Frass Weight Research Articles

Compensation of physiological traits under simulated drought and herbivory has functional consequences for fitness in soybean (Glycine max (L.) Merrill)

Soybean (Glycine max (L.) Merrill), one of the most valuable crops in the world, faces serious challenges due to drought and insect herbivory. Although well studied independently, we lack a comprehensive understanding of interactive effects of drought × herbivory on both soybean and herbivore traits. A holistic examination of soybean morpho-physiology (above and below-ground traits including root morphology) and herbivore performance can help us understand the potential consequences of these two major stressors on soybean yield and fitness. To this end, we imposed simulated-drought and herbivory by soybean looper (SBL) (Chrysodeixis includens Walker) and assessed both host and herbivore performance. Morpho-physiological traits of soybean including shoot height, chlorophyll content, root morphology, photosynthesis, stomatal conductance, and transpiration were measured. Additionally, growth and feeding behavior of SBL were also assessed to analyze the impacts of drought × herbivory on both host and herbivore. Our results show that certain physiological traits were significantly upregulated under drought × herbivory indicating compensation. We also observed that SBL frass weight, and scale of damage was lower on simulated-drought-experienced plants and, in choice assays, SBL preferred well-watered plants. In addition to lower yields observed under simulated-drought and herbivory interaction, soybeans that experienced both drought and herbivory had the highest number of aborted pods. Our study shows that simulated drought and herbivory have synergistic negative impacts on soybean morpho-physiology and support plant vigor hypothesis. Simulated drought negatively impacted SBL performance and made them less attracted to the soybeans that experienced water stress. Ultimately, the interactive effects of these stressors have negative consequences on soybean yield and fitness. This study demonstrates the need to integrate biotic and abiotic stressors for a better understanding of interactive effects on host and herbivores to make informed decisions for breeding and pest management strategies.

Effects of industrial pollution and ambient air temperature on larval performance and population dynamics of Eriocrania leafminers (Lepidoptera)

Pollution is an integral part of global environmental change, yet the combined and interactive effects of pollution and climate on terrestrial ecosystems remain inadequately understood. This study aims to explore whether pollution alters the impacts of ambient air temperature on the population dynamics of herbivorous insects. Between 1995 and 2005, we studied populations of two closely related moths, Eriocrania semipurpurella and E. sangii, at eight sites located 1 to 64 km from a large copper‑nickel smelter in Monchegorsk, Russia. We found that pollution and temperature influence the performance of Eriocrania larvae mining in the leaves of mountain birch, Betula pubescens var. pumila, through multiple pathways. This is evident from the unconsistent changes observed in larval and frass weight, mine area, and leaf size. We found increases in both leaf quality and larval weight with decreasing pollution levels at both spatial and temporal scales and attributed these to the impact of sulphur dioxide, rather than trace elements (nickel and copper). The quality of birch leaves increased with spring (May) temperatures, enabling Eriocrania larvae to achieve greater weight while consuming less biomass. During the larval growth period (early June to early July), Eriocrania larvae increased their consumption with rising temperatures, presumably to compensate for increased metabolic expenses. Contrary to our expectations, the per capita rate of population change did not correlate with larval weight and did not vary along the pollution gradient. Nevertheless, we detected interactive effects of pollution and climate on the rate of population change. This rate decreased with rising winter temperatures in slightly polluted and unpolluted sites but remained unchanged in heavily polluted sites. We conclude that pollution disrupts mechanisms regulating the natural population dynamics of Eriocrania moths.

Competition between Two Species of the Genus Sitophilus (Coleoptera: Curculionidae) on Wheat and Barley

Species can coexist and infest stored products at different population densities. We evaluated the population growth of Sitophilus oryzae (L.) and Sitophilus granarius (L.) (Coleoptera: Curculionidae) on wheat and barley in laboratory conditions. Ten adults of each species were placed in vials containing wheat or barley alone or in combination, and the number of adults was counted after 65 and 120 days. These tests were performed at 25 and 30 °C. Moreover, the number of damaged grain kernels and the weight of frass produced were also recorded. In general, the simultaneous presence of both species had a negative effect on the population growth of either S. oryzae or S. granarius. Nevertheless, no significant differences were noted regarding the number of damaged kernels and the weight of frass in most of the combinations tested. Moreover, the temperature seems to have a negative effect if both species were combined, especially at 30 °C. Our results showed that there was competition in the progeny production capacity when both species were together, but this competition was temperature and commodity-mediated.

