputs is easier and cost-effective to use.
This study demonstrated that mating disruption with CheckMate DBM-F will significantly enhance the current IPM practices by reducing pest populations, contributing to insecticide resistance management, and reducing pest management costs. Additional studies, with fewer pesticide applications that allow larvae to survive and cause some damage, might further help understand the role of mating disruption where pest populations are not managed as effectively as in this field.
Acknowledgments: Thanks to the PCA and the grower for their research collaboration, Tamas Zold for his technical assistance in data collection, Ingrid Schumann for market research of pesticide pricing, and Suterra for the financial support.
Dara, S. K. 2019. The new integrated pest management paradigm for the modern age. J. Int. Pest Manag. 10: 12.
Dara, S. K. 2020. Arthropod resistance to biopesticides. Organic Farmer 3 (4): 16-19.
Endersby, N. M., K. Viduka, S. W. Baxter, J. Saw, D. G. Heckel, and S. W. McKechnie. 2011. Widespread pyrethroid resistance in Australian diamondback moth, Plutella xylostella (L.), is related to multiple mutations in the para sodium channel gene. Bull. Entomol. Res. 101: 393.
Ferré, J., M. D., Real, J. Van Rie, S. Jansens, and M. Peferoen. 1991. Resistance to the Bacillus thuringiensis bioinsecticide in a field population of Plutella xylostella is due to a change in a midgut membrane receptor. Proc. Nat. Acad. Sci. 88: 5119-5123.
Leibee, G. L. and K. E. Savage. 1992. Evaluation of selected insecticides for control of diamondback moth and cabbage looper in cabbage in Central Florida with observations on insecticide resistance in the diamondback moth. Fla. Entomol. 75: 585-591.
Pu, X., Y. Yang, S. Wu, and Y. Wu. 2009. Characterisation of abamectin resistance in a field-evolved multiresistant population of Plutella xylostella. Pest Manag. Sci. 66: 371-378.
Zhao, J-Z., H. L. Collins, Y-X. Li, R.F.L. Mau, G. D. Thompson, M. Hertlein, J. T. Andaloro, R. Boykin, and A. M. Shelton. 2006. Monitoring of diamondback moth (Lepidoptera: Plutellidae) resistance to spinosad, indoxacarb, and emamectin benzoate. J. Econ. Entomol. 99: 176-181.
Several crown, fruit, and foliar diseases cause significant yield losses to strawberry. Gray mold or Botrytis fruit rot caused by Botrytis cinerea, mucor fruit rot by Mucor spp., and Rhizopus fruit rot by Rhizopus spp. are common fungal diseases in California. Botrytis cinerea is more prevalent and damaging fungus among these pathogens warranting regular fungicidal applications. Fungal spores survive in plant debris and soil and infection can occur before flower initiation. Both flowers and fruits are subjected to infection. Severely infected flowers fail to develop into fruits. Infection on developing or ripe fruit occurs as brown lesions, usually under calyxes. Infected areas rot and become dry and leathery under dry conditions or produce a thick, gray mat of spores under cool, moist conditions.
Mucor spp. invade the fruit through ruptured skin and cause leaky fruit rot. Under high humidity, profuse fungal growth of white, tough filaments with black spore-bearing structures is seen covering the fruit. In the case of Rhizopus fruit rot, discolored, water-soaked spots develop on fruit eventually leading to wilting. Similar to the Mucor fruit rot, Rhizopus rot also leads to leaky fruits and development of black spore-bearing structures on white mycelia under high humidity. Both pathogens survive in dead and decaying plant material and can persist in the field.
In a fall-planted conventional strawberry, growers usually make 12 or more fungicidal applications during a four-month period to control Botrytis and other fruit rots. Although fungicides with different modes of action are present and growers try to rotate them, fungicide resistance in B. cinerea is common and effective integrated disease strategies are necessary. Using biostimulants that might improve plant's ability to withstand diseases and alternating chemicals with biological fungicides could be some options to mitigate chemical fungicide resistance. Previous studies looked at the response of fruit diseases to various treatments that received biological soil amendments (Dara, 2020a), soil fungicides (Dara, 2020b), or chemical and biological fungicides (Dara, 2019). This study was conducted to evaluate the efficacy of some biological fungicides along with a chemical fungicide primarily against Botrytis fruit rot.
