Quality parameters of wheat grain and flour as influenced by treatments with natural zeolite and diatomaceous earth formulations,grain infestation status and endosperm vitreousness

This study investigated the changes in quality parameters of wheat (mealy and vitreous) non-infested and infested with Sitophilus oryzae (L.) caused by treatments with inert dusts: natural zeolite, two diatomaceous earths from Serbia, and a commercial product enhanced DE Protect-It^®.Inert dust treatments, regardless of infestation status, significantly reduced wheat test weight. This was more marked in mealy (8.3%) rather than in vitreous wheat grain (2.7%). Content of silicon dioxide (SiO₂) in flour from infested lots was significantly higher than in non-infested ones. Treatments with all formulations of inert dusts significantly affected flour water absorption in the non-infested wheat lots. Non-infested high vitreous wheat treated with Protect-It^® showed the highest moisture absorption (61.9 g.100 g⁻¹) in comparison with the control (59.7 g.100 g⁻¹). Significant improvement in dough rheology was observed in the infested soft and hard wheat, particularly through rise of dough energy. Small-deformation tests implied certain dough weakening effects of inert dusts in vitreous wheat but this was not observed in standard large-deformation rheological tests.Application of inert dusts shows an ability to improve some aspects of the technological quality of wheat.     

Detection of External and Internal Insect Infestation in Wheat by Near-Infrared Reflectance Spectroscopy

Near-infrared spectroscopy (NIR) in the reflectance mode was investigated for the rapid, automatic and non-destructive detection of insect stored-grain pests external or internal to wheat kernels. Convincing calibration performance was obtained for external adult Oryzaephilus surinamensis (L) (saw-toothed grain beetle) in unmilled samples including varieties Beaver (soft wheat) and Mercia (hard wheat) at two moisture contents. With this large substrate variability, the method could differentiate between uninfested samples and samples with approximately 270 insects kg⁻¹ or more. Milling made no improvement. Large spectral differences were observed between uninfested kernels and kernels infested internally with Sitophilus granarius (L) (grain weevil) larvae or pupae, arising from both a changed chemical composition and physical structure. Single uninfested and infested kernels were discriminated by their second derivative (d²) spectra. For both external and internal infestation there was substantial evidence that insect protein and/or chitin and moisture were being detected. NIR should be useful as a rapid method of detection.     

A comparison of screening methods for insect contamination in wheat

In collaboration with the United States Department of Agriculture and a number of major milling companies, the “Insect-Detect” immunoassay for analyzing insect contamination in grains has been compared with three more traditional methods, X-ray analysis, cracking and flotation, and the insect fragment test (IFT). Testing was carried out in blind fashion using clean wheat samples that were spiked with differing numbers of grain kernels infested with late instar larvae of the granary weevil (Sitophilus granarius (L.)). Three different laboratories analyzed the samples for each of the four methods. The collaborative trials showed that the insect immunoassay clearly provided the most accurate measurement of actual insect infestation, followed by X-ray analysis. While both cracking and flotation and IFT procedures provided a general measure of contamination, they showed much greater variability.     

Susceptibility of Ethiopian wheat varieties to granary weevil and rice weevil infestation at optimal and sub-optimal temperatures