Competition of Rhyzopertha dominica and Sitophilus oryzae on six sorghum varieties

We tested the effect of simultaneous infestation by adults of the lesser grain borer, Rhyzopertha dominica (F.) and the rice weevil, Sitophilus oryzae (L.) on six sorghum varieties. For this purpose, vials containing sorghum and either each species alone or both species were placed at 30 °C and 65% relative humidity. After ten days, all parental adults were removed and the vials were returned to the same conditions. Five weeks later the vials were emptied, to record adult emergence, the percentage of insect damaged kernels (IDK), and frass weight. Our results indicated that progeny production capacity for both species was not affected by the simultaneous presence of R. dominica and S. oryzae, and that adult emergence was more of a variety- mediated parameter. Both species had previously shown similar preferences towards specific sorghum varieties. IDK and frass were higher in vials containing R. dominica alone rather than S. oryzae alone, but these indicators were not always related to progeny production. Specifically, the most and the least frass production was noted on Sumac and PE sorghum varieties for both species, respectively. When the two species were placed together in the same vial, the most frass production was noted in the Non-Waxy Burgundy and Sumac varieties. Our results suggest that varietal resistance in sorghum could be utilized to help reduce post-harvest infestations by S. oryzae and R. dominica.

Developing a Feeding Assay System for Evaluating the Insecticidal Effect of Phytochemicals on Helicoverpa armigera.

Helicoverpa armigera, a lepidopteran insect, is a polyphagous pest with a worldwide distribution. This herbivorous insect is a threat to plants and agricultural productivity. In response, plants produce several phytochemicals that negatively impact the insect's growth and survival. This protocol demonstrates an obligate feeding assay method to evaluate the effect of a phytochemical (quercetin) on insect growth, development, and survival. Under controlled conditions, the neonates were maintained until the second instar on a pre-defined artificial diet. These second-instar larvae were allowed to feed on a control and quercetin-containing artificial diet for 10 days. The insects' body weight, developmental stage, frass weight, and mortality were recorded on alternate days. The change in body weight, the difference in feeding pattern, and developmental phenotypes were evaluated throughout the assay time. The described obligatory feeding assay simulates a natural mode of ingestion and can be scaled up to a large number of insects. It permits one to analyze phytochemicals' effect on the growth dynamics, developmental transition, and overall fitness of H. armigera. Furthermore, this setup can also be utilized to evaluate alterations in nutritional parameters and digestive physiology processes. This article provides a detailed methodology for feeding assay systems, which may have applications in toxicological studies, insecticidal molecule screening, and understanding chemical effects in plant-insect interactions.

Competition between Prostephanus truncatus and Sitophilus oryzae on maize: the species that gets there first matters

AbstractLaboratory tests were carried out in order to examine the population growth of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and Sitophilus oryzae (L.) (Coleoptera: Curculionidae) on maize. These two species were placed either simultaneously or one species was allowed to colonize the kernels 7 days earlier than the other, at two temperatures, 26 and 30 °C for 65 days. Apart from progeny production, grain quality parameters, such as insect-damaged kernels (IDK) and undamaged kernels (NDK), the weight of frass and kernel weight were measured. Our data confirms that temperature plays a key role in the competition of these two species; P. truncatus seems to perform better at the higher temperature (30 °C), regardless of the presence of an additional species. Moreover, the results of the present study demonstrates that P. truncatus outcompetes S. oryzae. Sitophilus oryzae produced fewer progeny than P. truncatus in all combinations. Given the outcome of a competition, we hypothesize that most of the kernel damage was due to feeding by P. truncatus. Based on these data, we surmise that P. truncatus has a competitive advantage as an invasive species in new areas with stored maize, even in the presence of S. oryzae.

Anoplophora glabripennis: Host choice, oviposition and performance of new hatched larvae on ‘resistant’ poplar species

