Grower Notes and Pest News
An update on the invasive spotted lanternfly, Lycorma delicatula: current distribution, pest detection efforts, and management strategies
Spotted lanternfly (Lycorma delicatula) is an invasive planthopper that was first detected in Pennsylvania in September, 2014 (Dara et al., 2015) and believed to have arrived as eggs attached to stone in a shipment of stone from Asia. This pest is native to China and has been reported in some other Asian countries. Since its first occurrence in Berks County in Pennsylvania, it has now spread to 13 counties in the state and was also reported in Delaware and New York in November, 2017 and in Virginia in January, 2018.
Fruit trees (apple, apricot, cherry, peach), ornamental or woody trees (birch, lilac, maple, poplar, tree of heaven), and vines (grape) are among more than 70 species of hosts that are infested by spotted lanternfly. The tree of heaven (Ailanthus altissima) is a favorite of the spotted lanternfly. Several invasive pests such as the brown marmorated stink bug and the Asian citrus psyllid first found in late 90s in Pennsylvania and Florida, respectively, have spread to other states and are now found in California. Considering its current distribution of the spotted lanternfly in Pennsylvania and other states and its potential to spread to other states, this article provides an update on recent efforts to monitor and control this pest.
Biology and damage
Eggs are deposited in masses and covered by a waxy substance. There are four nymphal instars. Female lanternflies are larger than males. Nymphs and adults feed on the phloem and excrete large volumes of liquid. Severe feeding damage results in oozing wounds on the trunk, and wilting and death of affected branches.
Egg masses of the spotted lanternfly. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture.
Fourth instar nymph of the spotted lanternfly. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture.
Adult spotted lanternfly infestations. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture.
White mold developing on the excretions of the spotted lanternfly. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture.
Monitoring and controlling
Preventing the movement: To prevent the spread of the spotted lanternfly, carefully inspect potential sources such as woody plant debris, yard waste, plants, or other objects. Destroy or disinfest the sources as appropriate to prevent the spread of the pest.
Removal of the host: Removing tree of heaven, a favorite host of the spotted lanternfly and an invasive species of tree, can reduce the risk of pest infestation and spread. Reducing the plant stand to 15% is considered a primary strategy for preventing the spread of spotted lanternfly. The tree should be removed with its entire root system when possible. If the tree was cut, its stump should be treated with herbicides to prevent regrowth. Care should be taken while removing the tree of heaven since the toxic plant sap can cause skin irritation, headaches, nausea, and in some cases cardiac problems. Sumac and black walnut trees also look similar to the tree of heaven, but when bruised, the leaves of the latter give out a rancid peanut butter odor.
Sticky bands: The Pennsylvania Department of Agriculture placed 13 counties under quarantine and is currently providing sticky bands for volunteers participating in the monitoring program to place on trees. Sticky bands are placed around the tree trunk about 4' from the ground to trap the nymphs and adults that are moving around. While younger nymphs can be captured on less sticky bands, stickier bands are necessary to capture older nymphs and adult hoppers. Those not participating in the volunteer program can purchase sticky bands or sticky substances from commercial vendors or make their own by wrapping a tape around the trunk and applying petroleum jelly or other materials on the tape. This strategy helps to detect and trap the pest infestations. More than 1.7 million spotted lanternflies were reported to be trapped in 2017 in Pennsylvania using sticky bands.
Spotted lanternfly nymphs and some adults trapped on a sticky band. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture.
Pesticides: Contact insecticides, bifenthrin and carbaryl and systemic insecticides, dinotefuran and imidacloprid appear to be effective in controlling the spotted lanternfly based on the studies conducted in Pennsylvania. Neem oil and insecticidal soap also provide some control. However, pesticide applications appear to be a short-term solution as they cannot prevent reinfestation.
Biocontrol agents:It is thought that toxic metabolites in the body of the spotted lanternfly and its brightly colored hindwings tend to deter general predators from feeding on the pest. However, the predatory wheel bug, Arilus cristatus (Hemiptera: Reduvidae) and stink bug, Apoecilus cynicus were found feeding on adult spotted lanternfles in Pennsylvania (Barringer and Smyers, 2016). Some egg parasitoids were also reported to be attacking the spotted lanternfly in China (Choi et al., 2014) and South Korea (Kim et al., 2011). Liu and Mottern (2017) found Ooencyrtus kuvanae, an egg parasitoid imported for controlling the gypsy moth (Lymantria dispar), attacking the egg masses of the spotted lanternfly in Pennsylvania in 2016. These native predators and introduced parasitoids could be potential biocontrol options for the spotted lanterfly.