Integrating varietal resistance with temperature manipulation during storage may provide a better option for protection of stored grains and may decrease reliance on the use of synthetic chemicals. The current study was conducted to determine the susceptibility of different varieties of wheat seed to the infestation by the granary weevil, Sitophilus granarius (L.), and rice weevil, Sitophilus oryzae (L.), at optimal (30 °C) and sub-optimal (19 °C) temperatures. Kernels of six wheat varieties namely, Danda'a, Digalu, ET-13-A2, Kakaba, Millennium, and Pavon-76 were examined over a period of 90 d. Significant interactions were detected between wheat varieties and storage temperature for progeny emergence, percentage of insect damaged kernels, grain weight loss, and amount of powder produced per gram of wheat. Kernels of Danda'a, infested with S. oryzae at 30 °C exhibited significantly lower mean progeny counts (13.3 live insects), lower percentage of grain weight loss (4.2%) and insect-damaged kernels (6.4%), and powder production (1.5 mg/g). Kernel weight and hardness index were negatively associated with percentage of insect damaged kernels and grain weight loss. Kernel diameter was positively associated with both of percentage of insect damaged kernels and grain weight loss. Wheat varieties with high Zeleny sedimentation values had lower percentage of insect-damaged kernels and grain weight loss. These results indicated that kernel weight, hardness index, and protein content are predominant factors contributing to wheat resistance against S. granarius and S. oryzae. The varieties Millennium and Danda'a can be considered with other integrated pest management approaches to reduce stored grain losses of wheat in Ethiopia.     

Detection and prediction of Sitophilus oryzae infestations in triticale via visible and near-infrared spectral signatures

Triticale is a hybrid of wheat and rye grown for use as animal feed. In Florida, due to its soft coat, triticale is highly vulnerable to Sitophilus oryzae L. (rice weevil) and there is interest in development of methods to detect early-instar larvae so that infestations can be targeted before they become economically damaging. The objective of this study was to develop prediction models of the infestation degree for triticale seed infested with rice weevils of different growth stages. Spectral signatures were tested as a method to detect rice weevils in triticale seed. Groups of seeds at 11 different levels (degrees) of infestation, 0–62%, were obtained by combining different ratios of infested and uninfested seeds. A spectrophotometer was used to measure reflectance between 400 and 2500 nm wavelength for seeds that had been infested at different levels with six different growth stages from egg to adult. The reflectance data were analyzed by several generalized linear regression and classification methods. Different degrees of infestation were particularly well correlated with reflectances in the 400–409 nm range and other wavelengths up to 967 nm, although later growth stages could be detected more accurately than early infestation. Stepwise variable selection produced the lowest mean square differences and yielded a high R² value (0.988) for the 4th instars, pupae and adults inside the seed. Models were developed to predict the level of infestation in triticale by rice weevils of different growth stages. Overall, this study showed a great potential of using reflectance spectral signatures for detection of the level of infestation of triticale seed by rice weevils of different growth stages.     

Susceptibility of ancient wheat species to storage pests Sitophilus granarius and Tribolium confusum

The feeding behavior of storage pests colonizing the spikelets of ancient wheats remains insufficiently investigated. Therefore, the aim of this study was to determine the susceptibility of emmer, spelt and common wheat grown under different agronomic conditions to storage pests, including the granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae) and the Tribolium confusum (du Val) (Coleoptera: Tenebrionidae). The experiment was performed on the spikelets of two non-free-threshing wheat species, spelt Triticum spelta (L.) cv. Wirtas and emmer Triticum diccocon (Schrank) cv. Bondka, and the grain of free-threshing common wheat Triticum aestivum (L.) cv. Bombona. The remaining experimental factors were different nitrogen fertilization rates and the application of a growth regulator. Two storage pest species, the S. granarius and the T. confusum, were introduced to the experimental grain and spikelets. The results after 6 months revealed that different nitrogen fertilization rates, the application of the growth regulator and wheat species did not affect the population size of S. granarius. After 12 months of incubation, no significant changes were found in the abundance of T. confusum in response to nitrogen fertilization, growth regulator or wheat species. After 12 months of incubation, wheat species exerted an inhibitory effect on the population size of S. granarius. Spelt was the most resistant and common wheat was the least resistant wheat species. The results of this study indicate that spelt was most resistant to storage pests, whereas common wheat grain was most abundantly colonized by storage pests.     

