Hermetic storage for control of common bean weevil,Acanthoscelides obtectus (Say)

This study evaluated hermetic storage as a method of controlling Acanthoscelides obtectus (Coleoptera: Chrysomelidae: Bruchinae) in stored beans. Recently harvested “vermelhinho” cultivar of the common red bean was used, which had already been infested by A. obtectus in the field. Beans with a moisture content of 15.0% wet basis were stored in silo bags (3 kg), plastic bottles (1.5 L), or non-hermetic glass containers (3 L) (control) for 120 days. The packages were stored in an acclimatized chamber at 25 °C with a relative humidity of 70 ± 5%. At time intervals of 0, 30, 60, 90, and 120 days, three packages of each treatment were opened, and analyses were performed to assess the infestation percentage by insect pests, moisture content, density, electrical conductivity, germination percentage, and cooking time. There was no increase in infestation by A. obtectus in the grains stored in the silo bags and plastic bottles during the 120 days of storage; however, there was a significant increase in infestation in the grains in non-hermetic storage (control). The quality of the beans correlated with infestation; it was not altered in the hermetic storage systems and decreased in the control sample. Hermetic storage of common beans is an effective tool in the control of A. obtectus.     

The susceptibility of animal feed containing Dried Distiller's Grains with Solubles to Tribolium castaneum (Herbst) infestation

Understanding the susceptibility of commercially available animal feeds which contain Dried Distiller's Grains with Solubles (DDGS) to insect infestation is the first step in developing a pest management strategy for a stored product. This study is a nascent analysis of animal feed containing DDGS susceptibility to Tribolium castaneum (Herbst) infestation, one of the most important post-harvest insect pests world-wide. Three types of animal feed containing 5–10% DDGS in their formula mixtures were obtained from two feed manufacturers in Indiana, USA including: crumbled poultry feed, pelletized juvenile frog feed, and pelletized adult frog feed. Besides commercially available animal feed, laboratory manufactured feed were simulated by mixing Flour/Yeast (F/Y), T. castaneum normal laboratory diet, with 10, 20, 30, 40, and 80% DDGS (% based on weight). Larval developmental time was used to evaluate feed susceptibility to T. castaneum infestation. The T. castaneum larval period was significantly increased when fed on pelletized adult frog feed, pelletized juvenile frog feed, and crumbled poultry feed (29.8 ± 0.5, 26.0 ± 0.3, and 21.9 ± 0.3 d respectively), compared with F/Y (16.1 ± 0.3 d). The larval period was significantly decreased however, when fed on ground poultry feed (15.5 ± 0.2 d). Insect development on laboratory manufactured feeds was similar to F/Y regardless of DDGS ratios added in this study (15.9–16.9 d). These results suggested that first; particle size (PS) was one of the influential factors on susceptibility of commercially available animal feed to T. castaneum apart from feed chemical composition, and second, adding 10–80% DDGS to the laboratory manufactured feed did not change feed susceptibility to T. castaneum infestation.     

Storage of mung bean (Vigna radiata [L.] Wilczek) and pigeonpea grains (Cajanus cajan [L.] Millsp) in hermetic triple-layer bags stops losses caused by Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Dry mung bean and pigeonpea grains that had sustained some insect damage but fumigated before the start of the experiment were stored in triple-layer hermetic bags (Purdue Improved Crop Storage (PICS™ bags) or woven polypropylene (PP) bags for 6 months. Some of the bags were artificially infested with cowpea bruchid Callosobruchus maculatus (F.) (PICS1, PP1) while others were not (PICS0, PP0). In an additional trial, PP bags containing the grains were treated with Actellic Super^® dust before being artificially infested (PP1Ac). Moisture content, live adult C. maculatus count, grain damage, weight loss, and seed germination were determined on a monthly basis. At six months, moisture contents of grain stored in PICS and PP bags remained below 12%. Storage in PICS bags halted multiplication of C. maculatus, and the initial damage level and weight of grains did not change. Conversely, in the PP bags, C. maculatus populations increased massively and seed damage reached 71.8 ± 1.9%, 76.9 ± 0.4%, and 60.3 ± 0.6% corresponding to weight losses of 14.5 ± 0.1%, 16.5 ± 0.2% and 12.5 ± 0.1% in PP0, PP1 and PP1Ac, respectively, in mung beans. With the pigeonpeas, seed damage reached 55.1 ± 0.6%, 95.7 ± 0.4% and 75.8 ± 0.9%, corresponding to weight losses of 13.0% ± 0.3%, 26.2 ± 0.2% and 13.5 ± 0.1%, in PP0, PP1 and PP1Ac, respectively. PICS bags are an effective tool for preserving mung beans and pigeonpeas against C. maculatus attack, and their performance is superior to that of Actellic Super^® dust.     