AbstractForests in north‐western China are comprised mainly of poplar trees, predominantly Populus alba var. pyramidalis (PAP). Both Populus deltoides cl. Beikang (PDB) and PAP are attacked by the Asian long‐horned beetle (ALB), but vary in their resistance to attack. To investigate performance of ALB on PDB and PAP, we evaluated: host‐locating time, feeding and oviposition; and larval survival rate and weight in single‐choice and two‐choice bioassays; and undertook a field single‐choice test. Results showed that there was no significant difference in the time that female ALB took to locate PDB and PAP in a cage bioassay, but males located PDB faster than PAP. Although not statistically significant, the mean weight of frass produced by adults feeding on PDB was less than on PAP in both the two‐choice and single‐choice experiments. The mean numbers of oviposition notch grooves on PDB and PAP in the single‐choice experiment were similar, but there were more oviposition notch grooves on PDB than on PAP in the two‐choice experiment. Survival rates of young larvae on PDB were significantly lower than on PAP. The average weights of larvae on PAP were significantly higher than on PDB in both two‐choice and single‐choice experiments. In the field experiment, mean numbers of oviposition notch grooves were significantly higher on PDB than on PAP, but mean weights and survival rates of larvae were significantly lower on PDB than on PAP, which suggested that PDB attracted ALB oviposition but showed strong resistant to developing ALB offspring. In conclusion, although PDB was more attractive for oviposition by ALB, it was still more resistant than PAP, providing a useful reference for selection of resistant varieties.

English

The present study was conducted to probe out the nutritive losses caused by Rhyzopertha dominica (F.) and Trogoderma granarium (Everts) were quantified in six rice genotypes (KSK-434, KSK-282, Irri-6, Shaheen basmati, Basmati 385 and Chenab basmati). Percent crude protein, ash and moisture content were measured for qualitative losses, while for quantitative losses, frass weight and weight loss were examined after infestation period of 90 days of. Highest weight losses (25.76%) and (15.37%) were observed in KSK-434 by infestation of R. dominica and T. granarium, respectively, compared with un-infested grains after a storage period of 90 days. Highest frass weight (8.57 g) was recorded for KSK-434 while relatively low frass weight (4.16 g) was recorded for Basmati 385 by infestation of R. dominica. Relatively low frass weights of 5.67, 4.46 and 4.01 g were recorded in KSK-434, Chenab basmati and Shaheen basmati, respectively by attack of T. granarium. Highest percentage moisture values (14.03 and 11.24%) were recorded for KSK-434 by infestations of both test insects compared to non-infested (controls). Percent crude protein was decreased (from 6.97% to the 4.92%) due to infestation of R. dominica values by strain were KSK-434 (4.54%), Shaheen basmati (4.89%) and chenab basmati (4.92%). In the case of T. granarium infestation, almost all the varieties sustained the low protein contents except KSK-434 (5.02%) and Basmiti 385 (5.17%) and Shaheen basmati, protein contents loss comparable to non-infested control (7.09%). Ash content was high in genotype KSK- 282 (0.68 %) compared to control. KSK-434 and Chenab basmati had relatively low ash percentage due to high infestation of T. granarium. R. dominica attack produced the highest percent ash content (0.66%) in KSK-282 and the least (0.44%) in KSK- 434. The tested rice genotypes were more susceptible to R. dominica than T. granarium among the different genotypes of selected cereals.

Extent and pattern of damage in wheat caused by three different species of storage insect pests

We investigated the extent and pattern of damage in wheat caused by Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), Trogoderma granarium Everts (Coleoptera: Dermestidae) and Rhyzopertha dominica F. (Coleoptera: Bostrichidae) over a period of 75 d. Damage parameters included numbers of damaged grains, their weight; numbers of undamaged grains, their weight; frass weight and percent weight loss. Results showed after 75 d, maximum damaged grains were 125.17 ± 22.88 by R. dominica followed 80.50 ± 6.91 by T. granarium and least were 20.00 ± 2.61 after 50 d by T. castaneum. For R. dominica and T. granarium damage to grains increased with time (P 0.05). Maximum percent weight loss was 7.02 ± 1.87 g by R. dominica followed by 2.89 ± 0.33 g by T. granarium and least 0.65 ± 0.08 g by T. castaneum. Maximum dead insects percentage was 82% after 25 d for R. dominica, 59.67 ± 3.44 for T. granarium after 50 d and 100.00 ± 0.00 for T. castenum after 50 or 75 d compared to other time periods (P < 0.05). Percent increase in population was recorded for T. granarium but not for other two species during 75 d period. Microphotography of damaged grains after 75 d to compare damage pattern showed R. dominica made circular holes (Fig. 1), T. granarium made irregular holes (Fig. 2) and T. castaneum made circular damage but it did not traverse grains (Fig. 3). Radius length of circular damage was more for T. castenum compared with for R. dominica (P < 0.05). Damage area was maximum by T. granarium followed by T. castenum and least by R. dominica while perimeter of damage was greatest by T. granarium followed by T. castenum and least by R. dominica (P < 0.05).

