Santa Maria strawberry grower, Dave Peck
Different people have defined sustainable agriculture or food production in different ways. In general, sustainable food production refers to the farming systems that maintain productivity indefinitely through ecologically balanced, environmentally safe, socially acceptable, and economically viable practices. It is a system that ensures food security for the growing population of the world by taking science, economics, human and environmental health, and social aspects into consideration.
Agriculture has evolved over thousands of years from subsistence farming meeting the needs of individual families to agribusiness catering to the needs of consumers around the world. Arthropod pests, diseases, and weeds (hereafter referred to as pests) have been an issue all along, but their management went through cyclical changes. Pest management initially started by using naturally available materials such as sulfur or plant-based pyrethrums that gradually evolved into using toxic natural or synthetic compounds. While pesticide use improved farm productivity and food affordability, indiscriminate use of synthetic broad-spectrum pesticides in the mid-1900s led to serious environmental and human health issues. Pesticide use regulations, the discovery of safer pesticides, and new non-chemical alternatives, in the past few decades, have improved pest management practices to some extent. Newer pesticides are also relatively less toxic to the environment. However, large quantities of synthetic chemical pesticides are still used in conventional farms along with other control options for managing a variety of pests to prevent yield losses and optimize returns. Lack of good agricultural practices or IPM awareness has also contributed to the excessive use of chemicals and the associated risk of resistance in pests and environmental contamination in some areas. For example, in some developing countries, or countries where pesticide use is not strictly regulated, highly toxic pesticides are used very close to the harvest date, causing serious health risks for consumers.
Under these circumstances, in recent years, consumer preference for chemical-free food gave impetus for organic production; thus, the acreage of organically produced fruits, vegetables, and nuts has been gradually increasing. Many stores now promote and sell fresh or processed organic foods, at premium prices, to those who can afford them. While organic farming is generally considered more challenging and less productive, growers are willing to take the risk as they try to meet the market demand and produce organically. However, managing weeds in organic farms continues to be a labor-intensive and expensive part of production. The labor shortage in many areas exacerbates manual weed control. In some crop and pest situations, control of pests with organically acceptable tools is not sufficient. Unmanaged pest populations can spread to other areas and/or crops, cause higher yield losses, and indirectly contribute to higher pesticide use on neighboring conventional farms.
Jimmy Klick (Driscoll's) and Sanjay Kumar Rajpoot (Rajpoot Industries and FarmX) with Todd Fitchette (Western Farm Press) in the background at the Santa Maria Strawberry Field Day in 2016
On the other hand, IPM offers an effective, practical, and sustainable solution where excessive use of chemical pesticides is limited, pest populations are effectively managed, and returns are optimized without having a negative impact on the environment. IPM is an approach where host plant resistance (selection of resistant cultivars), modification of planting dates, crop density, irrigation and nutrient management or use of trap crops (cultural control), conservation or augmentation of natural enemies (biological control), pheromones for mating disruption or to attract and kill (behavioral control), traps, netting, and vacuums (mechanical control), chemicals from various mode of action groups (chemical control), plant extracts (botanical control), and entomopathogens or their derivatives (microbial control) are used in a balanced manner. It is a comprehensive approach where all available strategies are considered to achieve pest control with minimal impact on the ecosystem. However, many consumers are not aware of the difference between organic and conventional practices or IPM strategies. Many perceive organic farming as a pesticide-free production system and as the only alternative to conventional farming with synthetic chemicals and nutrients. Organic farming also uses pesticides, fertilizers, and hormones of natural origin. For example, potassium salts of fatty acids are used against insects, mites, and fungal diseases. Mined sulfur is used as a miticide and fungicide. Popular organic insecticides, based on pyrethrins extracted from Chrysanthemum cinerariaefolium flowers, are very toxic to natural enemies, honey bees, and fish although they are less stable in the environment than synthetic pyrethroids. The bacterium, Bacillus thuringiensis, which is the source of the toxic insecticidal protein in genetically modified corn, cotton, soybean, and other crops, is widely used in organic farming for managing lepidopteran pests. Organic produce is also perceived to be healthier than conventional produce although several studies showed that there was no such difference. A thorough understanding of conventional, organic, and IPM-based production could influence consumers' preference and allows them to make informed, practical, and science-based decisions.