Estimating economic damage to cocoa bean production with changes in the spatial distribution of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in response to climate change

Cocoa is a crop that serves as a major source of income in some countries, but its production has been affected by red flour beetles, Tribolium castaneum (Herbst). In this study, we aimed to predict the global potential distribution of T. castaneum under the current climate and in response to climate change (2050 and 2100). In addition, we attempted to use the results for estimating damage and economic losses in the major cocoa beans-producing countries. The CLIMEX model was used to evaluate the climatic suitability of regions for T. castaneum, and the economic damage was estimated by incorporating a series of published models and published data. The results showed that the potential distribution of T. castaneum was consistent with that of cocoa beans-producing countries, and as expected, at the local-level, T. castaneum was concentrated in cocoa cultivation areas. It was estimated that up to 50% damage to cocoa beans and economic loss of 3.16 billion US dollars due to production loss could occur. This study is the first attempt to estimate the economic damage to cocoa bean production by predicting the potential distribution of T. castaneum. Further, this study not only provides insight to combine the potential distribution of a species and an estimation of the related economics, but also provides basic data for establishing an effective monitoring/controlling strategy for preventing damage by T. castaneum.     

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.     

Development and progeny performance of Tribolium castaneum (Herbst) in brewer’s yeast and wheat (patent) flour at different population densities

The effects of brewer's yeast and wheat patent flour on Tribolium castaneum (Herbst) life parameters at different population densities (1, 2, 5 and 10 pairs) were examined. A standard diet (95% wheat flour + 5% brewer's yeast) was used as control. The effect was examined on the duration of egg, larval and pupal stages, total development cycle, first adult emergence, eclosion period, the total number of offspring, number of offspring per female and body weight of adult offspring. For each diet type and population density, adults were allowed to feed and oviposit for 7 days before removal from diets. A longer larval stage was recorded in brewer's yeast (between 23.88 and 26.25 days, depending on population density) and patent flour (17.63–23 days) compared to the standard diet (12.88 and 13.38 days). The longest eclosion period was recorded in patent flour (19–21.23 days), which was the only diet unaffected by population density. In the brewer's yeast and standard diet, the period of eclosion was prolonged with the increase in population density. The lowest number of progeny was recorded in patent flour (44.29–49.63 insects), followed by brewer's yeast (22.86–177 insects), while the highest number of progeny (107.25–313.38 insects) was recorded in the standard diet. Population density did not affect the total number of progeny in patent flour, which remained low at all densities, while in the brewer's yeast and standard diet the rise in population densities caused a rise in progeny numbers. The type of diet did not affect the body weight of adult progeny: the highest body mass of progeny was recorded at the lowest population density and the lowest mass at the highest. This study provides insight into poorly researched development cycle and reproductive strategies of T. castaneum on brewer's yeast and patent flour, which are important stored products.     

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.     

