Performing Department
Northeast Res & Extension Cntr
Non Technical Summary
Rice is a major crop of the United States with over 2.9 million acres of rice harvested in 2020. After rice is harvested, it is stored as rough rice in large bins either on-farm or in commercial sites where it is dried using natural air that is pumped into the bin over many days. During rice storage, rice can be infested by a number of stored product insects that infest raw grains. In stored bulk grain, the most damaging pests are internal feeders such as the rice weevil (Sitophilus oryzae) and lesser grain borer (Rhyzopertha dominica). Stored product insects can cause direct product loss through feeding damage, insect fragments in food, and can cause health hazards including allergic reactions. Infestations inside processing facilities and resulting product recalls can result in millions of dollars of economic loss.Insect pest management is a vital part of the overall strategy to reduce loss and damage in bulk rough rice. The rice industry uses a variety of techniques to control for insects including sanitation and a multitude of insecticides. Methyl bromide has historically been used to control insects in food production and storage facilities. However, methyl bromide depletes the ozone layer in the atmosphere, and it is therefore no longer used in rice storage in compliance with the Montreal Protocol. Other insecticides used in grain bins include sulfuryl fluoride and phosphine. However, there have been increasing levels of resistance to phosphine in stored product insects. Evaluations of new control strategies that have potential for adoption are needed.Microwave technology is a potential alternative to remove insects from grains. This technology has been used to kill insects in white maize, barley and rye. With few studies being conducted in rice. More studies are needed to determine the efficacy of microwave in controlling insects in rice and how this technology could influence rice quality. This research could have potential for integrated pest management for the rice industry.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
Rice (Oryza sativa) is a major crop of the United States with over 2.9 million acres of rice harvested in 2020 (1). Arkansas was the top producer of rice, harvesting 48% of the rice grown in the U.S. in 2020 (1). After rice is harvested, it is stored as rough rice in large bins either on-farm or in commercial sites where it is dried using natural air that is pumped into the bin over many days. During rice storage, rice can be infested by a number of stored product insects that infest raw grains. In stored bulk grain, the most damaging pests are internal feeders such as the rice weevil (RW, Sitophilus oryzae), lesser grain borer (LGB, Rhyzopertha dominica), and Angoumois grain moth (AGM, Sitotroga cerealella) (2). Stored product insects can cause direct product loss through feeding damage and consumption, insect fragments in food, and can cause health hazards including allergic reactions. Infestations inside processing facilities and resulting product recalls can result in millions of dollars of economic loss.Insect pest management is a vital part of the overall strategy to reduce loss and damage in bulk rough rice. The rice industry uses a variety of techniques to control for insects including sanitation and a multitude of insecticides. Methyl bromide has historically been used to control insects in food production and storage facilities. However, methyl bromide depletes the ozone layer in the atmosphere (3), and it is therefore no longer used in rice storage in compliance with the Montreal Protocol (4). Other insecticides used in grain bins include sulfuryl fluoride and phosphine. However, there have been increasing levels of resistance to phosphine in species such as the LGB and the red flour beetle (RFB, Tribolium castenum) (5). Evaluations of new control strategies that have potential for adoption are needed.Beginning in the 1960s and 70s, infrared radiation (IR) was starting to be considered as a possible method for disinfesting grains of stored-product insects as well as fungi. These studies show promise at disinfesting grains of LGB, RFB, and other stored-product insects (6-12). These older studies focused mostly on wheat (Triticum aestivum) (9-12) with only a few studies on rice (6, 7, 13, 14).Microwave technology is another potential alternative to remove insects from grains. Ramierez-Rojas et al. (15) examined the effects of heating white maize with a microwave radio frequency of 12kW at 50°C for 3 min achieved 100% mortality of 4th instar larvae of the maize weevil (MW, Sitophilus zeamais). Vadivambal et al. (16) found barley and rye treated with 500 W at 28 sec resulted in 100% mortality of RFB, the rusty grain beetle (Crypotlestes ferrigineus) and the granary weevil (Sitophilus granaries). Other studies on wheat (17-19) and on various legumes (20) have been conducted. However, after an extensive literature search, two studies have examined the effects of microwave on insects in rice. Zhao et al. (21) found 100% mortality of adult and eggs of rice weevil when exposed to microwaves above 0.017 kWh/kg. Nakakita et al. (22) found microwave to be effective in killing six species of stored product insects when temperatures of rough rice reached 60° C. It is unclear from these studies how the quality of rice was affected. More studies are needed to determine the efficacy of microwave in controlling insects in rice and how this technology could influence rice quality. This research could have potential for integrated pest management for the rice industry.Objective 1. To assess the effects of microwave technology in disinfesting (decontaminate) rice. Can this technology be used to kill insects in rough rice, brown rice and rice flour?Objective 2. To examine the effect of microwave technology on the susceptibility of rough rice, brown rice and rice flour to insect infestation.LITERATURE CITEDUnited States Department of Agriculture, Economic Research Service (2021) https://www.ers.usda.gov/topics/crops/rice/rice-sector-at-a-glance/#production (last assessed 6-14-2021.McKay, T., A. L. White, L. Starkus, F. H. Arthur, and J. F. Campbell. 2017. Seasonal patterns of stored-product insects at a rice mill. J. Econ. Entomol. 110: 1366-1376.EPA. 2013. The phaseout of methyl bromide. http://www.epa.gov/ozone/mbr/.EPA. 2016. Methyl bromide. https://www.epa.gov/ods-phaseout/methyl-bromide.Cato, A. J., B. Elliot, Nayak, M. K. and T. W. Phillips. 2017. Geographic variation in phosphine resistance among North American populations of the red flour beetle (Coleoptera: Tenebrionidae). J. Econ. Entomol. 110: 1359-1365.Tilton, E. W. and H. W. Schroeder. 1963. Some effects of infrared irradiation on the mortality of immature insects in kernels of rough rice. J. Econ. Entomol. 56:727-730.Faulkner, M. D. and F. T. Wratten. 1969. The Louisiana State University infrared preheat rice dryer, 101-22. In 61st Annual Progress Report. Rice Experiment Station, Crowley, Louisiana, Louisiana State University, Agricultural Experiment Station.Cogburn, R. R., J. H. Brower, and E. W. Tilton. 1971. Combination of gamma and infrared radiation for control of the Angoumois grain moth in wheat. J. Econ. Entomol. 64:923-925.Kirkpatrick, R. L., J. H. Brower, and E. W. Tilton. 1972. A comparison of microwave and infrared radiation to control rice weevils (Coleoptera: Curculionidae) in wheat. J. Kansas Entomol. Soc. 45:434-438.Kirkpatrick, R. L. 1974. The use of infrared and microwave radiation for control of stored-product insects. Proceedings of the First International Working Conference on Stored-Product Entomology pp. 431-437.Kirkpatrick, R. L. 1975. Infrared radiation for control of lesser grain borers and rice weevils in bulk wheat (Coleoptera: Bostrichidae and Curculionidae). J. Kansas Entomol. Soc. 48:100-104.Kirkpatrick, R. L. and A. Cagle. 1978. Controlling insects in bulk wheat with infrared radiation. J. Kansas Entomol. Soc. 51:386-393.Cogburn, R. R. 1967. Infrared radiation effect on reproduction by three species of stored-product insects. J. Econ. Entomol. 60:548-550.Hampton, R. M., G. G. Atungulu, Z. Odek, V. Rolland, T. J. Siebenmorgen, S. A. Wilson and T. McKay. 2019. Assessment of Rhyzopertha domestica (F.) progeny and feeding damage on rice dried with infrared radiation. J. Stor. Prod. Res. 81: 69-75.Ramirez-Rojas, N.Z, Ceron-Garcia, A., Salas-Araiza, M.D, Estrada-Garcia, H. J., Rojas-Laguna, R., and M. E. Sosas-Morales. 2020. Radio frequency heating against Sitophilus zeamais Motschulsky in white maize. J. Stor. Prod. Res. 89. DOI: 10.1016/j.jspr2020.101730.Vadivambal, R., D. S Jayas, and D. D. G. White. 2008. Mortality of stored-grain insects exposed to microwave energy. Trans. ASABE. 51: 641-647.Halverson, S. L., W. E. Burkholder, T. S. Bigelow, E. V. Nordheim, and M. E. Misenheiner. 1996. High-power microwave radiation as an alternative insect control method for stored products. J. Econ Entmol. 89: 1638-1648.Vadivambal, R., Jayas, D. S., and N. D. G. White. 2007. Wheat disinfestation using microwave energy. J. Stor. Prod. Res. 43: 508-514.Keszthelyi, S., Nyari, A., and F. Pal-Fam. 2020. Assessment of short-term mortality of granary weevil, Sitophilus granarius (Coleoptera: Curculionidae) triggered by different microwave irradiation powers. Inter. J. Pest Manag. 66: 222-226.Dalmoro, A. et al. 2018. On the relevance of thermophysical characterization in the microwave treatment of legumes. Food & Function 9: 1816-1828.Zhao, S. M.et al.2007. A thermal lethal model of rice weevils subjected to microwave irradiation. J. Stor. Prod. Res. 43: 430-434.Nakakita, H., O. Imura, and H. Nabetani. 1989. Application of electromagnetic waves for control of stored-product insects. Part I Effects of microwaves on susceptibilities on insect and quality of rice. J. Japan. Soc. For Food Sci and Tech. 36: 267-273.Rees, D. 2007. Insects of Stored Grain. CSIRO Publishing, Canberra, Australia