IPM encourages the use of all available control options in a manner that maintains productivity without compromising environmental and human safety. IPM-based food production can be a better alternative than organic production for various reasons (Table 1). While several growers already adopt IPM practices, an IPM label or seal can authenticate the production system.
Table 1. Comparison of various food production systems
Since pest control efficacy, productivity, and operational costs are optimized for affordable food production without compromising health aspects, an IPM-based/branded food production system, which utilizes both modern and traditional technologies, might offer a better alternative to the organic system. IPM-based production allows the use of chemical pesticides to address critical pest issues when needed, without losing the focus on environmental safety and sustainability. Agriculture is a global enterprise and California agriculture leads and influences farming practices around the world. While food production with an organic seal can continue, shifting to production with an IPM seal might be a practical and sustainable approach.
Dara, S. K. 2015. Producing with the seal of IPM is a practical and sustainable strategy for agriculture. UCANR eJournal Strawberries and Vegetables. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19735
Gold, M. V. 2007. Sustainable agriculture: definitions and terms. USDA-NAL, Beltsville, MD. https://www.nal.usda.gov/afsic/sustainable-agriculture-definitions-and-terms#toc2
NPIC. 2014. Pyrethrins general fact sheet. http://npic.orst.edu/factsheets/pyrethrins.pdf
Unsworth J. 2010. History of pesticide use. http://agrochemicals.iupac.org/index.php?option=com_sobi2&sobi2Task=sobi2Details&catid=3&sobi2Id=31
On June 13, the Small Farm Program partnered with UCCE Small Farm Advisor Margaret Lloyd to conduct a tour of wholesale produce markets for Sacramento region farmers. During the bus ride from Woodland to San Francisco, I described the packaging and grading standards that farmers must comply with when selling wholesale.
Cook's Company was established as a wholesaler to Bay Area restaurants in 1985 by chefs Ric Tombari and Elaine Jones Tombari, the generous funders of this tour. Cooks buys from about 300 farms, and delivers to Bay Area restaurants all seven days of the week. Cooks takes same day orders and has no minimum purchase requirements.
Ric greeted our group warmly and then led us through the warehouse while enthusiastically sharing a wide variety of tips that can enhance the viability of small-scale farms selling to restaurants, including:
- wait until your farm has something really good to offer before approaching a potential buyer;
- have a good story about your farm when talking to prospective customers
- seek out new customers in places where there are lots of restaurants;
- sell your berries in open flats because they will look farm fresh, when compared with berries in clamshells;
- remember that chefs want similarly sized tomatoes in a variety of colors; and
- consider unusual forms of produce, such as Fava bean leaves, Savoy spinach (salad dressing clings well to its bumpy surface), baby turnips and Kennebec (chip) potatoes.
The organic food delivery company, Good Eggs, moved into part of a new $24 million 82,000 warehouse at the Wholesale Produce Market in 2015. It packages and delivers produce, meat, dairy products, meal kits, flowers, condiments and wine from local farms and food businesses that customers buy online. Designed to “bring the farmers market to your door”, it was founded in 2011 and expanded quickly into Los Angeles, New York and New Orleans, but closed all of its operations except for the San Francisco facility in August 2015. Its founder, Rob Spiro, stated that Good Eggs did not realize how complicated it is to create a new category that requires a different approach to supply chains, logistics, and commerce – in order to get food from local producers to consumers' kitchens. During our visit, Produce Category Manager Ben Hartman commented that they had to add imported products because consumers wanted some items year-round. Good Eggs begins receiving deliveries at 4:30AM. It delivers seven days a week; orders received by 1PM can be delivered in the evening.
Our final stop was Bay Cities Produce in San Leandro. The family-owned business supplies produce primarily to institutions, foodservice and government organizations in the East and South Bay Area. It carries a full line of fresh, frozen, and custom cut produce (both conventional and organic), including sliced, diced and julienne vegetables. Bay Cities also supplies whole peeled vegetables, salad mixes and cleaned lettuces. Much of the produce is hand cut, which means that customers have transferred their employee safety risk to Bay Cities. After signing in and donning lab coats, hair net and beard nets, we observed many examples of Bay Cities' commitment to cleanliness, sanitation and food-safety during our tour. Vince Del Masso explained that the company spends over $500,000 annually on its food safety program to meet its customers' high food safety requirements. Bay Cities buys most of its produce from California farms. It will provide technical assistance regarding food safety practices to smaller-scale farmers who are interested in becoming its suppliers.