This study was conducted at a research strawberry field at the Shafter Research Station. Strawberry cultivar San Andreas was planted on 31 October 2019. Other than regular irrigation and fertigation, plants in this study were not treated with any agricultural inputs for agronomic or pest management purposes. Treatments included i) untreated control, ii) Elevate 50 WDG (fenhexamid) at 8 oz/ac, iii) Serifel (Bacillus amyloliquefaciens) at 8 oz/ac, iv) ProBlad Verde (Banda de Lupinus albus doce – BLAD, a polypeptide from sweet lupine) at 36 fl oz with Cinnerate (cinnamon oil) at 0.25% followed by ProBlad Verde at 36, 43, and 43 fl oz/ac on subsequent applications, and v) ProBlad Verde at 36 fl oz with Cinnerate at 0.25% followed by three subsequent applications of ProBlad Verde at 32 fl oz/ac. Each treatment had a 3.2' wide and 14' long plot with two rows of plants and replicated four times in a randomized complete block design. Treatments were applied using a CO2-pressurized backpack sprayer using a 45 gpa spray volume on 26 March, 2, 10, and 20 April 2020. Flowers and fruits were removed from all the plants before the first application. Fruit was harvested on 14 and 27 April and 2 and 10 May and stored in vented plastic containers for postharvest quality assessment. The severity of Botrytis and other fruit rots was recorded 3 and 5 days after harvest on a scale of 0 to 4 where 0=no disease, 1=1-25% fruit with fungal infection, 2=26-50% infection, 3=51-75%, and 4=76-100%. Compared to Botrytis fruit rot, other rots occurred as mixed infections at different times and it was not possible to accurately measure them separately. Data presented in this study primarily represent Botrytis fruit rot with other fruit rots included on some data sets. Data were subjected to analysis of variance using Statistix software to compare disease severity for individual harvest dates and their average.
Fruit rots occurred from low to moderate levels during the observation period. Disease severity followed the usual trend with higher levels 5 days after harvest compared to 3 days after harvest. Compared to untreated control, disease severity was numerically lower in some treatments especially 3 days after harvest, but differences were not statistically significant (P > 0.05) when individual harvest dates or their average were considered. The average disease severity from four harvests was 0.25 in Elevate and Serifel, 0.50 in ProBlad Verde low rate with Cinnerate, and 0.81 in ProBlad Verde high rate with Cinnerate treatment and untreated control 3 days after harvest. The average disease severity was 1.13 for Serifel, 1.19 for Elevate and the low rate of ProBlad Verde with Cinnerate, 1.81 for the high rate of ProBlad Verde with Cinnerate, and 2.0 for untreated control 5 days after harvest. Although statistically significant differences could not be found among treatments, this study indicates the potential of non-chemical alternatives and warrants additional studies for further investigation.
Acknowledgements: Thanks to BASF and Sym-Agro for funding this study and Marjan Heidarian Dehkordi and Zach Woolpert for the technical assistance.