Effectiveness of hermetic containers in controlling paddy rice (Oryza sativa L.) storage insect pests

Naturally infested paddy rice was used to compare the effectiveness of polypropylene bags and hermetic storage containers over 12 months of storage in a warehouse. Insect pest identification as well as the infestation level, percentage of damaged grain, weight loss, and moisture content were evaluated. Five insect species associated with stored rice were identified during the storage period, namely lesser grain borer (Rhyzopertha dominica), red flour beetle (Tribolium castaneum), rice/maize weevil (Sitophilus spp.), angoumois grain moth (Sitotroga cerealella) and flat grain beetle (Cryptolestes ferrugineus). The lesser grain borer was the most predominant species with an average incidence above 70% after twelve months of storage, followed by the rice/maize weevil with an incidence of 17%. When compared to hermetic storage containers, polypropylene bag showed the highest mean infestation level with 233.3 individuals/kg after six months of storage, representing about 8-fold of the number of insects recorded in hermetic containers after six months of storage. In polypropylene container, the percentage of damaged grain and weight loss increased significantly achieving a maximum of 6.98% and 5.56% respectively, whereas using hermetic containers the highest percentage of damaged grain reached was 3.24% in polyethylene drum and the weight loss was 1.62% in GrainSafe bag. The results from the study show that the use of hermetic storage containers is a green alternative for safe storage of paddy rice, for 12 months without application of pesticides, bringing multiple advantages for smallholder farmers, lever food security and income generation for smallholder farmers and rice milling companies.     

Comparative performance of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) across populations,resource types and structural forms of those resources

The significance of Tribolium castaneum (Herbst) as a pest of stored grains will likely be influenced by the relative availability of different resources regionally and the beetles’ ability to utilize each of them. Therefore the performance across the life cycle of laboratory and field populations of T. castaneum on commonly available structural forms of wheat and sorghum, as conventional resources, was quantified and compared to that on cotton seed. The latter is not usually associated with T. castaneum, but large beetle infestations have been recorded commonly in cotton gins in Australia. The highest number of individuals of each stage (from a given number of eggs) developed on wheat and sorghum flour and kibbled seeds. Cotton seed did not support the development of laboratory population beetles and all neonate larvae died before pupation. In contrast, some of the field population larvae did develop on cotton flour, but their number was significantly lower in comparison to development on wheat and sorghum. Field population beetles produced significantly more eggs than did laboratory population beetles, on both the whole seed and flour. Field population females had a consistently higher fecundity (～78% more eggs) than the laboratory population females, at least over the first three weeks of adult life. These results suggest that field populations of T. castaneum should be used in experiments if we are to develop a more realistic understanding of the field ecology of this species. The relative rate at which these insects infest available resources in the field also warrants further investigation.     

Demographic studies of Tribolium castaneum (Coleoptera: Tenebrionidae) on various barley cultivars

Rust-red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is one of the serious insect pests of cereal grains and other stored products throughout the world. In this research, demographic parameters of T. castaneum in response to feeding on ten barley cultivars (Behrokh, Bahman, Nosrat, Fajr 30, Makuyi, Sahra, Lout, Neek, Abidar and Sahand) were studied at 30 ± 1 °C, relative humidity of 75 ± 5% and darkness conditions. The longest larval period was on cultivars Makuyi and Fajr30, and the shortest period was on cultivar Lout. The fecundity, hatch rate, net reproductive rate, intrinsic rate of increase, and finite rate of increase was the lowest on cultivars Makuyi and Fajr30. Positive correlations were observed between the larval period, larval and pupal period, and doubling time with the grain hardness index. Moreover, there were negative correlations between the fecundity, hatch rate, R₀ and λ with the grain hardness index. The results showed that cultivars Makuyi and Fajr30 were unsuitable diets for feeding of T. castaneum, and could be suggested to be grown in areas with high potential for T. castaneum infestation.     