Entomopathogens are microorganisms that are pathogenic to arthropods such as insects, mites, and ticks. Several species of naturally occurring bacteria, fungi, nematodes, and viruses infect a variety of arthropod pests and play an important role in their management. Some entomopathogens are mass-produced in vitro (bacteria, fungi, and nematodes) or in vivo (nematodes and viruses) and sold commercially. In some cases, they are also produced on small scale for non-commercial local use. Using entomopathogens as biopesticides in pest management is called microbial control, which can be a critical part of integrated pest management (IPM) against several pests.
Some entomopathogens have been or are being used in a classical microbial control approach where exotic microorganisms are imported and released for managing invasive pests for long-term control. The release of exotic microorganisms is highly regulated and is done by government agencies only after extensive and rigorous tests. In contrast, commercially available entomopathogens are released through inundative application methods as biopesticides and are commonly used by farmers, government agencies, and homeowners. Understanding the mode of action, ecological adaptations, host range, and dynamics of pathogen-arthropod-plant interactions is essential for successfully utilizing entomopathogen-based biopesticides for pest management in agriculture, horticulture, orchard, landscape, turf grass, and urban environments.
Important entomopathogen groups and the modes of their infection process are described below.
There are spore-forming bacterial entomopathogens such as Bacillus spp., Paenibacillus spp., and Clostridium spp, and non-spore-forming ones that belong to the genera Pseudomonas, Serratia, Yersinia, Photorhabdus, and Xenorhabdus. Infection occurs when bacteria are ingested by susceptible insect hosts. Pseudomonas, Serratia and Yersinia are not registered in the USA for insect control.Several species of the soilborne bacteria, Bacillus and Paenibacillus are pathogenic to coleopteran, dipteran, and lepidopteran insects. Bacillus thuringiensis subsp. aizawai, Bt subsp. kurstaki, Bt subsp. israelensis, Bt subsp. sphaericus, and Bt subsp. tenebrionis are effectively used for controlling different groups of target insects. For example, Bt subsp. aizawai and Bt subsp. kurstaki are effective against caterpillars, Bt subsp. israelensis and Bt subsp. sphaericus target mosquito larvae, and Bt subsp. tenebrionis is effective against some coleopterans.
When Bt is ingested, alkaline conditions in the insect gut (pH 8-11) activate the toxic protein (delta-endotoxin) that attaches to the receptors sites in the midgut and creates pore in midgut cells. This leads to the loss of osmoregulation, midgut paralysis, and cell lysis. Contents of the gut leak into insect's body cavity (hemocoel) and the blood (hemolymph) leaks into the gut disrupting the pH balance. Bacteria that enter body cavity cause septicemia and eventual death of the host insect. Insects show different kinds of responses to Bt toxins depending on the crystal proteins (delta-endotoxin), receptor sites, production of other toxins (exotoxins), and requirement of spore. The type responses below are based on the susceptibility of caterpillars to Bt toxins.
Type I response – Midgut paralysis occurs within a few minutes after delta-endotoxin is ingested. Symptoms include cessation of feeding, increase in hemolymph pH, vomiting, diarrhea, and sluggishness. General paralysis and septicemia occur in 24-48 hours resulting in the death of the insect. Examples of insects that show Type I response include silkworm, tomato hornworm, and tobacco hornworm.
Type II response – Midgut paralysis occurs within a few minutes after the ingestion of delta-endotoxin, but there will be no general paralysis. Septicemia occurs within 24-72 hours. Examples include inchworms, alfalfa caterpillar, and cabbage butterfly.
Type III response – Midgut paralysis occurs after delta-endotoxin is ingested followed by cessation of feeding. Insect may move actively as there will be no general paralysis. Mortality occurs in 48-96 hours. Higher mortality occurs if spores are ingested. Insect examples include Mediterranean flour moth, corn earworm, gypsy moth, spruce budworm.