Microbial control agents: Entomopathogenic fungi Beauveria bassiana, Isaria fumosorosea, and Metarhizium brunneum may also play a role alone or in combination with azadirachtin for controlling spotted lanternfly and researchers should explore microbial control.
Refer to the earlier article on the pest biology and damage at http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=15861
Spotted lanternfly in Entomology Today: https://entomologytoday.org/2015/12/17/be-prepared-for-spotted-lanternfly/
Barringer, L. E. and E. Smyers. 2016. Predation of the spotted lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae) by two native hemiptera. Entomol. News 126: 71-73. https://doi.org/10.3157/021.126.0109
Choi, M. Y., Z.Q. Yang, X. Y. Wang, Y. L. Tang, and Z. R. Hou. 2014. Parasitism rate of egg parasitoid Anastatus orientalis (Hymenoptera: Eupelmidae) on Lycorma delicatula (Hemiptera: Fulgoridae) in China. Korean J. Appl. Entomol. 53: 135–139.
Dara, S. K., L. Barringer, and S. P. Arthurs. 2015. Lycorma delicatula (Hemiptera: Fulgoridae): A new invasive pest in the United States. J. Integ. Pest Mngmt. 6(1): 20. https://doi.org/10.1093/jipm/pmv021
Kim, I. K., S. H. Koh, J. S. Lee, W. I. Choi, and S. C. Shin. 2011b. Discovery of an egg parasitoid of Lycorma delicatula (Hemiptera: Fulgoridae) an invasive species in South Korea. J. Asia Pac. Entomol. 14: 213–215.
Liu H. and J. Mottern. 2017. An old remedy for a new problem? Identification of Ooencyrtus kuvanae (Hymenoptera: Encyrtidae), and egg parasitoid of Lycorma delicatula (Hemiptera: Fulgoridae) in North America. J. Ins. Sci. 17: 1-6. https://doi.org/10.1093/jisesa/iew114
The biopesticides market has been experiencing a rapid growth in recent years; however, plant- and microorganism-based biopesticides have been used for centuries for controlling pests. According to 17th century records, plant extracts such as nicotine were some of the earliest agricultural biopesticides used to control plum beetles and other pests (BPIA, 2017). Experimentation involving biological controls against lepidopteran pests were performed as early as 1835, during Agostine Bassi's efficacy demonstrations of the white muscardine disease caused by a fungus now known as Beauveria bassiana against lepidopteran pests (BPIA, 2017). Further, the use of mineral oils as plant protectants was cited in experiments during the 19th century (BPIA, 2017).
In the early 20th century, an increasing number of studies involving biopesticides emerged during the rapid institutional expansion of agricultural research (Stoytcheva, 2011). The bacterium Bacillus thuringiensis (Bt) was the initial biopesticide and has the most widespread use to this day. In 1901, Bt was isolated from a diseased silkworm by Japanese biologist Shigetane Ishiwata. Ten years later, German researcher Ernst Berliner rediscovered it in a diseased flour moth caterpillar (BPIA, 2017). Other commercial success stories from the 1980s and 1990s involve the use of Agrobacterium radiobacter to prevent crown gall on woody crops (Escobar and Dandekar, 2003) as well as utilizing Pseudomonas fluorescens for the prevention of fire blight in orchards with streptomycin-resistant pathogen populations (Stockwell et al., 2010).
Resurgence in academic and industrial research for biopesticide development occurred in response to rising costs associated with the overuse of synthetic chemicals. Increasing biopesticide adoption has resulted, in part due to rapid expansion of organic agriculture during the past decade (Eze et al., 2016). As a result, the development of new biopesticides has continued to increase since the mid-1990s. Over 100 active ingredients have been registered with the United States Environmental Protection Agency (USEPA) Biopesticides Division since 1995 (EPA, 2017). The increasing cost of developing chemical pesticides (Fig. 1) could also have contributed to the rise in biopesticide registration (McDougall, 2016).