Effect of low pressures on the survival of cocoa pests at 18°C

This study forms part of an effort to eliminate the need for fumigation with methyl bromide to control insect infestations in stored cocoa beans, through development of novel alternative vacuum-hermetic technology. In this communication, the effects of low pressures and exposure time were studied on the mortality of insects at a temperature of 18°C, chosen to simulate cocoa bean storage conditions in temperate climates.Three insect species were used, two of which are major pests of cocoa beans in producer countries, Ephestia cautella (Walker), and Tribolium castaneum (Herbst), while the third, Oryzaephilus surinamensis (L.), is a potential storage pest in temperate climates. For T. castaneum and E. cautella the egg stage was the most resistant to 55±10 mm Hg at 18°C, the times needed to obtain 99% egg mortality were 96 and 149 h, respectively. For O. surinamensis, the adult stage was the most resistant with 164 h being required to obtain 99% mortality.     

Assessment of eight rice cultivars flour for feeding resistance to Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is an important pest of processed stored grains worldwide. Study of life history, feeding efficiency and digestive function of an insect on different host cultivars can indicate their resistance for the insect's population increase. Due to the economic importance of T. castaneum on stored rice flour, this research was aimed to investigate the life history, feeding indices and digestive enzymatic activity of T. castaneum on flour of eight rice cultivars (Ali-Kazemi, Dom-Siah, Fajr, Gilaneh, Gohar, Hashemi, Khazar, and Neda). A delay in the developmental time of T. castaneum was detected on cultivar Gohar. The lowest fecundity and egg fertility were observed on cultivar Gohar. Feeding indices of fourth instar larvae were the lowest on cultivars Gohar and Neda. The amylolytic activity of fourth instar larvae was the highest on cultivars Hashemi, Dom-Siah, Ali-Kazemi and Gilaneh, and the lowest on cultivar Gohar. Also, the highest and lowest proteolytic activities of fourth instar larvae were on cultivars Khazar and Hashemi, respectively. Significant correlations were detected between tested parameters of T. castaneum with starch and protein value of examined cultivars flour. The results of cluster analysis indicate that Dom-Siah, Hashemi and Ali-Kazemi are relatively susceptible cultivars, and other tested cultivars, especially Gohar, are relatively resistant cultivars for feeding of T. castaneum. The resistant rice cultivars could be further evaluated to identify secondary biochemicals that contribute to T. castaneum resistance.     

Investigating Dried Distiller's Grains with Solubles vulnerability to Tribolium castaneum (Herbst) infestation by using choice and no-choice experiments

Demand for Dried Distiller's Grains with Solubles (DDGS) in international markets and the United States has increased during the past few years. Knowledge of DDGS supplemented animal feed vulnerability to insect infestation is critical for safe feed storage. To assess this vulnerability, it is necessary to know how DDGS is susceptible to insect infestation, while stored as raw ingredient. This research focused on the susceptibility of different types of DDGS (raw and ground) to red flour beetle, T. castaneum, infestation under 30% and 50% relative humidity (r.h.) regimes. Larval period at 30% r.h. increased 2–3 fold on raw DDGS diets with larger particle sizes (PSs) compared with their normal laboratory diet, a mixture of flour and yeast (9:1) (F/Y). However, grinding DDGS samples and increasing the r.h. to 50% decreased the amount of time required for insect development thus increasing DDGS vulnerability to T. castaneum infestation compared with raw DDGS at r.h. of 30%. As was expected, T. castaneum egg and pupal development were not affected by diet or humidity. The results suggested that DDGS as a raw ingredient at 30% r.h. was not a suitable food source for T. castaneum and given a choice, the majority of T. castaneum adults prefer laboratory diet over DDGS. Additionally, fecundity was significantly lower on DDGS compared with the control diets (F/Y and ground corn (GCORN)). These results indicated that these types of DDGS were not suitable developmental diets compared with the F/Y diet if stored at 30% r.h. with larger PSs.     