Type IV response – Insects are naturally resistant to infection and older instars are less susceptible than the younger ones. Midgut paralysis occurs after delta-endotoxin is ingested followed by cessation of feeding. Insect may move actively as there will be no general paralysis. Mortality occurs in 72-96 or more hours. Higher mortality occurs if spores are ingested. Cutworms and armyworms are examples for this category.
Unlike caterpillars, the response in mosquitoes is different where upon ingestion of Bt subsp. israelensis delta-endotoxin, the mosquito larva is killed within 20-30 min.
While Bt with its toxic proteins is very effective as a biopesticide against several pests, excessive use can lead to resistance development. Corn earworm, diamondback moth, and tobacco budworm are some of the insects that developed resistance to Bt toxins. Genetic engineering allowed genes that express Bt toxins to be inserted into plants such as corn, cotton, eggplant, potato, and soybean and reduced the need to spray pesticides. However, appropriate management strategies are necessary to reduce insect resistant to Bt toxins in transgenic plants.
Paenibacillus popilliae is commonly used against Japanese beetle larvae and known to cause the milky spore disease. Although Serratia is not registered for use in the USA, a species is registered for use against a pasture insect in New Zealand. In the case of Photorhabdus spp. and Xenorhabdus spp., which live in entomopathogenic nematodes symbiotically, bacteria gain entry into the insect host through nematodes. Biopesticides based on heat-killed Chromobacterium subtsugae and Burkholderia rinojensis are reported to have multiple modes of action and target mite and insect pests of different orders.
Entomopathogenic fungi typically cause infection when spores come in contact with the arthropod host. Under ideal conditions of moderate temperatures and high relative humidity, fungal spores germinate and breach the insect cuticle through enzymatic degradation and mechanical pressure to gain entry into the insect body. Once inside the body, the fungi multiply, invade the insect tissues, emerge from the dead insect, and produce more spores. Natural epizootics of entomophthoralean fungi such as Entomophaga maimaiga (in gypsy moth), Entomophthora muscae (in flies), Neozygites fresenii (in aphids), N. floridana (in mites), and Pandora neoaphidis (in aphids) are known to cause significant reductions in host populations. Although these fastidious fungi are difficult to culture in artificial media and do not have the potential to be sold as biopesticides they are still important in natural control of some pest species. Hypoclealean fungi such as Beauveria bassiana, Isaria fumosorosea, Hirsutella thompsonii, Lecanicillium lecanii, Metarhizium acridum, M. anisopliae, and M. brunneum, on the other hand, are commercially sold as biopesticides in multiple formulations around the world. Fungal pathogens have a broad host range and are especially suitable for controlling pests that have piercing and sucking mouthparts because spores do not have to be ingested. However, entomopathogenic fungi are also effective against a variety of pests such as wireworms and borers that have chewing mouthparts.
Related to fungi, the spore-forming microsporidium, Paranosema (Nosema) locustae is a pathogen that has been used for controlling locusts, grasshoppers, and some crickets. When P. locustae is ingested, the midgut tissues become infected, followed by infection in the fat body tissues. The disease weakens and eventually kills the orthopteran host within a few weeks.
Various insects killed by different species of entomopathogenic fungi
Entomopathogenic nematodes are microscopic, soil-dwelling worms that are parasitic to insects. Several species of Heterorhabditis and Steinernema are available in multiple commercial formulations, primarily for managing soil insect pests. Infective juveniles of entomopathogenic nematodes actively seek out their hosts and enter through natural openings such as the mouth, spiracles, and anus or the intersegmental membrane. Once inside the host body, the nematodes release symbiotic bacteria that kill the host through bacterial septicemia. Heterorhabditis spp. carry Photorhabdus spp. bacteria and Steinernema spp. carry Xenorhabdus spp. bacteria. Phasmarhabditis hermaphrodita is also available for controlling slugs in Europe, but not in the USA.
Infective juvenile of Steinernema carpocapsae entering the first instar larva of a leafminer through its anus.
Nematodes in beet armyworm pupa (left) and termite worker (right).