Fig. 1. Costs to discover and develop a synthetic agricultural chemical. (Based on McDougall 2016)
Biopesticides currently represent approximately 5% of the total pesticide market (Olson, 2015). However, the biopesticides market is experiencing rapid growth of about three times the rate associated with conventional agricultural chemicals (Chandler et al., 2011). The trend toward the use of biopesticides is growing stronger for two major reasons; the first is the fact that biologicals alone and in combination with chemicals have the potential to provide superior yields and quality (Yadav et al., 2013; Dara, 2015 & 2016; BPIA, 2017;). Secondly, increasing regulatory restriction on chemicals has established restrictive barriers to bringing new products to market while countries such as Europe simultaneously are eliminating pesticide active ingredients at a rapid rate (Erbach, 2012) (Fig. 2).
Fig.2. Numbers of new agricultural chemical leads and launches from 1995-2010 (Based on data from Ag Chem New Compound Review, 2010).
Over 200 biopesticide products are currently sold in the US, in comparison to only 60 comparable products in the European Union. Overall, more than 225 microbial biopesticides are presently manufactured within 30 countries that belong to the Organization for Economic Cooperation and Development. Approximately 45% of the total biopesticide use occurs in USA, Canada, and Mexico, whereas Asia uses around 5% of biopesticides sold globally (Kumar & Singh, 2016).
According to Berkshire Hathaway, the global biopesticides market is projected to reach a value of $8.8 billion by 2022, representing annual average growth of 17% from 2016 (Brzoskiewicz, 2018). Primary growth factors affecting the biopesticides market include growth in crop production, ease of application, increase the in need for organic food, and growing preference for sustainable pest control methods. Although biopesticides currently account for approximately 2% of the plant protectants used globally, the growth rate indicates an increasing trend during the past two decades, wherein the global use of biopesticides is increasing steadily by 10% every year (Brzoskiewicz, 2018).
Biostimulants are a recent emergent area within which functionality and regulatory guidelines may not be as well-defined as those for biopesticides. A plant biostimulant is defined as “any substance or microorganism applied to plants with the aim to enhance nutrition efficiency, abiotic stress tolerance and/or crop quality traits, regardless of its nutrients content” (du Jardin, 2015, p. 3). Chatzikonstantinou (2017) regarded fertilizers and biostimulants as being a part of the same family, with reasoning based in their similarities for helping plants to simulate nutrients, boosting tolerance to abiotic stress factors, and increasing the quality of crops. There are currently no federal statutory definitions for biostimulants in the US, and uncertainty exists in both federal and state regulatory agencies in terms of how to develop guidelines for plant biostimulant categories (Russell, 2015).
Ag Chem New Compound Review. 2010. Vol 28.
(BPIA). Biological Products Industry Alliance. 2017. History of biopesticides. http://www.bpia.org/history-of-biopesticides/
Brzoskiewicz, R. 2018. Biopesticides market: Global forecast to 2022. http://www.satprnews.com/2018/01/15/biopesticides-market-global-forecast-to-2022/
Chandler, D., A. Bailey, G.M. Tatchell, G. Davisdon, J. Greaves, et al. 2011. The development, regulation and use of biopesticides for integrated pest management. Phil Trans R Soc B 366: 1987–1998.
Chatzikonstantinou, L. 2017. Why biostimulants and fertilizers are part of the same family. http://www.biostimulants.eu/2017/05/why-biostimulants-fertilizers-are-part-of-the-same-family/
du Jardin, P. 2015. Plant biostimulants: Definition, concept, main categories and regulation. Sci Hort 196: 3–14.
Dara, S. K. 2015. Root aphids and their management in organic celery. CAPCA Adviser 18(5): 65-70.
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.
Erbach, G. 2012. Pesticide legislation in the EU: Towards sustainable use of plant protection products. Library briefing, Library of the European Parliament 120291REV1: 1-6.
(EPA). U.S. Environmental Protection Agency. 2017. Biopesticide active ingredients. https://www.epa.gov/ingredients-used-pesticide-products/biopesticide-active-ingredients
Escobar, M.A. and A.M. Dandekar. 2003. Agrobacterium tumefaciens as an agent of disease. Trends Pl Sci. 8(8): 380-396.
Eze, S.C., C.L. Mba, and P.I. Ezeaku. 2016. Analytical review of pesticide formulation trends and application: The effects on the target organisms and environment. Int Jour Sci Env Tech 5(1): 253-266.
