Rapid Report Received: 25 August 2009
Revised: 31 October 2009
Accepted: 22 November 2009
Published online in Wiley Interscience: 1 February 2010
(www.interscience.wiley.com) DOI 10.1002/ps.1915
Novel use of nanostructured alumina as an insecticide Teodoro Stadler,a Micaela Butelerb∗ and David K Weaverb Abstract BACKGROUND: The worldwide need to produce an inexpensive and abundant food supply for a growing population is a great challenge that is further complicated by concerns about risks to environmental stability and human health triggered by the use of pesticides. The result is the ongoing development of alternative pest control strategies, and new, lower-risk insecticidal molecules. Among the recent technological advances in agricultural science, nanotechnology shows considerable promise, although its development for use in crop protection is in its initial stages. RESULTS: This study reports for the first time the insecticidal effect of nanostructured alumina. Two species were used as model organisms, Sitophilus oryzae L. and Rhyzopertha dominica (F.), which are major insect pests in stored food supplies throughout the world. Both species experienced significant mortality after 3 days of continuous exposure to treated wheat. Nine days after treatment, the median lethal doses (LD50 ) observed ranged from 127 to 235 mg kg−1 . CONCLUSION: Comparison of these results with recommended rates for commercial insecticidal dusts suggests that inorganic nanostructured alumina may provide a cheap and reliable alternative for control of insect pests. This study expands the frontiers for nanoparticle-based technologies in pest management. Further research is needed to identify its mode of action and its non-target toxicity, and to determine the potential of other nanostructured materials as pest control options for insects. c 2010 Society of Chemical Industry Keywords: nanostructure; alumina; insecticide; stored products
1
INTRODUCTION
Pest Manag Sci 2010; 66: 577–579
2
MATERIALS AND METHODS
2.1 Synthesis of nanostructured material NSA was obtained by the combustion synthesis technique using a redox mixture, with glycine as fuel and aluminum nitrate as oxidizer.10 2.2 Test insects The species tested were adults of two primary grain pests, the rice weevil, S. oryzae, and the lesser grain borer, R. dominica. Insects were obtained from colonies with no history of exposure to insecticides, reared on Buck variety winter wheat mixed with brewers’ yeast (1% w/w). Insects were reared at 28 ± 1 ◦ C and 70 ± 5% RH in the dark. The desired RH was maintained by using a saturated solution of sodium chloride.11 Adults used in all
∗
Correspondence to: Micaela Buteler, Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, USA. E-mail:
[email protected]
a Instituto de Medicina y Biología Experimental de Cuyo (IMBECU), Centro Científico Tecnol´ogico CONICET-Mendoza, Argentina b Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, USA
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c 2010 Society of Chemical Industry
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The worldwide need to produce an inexpensive and abundant food supply for a growing population is a great challenge that is further complicated by concerns about risks to environmental stability and human health triggered by the use of pesticides.1,2 The result is ongoing development of sustainable cropping practices, alternative integrated pest control strategies, and new, lower-risk insecticidal molecules. Among the most recent technological advances in agricultural science, nanotechnology shows considerable promise for use in crop and foodstuff protection, although development of the use of such materials is in its initial stages. Nanostructured materials, types of nanomaterial, are defined as materials whose structural elements – clusters, crystallites or molecules – have dimensions in the 1–100 nm range.3 Over the past decade, there has been an explosion in academic and industrial interest in these nanomaterials, which arises from the novel properties that emerge from materials at this scale, such as changes in electrical conductivity, surface chemistry and reactivity.4 – 7 In agriculture, the use of nanoparticles that encapsulate pesticides can improve delivery systems and therefore limit undesirable impacts.8 Nanocapsules or liposomes are already being incorporated in the development and formulation of agrochemicals.9 The present study aimed to investigate the potential of nanostructured particles as insecticides. This was tested using nanostructured alumina (NSA) on two model insect species, Sitophilus oryzae L. (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), which are
major pests of dry grains in storage, milling and food processing facilities worldwide.
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T Stadler, M Buteler, DK Weaver
Day 3 Day 9
100
100 80 Mortality (%)
Mortality (%)
80
Day 3 Day 9
60 40 20
60 40 20
0 0
125
250
500
0
1000
0
Dose (mg kg−1)
125
250
500
1000
Dose (mg kg−1)
Figure 1. Response of Sitophilus oryzae to continuous exposure to wheat treated with NSA after 3 and 9 days.