Similar to bacteria, entomopathogenic viruses need to be ingested by the insect host and therefore are ideal for controlling pests that have chewing mouthparts. Several lepidopteran pests are important hosts of baculoviruses including nucleopolyhedroviruses (NPV) and granuloviruses (GV). These related viruses have different types of inclusion bodies in which the virus particles (virions) are embedded. Virus particles invade the nucleus of the midgut, fat body or other tissue cells, compromising the integrity of the tissues and liquefying the cadavers. Before death, infected larvae climb higher in the plant canopy, which aids in the dissemination of virus particles from the cadavers to the lower parts of the canopy. This behavior aids in the spread of the virus to cause infection in healthy larvae. Viruses are very host specific and can cause significant reduction of host populations. Examples of some commercially available viruses include Helicoverpa zea single-enveloped nucleopolyhedrovirus (HzSNVP), Spodoptera exigua multi-enveloped nucleopolyhedrovirus (SeMNPV), and Cydia pomonella granulovirus (CpGV).
Most entomopathogens typically take 2-3 days to infect or kill their host except for viruses and P. locustae which take longer. Compared to viruses (highly host specific) and bacteria (moderately host specific), fungi generally have a broader host range and can infect both underground and aboveground pests. Because of the soil-dwelling nature, nematodes are more suitable for managing soil pests or those that have soil inhabiting life stages.
Biopesticides based on various entomopathogenic microorganisms and their target pests
Microbial control and Integrated Pest Management
There are several examples of entomopathogen-based biopesticides that have played a critical role in pest management. Significant reduction in tomato leaf miner, Tuta absoluta, numbers and associated yield loss was achieved by Bt formulations in Spain (Gonzalez-Cabrera et al, 2011). Bt formulations are also recommended for managing a variety of lepidopteran pests on blueberry, grape, and strawberry (Haviland, 2014; Zalom et al, 2014; Bolda and Bettiga, 2014; Varela et al, 2015).
Lecanicellium muscarium-based formulation reducedgreenhouse whitefly (Trialeurodes vaporariorum) populations by 76-96% in Mediterranean greenhouse tomato (Fargues et al, 2005). In other studies, B. bassiana applications resulted in a 93% control of twospotted spider mite (Tetranychus urticae) populations in greenhouse tomato (Chandler et al, 2005) and 60-86% control on different vegetables (Gatarayiha et al, 2010). The combination of B. bassiana and azadirachtin reduced rice root aphid (Rhopalosiphum rufiabdominale) and honeysuckle aphid (Hyadaphis foeniculi) populations by 62% in organic celery in California (Dara, 2015a). Chromobacterium subtsugae and B. rinojensis caused a 29 and 24% reduction, respectively, in the same study. IPM studies in California strawberries also demonstrated the potential of entomopathogenic fungi for managing the western tarnished plant bug (Lygus hesperus) and other insect pests (Dara, 2015b, 2016). Entomopathogenic fungi also have a positive effect on promoting drought tolerance or plant growth as seen in cabbage (Dara et al, 2016) and strawberry (Dara, 2013) and antagonizing plant pathogens (Dara et al, 2017)
Application of SeMNPV was as efficacious as methomyl and permithrin in reducing beet armyworms (S. exigua) in head lettuce in California (Gelernter et al, 1986). Several studies demonstrated PhopGV as an important tool for managing the potato tubermoth (Phthorimaea operculella) (Lacey and Kroschel, 2009).
The entomopathogenic nematode, S. feltiae,reduced raspberry crown borer (Pennisetia marginata) populations by 33-67% (Capinera et al, 1986). For managing the branch and twig borer (Melagus confertus) in California grapes, S. carpocapsae is one of the recommended options (Valera et al, 2015).
Entomopathogens can be important tools in IPM strategies in both organic and conventional production systems. Depending on the crop, pest, and environmental conditions, entomopathogens can be used alone or in combination with chemical, botanical pesticides or other entomopathogens.
Acknowledgements: Thanks to Dr. Harry Kaya for reviewing this article.
Bolda, M. P. and L. J. Bettiga. 2015. UC IPM Pest Management Guidelines: Caneberries. UC ANR Pub. 3437.
Capinera, J. L., W. S. Cranshaw, and H. G. Hughes. 1986. Suppression of raspberry crown borer Pennisetia marginata (Harris) (Lepidoptera: Sesiidae) with soil applications of Steinernema feltiae (Rhabditida:Steinernematidae). J. Invertebr. Pathol. 48: 257-258.