Water sorption and cooking time of red kidney beans (Phaseolus vulgaris L.): part I – Effect of freezing and drying conditions on water sorption and cooking time

Water sorption and cooking time of kidney beans were determined. The beans were manually harvested at 19.2 ± 0.1% moisture content and stored at ?20 and ?10 °C for about half a year. The beans were further dried at 30, 40 and 50 °C inside a thin‐layer drier for 7.5 h or under room conditions for 4 week. The freezing storage temperature before the beans were dried did not influence their cooking time and water sorption. The saturated kernel volumes decreased approximately 7% after drying. The beans decreased their sphericity during water sorption and had a larger swelling ratio in the thickness direction than in other directions. Lower initial moisture content, especially with a higher drying temperature, decreased water sorptivity and resulted in higher percentage of uncooked kernels if the beans were not soaked before cooking. However, there was no relationship between initial moisture content and uncooked percentage if the beans were soaked before cooking. High drying temperature resulted in hard‐to‐cook (HTC) phenomenon.     

Food oils as kairomones for trapping Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults

Insect infestation in the grain-based food in storage is often reported; Tribolium castaneum is a major pest. Determination of its population size using traps is entangled with the management attempts. Pheromone traps developed for T. castaneum often use kairomones with its aggregation pheromone 4,8-dimethyldecanal (4,8 DMD). However, low trapping efficacy is reported, and the information on promising kairomones is insufficient. The objective of this research was to evaluate the performance of some locally-available food oils as kairomones, alone and in combination with the pheromone for trapping T. castaneum adults. In the first experiment, the attraction of T. castaneum adults towards different food oils, the pheromone or the commercial kairomone was tested. In the second experiment, the attraction of T. castaneum to effective food oils + pheromone was determined under laboratory condition. In the third experiment, the attraction of T. castaneum by effective food oils + pheromone was evaluated under warehouse condition. Under laboratory condition, the highest attraction of T. castaneum adults was demonstrated by mee (Madhuca longifolia) and coconut (Cocos nucifera) oils. Either of these two oils when combined with the pheromone attracted more adults than the pheromone alone. Furthermore, attraction of T. castaneum adults by the two oils separately was similar to the commercially-available combination of pheromone and the kairomone. In contrast, under warehouse condition, the combination of mee oil and pheromone attracted T. castaneum adults similar to the commercially-available combination of pheromone and the kairomone. However, the attraction by the combination of coconut oil and pheromone was lower than that, and similar to the pheromone only. This study emphasizes the potential use of food oils as kairomones to trap T. castaneum adults, and augment the efficiency of pheromone traps available for this species.     

Laboratory evaluation of development and survival of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) under constant temperatures

The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is a serious pest of stored products. The effect of temperature on the development and survival of this species was determined at five constant temperatures (20, 25, 30, 32.5 and 35 °C) in the laboratory. Results showed a temperature-dependent development of T. castaneum. Data were fitted to the nonlinear Briere model, which for the total immature period estimated the lower threshold at 20.2 °C, the upper developmental threshold at 35.3 °C, and the temperature for maximum developmental rate at 31.2 °C. The Ikemoto and Takai linear model indicated that 659.7 degree-days above a threshold of 16.9 °C were needed to complete immature development from egg to adult emergence. Survival of immature stages varied significantly across temperatures and was well described by an extreme-value function. The model indicated that the highest survival (73.0%) was estimated to occur at 27.4 °C. The curve shows a skewed bell shape, indicating that survival decreases at both ends of the temperature range. These results are useful tools for the prediction of T. castaneum phenology, as well as for its management.     