Field trials on the efficacy of Beauveria bassiana,diatomaceous earth and Imidacloprid for the protection of wheat grains from four major stored grain insect pests

We assessed the insecticidal efficacy of Beauveria bassiana, diatomaceous earth (DE) and the neonicotinoid Imidacloprid against four major insect species of stored grain pests during field trials conducted on small farms located in four districts of Punjab, Pakistan. In each district, a 40 kg lot of wheat grain was admixed with B. bassiana (3 × 10¹⁰ conidia kg⁻¹), DE (150 ppm) and Imidacloprid (5.0 ppm) alone and in different combinations. Each lot was divided subsequently into four equal parts (10 kg each), packed in polypropylene bags, artificially infested, labeled and stored at the farms under natural environmental conditions up to 6 months. Sampling was carried out every 30 d to record the total number of dead and alive adults, as well as the percent of grain damage in treated and untreated (control) grains. Results revealed a significant difference among the treatments, test insect species and the storage period. For each district, the combined treatments provided better control of all tested insect species compared with each treatment alone. The least number of surviving adults and minimum percent grain damage was observed for Imidacloprid and DE combination, but was outperformed by the DE treatment with B. bassiana for long-term protection. For all grain protectants, we obtained the same order of susceptibility level among the test species (i.e. Liposcelis paeta > Cryptolestes ferrugineus > Rhyzopertha dominica > Tribolium castaneum). The results of the present study suggested that DE, insect pathogenic fungi and Imidacloprid can be effectively used for the protection of wheat stored at small-scale farmer's fields.     

Triple bag hermetic technology for post-harvest preservation of Bambara groundnut (Vigna subterranea (L.) Verdc.)

Experiments were conducted to evaluate the performance of hermetic triple bagging using Purdue Improved Crop Storage (PICS) bags for storage of Bambara groundnut (Vigna subterranea (L.) Verdc.). One set of experiments used grain heavily infested by Callosobruchus maculatus (F.) while a second set began with a low level infestation. Each experiment consisted of V. subterranea grain kept in four replicate 50 kg PICS bags or two replicate woven bags as controls. Two to five days after the beginning of the experiments, oxygen level inside the bags averaged about 21% (v/v) in the controls but decreased significantly in PICS bags, reaching 10% (v/v) with the heavily infested grain but falling only slightly in the lightly infested grain. After 7 months of storage, (i) the number of C. maculatus adults found between and within the grains, (ii) the 100 seed weight, (iii) the number of seed with holes, and (iv) the percentage germination of grain stored in PICS bags did not differ from what had been measured on the day that the experiment was set up. In woven bags, by contrast, there was a massive increase in C. maculatus numbers with means of 309 and 251 adults per 500 g in heavily and lightly infested grain, respectively. Grain weight losses in the woven bag controls ranged from 8 to 19% and the percentage of C. maculatus emergence holes per 100 seed increased from 51 to 135%.     

Effects of flameless catalytic infrared radiation on Sitophilus oryzae (L.) life stages

A laboratory benchtop flameless catalytic infrared emitter was evaluated against all life stages of the rice weevil, Sitophilus oryzae (L.), an insect species associated with stored wheat. The emitted infrared radiation was in the 3-7 μm range. A non-contact infrared thermometer measured grain temperatures continuously during exposures of infested wheat. Insect mortality was a function of the final grain temperature attained. In general, higher grain temperatures were attained when using 113.5 versus 227.0 g of wheat, and at 8.0 cm from the emitter versus 12.7 cm, and during a 60 s exposure versus a 45 s exposure. Complete mortality of all life stages of S. oryzae was achieved at 8.0 cm from the emitter using 113.5 g of wheat, with a 60 s exposure; the mean grain temperatures attained ranged from 108.4 to 111.8 °C. The log odds ratio tests showed that eggs (0 days old) were the least susceptible stage to infrared radiation, followed by adults within kernels (28 days old), pupae (24 days old), young larvae (7 days old), larvae that were 14-21 days old, and adults (42 days old). These data using small amounts of grain indicate infrared radiation from the flameless catalytic emitter to be a viable option for disinfesting wheat containing various life stages of S. oryzae.     