Dara, S. K. 2019. Five shades of gray mold control in strawberry: evaluating chemical, organic oil, botanical, bacterial, and fungal active ingredients. UCANR eJournal of Entomology and Biologicals. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=30729
Dara, S. K. 2020a. Improving strawberry yields with biostimulants and nutrient supplements: a 2019-2020 study. UCANR eJournal of Entomology and Biologicals. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=43631
Dara, S. K. 2020b. Impact of drip application of fungicides on strawberry health and yields. UCANR eJournal of Entomology and Biologicals. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=43632
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
Integrated pest management, commonly referred to as IPM, is a concept of managing pests that has been in use for several decades. The definition and interpretation of IPM vary depending on the source, such as a university, institute, or a researcher, and its application varies even more widely depending on the practitioner. Here are a few examples of its definitions and interpretations:
“IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimizes risks to human health, beneficial and nontarget organisms, and the environment.” UC IPM
“Integrated Pest Management, or IPM, is an approach to solving pest problems by applying our knowledge about pests to prevent them from damaging crops, harming animals, infesting buildings or otherwise interfering with our livelihood or enjoyment of life. IPM means responding to pest problems with the most effective, least-risk option.” IPM Institute of North America
“A well-defined Integrated Pest Management (IPM) is a program that should be based on prevention, monitoring, and control which offers the opportunity to eliminate or drastically reduce the use of pesticides, and to minimize the toxicity of and exposure to any products which are used. IPM does this by utilizing a variety of methods and techniques, including cultural, biological and structural strategies to control a multitude of pest problems.” Beyond Pesticides
“IPM is rotating chemicals from different mode of action groups.” A grower
These definitions and interpretations represent a variety of objectives and strategies for managing pests. IPM is not a principle that can/should be strictly and equally applied to every situation, but a philosophy that can guide the practitioner to use it as appropriate for the situation. For example, varieties that are resistant to arthropod pests and diseases are available for some crops, but not for others. Mating disruption with pheromones is widely practiced for certain lepidopteran and coleopteran pests, but not for several hemipteran pests. Biological control is more readily employed for greenhouse pests, but not to the same extent under field conditions. While chemical pesticides should be used as the last resort, in principle, sometimes they are the first line of defense to prevent damage to the transplants by certain pests or area-wide spread of certain endemic or invasive pests and diseases.
Crop production is an art, science, and business, and by adding environmental and social factors, IPM – an approach used in agriculture – can also be influenced by a number of factors. Each grower has their own strategy for producing crops, minimizing losses, and making a profit in a manner that is acceptable to the society, safe for the consumers, and less disruptive to the environment. In other words, “IPM is an approach to manage pests in an economically viable, socially acceptable, and environmentally safe manner”. Keeping this simple, but loaded, definition in mind and considering recent advances in crop production and protection, communication technology, and globalization of agriculture and commerce, here is the new paradigm of IPM with its management, business, and sustainability aspects.
I. Management Aspect
There are four major components in the IPM model that address the various pest management options, the knowledge and resources the grower has in order to address the pest issue, planning and organization of information to take appropriate actions, and maintaining good communication to acquire and disseminate knowledge about pests and their management.
1. Pest Management:
The concept of pest control has changed to pest management over the years knowing that a balanced approach to managing pest populations to levels that do not cause economic losses is better than eliminating for environmental and economic reasons. Although the term control is frequently used in literature and conversations, it generally refers to management. A thorough knowledge of general IPM principles and various management options for all possible pest problems is important as some are preventive and others are curative. It is also essential to understand inherent and potential interactions among these management options to achieve maximum control. The following are common control options that can be employed at different stages of crop production to prevent, reduce, or treat pest infestations. Each of them may provide only a certain level of control, but their additive effect can be significant in preventing yield losses.
a. Host plant resistance: It involves the use of pest resistant and tolerant cultivars developed through traditional breeding or genetic engineering. These cultivars possess physical, morphological, or biochemical characters that reduce the plant's attractiveness or suitability for the pest to feed, develop, or reproduce successfully. These cultivars resist or tolerate pest damage and thus reduce the yield losses.
b. Cultural control: Changing agronomic practices to avoid or reduce pest infestations and damage refers to cultural control. Adjusting planting dates can help escape pest occurrence or avoid most vulnerable stages. Modifying irrigation practices, fertilizer program, plant or row spacing, and other agronomic practices can create conditions that are less suitable for the pest. Destroying crop residue and thorough cultivation will eliminate breeding sites and control soil-inhabiting stages of the pest. Crop rotation with non-host or tolerant crops will break the pest cycles and reduce their buildup year after year. Choosing clean seed and plant material will avoid the chances of introducing pests right from the beginning of the crop production. Sanitation practices to remove infected/infested plant material, regular cleaning field equipment, avoiding accidental contamination of healthy fields through human activity are also important to prevent the pest spread. Intercropping of non-host plants or those that deter pests or using trap crops to divert pests away from the main crop are some of the other cultural control strategies.