Insecticidal Property of Black Seed (Nigella sativa) Powder as an Eco-friendly Management of Skin Beetle Dermestes maculatus (Coleoptera: Dermestidae) in Atlantic Codfish Gadus morhua (Gadiformes: Gadidae)

&#x0D; The bio-pesticidal potential of Nigella sativa seed powder in the management of Dermestes maculatus in codfish (Gadus morhua) was evaluated in the laboratory. D. maculatus beetles were obtained from naturally infested smoked fish, cultured at ambient temperature for the establishment of new stock and same age adults. Purchased N. sativa seeds were ground into fine powder, weighed at 0.4 g, 0.8 g, 1.2 g, 1.6 g and 2.0 g for use in the bioassay. The treatments were separately added into 40 g codfish kept in Kilner jar into which two sexed pairs of D. maculatus were introduced and observed. From the results, the number of the developmental stages (larvae, pupae and adults) of D. maculatus in codfish treated with N. sativa seed powder was inversely proportional to the concentration of the seed powder. Thus, an increase in the concentration of N. sativa powder generated reduction in the mean number of D. maculatus progeny found in the codfish after 35 days as follows: at 0.4 g, progeny development was (103.50, 7.75, 2.50) and 77.00, 8.25 and 1.00 at 2.0 g respectively for larva, pupa and adult stages. Percentage protection conferred by the botanical on D. maculatus showed that all the doses applied were effective. Corrected mortality of D. maculatus adults after 45 days of exposure to the different doses of N. sativa treatments also increased with an increase in concentration of N. sativa from 0.4 g to 2.0 g. Frass weight generated by D. maculatus activity in codfish treated with N. sativa powder was high in codfish treated at 1.6 g. Finally, N. sativa characterized both qualitatively and quantitatively for phytochemicals, proved the secondary metabolites with bio-pesticide potentials against D. maculatus such as phenols, Alkaloid, flavonoid, terpenoid, saponin, tannin, Cardiac glycoside, anthraquinone, steroid and oxalate in different proportion, therefore, should be utilized in Integrated Pest Management program of stored codfish.

Evaluation of Plastic Packaging for Prevention of Damage to Wheat by Trogoderma granarium (Coleoptera: Dermestidae), and Suitability of Phosphine Fumigation

We evaluated 4 types of plastic packaging containing whole wheat grains for damage to packaging in the form of scratches (damage through which insects cannot enter packages), holes (damage through which insects can enter packages), and penetrations (insects entering the packaging through holes) by Trogoderma granarium (Everts) (Coleoptera: Dermestidae) during the third and fourth instars. The plastic packaging used in this study was opaque polyethylene (high density), polypropylene, transparent polyethylene (low density), and polyvinylchloride with thicknesses of 0.021, 0.023, 0.026, and 0.036 mm, respectively. After 90 d, damage (scratches) was common with polypropylene and transparent polyethylene packaging, less so with opaque polyethylene, and no damage was found with polyvinylchloride packaging. Holes were more frequent in polypropylene, followed by opaque polyethylene, but none in the other forms of packaging. Insect penetrations were more frequent in opaque polyethylene, followed by polypropylene, but none in other forms of packaging. We also determined the number of damaged grains, weight of damaged grains, number of undamaged grains, weight of undamaged grains, weight of frass, and percent weight loss of grains caused by insects in the aforementioned types of packaging, and compared this with a fifth treatment consisting of open (unpackaged) grains infested by T. granarium larvae. We found that there was more damage to grain, greater weight loss of damaged grain, greater weight of frass, and higher percentage of weight loss of grains in unpackaged wheat, followed by opaque polyethylene and polypropylene, but not in transparent polyethylene or polyvinylchloride packaging. Microphotography after 90 d to measure the lengths of openings showed the maximum lengths in scratches and holes in opaque polyethylene, followed by polypropylene, although scratches in transparent polyethylene did not have openings for measurement. Following this, the types of packaging that were resistant to damage, i.e., transparent polyethylene and polyvinylchloride, were evaluated further for phosphine fumigation efficacy in terms of mortality of T. granarium. Fumigation results showed that in 24 h more larval mortality occurred in transparent polyethylene than in polyvinyl chloride, making transparent polyethylene overall a better foodstuff packaging material for protection from T. granarium.