Evaluations of the new deltamethrin-treated all-in-one hermetic bag for the control of the Khapra beetle,Trogoderma granarium (Everts)

The khapra beetle, Trogoderma granarium (Everts), is a highly destructive stored product insect that presents a significant threat to stored bagged grain. Hermetic packaging is designed to maintain the quality and safety of stored grain, while continually protecting the grain from insect infestations during storage. The objective of this research was to evaluate a prototype deltamethrin, all-in-one treated hermetic bag on contact efficacy, larval mobility, and the control of T. granarium in artificially infested wheat. The insecticidal activity of the deltamethrin-treated packaging was tested against larvae and adults of T. granarium through contact bioassays. There was a significant reduction in responsive adults after 5 day and >86% of larvae were unresponsive after 9 d of exposure on the treated bag. Trogoderma granarium movement toward a food bait was <10% after a 24 h exposure on the treated bag compared to ~45% of larvae on untreated bag. Lots of 15 kg of wheat were artificially infested with 100 T. granarium larvae and placed inside treated and untreated storage bags, sealed, and stored in a semi-field warehouse, and observed after 2, 6, and 8-weeks for T. granarium survival and grain quality attributes. The weight and number of insect damaged kernels was lower across all storage intervals for grain held in the treated bags, as compared with control bags. Live adult T. granarium were observed at 2-weeks in treated and untreated bags, but there were no live adults observed after 8-weeks of storage in both bags. The new prototype hermetic bags maintained positive grain qualities, however more information on the hermetic parameters are needed to understand how some individuals survived.     

Influence of medium and physical disturbances during rearing on development and numbers of Sitophilus progeny

Four Sitophilus populations (Sitophilus zeamais Motschulsky from Mexico, S. zeamais from Arkansas, U.S.A., Sitophilus oryzae L., and Sitophilus granarius L.) were studied. Hard red winter wheat, sorghum, and maize were used to determine effects of rearing media on progeny production of insects from the four populations.Mechanically disturbing infested samples to remove newly-emerged adult weevils every 48 hr reduced numbers of progeny surviving to the adult stage, especially for Arkansas S. zeamais and S. granarius reared in any of the three grains.With one exception, reproduction for all populations in all three grains was highest when parents were reared in wheat; other differences are discussed. Also, progeny developmental periods for all four populations were shortest when parents were reared in wheat. Progeny of all four populations had the longest developmental periods when reared in maize regardless of the medium in which their parents were reared.In 250 g samples of wheat, and 125 g samples of sorghum, 50 parent S. oryzae produced statistically as many progeny as in 500 g and 625 g samples of wheat and 250, 500, and 625 g samples of sorghum, respectively. In maize, 625 g samples produced significantly more progeny than 500 g samples.Sex ratios of progeny from each grain were 1:1, except that females of S. oryzae reared in maize outnumbered males.     

The uptake and translocation of malathion by the stored wheat grain

Malathion residues are found chiefly in regions of high lipid content in the individual wheat grain; mainly in the germ and scutellum, and seldom in the starchy endosperm. Malathion applied directly to the endosperm is rapidly transported to other regions. This has been established using gas-liquid chromatography, and also using radioactively labelled malathion.Some grains have an enhanced affinity for malathion, and this property is not related to the size or weight of the grain. The current methods for calculating and applying safe limits for pesticide residual levels in grain are criticised in the light of these results.Some aspects of how Sitophilus granarius larvae, living within the wheat grain, are affected by externally applied malathion are also considered.     

The influence of Rhyzopertha dominica (F.) on the technological quality of cereal grains treated with diatomaceous earth