Chanlder, D., G. Davidson, and R. J. Jacobson. 2005. Laboratory and glasshouse evaluation of entomopathogenic fungi angainst the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), on tomato, Lycopersicon esculentum. Biocon. Sci. Tech. 15: 37-54.
Dara, S. K. 2013. Entomopathogenic fungus Beauveria bassiana promotes strawberry plant growth and health. UCANR eJournal Strawberries and Vegetables, 30 September, 2013. (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11624)
Dara, S. K. 2015a. Reporting the occurrence of rice root aphid and honeysuckle aphid and their management in organic celery. UCANR eJournal Strawberries and Vegetables, 21 August, 2015. (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=18740)
Dara, S. K. 2015b. Integrating chemical and non-chemical solutions for managing lygus bug in California strawberries. CAPCA Adviser 18 (1) 40-44.
Dara, S. K. 2016. IPM solutions for insect pests in California strawberries: efficacy of botanical, chemical, mechanical, and microbial options. CAPCA Adviser 19 (2): 40-46.
Dara, S. K., S.S.R. Dara, and S.S. Dara. 2016. First report of entomopathogenic fungi, Beauveria bassiana, Isaria fumosorosea, and Metarhizium brunneum promoting the growth and health of cabbage plants growing under water stress. UCANR eJournal Strawberries and Vegetables, 19 September, 2016. (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22131)
Dara, S.S.R., S. S. Dara, S. K. Dara, and T. Anderson. 2017. Fighting plant pathogenic fungi with entomopathogenic fungi and other biologicals. CAPCA Adviser 20 (1): 40-44.
Fargues, J., N. Smits, M. Rougier, T. Boulard, G. Rdray, J. Lagier, B. Jeannequin, H. Fatnassi, and M. Mermier. 2005. Effect of microclimate heterogeneity and ventilation system on entomopathogenic hyphomycete infectiton of Trialeurodes vaporariorum (Homoptera: Aleyrodidae) in Mediterranean greenhouse tomato. Biological Control 32: 461-472.
Gatarayiha, M. C., M. D. Laing, and M. Ray. 2010. Effects of adjuvant and conidial concentration on the efficacy of Beauveria bassiana for the control of the two-spotted spider mite, Tetranychus urticae. Exp. Appl. Acarol. 50: 217-229.
Gelernter, W. D., N. C. Toscano, K. Kido, and B. A. Federici. 1986. Comparison of a nuclear polyhedrosis virus and chemical insecticides for control of the beet armyworm (Lepidopter: Noctuidae) on head lettuce. J. Econ. Entomol. 79: 714-717.
González-Cabrera, J., J. Mollá, H. Monton, A. Urbaneja. 2011. Efficacy of Bacillus thuringiensis (Berliner) in controlling the tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). BioControl 56: 71–80.
Haviland, D. R. 2014. UC IPM Pest Management Guidelines: Blueberry. UC ANR Pub. 3542.
Lacey, L. A. and J. Kroschel. 2009. Microbial control of the potato tuber moth (Lepidoptera: Gelechiidae). Fruit Veg. Cereal Sci. Biotechnol. 3: 46-54.
Varela, L. G., D. R. Haviland, W. J., Bentley, F. G. Zalom, L. J. Bettiga, R. J. Smith, and K. M. Daane. 2015. UC IPM Pest Management Guidelines: Grape. UC ANR Pub. 3448.
Zalom, F. G., M. P. Bolda, S. K. Dara, and S. Joseph. 2014. UC IPM Pest Management Guidelines: Strawberry. UC ANR Pub. 3468.
Male spotted wing drosophila adult. Photo by Gevork Arakelian, Los Angeles County Ag Commissioner's Office
Spotted wing drosophila (SWD), Drosophila suzukii is a pest of several small fruit in California and other states. SWD belongs to the group of flies that are generally known as vinegar flies or lesser fruit flies. It was initially known as cherry fruit fly in 1930s and is now referred to as spotted wing drosophila. SWD can be distinguished from other Drosophila spp. based on the following traits:
- Females have a hard and dark (sclerotized) ovipositor with prominent serrations or saw-teeth that enable the fly to lay eggs in intact ripening fruit.