c. Biological control: Natural enemies such as spiders, predators, and parasitic wasps can be very effective in causing significant reductions in pest populations in certain circumstances. Periodical releases of commercially available natural enemies or conserving natural enemy populations by providing refuges or avoiding practices that harm them are some of the common practices to control endemic pests. To address invasive pest issues, classical biological control approach is typically employed where natural enemies from the native region of the invasive pest are imported, multiplied, and released in the new habitat of the pest. The release of irradiated, sterile insects is another biological control technique that is successfully used against a number of pests.
d. Behavioral control: Behavior of the pest can be exploited for its control through baits, traps, and mating disruption techniques. Baits containing poisonous material will attract and kill the pests when distributed in the field or placed in traps. Pests are attracted to certain colors, lights, odors of attractants or pheromones. Devices that use one or more of these can be used to attract, trap or kill pests. Pheromone lures confuse adult insects and disrupt their mating potential, and thus reduce their offspring.
e. Physical or mechanical control: This approach refers to the use of a variety of physical or mechanical techniques for pest exclusion, trapping (in some cases similar to the behavioral control), removal, or destruction. Pest exclusion with netting, handpicking or vacuuming to remove pests, mechanical tools for weed control, traps for rodent pests, modifying environmental conditions such as heat or humidity in greenhouses, steam sterilization or solarization, visual or physical bird deterrents such as reflective material or sonic devices are some examples for physical or mechanical control.
f. Microbial control: Using entomopathogenic bacteria, fungi, microsporidia, nematodes, and viruses, and fermentation byproducts of microbes against arthropod pests, fungi against plant parasitic nematodes, and bacterial and fungal antagonizers of plant pathogens generally come under microbial control.
g. Chemical control: Chemical control typically refers to the use of synthetic chemical pesticides, but to be technically accurate, it should include synthetic chemicals as well as chemicals of microbial or botanical origin. Although botanical extracts such as azadirachtin and pyrethrins, and microbe-derived toxic metabolites such as avermectin and spinosad are regarded as biologicals, they are still chemical molecules, similar to synthetic chemicals, and possess many of the human and environmental safety risks as chemical pesticides. Chemical pesticides are categorized into different groups based on their mode of action and rotating chemicals from different groups is recommended to reduce the risk of resistance development. Government regulations restrict the time and amount of certain chemical pesticides and help mitigate the associated risks.
The new RNAi (ribonucleic acid interference) technology where double-stranded RNA is applied to silence specific genes in the target insect is considered as a biopesticide application. Certain biostimulants based on minerals, microbes, plant extracts, seaweed or algae impart induced systemic resistance to pests and diseases, but are applied as amendments without any claims for pest or disease control. These new products or technologies can fall into one or more abovementioned categories.
As required by the crop and pest situation, one or more of these control options can be used throughout the production period for effective pest management. When used effectively, non-chemical control options delay, reduce, or eliminate the use of chemical pesticides.
2. Knowledge and Resources:
The knowledge of various control options, pest biology and damage potential, and suitability of available resources enables the grower to make a decision appropriate for their situation.
a. Pest: Identification of the pest, understanding its biology and seasonal population trends, damaging life stages and their habitats, nature of damage and its economic significance, vulnerability of each life for one or more control options, host preference and alternate hosts, and all the related information is critical for identifying an effective control strategy.
b. Available control options: Since not all control options can be used against every pest, the grower has to choose the ones that are ideal for the situation. For example, systemic insecticides are more effective against pests that mine or bore into the plant tissue. Pests that follow a particular seasonal pattern can be controlled by adjusting planting dates. Commercially available natural enemies can be released against some, while mating disruption works well against others. Entomopathogenic nematodes can be used against certain soil pests, bacteria and viruses against pests with chewing mouthparts such as lepidoptera and coleopteran, and fungi against sucking pests.
c. Tools and technology: A particular pest can be controlled by certain options, but they may not all be available in a particular place, for a particular crop, or within the available financial means. For example, the release of natural enemies may be possible in high-value speciality crops, but not in large acreage field crops. A particular pesticide might be registered against a pest on some crops, but not on all. Use of netting or tractor-mounted vacuums can be effective, but very expensive limiting their availability to those who can afford.