Laboratory bioassays (temperature 26 ± 1 °C and 60 ± 5% r. h.) were performed to evaluate the insecticidal effect of three different diatomaceous earths (DE) against Rhyzopertha dominica (F.) in wheat, triticale and rye. In order to achieve this, the amount of damaged kernels, amount of debris, wet gluten content, gluten index and rheological properties were assessed in infested samples, infested samples treated with DE Protect-It and two DEs originating from Serbia (S-1 and S-2) and were compared to control (uninfested) samples using Chopin Mixolab. The most susceptible to beetle infestation were rye sample and wheat variety Planeta. The lowest weight of damaged grain was found after applying DE Protect-It to all grain types. The amount of damaged kernels, the amount of debris and loss of mass were the highestin sample treated with DE S-2. While infestation resulted in increase in the amount of damaged kernels and debris and decrease in wet gluten content, and provoked weakening of gluten network structure as well as starch damage, an addition of DE, especially Protect-It, resulted in grain samples of similar technological quality to control (uninfested) sample. The susceptibility of different cereals used in breadmaking to infestation by R. dominica, as well as their response to the insecticidal effect of diatomaceous earth largely varied. Both cereal type and quality, as measured by wet gluten content and gluten index, influenced grain response to infestation. Insecticidal effect of diatomaceous earth, especially DE S-1and DE S-2, was the least effective in terms of triticale. These findings suggest that the application of DE in cereals storage management might largely be affected with grain type as well as grain composition and technological quality.     

Disinfestation of stored wheat grain and flour using gamma rays and microwave heating

Samples of wheat grain and flour (20 gm of each) were infested with 20 larvae or 5 pairs of adult insects of Tribolium confusum, Lasioderma serricorne, Corcyra cephalonica or Rhyzopertha dominica. The infested samples were tested as follows : (1) microwave heating at four temperature levels 40, 45,50 and 55 °C, for exposure times from10 to 50 s; (2) gamma irradiation over the dose range of 0.5-4 KGy; (3) gamma irradiation + microwave heating. Complete kill of all stages tested was achieved at 50 °C with an exposure time of 50 s. A dose of 2 KGy induced 100% mortality of R. dominica after three days, but it took up to 7 days for all T. confusum and L. serricorne adults to die after a 4-KGy exposure. All insects died within 24 h when exposed to the combination of 1KGy + 50 °C for 30 s.Biochemical analyses on the samples of wheat grain and flour subjected to those treatments at which high mortality was obtained generally showed no detectable changes in the quality of protein, fat, fiber, carbohydrates or ash. The germination of wheat grain was lowered after treatment with microwave radiation but was not affected by a dose of 1 KGy gamma radiation.     

Comparison of insect detection efficiency by different detection methods

Detection percentage of stored grain insects using different separation methods was determined. The stored grain insects tested were: Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.), Sitophilus oryzae (L.), and Tribolium castaneum (Herbst). To determine the detection percentage, 1 or 100 adults of the four insect species, and 1 or 100 young or old larvae of T. castaneum were introduced into wheat with 14 ± 1%, 16 ± 1%, or 18 ± 1% moisture content. The following four methods were used to separate the introduced insects from the infested wheat: Berlese funnel (Berlese), shaking grain on a metal sieve (Metal sieve), shaking grain on an acrylic device (Acrylic sieve), and microwave heating. For all detection methods, wheat moisture content did not influence the detection percentage. Detection method and insect species influenced the recovery percentage. For example, Metal sieve and Acrylic sieve methods had a higher recovery percentage of adults of O. surinamensis and T. castaneum than for S. oryzae and R. dominica. There was no significant difference in recovery percentage of the larvae and adults between the Metal sieve and Acrylic sieve methods, with the exception of weevils. The Berlese method had the lowest recovery percentage of introduced insects, with the exception of weevils, while the Microwave method had the highest or the second highest recovery percentage. Generally, the recovery percentage of the young larvae was lower than that of adults. The Microwave method could improve detection accuracy for larvae.     

The effect of wheat grain composition, cuticular lipids and kernel surface microstructure on feeding, egg-laying, and the development of the granary weevil, Sitophilus granarius (L.)