- Antennae with branched bristle-like part called arista.
- Males have a distinctive dark spot at the tip of each wing.
- Males also have two dark bands (combs) of 3-6 teeth on each front leg.
Sclerotized ovipositor of SWD (right) compared to the normal ovipositor of a vinegar fly (left).
Distinctive combs on the front legs of male spotted wing drosophila. Photo by Gevork Arakelian.
Origin and distribution: It is traditionally known to be a pest in Asia, but it is now reported in Neotropics, North America, and Europe. In the US, it has been reported in Hawaii, Washington, Oregon, California, Utah, Minnesota, Michigan, Missouri, Louisiana, West Virginia, Pennsylvania, North Carolina, South Carolina, and Florida.
Host range: They generally infest thin-skinned fruit and prefer temperate climate. Host range includes apple, blackberry, blueberry, cherry, dogwood, grape, mulberry, peach, persimmons, plum, raspberry, and strawberry. Non-crop hosts that support SWD populations include barberry, brambles (wild raspberry and blackberry), buckthorn, cotoneaster, currant, dogwood, elderberry, fig, honeysuckle, laurel, mulberry, nightshade, oleaster, orange jasmine, pin cherry, pokeweed, purple flowering raspberry, spicebush, sweet box, and yew.
Biology: SWD prefer 68-86 oF and overwinter as adults. Various sources suggested 5-10 generations per year. Eggs are translucent to milky-white. Females lay an average of 384 eggs at 7-16 per day and there can be 1-3 eggs per oviposition site. Multiple females may deposit eggs in the same fruit. Eggs hatch in 2-72 hours and larval stage lasts for 3-13 days. Larvae milky-white with a legless body tapering towards the anterior end (towards the head). Mouthparts are dark and sclerotized. Pupation takes place inside the fruit or in the soil and lasts for 3-15 days. Pupae are reddish brown and have two spiracles (breathing tubes) at the anterior end. Adults are small (2-3 mm) flies. Life cycle takes anywhere from 21-25 days at 59 oF to 7 days at 82 oF. Females can start laying eggs within 1 day after their emergence and can lay more than 400 eggs in their lifetime. Based on the degree day (DD) calculations, egg, larval, and pupal stages require 20.3, 118.1, and 200 DD.
Damage: Other fruit flies usually infest overripe and fallen fruit, but SWD infests fresh fruit because of its powerful ovipositor. Adults feed on fallen fruit but lay their eggs under the skin of intact fruit. Softening and collapse of the tissue results from larval feeding inside the fruit. Oviposition holes can be seen on the fruit with close observation. In addition to the direct damage, SWD makes the infested fruit vulnerable to other pests and diseases. Monitoring SWD is very important to avoid harvesting and marketing infested berries.
Monitoring: Use traps made with apple cider vinegar or yeast-sugar solutions for early detection of SWD. There are numerous studies using a variety of containers and attractants. Pherocon traps and lures are commercially available for SWD monitoring.
Management: A variety of organic and conventional management options are available.
Cultural – Discard fallen and unmarketable fruit in the field to prevent infestation. Remove wild hosts in the vicinity that might harbor SWD populations.
Botanical – Pyrethrins and azadirachtin products are used in multiple studies.
Chemical – Research indicates that organophosphates, pyrethroids, and spinosyns are among the chemicals that can be used against SWD. Remember to rotate chemicals among different mode of action groups to reduce the risk of resistance development.
Microbial – Entomopathogenic fungi (Beauveria bassiana or Isaria fumosorosea) and bacteria-based products such as Grandevo (Chromobacterium subtsugae) and Venerate (Burkholderia rinojensis) against adults, and entomopathogenic nematodes (Heterorhabditis spp. and Steinernema spp.) against pupae that form outside the fruit can be used.
This is a re-post from CWGA.