This is a critical component where diagnostic and preventive or curative decisions are made based on available and affordable control options.
3. Planning and Organization:
This component deals with the management aspect of the of the new IPM model for data collection, organization, and actual actions against pest infestations.
a. Pest monitoring: Regularly monitoring the fields for pest infestation and spread is a basic step in crop protection. Early detection in many cases can help address the pest situation by low-cost spot treatment or removal of pests or infected/infested plant material. When pest infestations continue to grow, regular monitoring is necessary to assess the damage and determine the time to initiate farm-wide control. Monitoring is also important to avoid calendar-based pesticide applications especially at lower pest populations that do not warrant treatments.
b. Managing information: A good recordkeeping about pests, their damage, effective treatments, seasonal fluctuations, interactions with environmental factors, irrigation practices, plant nutrition, and all related information from year to year will build the institutional knowledge and prepares the grower to take preventive or curative actions.
c. Corrective actions: Taking timely action is probably the most important aspect of IPM. Even with all the knowledge about the pest and availability of resources for its effective management, losses can be prevented only when corrective actions are taken at the right time. Good farm management will allow the grower to take timely actions. These actions are not only necessary to prevent damage on a particular farm, but also to prevent the spread to neighboring farms. When pest management is neglected, it leads to area-wide problems with larger regulatory, social, and economic implications.
Good communication to transfer the individual or collective knowledge for the benefit of everyone is the last component of the new IPM model. Modern and traditional communication tools can be used for outreach as university and private researchers develop information about endemic and invasive pests, emerging threats, and new control strategies.
a. Staying informed: Growers and pest control professionals should stay informed about existing and emerging pests and their management options. Science-based information can be obtained by attending extension meetings, webinars, or workshops, reading newsletter, trade, extension, or scientific journal articles, and keeping in touch with researchers and other professionals through various communication channels. Well-informed growers can be well prepared to address pest issues.
b. Communication within the group: Educating farm crew through periodical training or communication will help with all aspects of pest management, proper pesticide handling, ensuring worker safety, and preventing environmental contamination. Knowledgeable field crew will be beneficial for effective implementation of pest management strategies.
c. Communication among growers: Although certain crop production and protection strategies are considered proprietary information, pests do not have boundaries and can spread to multiple fields when they are not effectively managed throughout the region. Sharing knowledge and resources with each other will improve pest control efficacy and benefit the entire grower community.
In addition to these four components with an IPM model, factors that influence profitable, safe, and affordable food production at a larger scale and their implications for global food security should also be included. There are two layers surrounding these four components addressing the business and sustainable aspects of food production.
II. Business Aspect:
Consumers want nutritious, healthy, and tasty produce that is free of pest damage at affordable prices. Growers try to meet this demand by producing food that meets all the consumer needs, while maintaining environmental and human safety and still being able to make a profit. Sellers evaluate the market demand and strategize their sales to satisfy consumers while making their own profit to stay in the business. In an ideal system, consumer, producer, and seller would maintain a harmonious balance of food production and sale. In such a system, food is safe and affordable to everyone, there will be food security all over the world, and both growers and sellers make a good profit with no or minimal risk to the environment in the process of food production. However, this balance is frequently disrupted due to i) consumers' misunderstanding of various food production systems, their demand for perfectly shaped fruits and vegetables at affordable prices or their willingness to pay a premium price for food items that are perceived to be safe, ii) growers trying to find economical ways of producing high quality food while facing with continuous pest problems and other challenges, and iii) sellers trying to market organic food at a higher price as a safer alternative to conventionally produced food. If growers implement good IPM strategies to produce safe food and consumers are aware of this practice and gain confidence in food produced in an IPM system, then sellers would be able to market what informed-consumers demand.