Adult feeding intensity, oviposition, and larval development of Sitophilus granarius (Coleoptera: Curculionidae) were observed on grain from three Polish wheat varieties (Begra, Korweta, and LGR 896/64a) washed with petroleum ether to remove cuticular lipids. Extraction of lipids did not cause any statistically significant changes in the physicochemical, biochemical and technological (milling, rheological and baking) properties of the wheat grain studied. Wheat grain washed with petroleum ether did not show any visible changes in the surface and morphology of the outer layer of the wheat grain. However, differences were noted in the microstructure of the kernel surface. Grain with a thicker seed coat (LGR 896/64a) was infested at a lower rate than the other varieties. Of the 18 hydrocarbons extracted from the grain surface, three compounds - n-heptacosane (C₂₇), n-nonacosane (C₂₉) and n-hentriacontane (C₃₁) - were found in significant amounts. In general, beetles produced 64-95% less dust and laid 7-16% fewer eggs in kernels from which cuticular lipids had been removed. This implies that these compounds have a major role in food selection and the search for an oviposition site prior to grain infestation.     

Detection of Rhyzopertha dominica larvae in stored wheat using ELISA: The impact of myosin degradation following fumigation

Hard red winter wheat kernels were infested with eggs of Rhyzopertha dominica. After 20 d, when the larvae reached the fourth instar, they were killed by exposing the infested kernels to phosphine gas for 24 h. The infested kernels were then divided into four portions and treated as follows: one portion was immediately frozen at −80 °C to avoid myosin degradation; the other three portions were kept at 32 °C and 65% relative humidity, and then frozen at −80 °C after 14, 28, and 56 d post-fumigation, respectively. Each treatment was replicated five times. Myosin was measured using a commercial enzyme linked immunosorbent assay (ELISA) method that specifically detects this protein (Biotect^®, Austin, TX). Myosin degradation was most rapid in the first 2 weeks after the larvae were killed, decreasing from 1.672 to 0.695 ng/well during this period (a 58.4% reduction). There were no significant differences in myosin degradation between samples that were 14, 28, and 56 d post-fumigation. Grain is often fumigated to control insects. Frequently, this occurs many weeks before the grain is milled and may be repeated during the storage period. Therefore, estimates using the ELISA test may underestimate internal insect infestation because of myosin degradation. Insect fragment estimates for previously fumigated grain could be underestimated by as much as 58%.     

Initial efficacy of pyrethroids,inert dusts,their low-dose combinations and low temperature on Oryzaephilus surinamensis and Sitophilus granarius

In this study, initial efficacy of three pyrethroids, two inert dusts and their low-dose combinations were investigated on adults of Sitophilus granarius and Oryzaephilus surinamensis at laboratory conditions. The insects were exposed to treatments on concrete surface. The LC₂₅ values of the pyrethroids and LD₂₅ values of the inert dusts were estimated and used for determining their combination effects. Mortality of insects was recorded 48 h after treatments. The effect of a low temperature, −18 °C was also assessed on both species. Exposure times to −18 °C were 15, 18, 22, 27, 33 and 40 min for S. granarius and 10, 12, 15, 19 and 23 min for O. surinamensis in main experiments. The treated insects were kept in the laboratory conditions for 24 h after cold treatments, then the mortalities were recorded. The LC₅₀ values estimated for deltamethrin, lambda-cyhalothrin and fenvalerate on S. granarius were 45.08, 43.34 and 465.00 mg ai/L; and on O. surinamensis were 0.65, 1.83 and 81.36 mg ai/L, respectively. The LD₅₀ estimated for zeolite on S. granarius was 10.32 g/m²; and kaolin was not effective on this species. The LD₅₀ values estimated for zeolite and kaolin on O. surinamensis were 7.7 g/m² and 12.0 g/m², respectively. Mortalities caused by deltamethrin + zeolite and lambda-cyhalothrin + zeolite combinations on S. granaries were 80.0% and 63.3%, respectively. The effects of combinations of the pyrethroids and zeolite or kaolin on O. surinamensis were also significantly higher than sum of their individual effects. It means the effects of these combinations were synergistic. The LT₅₀ values estimated at −18 °C were 33 min for S. granarius and 16 min for O. surinamensis. The results obtained from this study can be used as basic and preliminary information for practical control programs of these pests in stored products.     