Kumar, S., and A. Singh. 2015. Biopesticides: Present status and the future prospects. J Fertil Pestic 6: e129. doi:10.4172/2471-2728.1000e129
McDougall, P. 2016. A consultancy study for CropLife International, CropLife America and the European Crop Protection Association. https://croplife.org/wp-content/uploads/2016/04/Cost-of-CP-report-FINAL.pdf
Olson, S. 2015. An analysis of the biopesticide market now and where it is going. Outlk Pest Mgmt 26: 203-206. DOI: 10.1564/v26_oct_04
Jones, R. 2015. Biostimulants: An OPP perspective. Association of American Pesticide Control Officials SFIREG Meeting Proceedings, Arlington, VA (September 2015). https://aapco.files.wordpress.com/2015/10/russ_jones_epa_biostimulants_sfireg_draft_09-2015.pdf
Stockwell, V.O., K. B. Johnson, D. Sugar, and J. E. Loper. 2010. Control of fire blight by Pseudomonas fluorescens A506 and Pantoea vagans C9-1 applied as single strains and mixed inocula. Phytopath 100(12): 1330-1339.
Stoytcheva, M (ed.). 2011. Pesticides: Formulations, effects, fate. Intech, Rijeka, Croatia.
Yadav, S.K, S. Babu, M. K. Yadav, K.Singh, G. S. Yadav, and S. Pal. 2013. A review of organic farming for sustainable agriculture in northern India. Int Jour Agr 2013: 1-8. http://dx.doi.org/10.1155/2013/718145/span>
Biopesticides are based on naturally occurring microorganisms, plant extracts or other materials and are regulated by the United States Environmental Protection Agency (EPA)'s Biopesticide Division. Biopesticides have been safely used for over 63 years and are generally subjected to reduced regulation compared to conventional chemical pesticides.
Biopesticides can be developed from plant extracts or entomopathogenic microorganisms. Graphic: Surendra Dara
The active ingredient in microbial pesticides consists of a microorganism, such as a bacterium, fungus, nematode, protozoan or virus. While microbials are capable of assisting in the management of many different types of pests, each type of microorganism tends to be relatively specific for a target pest or group of pests. Biochemical pesticides are based on naturally occurring substances, which function by providing pest management through non-toxic mechanisms. Biochemical pesticides may function by disrupting or interfering with mating, such as in the case of insect sex pheromones or various plant extracts which serve as insect attractants used with traps. Conventional pesticides, by contrast, are generally synthetic materials that directly kill or inactivate the pest (Leahy et al., 2014).
Typically, samples of microorganisms or infected arthropods are collected from natural environments. Samples are taken to the laboratory and plated on media; thereafter, various colonies form from the collected samples. Individual colonies of interest may be selected, suspended, and examined for pesticidal activity during laboratory bioassays (Taylor, 1988). As part of the laboratory bioassay process, researchers screen candidates against a number of potential targets, which may vary widely, depending upon institutional goals and availability.
A key initial task is identification and characterization of the pesticidal compounds sourced from the plants or microbes collected in natural settings (Strobel and Daisy, 2003). Part of this process involves isolating and eliminating any compounds which have potential human health implications or may negatively impact non-targets organisms (USDA, 2017b). Additionally, analytical assays based on bioactive chemistry are developed to ensure quality control during the manufacturing process (Strobel and Daisy, 2003).
Several steps are involved with product and process development. First, user-friendly formulations are developed in both lab and pilot facilities. Next, manufacturing processes are developed and scaled in arenas including lab, pilot, and manufacturing facilities (Strobel and Daisy, 2003). Thereafter, field studies are conducted and data are gathered for the regulatory submissions which support product registration (USDA, 2017a).
Biopesticide registration process
A special committee has been established within the EPA due to the fact that it is often challenging to determine whether a substance meets the criteria for classification as a biochemical pesticide (Leahy et al., 2014). The Biopesticide Pollution Prevention Division (BPPD) of the EPA is charged with data review required for registration. Requirements for registration include acute studies consisting of oral, inhalation, intravenous, and dermal tests, in addition to eye and skin studies in rodents. A product chemistry review involving a five-batch analysis is also required by BPPD. Microbiology and quality control investigations assure that material is free of human pathogens. Ecological effects, including impact on non-target birds, fish, Daphnia, honeybees, lacewings, ladybeetles, and parasitic wasps is additionally determined. The review process is taken one step further during the endangered species review. Finally, the matter of the Exemption from Tolerance Petition for Food Use is addressed (EPA, 2017). It should be noted that efficacy data are required in addition to the aforementioned topics when attempting to register a new biopesticide in California (CDPR, 2017). There are several examples of successful pesticides which are sourced from natural products and registered as chemical pesticides (Fig. 1).