Assessment of Rhyzopertha dominica (F.) progeny and feeding damage on rice dried with infrared radiation

Infrared radiation (IR) is a method of drying grains that eliminates insect and microbial pests. It is unknown if IR could cause grains to be more susceptible to insects. Thus, the effects of IR on Rhyzopertha dominica development and feeding damage using long-grain rice varieties, Clearfield XL745 (hybrid) and CL152 (pureline), were examined. Rough rice was dried with three IR intensities: 2.15, 2.83, and 10.84 kW/m2. The number of progeny developed, feeding damage, and frass weight after IR-drying were compared with air-drying methods for rough rice and rice milled to brown rice after drying. Since R. dominica develop internally, X-ray technology was used to examine internal progeny and feeding damage. Progeny development and kernel damage appeared to be more affected by fraction (brown rice) than the cultivar of rice or intensity of IR used, with more progeny produced on brown rice than rough rice. An IR intensity of 10.84 kW/m2 increased the number of overall progeny, the amount of adults, and frass produced on CL152 brown rice. An intensity of 10.84 kW/m2 also increased the amount of larvae observed for both varieties and fractions. The intensity of 10.84 kW/m2, under the conditions of this study, is not recommended for drying rice.

Competition of three stored-product bostrychids on different temperatures and commodities

We evaluated the competition among three species of stored-product Bostryhidae: Rhyzopertha dominica, Prostephanus truncatus and Dinoderus porcellus. In this context, ten adults of each species were placed in vials, either alone or in all possible combinations of two or three species. The experiments were carried out on wheat and maize, at 25 and 30° C. Sixty-five days later, the adult progeny production in the vials was recorded, as well as the weight of damaged and undamaged kernels, the number of grains with more than 1 hole and the weight of frass. On wheat, when each species was alone, progeny production of R. dominica on wheat was, for both temperatures, higher than that for the other two species. There was practically no progeny production on wheat for P. truncatus, but offspring numbers of D. porcellus were, in some cases, comparable with those for R. dominica. In contract, on maize, P. truncatus progeny production was constantly higher than the other two species, regardless of the species’ combination. In general, R. dominica prevailed on wheat, while P. truncatus in maize. However, the simultaneous presence of D. porcellus had a detrimental effect on progeny production of the other two species, while the presence of the other two species increased D. porcellus progeny production, in some of the combinations tested. On wheat and maize, the number of damaged kernels was higher in the combinations that R. dominica and P. truncatus, respectively, were present. When the species were alone, however, D. porcellus produced the higher amount of frass. Paradoxically, despite the absence of P. truncatus progeny on wheat, some damaged kernels were recorded when this species was alone in this commodity. Temperature had no effect on progeny production of D. porcellus. Our results showed that different species of Bostrychidae can coexist in stored grains, and specific displacement conclusions can be drawn according to the commodities and temperatures.

Competition of three species of Sitophilus on rice and maize.

Laboratory tests were carried out in order to examine competition among three congeneric species on rice and maize: the granary weevil, Sitophilus granarius, the rice weevil, Sitophilus oryzae and the maize weevil, Sitophilus zeamais. For this purpose, a total of 30 adults were placed in vials that contained 50 g or either rice or maize: 30 adults of S. granarius, 30 adults of S. oryzae, 30 adults of S. zeamais, 15 adults of S. granarius+15 adults of S. oryzae, 15 adults of S. granarius+15 adults of S. zeamais, 15 adults of S. oryzae +15 adults of S. zeamais, and 10 adults of S. granarius+10 adults of S. oryzae+10 adults of S. zeamais. After 62 days at 30°C and 65% relative humidity the number of individuals of each species were counted. Insect damaged kernels (IDK), weight of frass and grain weight were measured. When each species was alone, S. granarius had the lowest numbers of adults in both grains, which did not exceed 34 adults/vial, and S. oryzae numbers were always higher than other species. For S. oryzae and S. zeamais, the numbers of adults were considerably higher on rice than on maize. On rice, S. oryzae numbers ranged between 281 and 563 adults per vial, while for S. zeamais between 137 and 372 adults per vial. At the same time, for both species on maize, adult numbers did not exceed 54 adults per vial. The number of S. oryzae adults were constantly higher than the other species in all combinations tested. Moreover, for rice, IDK in the vials that contained S. oryzae, either alone or in combination with other species, was higher than all the other combinations. Similarly, grain weight was lower in the vials that contained S. oryzae compared to the other species combinations. In general, for S. oryzae and S. zeamais progeny production was increased with the increase of the number of the initial adults that had been placed inside the vials. At the same time, progeny production of all three species was not affected by the presence of another species inside the vial. Given that the coexistence of congeneric species in the same stored product ecosystem is often reported, our results highlight some of the inferences that are necessary in order to predict the potential outcome of competition patterns. Apart from its ecological significance, the prediction of the superior species in mixed species communities, can guide and time any control measures, on a more species-targeted basis.