Figure 2. Response of Rhyzopertha dominica to continuous exposure to wheat treated with NSA after 3 and 9 days.
experiments were of unknown sex, mating status and age. Wheat used for the experiments was clean, with little dockage (0.1%). The moisture content of the wheat, as determined by a moisture analyzer (model MX-50; A&D Company, Ltd), was 10.5 ± 0.5%.
for S. oryzae. This occurred only for the data collected after 3 days of exposure to treated wheat, so these data are not presented.
3 2.3 Dry dust application of NSA Toxicity to S. oryzae and R. dominica was assessed using dry dust applications and evaluated at four different concentrations of the product: 1000, 500, 250 and 125 mg kg−1 . A quantity of 60 mg of NSA was mixed thoroughly with 60 g of wheat to prepare an even distribution of the dust through the entire grain mass. Then, 30 g of treated wheat was transferred into a dry and clean PVC petri dish (9.5 cm diameter). Serial 1 : 1 dilutions were conducted to achieve the desired concentrations in wheat. A petri dish containing 30 g of untreated wheat was used as control. All the petri dishes were placed in temperature-controlled incubators. Temperature and humidity inside the chambers were identical to rearing conditions, and monitored with HOBO data recorders (Onset Computer Corp., Bourne, MA). Each experiment consisted of six petri dishes per concentration, containing ten insects each, and was replicated twice with each insect species. Adult mortality was assessed 3 and 9 days after continuous exposure to the treated wheat. The data were analyzed using a mixed-model approach,12 with mortality as the response variable and concentration and date of observation as main effects. Date of observation was the repeated measure. The variance–covariance structure was modelled as compound symmetry. Control mortality was rare, and, where corrections for mortality were necessary, these were accomplished using Abbott’s formula.13 The data were logarithmically transformed to better meet homogeneity of variance. The LC50 and LC95 values (mg kg−1 ) and 95% confidence limits (95% CLs) were calculated by probit analysis.12 The chisquare value was used to measure the goodness of fit of the probit regression line. A significant chi-square value indicated that the probit model failed to fit the observed dose–response data well
RESULTS
Exposure of the insects to wheat treated with NSA significantly reduced survival in both species (Figs 1 and 2). There was a significant exposure time (df = 1, 97, F = 171.98, P < 0.0001; df = 1, 97, F = 122.73, P < 0.0001) as well as a concentration effect (df = 4, 97, F = 241.73, P < 0.0001; df = 4, 97, F = 153.83, P < 0.0001) on mortality in R. dominica and S. oryzae respectively. Mortality in both species increased as exposure interval and product concentration increased (Figs 1 and 2). After 3 days of continuous exposure to NSA at a dose of 1000 mg kg−1 , mortality was around 95%, and after 9 days no survival was detected in any of the species tested. After 3 days of continuous exposure to 500 mg kg−1 , 20% of the S. oryzae and 40% of the R. dominica adults were dead. After 9 days of continuous exposure to 250 mg kg−1 , 80% of the adults of both species were dead (Table 1 shows the median lethal doses to 50 and 95% of the test population – LD50 and LD95 values).
4
DISCUSSION
This study presents the discovery of the insecticidal effect of NSA and presents the potential for new frontiers of nanoparticlebased technologies in pest management. Mortality due to NSA was observed at rates comparable with those recommended for commercially available insecticidal dusts, which range from 500 to 5000 mg kg−1 , depending on the mineral composition of the dust, the type of formulation and environmental conditions.14,15 Thus, this inorganic nanostructured material may provide a cheap, reliable and safe alternative in insect pest control. The data obtained in this study with NSA warrant further research to explore the potential of this product to manage
Table 1. Probit analysis of mortality data following treatment with NSA Species
Exposure time (days)
LD50 (mg kg−1 ) (95% CL)
LD95 (mg kg−1 ) (95% CL)
Slope (SE)
9 3 9
177 (104–235) 438 (396–489) 149 (127–169)
461 (330–1081) 1382 (1382–1796) 503 (417–660)
3.94 (1.04) 3.29 (0.27) 3.11 (0.34)
Sitophilus oryzae Rhyzopertha dominica
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Pest Manag Sci 2010; 66: 577–579
Nanostructured alumina as insecticide
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stored-product pests, as well as other insects. Further research is needed to identify mode of action and potential non-target toxicity and to determine the potential of other nanostructured materials as control options for insects in general.
ACKNOWLEDGEMENTS The authors thank Dr G. Lascalea, CCT-CONICET-Mendoza, for synthesizing NSA. This research was supported using funds provided by the Montana Agricultural Experiment Station and by ´ the ‘Consejo Nacional de Investigaciones Científicas y Tecnicas’, Argentina.
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