III. Sustainability Aspect:
As mentioned earlier, IPM is an approach to ensure economic viability at both consumer and producer level (seller is always expected to make a profit), environmental safety through a balanced use of all available pest control options, and social acceptability as food is safe and affordable.
While organic food production is generally perceived as safe and sustainable, the following examples can explain why it is not necessarily true. Organic food production is not pesticide-free and some of the pesticides used in an organic system are as harmful to humans and non-target organisms as some chemical pesticides. Certain organically accepted pesticides have toxins or natural chemical molecules that are very similar to those in synthetic pesticides. In fact, some synthetic pesticides are manufactured imitating the pesticidal molecules of natural origin. Mechanical pest control practices such as vacuuming or tilling utilize fossil fuels and indirectly have a negative impact on the environment. For example, diesel-powered tractors are operated for vacuuming western tarnished bug in strawberry 2-3 times or more each week while a pesticide application typically requires the use of tractor once every 7-14 days. To control certain pests, multiple applications of organic pesticides might be necessary with associated costs and risks, while similar pest populations could be controlled by fewer chemical pesticide applications. It is very difficult to manage certain plant diseases and arthropod pests through non-chemical means and inadequate control not only leads to crop losses, but can result in their spread to larger areas making their control even more difficult. Many growers prefer a good IPM-based production to an organic production for the ease of operation and profitability. However, they continue to produce organic food to stay in business.
While middle and upper-class consumers may be willing to pay higher prices for organically produced food, many of the low-income groups in developed and underdeveloped countries cannot afford such food. Organic food production can lead to social inequality and a false sense of wellbeing for those can afford. Food security for the growing world population is necessary through optimizing input costs, minimizing wastage, grower adoption of safe and sustainable practices, and consumer confidence in food produced through such practices. IPM addresses all the economic, environmental, and social aspects and provides safe and affordable food to the consumers and profits to producers and sellers, while maintaining environmental health.
- Author: Surendra K. Dara
- Author: Sumanth S. R. Dara
- Author: Suchitra S. Dara
- Author: Ed Lewis
Eggs, nymphs, and adult silverleaf whitefly on zucchini. Photo by Surendra Dara
A study was conducted in the summer of 2017 to evaluate the efficacy of various chemical, botanical, and microbial pesticides against arthropod pests on zucchini. Zucchini plants initially had a high aphid infestation, but populations gradually declined due to natural control by lady beetle activity. However, heavy silverleaf whitefly (Bemisia tabaci) infestations developed by the time the study was initiated. Other pests that were present during the study period were aphids (possibly melon aphids), the western flower thrips (Frankliniella occidentalis), and the pacific spider mite (Tetranychus pacificus).
Pacific spider mite (egg, male, and females), western flower thrips larva, and unknown aphids on zucchini. Photo by Surendra Dara
Experiment was conducted using a randomized complete block design with 10 treatments. Each treatment had two 38” wide and 300' long rows of zucchini replicated four times. Treatments included i) untreated control, ii) Sivanto 200 SL (flupyradifurone) 14 fl oz/ac, iii) Sequoia (sulfoxaflor) 2.5 fl oz/ac, iv) Venerate XC (heat-killed bacterium, Burkholderia rinojensis strain A396) 4 qrt/ac, v) PFR-97 20% WDG (entomopathogenic fungus, Isaria fumosorosea Apopka strain 97) 2 lb/ac, vi) I1800AA (undisclosed botanical extract) 10.3 fl oz/ac, vii) I1800A 12.7 fl oz, viii) I1800A 17.1 fl oz, ix) I1800A 20.5 fl oz, and x) VST-00634LC (based on a peptide in spider venom) 25%. A spray volume of 50 gpa for all treatments except for VST-00634LC, which had 25 gpa. Treatments were applied on 28 August and 4 September, 2017 using a tractor-mounted sprayer with three Teeject 8003vs flat spry nozzles that covered the top and both sides of each bed.