CWGA Legislative Action Alert – Members located in Marin County and Surrounding Areas:
Marin County is in the process of correcting an omission in the land use code that for the last 15 years has left ranchers in Marin without a pathway to commercial livestock slaughter in the county. On March 14th, the Board of Supervisors will meet to consider changes to the development code that would allow ranchers to conduct small-scale on-farm slaughter of poultry as well as allow a mobile slaughter unit to provide small-scale USDA-licensed slaughter of all species on ranches in the county. Both of these proposed rules would make it possible for ranchers to bring product to market without traveling across the state, submitting animals to stressful travel and costing the farms time and money. Anyone who has an interest in Marin's ranching community and/or locally produced meat should plan to write letters to the Board of Supervisors and speak at the March 14th meeting. Letters can be sent to the Board of Supervisors at BOS@marincounty.org.
The proposed rules would specifically allow:
1. On-farm slaughter by a rancher of his/her own poultry (chickens, turkeys, ducks, geese) for commercial sale without a use permit. This would be limited to 20,000 chickens (or equivalent) per year and only in lands zoned A3 - A60 (lands zoned A2 or ARP as well as those located in the Coastal Zone would be excluded). Ranchers would be able to process animals that are raised "on the same site or on other agricultural properties located in Marin County that are owned or leased by the processing facility owner or operator” but rabbits (traditionally included in the definition of “poultry”) would be excluded from this rule. Additionally, these processing activities would be limited to 5000 square feet.
2. Mobile Slaughter Units (MSUs) could provide USDA-licensed slaughter services to ranchers for all species without a use permit on lands zoned A3 - A60 (lands zoned A2 or ARP as well as those located in the Coastal Zone would be excluded). MSU's could not operate on any single property for more than 3 consecutive days and up to 12 total days within a calendar month unless the rancher secures a temporary use permit. Ranchers from other properties could bring their animals to where an MSU is in operation to have their animals processed. The unit would have to be located more than 100 feet away from any property lines.
3. Stationary slaughterhouses providing USDA-licensed slaughter services for all species would NOT be allowed in Marin County.
On March 14th, the Board of Supervisors has the power to approve, deny or even change these recommendations up to and including:
• Re-inserting rabbits into number 1 above.
• Allowing numbers 1 and 2 above in lands zoned A2 or ARP (the Board cannot at this time change the land use rules for farms in the Coastal Zone).
• Reversing or modifying the recommendation in number 3 in order to allow for some form of brick-and-mortar USDA slaughterhouse.
Substantial pushback from those who oppose ranching and livestock slaughter is expected at the March 14th meeting. It is very important for the Board of Supervisors to hear from the agricultural community on this issue, and members of the public who value local meats produced on local lands should also speak. Potential talking points might include:
• Raising pastured livestock is one of the oldest and most appropriate uses of Marin's coastal grasslands
• Without access to local slaughter services, ranches incur great cost in money, time and fuel to truck animals out of the area …just so they can be sold back to Bay Area consumers.
• Slaughter services are an essential part of the ranching business. Raising animals in an ecologically sound fashion is a fruitless endeavor if those animals cannot affordably be brought to market.
• New and small-scale ranchers are particularly paralyzed by the costs and complexity of working with distant slaughter facilities.
Also being recommended by the Planning Commission is a new rule to require use permits for ranchers in lands zoned ARP if they want to conduct educational tours. Until now, these activities have been considered “principally permitted” (i.e. a by-right activity that requires no permit or permission from the county). In the development code, “educational tour” is defined as: "Interactive excursion for groups and organizations for the purpose of informing them of the unique aspects of a property, including agricultural operations and environmental resources.” This has historically included school visits, chef/buyer tours, tours by organizations such as MALT or AIM, as well as open-farm type programming to help connect with new CSA members and other customers. Lands zoned A3-A60 would be unaffected by this change, but for those in ARP lands, the requirement to secure a use permit could mean $5,000-10,000 and extensive review by county Planning before allowing one of these activities to take place on your land. Given the growing interest by the public in visiting farms and ranches as well as the importance of transparency in the food system, this may pose a problem for many ranchers. Making your voice heard on this issue is recommended as well.
Again, on both matters, letters should be sent to: BOS@marincounty.org and please plan to speak on Tuesday, 3/14 (time TBD) in Suite 330 of the Marin Civic Center.
For questions contact Vince Trotter, Agricultural Ombudsman for Marin County at 415-524-7394 or firstname.lastname@example.org.