Fig. 1. Chemical pesticides developed from natural sources. Graphic: Melissa O'Neal
Abamectin is an insecticide/miticide derived from Streptomyces avermitilis, a microorganism found in soil. Its mode of action involves interference with neurotransmission (CDPR, 1993). Tebufenozide is an insect growth disruptor which interferes with insect molting hormones (Smagghe et al., 2012). The spinosyns are a family of chemicals produced by fermentation of Saccharopolyspora bacteria which are toxic due to disruption of neurotransmitters in both target and non-target organisms (Kirst, 2010). Azoxystrobin is a synthetic material derived from phytotoxic compounds which naturally occur in the mushrooms Oudemansiella mucida and Strobilurus tenacellus. Its mode of action is disruption of energetic reactions involving ATP synthesis (AgChemAccess, 2015). Finally, pyrethrins are naturally occurring materials derived from the chrysanthemum (Chrysanthemum cinerariaefolium) flowers and acts as a contact nerve poisons (Extoxnet, 1994).
The following tables 1-5 provide an overview of some of the commercial biopesticides currently registered in the US and other countries for controlling insects, mites, plant pathogenic fungi, and plant parasitic nematodes.
Table 1. Microbial insecticides and acaracides.
Table 2. Plant extract and oil insecticides and acaricides.
Table 3. Microbial fungicides.
Table 4. Non-microbial fungicides.
Table 5. Bionematicides.
AgChemAccess. 2015. Azoxystrobin. http://www.agchemaccess.com/Azoxystrobin.
(CDPR). California Department of Pesticide Regulation. 1993. Abamectin Avert Prescription Treatment 310 (Section 3 Registration) Risk Characterization Document. http://www.cdpr.ca.gov/docs/risk/rcd/abamectin.pdf
(CDPR). California Department of Pesticide Regulation. 2017. How to apply for pesticide product registration. http://www.cdpr.ca.gov/docs/registration/instructions.htm
(EPA). U.S. Environmental Protection Agency. 2017. Biopesticides. https://www.epa.gov/pesticides/biopesticides#what
Extoxnet. 1994. Pesticide information profile: Pyrethrins. http://pmep.cce.cornell.edu/profiles/extoxnet/pyrethrins-ziram/pyrethrins-ext.html
Kirst, H.A. 2010. The spinosyn family of insecticides: realizing the potential of natural products research. J Antibiot 63(3): 101-11. doi: 10.1038/ja.2010.5.
Leahy, J., M. Mendelsohn, J. Kough, R. Jones, and N. Berckes. 2014. Biopesticide oversight and registration at the U.S. Environmental Protection Agency. In Biopesticides: State of the Art and Future Opportunities; Coats, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.
Smagghe, G., L.E. Gomez, and T.S. Dhadialla. 2012. Insect growth disruptors. Adv Ins Phys 43: 1-552.
Strobel, G. and B. Daisy. 2003. Bioprospecting for microbial endophytes and their natural products. Microbiol Mol Bio Rev 67(4): 491-502.
Taylor, J.K. 1988. Quality assurance of chemical measurements. Chelsea, MI: Lewis.
(USDA). United States Department of Agriculture. 2017a. About AMS.
(USDA). United States Department of Agriculture. 2017b. USDA FY 2016 avoiding harm from invasive species (USDA Do No Harm 2016 Report, Part 2). https://www.invasivespeciesinfo.gov/docs/resources/usdanoharm20170119.docx
California is the leading producer of tomatoes, especially for the processing market (CDFA, 2017). Tomato is the 9th most important commodity in California valued at $1.71. Processed tomatoes are ranked 6th among the exported commodities with a value of $813 million. While good nutrient management is necessary for optimal growth, health, and yields of any crop, certain products that contain minerals, beneficial microbes, biostimulants, and other such products are gaining popularity. These materials are expected to improve crop health and yield, impart soil or drought resistance, induce systemic resistance, or improve plant's immune responses to pests, diseases, and other stress factors (Berg, 2009; Bakhat et al., 2018; Chandra et al., 2018; Shameer and Prasad, 2018). Maintaining optimal plant health through nutrient management is not only important for yield improvement, but it is also an important part of integrated pest management strategy as healthy plants can withstand pest and disease pressure more than weaker plants and thus reduce the need for pesticide treatments.