Pest populations were counted before the first spray application and 4 days after each application. On each sampling date, one mid-tier leaf was collected from each of the five randomly selected plants within each plot. A 2-square inch disc was cut out from the middle of each leaf and the number of aphids, eggs and nymphs of silverleaf whitefly, larvae of western flower thrips, and eggs and mobile stages of pacific spider mite were counted under a dissecting microscope. Data were analyzed using Statistix software and Tukey's HSD test was used to separate significant means.
Spraying, sampling, and counting
Efficacy varied among different treatments and for different pests.
Aphid: There was a general decline in aphid populations during the study period and there was no difference (P > 0.05) among the treatments (Fig. 1).
Fig. 1. Aphid numbers and percent change from pre-treatment counts
Western flower thrips: Nymphal numbers declined in most of the treatments during the observation period (Fig. 2). However, significant differences (P = 0.0220) only after the second spray application where Sivanto treatment had significantly fewer thrips than Venerate treatment (Fig. 2). There was a 92.5% decline by the end of the study, compared to the pre-treatment counts, from PFR-97 application, followed by 88.1% decline in Sivanto, 85.4% in VST-00634, and 82.9% in I1800AA at 10.3 fl oz.
Fig. 2. Western flower thrips larvae and percent change from pre-treatment counts
Pacific spider mite: There was an increase in mite eggs in all treatments after the first spray application followed by a decline after the second one without significant differences (P > 0.05) (Fig. 3) Similar trend was also seen in mobile stages in some treatments. Number of mobile stages was significantly different (P = 0.0025) only after the first spray where untreated control, PFR-97, Venerate, and I1800AA at 20.5 fl oz had the lowest. When percent change in egg numbers from the pre-treatment counts, only I1800AA treatments reduced egg numbers after the second spray with a 33.8% decline at 10.3 fl oz rate, 35.7% at 20.5 fl oz, and 60% at 17.1 fl oz. There was also a decline in the mobile stages after the second spray with 54.1% reduction in untreated control to 67.7% in PFR-97 treatment.
Fig. 3. Pacific spider mite egg and mobile stages and percent change from pre-treatment counts
Silverleaf whitefly: There was a general increase in the egg and nymphal stages of whitefly during the study (Fig. 4). Significant differences were seen pre-treatment counts of egg (P = 0.0330) and nymphal stages (P = 0.0011), and after the second spray in nymphal stages (P = 0.0220). Compared to the untreated control, both Sivanto and Sequoia resulted in a significant reduction in egg numbers after the first spray, whereas Sequoia, Venerate, and I1800AA at 20.5 fl oz reduced nymphal stages after the second spray. When the percent change from the pre-treatment counts was compared, only Sivanto and Sequoia reduced whitefly egg numbers after both sprays. There was also a reduction in eggs after the first spray from I1800AA at 17.1 fl oz. However, there was a reduction in nymphal stages after the first spray in Sivanto, I1800AA at 17.1 fl oz, and VST-00634, and after the second spray in Sivanto, Sequoia, Venerate, and I1800AA at 17.1 and 20.5 fl oz.
Fig. 4. Silverleaf whitefly egg and nymphal stages and percent change from pre-treatment counts
All arthropod pests: When all data were combined for different pests and their life stages, Sivato, Sequia, and PF-97 resulted in a significant (P = 0.0001) decline in pest numbers compared to untreated control after the first spray. Only Sivanto and Sequoia caused such a reduction (P = 0.0048) after the second spray.
Fig. 5. All arthropod pest numbers and percent change from pre-treatment counts
In general, both the chemical pesticides (Sivanto and Sequoia) provided a very good pest control. The efficacy of the botanical extract was moderate to good depending on the pest, life stage, or the application date. Spider venom-based product also provided a good control while microbial products had a moderate impact. Although chemical pesticides appeared to be very efficacious, non-chemical alternatives were also effective. It is important to consider all these options to apply in combinations or rotations to obtain desired pest suppression without posing the risk of insecticide resistance.
Acknowledgements: Thanks for the financial support of Arysta LifeScience, CertisUSA, Dow AgroSciences, and Vestaron, and the technical assistance of Neal Hudson.