Response of different population sizes to traps and effect of spinosad on the trap catch and progeny adult emergence in Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Tribolium castaneum is a major pest in stored products throughout the world. Male T. castaneum adults produce aggregation pheromone 4,8-dimethyldecanal (4,8 DMD) which is synthetically developed and available for monitoring T. castaneum populations but low trapping by 4,8 DMD is reported. Effects of biorational insecticides on orienting to pheromone and progeny production is shown but such tests using spinosad has areas for further discovery. Therefore the objective of this research was to determine the effect of population size and spinosad exposure on the trap catch and progeny production in T. castaneum adults. In the first experiment, T. castaneum adults were released at different population sizes and the attraction to the pheromone traps was determined. The second experiment tested attraction of T. castaneum adults pre-exposed to spinosad to the pheromone traps. In the third experiment, progeny production of T. castaneum adults exposed to spinosad was assessed. The trapping of T. castaneum is increased at high population sizes and pre-exposure to spinosad while progeny was reduced on exposure to spinosad showing sex-based effects. This study concludes with management opportunities for different population levels of T. castaneum through effects of spinosad on pheromone perception and progeny production.     

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.     

Aggregation pheromone 4,8-dimethyldecanal and kairomone affect the orientation of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults

Tribolium castaneum, the red flour beetle, is a major pest of stored products throughout the world. The male T. castaneum adults biosynthesize and release the aggregation pheromone 4,8-dimethyldecanal (4,8 DMD), and the monitoring traps having the synthetic form of this pheromone and kairomone are commercially available. However, certain information available on the response of T. castaneum adults to the strength of pheromone and the nature of air flow is inadequate and thus limits the potential use of this compound. The objectives of this research were to determine if the orientation of adult beetles to the synthetic form of the pheromone 4,8 DMD is affected by the distance from the pheromone, its concentration and air movement. Experimental design was completely randomized design with three replicates. The T. castaneum adults released at different distances from the pheromone placed at varying concentrations tested their orientation to the pheromone with the presence or absence of air flow. The control experiments were conducted without the pheromone. A separate experiment tested if exposure to 4,8 DMD alters the direction of movement in T. castaneum adults. The maximum trap catch (24%) was obtained with 0.5 μL of 4,8 DMD and when the beetles were released at distances up to 60 cm from the pheromone. The percentage of beetles trapped declined when the beetles were released 60–120 cm from the pheromone. The average angles on beetle turning during their orientation were significantly higher in the presence of pheromone than the respective controls. Air movement downstream of the pheromone trap increased the percentage beetles trapped compared to that in the absence of air flow. It is concluded that the orientation of T. castaneum adults is affected by the concentration of 4,8 DMD, distance from the pheromone and the air movement.     

Storage of chickpea grains (Cicer arietinum L.) in triple layer bags prevent losses caused by Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) under laboratory conditions

Present study envisages the potential of triple layer bags for reducing pulse beetle infestation under laboratory conditions over six months of storage. It was observed that when chickpea grain was stored in jute bags with bruchid infestation, the germination percentage decreased significantly from 84.67 to 18.67% in six months of storage. But, the grain stored in jute bags without infestation the germination percentage decreased from 92.00 to 73.33% only. On the other hand, grains stored in triple layer bags with bruchid infestation, the germination percentage merely decreased from 86.00 to 78.33% in six months of storage and triple layer bags without infestation the germination percentage only decreased from 91.67 to 90.67%. The per cent grain damage over a period of six months storage also increased significantly from 14.54 to 70.67% and 0.00–26.45% in jute bag with bruchid infestation and jute bag without infestation, respectively. However, per cent grain damage in triple layer bags with bruchid infestation increased only from 15.15 to 25.70% and triple layer bags without bruchid infestation showed negligible increase from 0.00 to 2.64% grain damage in six months of storage. The corresponding per cent weight loss of infested grain was increased significantly from 8.51 to 55.67% in six months of storage in jute bag with bruchid infestation and from 0.00 to 15.08% in jute bag without infestation. Whereas, per cent weight loss of infested grain in triple layer bags with bruchid infestation increased only from 7.83 to 15.70 in six months of storage and triple layer bags without bruchid infestation recorded a mere per cent increase in weight loss from 0.00 to 1.48%. Benefit cost ratio showed that grains stored in triple layer bags for 6 months has highest benefit cost ratio (1.23) compared to jute bag storage (0.39).