Insecticidal effect of spinetoram against six major stored grain insect species

Spinetoram is a novel insecticide that belongs to the spinosyn class of insecticidal chemicals. The efficacy of spinetoram against numerous insect pest species in a variety of field crops has been well demonstrated. However, there are no data available for the effectiveness of spinetoram against stored grain insects. In the present study, we evaluated spinetoram as a grain protectant, against six stored-product Coleoptera. The species tested were: the rice weevil, Sitophilus oryzae, the lesser grain borer, Rhyzopertha dominica, the larger grain borer, Prostephanus truncatus, the confused flour beetle, Tribolium confusum, the granary weevil, Sitophilus granarius and the sawtoothed grain beetle, Oryzaephilus surinamensis. All species were tested at the adult stage, on wheat (or maize in the case of P. truncatus) treated to achieve spinetoram concentrations of 0.01, 0.1, 0.5, 1, 2, 5 and 10 ppm. Mortality was recorded after 1, 2, 7, 14 and 21 d of exposure, and 65 d later the wheat and maize were examined for offspring emergence. Among the species examined, P. truncatus and R. dominica were by far the most susceptible, given that mortality was close to 100% after 7 d on wheat treated or maize with 0.1 ppm of spinetoram. At this concentration, progeny production of P. truncatus and R. dominica was negligible. On the other hand, T. confusum was the least susceptible; mortality reached 95% only at 10 ppm, and only after 14 d of exposure. Similarly, O. surinamensis was of limited susceptibility to spinetoram; mortality reached 95% only after 14 d of exposure on wheat treated with 5 ppm. Nevertheless, offspring emergence of these species was extremely low. For S. granarius and S. oryzae, complete (100%) mortality was recorded after 14 d of exposure, at 0.5 and 1 ppm, respectively. At these concentrations or higher, progeny production was notably reduced. The results of the present study demonstrate that spinetoram is effective as a grain protectant, but its efficacy varies according to the target species, concentration and exposure interval.     

Effectiveness of spinosad and spinetoram against three Sitophilus species: Influence of wheat endosperm vitreousness

The influence of wheat endosperm vitreousness on the effectiveness of spinosad and spinetoram against lab populations of Sitophilus granarius, Sitophilus oryzae (from Serbia) and Sitophilus zemais (from Serbia and Slovenia) were evaluated in a laboratory conditions. Characteristics of two test wheat varieties were determined, i.e. a variety with high (HVWG) and another with low (LVWG) endosperm vitreousness. Spinosad and spinetoram were applied at the doses of 0.5, 1 and 2 mg/kg (ppm) to both wheat varieties. Mortality was assessed after 7, 14 and 21 days, while impact on progeny production/reduction PR (%) was assessed after 8 weeks. All doses of spinosad applied to the HVWG variety and 1–2 mg applied to the LVWG variety achieved high mortality (93–100%) of S. granarius after 14 days, while high mortality of the other test species (97–100%) was achieved by 1–2 mg doses on the HVWG and 2 mg on LVWG varieties. After 14 days, all doses of spinetoram achieved high mortality (96–100%) of S. granarius on both wheat varieties, while high mortality of S. oryzae (97–100%) and both populations of S. zeamais (93–100%) was achieved using 1–2 mg doses on the HVWG and 2 mg dose on the LVWG variety. The highest S. granarius PR (>90%) was found in both wheat varieties treated with 2 mg/kg of spinosad or spinetoram, while the highest PR of S. zeamais was observed in HVWG treated with 2 mg/kg of spinosad and 1–2 mg/kg of spinetoram, and in LVWG treated with 2 mg/kg of spinetoram. The greatest PR (91–94%) of S. oryzae in both wheat varieties was observed only in grain treated with 2 mg/kg spinetoram. In general, endosperm vitreousness was found to influence the effectiveness of spinosyns to all Sitophilus species, especially their doses not causing high mortality.