Project Methods
Insect ColoniesTwo insect species will be used for this study. Maize weevils and red flour beetles will be obtained from colonies established at Arkansas State University. The colonies will be reared on brown rice and wheat flour, respectively, and maintained at 27° C and ~60% relative humidity.Rice AcquisitionRice harvested in Arkansas during the summer 2021 growing season will be acquired and sent to the University of Arkansas' Grain Processing and Engineering Laboratory (Food Science Department, Fayetteville, AR). The samples will be cleaned to remove debris and dried to ~13% moisture. Samples will consist of rough rice (cleaning only), milled brown rice and rice flour.For Objective 1, we will determine the effect of microwave intensities of 1, 2, and 3 kW at 30, 60 and 90 sec on adult maize weevil mortality infesting rough rice and brown rice. We will also conduct the same experiment on adult red flour beetles infesting rice flour. For each treatment, 10 adult beetles will be placed within the grain sample, with five replicates per treatment. The control treatment will be 0 kW intensity for the same time durations. Once the samples have been treated, the weevils will be immediately examined for knockdown (insects on their backs and incapable of righting themselves without assistance). Assessment of knockdown will be done 15, 30, 60, 90 min, and after 24 hr. If there are adults that are actively moving at these time frames, they will be removed and placed in vials containing brown rice and they will be monitored for progeny development. We will also assess the mortality of RFB eggs, larvae and pupae using the same microwave intensities and durations as above. After microwave treatment, all eggs and pupae will be placed on rice flour and they will be monitored for progeny development. RFB larvae will be assessed for mortality and morbidity using the same procedures as mentioned above for adults.Rice Quality AssessmentMilling, pasting viscosity profiles, color and protein analysis will be conducted by Dr. Griffiths Atungulu (University of Arkansas' Grain Processing and Engineering Laboratory).For Objective 2, we will determine the effect of microwave technology on the susceptibility of rough rice, brown rice and rice flour to insect infestation. Rough rice, brown rice and rice flour will each be treated with microwave intensities of 1, 2, and 3 kW at 30, 60 and 90 sec durations. Control treatments will be 0 kW intensity for each time duration as well as a control where the rice product will not be placed in the microwave apparatus. For each of the treatments, approximately 4.5 g of rice product will be placed in 5-dram vials. Once vials are filled, ten unsexed adult weevils (brown rice and rough rice treatments) or red flour beetles (rice flour treatments) will be placed in each vial (assuming a 1:1 sex ratio) and stored in an incubator at 27°C and 60% RH. Adults will be removed after 7 days. Vials will be checked biweekly until the 28th day when daily checks will be done to look for adult emergence. The development period for maize weevil and red flour beetle varies depending on temperature and humidity; however, under preferred conditions the expected development time is approximately 30 days (23). Therefore, after 50 days, when no further signs of adult emergence are seen, vials will be placed in a freezer to stop further development and progeny feeding.The number of adults will be counted. All data will be analyzed using SAS® version 9.4 software (SAS Institute, Cary, NC). The progeny analysis will be done using the total counts from sieving. ANOVA tests will be done to see if microwave intensity, duration, rice fraction (brown/rough rice/rice flour), or their interactions caused significant differences in the amount of overall progeny.For rough rice and brown rice treatments, kernels with and without damage will be counted and the amount of feeding damage to each kernel will be categorized into levels of damage recorded 0 to 4 (no damage, 1-25%, 25-50%, 50-75%, and 75-100% damage, respectively). The number of kernels in each of the category levels will be counted. As an additional assessment of feeding damage, the amount of frass (excrement and any residual dust from the rice) in each vial will be weighed to the nearest 0.05 g.A four-way ANOVA test will be used to examine if there are differences in frass weight among microwave treatments for both rough rice and brown rice. When there are significant differences, post-hoc LSMeans tests in SAS will be used to separate means.