Experimental plots, transplanting, and treatment details.
A study was initiated in the summer 2017 to evaluate the impact of various treatment programs on tomato plant health and yield. Processing tomato cultivar Rutgers was seeded on 7 June and transplanted on 18 July, 2017 using a mechanical transplanter. Monoammonium phosphate (11-52-0) was applied at 250 lb/ac as a side-dress on 7 August as a standard for all treatments. Since planting was done later in the season, crop duration and harvesting period were delayed due to the onset of fall weather. Plots were sprinkler irrigated daily or every other day for 3-4 hours for about 2 weeks after transplanting. Drip irrigation was initiated from the beginning of August for 12-14 hours each week and for a shorter period from mid October onwards.
There were five treatments in the study including the standard. Each treatment had a 38” wide and 300' long bed with a single row of tomato plants. Treatments were replicated four times and arranged in a randomized complete block design. Different materials were applied through drip using a Dosatron injector system, sprayed at the base of the plants with a handheld sprayer, or as a foliar spray using a tractor-mounted sprayer based on the following regimens.
- AgSil® 21 at 8.75 fl oz/ac in 100 gal of water through drip (for 30 min) every 3 weeks from 31 July to 13 November (6 times). AgSil 21 contains potassium (12.7% K2O) and silicon (26.5% SiO2) and is expected to help plants with mineral and climate stress, improve strength, and increase growth and yields.
- Yeti BloomTM at 1 ml/gallon of water. Applied to the roots of the transplants one day before transplanting followed by weekly field application through the drip system from 7 August to 13 November (15 times). Yeti is marketed as a biostimulant and has a consortium of beneficial bacteria - Pseudomonas putida, Comamonas testosterone, Citrobacter freundii, and Enterobacter cloacae. Yeti Bloom is expected to enhance the soil microbial activity and helps with improved nutrient absorption.
- Tech-Flo®/Tech-Spray® program contained five products that supplied a variety of macro and micro nutrients. Products were applied through drip (for 30 min) at the following rates and frequencies in 300 gal of water.
- Tech-Flo All Season Blend #1 1 qrt/ac in transplant water and again at first bloom on 28 August.
- Tech-Flo Cal-Bor+Moly at 2 qrt/ac at first bloom on 28 August.
- Tech-Flo Omega at 2 qrt/ac in transplant water and again on 11 September (2 weeks after the first bloom).
- Tech-Flo Sigma at 2 qrt/ac on 11 September (2 weeks after the first bloom).
- Tech-Spray Hi-K at 2 qrt starting at early color break on 25 September with three follow up applications every two weeks.
- Innovak Global program contained four products.
- ATP Transfer UP at 2 ml/liter of water sprayed over the transplants to the point of runoff just before transplanting. Three more applications were made through drip (for 30 min) on 7 and 21 August and 4 September. This product contains ECCA Carboxy® acids that promote plant metabolism and expected to impart resistance to stress factors.
- Nutrisorb-L at 40 fl oz/ac applied through drip (for 30 min) on 31 July, 14 August (vegetative growth stage), 4 and 18 September, and 2 October (bloom through fruiting). Nutrisorb-L contains polyhydroxycarboxylic acids, which are expected to promote root growth and improve nutrient and water absorption.
- Biofit®N at 2 lb/ac through drip (for 30 min) on 31 July, 21 August (3 weeks after the first), and 4 September (at first bloom). Biofit contains a blend of beneficial microbes – Azotobacter chroococcum, Bacillus subtilis, B. megaterium, B. mycoides, and Trichoderma harzianum. This product is expected to improve the beneficial microbial activity in the soil and thus contribute to improved soil structure, root development, plant health, and ability to withstand stress factors.
- Packhard at 50 fl oz/ac in 50 gal of water as a foliar spray twice during early fruit development (on 11 and 18 September) and every 2 weeks during the harvest period (four times from 2 October to 13 November). Contains calcium and boron that improve fruit quality and reduce postharvest issues.
A 50' long area was marked in the center of each plot for observations. Plant health was monitored on 1, 8, and 22 August by examining each plant and rating them on a scale of 5 where 0 represented a dead plant and 5 represented a very healthy plant. Yield data were collected from 11 October to 5 December on eight harvest dates by harvesting red tomatoes from each plot. On the last harvest date, mature green tomatoes were also harvested and included in the yield evaluation. Data were analyzed using analysis of variance and Tukey's HSD test was used for means separation.
Results and discussion
There was no statistically significant difference (P > 0.05) in the health of the plants in August (Fig. 1) or in the overall seasonal yield (Fig. 2) among treatments. The average health rating from three observations was 3.94 for the standard, 4.03 for AgSil 21, 4.45 for Yeti Bloom, 4.38 for Tech-Flo/Spray program, and 4.35 Innovak Global program.
Fig. 1. Plant health on a 0 (dead) to 5 (very healthy) rating on three observation dates.
When the seasonal total yield per plot was compared, Yeti Bloom had 194.1 lb followed by, Innovak program (191.5 lb), AgSil 21 (187.3 lb), the standard (147.4 lb) and Tech-Flo/Spray program (136.5 lb). Due to the lack of significant differences, it is difficult to comment on the efficacy of treatments, but the yield from AgSil 21 was 27% more than the standard while yields from Innovak program and Yeti Bloom were about 30% and 32% higher, respectively.
Fig. 2. Seasonal total yield/plot from different treatments.
Fig. 3. Percent difference in tomato yield between the standard and other treatment programs.
Studies indicate that plants can benefit from the application of certain minerals such as silicon compounds and beneficial microorganisms, in addition to optimal nutrient inputs. Silicon is considered as a beneficial nutrient, which triggers the production of plant defense mechanisms against pests and diseases (Bakhat et al., 2018). Although pest and disease conditions were not monitored in this study, silverleaf whitefly (Bamisia tabaci) infestations and mild yellowing of foliage in some plants due to unknown biotic or abiotic stress were noticed. AgSil 21 contains 26.5% of silica as silicon dioxide and could have helped tomato plants to withstand biotic or abiotic stress factors. Similarly, beneficial microbes also promote plant growth and health through improved nutrient and water absorption and imparting the ability to withstand stresses (Berg, 2009; Shameer and Prasad, 2018). Beneficial microbes in Yeti Bloom and BiofitN might helped the tomato plants in withstanding stress factors and improved nutrient absorption. Other materials applied in the Innovak program might have also provided additional nutrition and sustained microbial activity.
The scope of the study, with available resources, was to measure the impact of various treatments on tomato crop health and yield. Additional studies with soil and plant tissue analyses, monitoring pests and diseases, and their impact on yield would be useful.
Acknowledgements: Thanks to Veronica Sanchez, Neal Hudson, Sean White, and Sumanth Dara for their technical assistance and the collaborating companies for free samples or financial assistance.
Bakhat, H. F., B. Najma, Z. Zia, S. Abbas, H. M. Hammad, S. Fahad, M. R. Ashraf, G. M. Shah, F. Rabbani, S. Saeed. 2018. Silicon mitigates biotic stresses in crop plants: a review. Crop Protection 104: 21-34. DOI: 10.1016/j.cropro.2017.10.008.
Berg, G. 2009. Plant-microbe interactions promoting plant growth and health: perspectives for controlled use of microorganisms in agriculture. Appl. Microbiol. Biotechnol. 84: 11-18. DOI: 10.1007/s00253-009-2092-7.
CDFA (California Department of Food and Agriculture). 2017. California agricultural statistics review 2015-2016. (https://www.cdfa.ca.gov/statistics/PDFs/2016Report.pdf)
Chandra, D., A. Barh, and I. P. Sharma. 2018. Plant growth promoting bacteria: a gateway to sustainable agriculture. In: Microbial biotechnology in environmental monitoring and cleanup. Editors: A. Sharma and P. Bhatt, IGI Global, pp. 318-338.
Shameer, S. and T.N.V.K.V. Prasad. 2018. Plant growth promoting rhizobacteria for sustainable agricultural practices with special reference to biotic and abiotic stresses. Plant Growth Regulation, pp.1-13. DOI: 10.1007/s10725-017-0365-1.
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.