Effect of Biomaterial Treatments on the Storage Stability and Quality of Cowpea

The insecticidal effect of four biomaterials namely, Garlic (Al. sativum), Ginger (Zingiber officinale), Black pepper (Piper guineese L.) and Lemon grass (Cymbopogon citrates Staph) leaf powders, applied at 10% and 5% concentration on Cowpea grains against the Cowpea weevils (Callosobruchus maculatus fab.) were evaluated after 42 days. Their effectiveness at both dosages on proximate composition, grain damage, progeny development, grain loss and frass weight were determined. Use of the biomaterials showed good retention of some nutrients like protein and fat and did not adversely affect the other nutritional parameters. The carbohydrate values of treated samples were slightly lower (54.47 – 58.55%) for 10% and (54.56 – 59.53) for 5%. than the control (60.83 – 61.24). There was no significant difference (p ≤ 0.05) in the ash contents among biomaterials. The biomaterials showed effective control of cowpea seed damage, weevil perforation index, progeny development, and weight loss and frass weight. These effects were more at 10% concentration than at 5%. Their efficacy in order of effectiveness are as follows black pepper > ginger > garlic > lemon grass. The biomaterials, especially black pepper and ginger are good alternative to the use of chemicals for preservation of cowpea.

English

Laboratory studies were conducted at the University of Port Harcourt to evaluate the response of dried yam chips as a host for Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). The test was conducted using four improved yam varieties namely; Adaka, Ame, Nwokpoko and Obiaturugo. Ten grams of each substrate of the dried yam chips were placed in plastic containers of 300 ml and each container was infested with three pairs of one to three days old P. truncatus. Data on insect developmental periods in the various dried chips, as well as the susceptibility of the substrates, weight gain on the chips and the weight of frass produced were recorded. The beetles exhibited differential levels of preference for the yam chips from different varieties. They developed better on Obiaturugo and Nwokpoko than on Adaka and Ame. The mean developmental period of P. truncatus on yam dried chips were 96.33 and 65.33 days for Obiaturugo and Nwokpoko, respectively but failed to develop on Adaka and Ame. There was significant difference (P<0.05) in weight between the amount of frass produced on Obiaturugo and that produced on the other substrates. Also, there was significant difference (P<0.05) in weight gained between Nwokpoko and the other substrates. The study has shown that of the dried chips from the four varieties of yam, only Nwokpoko and Obiaturugo were found to be possible hosts of P. truncatus and thus need protection against the pest during storage. Key words: Prostephanus truncatus, infestation, yam, chips.

Comparing Dermestes maculatus (DeGeer) Infestation of Cured Tropical Freshwater Fishes [Oreochromis niloticus (Linnaeus) and Clarias gariepinus (Burchell)

A multiple choice test was used to determine the rate of infestation of D. maculatus on two cured fish species of commercial importance. All the treatments had three replicates and were arranged in randomized complete block design. The infested and non-infested dried fish were subjected to a taste panel of four to evaluate the texture and taste quality of the fish before and after infestation. Percentage weight loss of the fish was also determined 30 days post infestation. A skewed 32% weight loss in C. gariepinus compared with 24.4% in O. niloticus was recorded. The study revealed that D. maculatus infestation rate (number of adults and larvae per fish specimen) was more in C. gariepinus than O. niloticus. Quality (taste and texture) damage was significantly greater in C. gariepinus than O. niloticus (p<0.05). The study also reveals that the entomo-fauna may feed on any material that has animal steroids. The effect of the pest infestation is discussed in the context of taste and texture characteristics, substrate fragmentation and frass weight. There is imperative need to develop appropriate pro-poor control measures which will minimize economic losses due to D. maculatus infestation of stored fish and fish products in the tropics.

Varietal screening and development of rice weevil, Sitophilus oryzae (L.) in advanced rice genotypes at different temperatures

The present study was conducted to screen out six rice genotypes including two course and four fine advanced varieties against Coleopterous insect rice weevil, Sitophilus oryzae (L.) under laboratory conditions. Weighing 100g sample of each genotype in plastic jars having capacity of 250g. Thirty adult insects of rice weevil, reared in laboratory were released in each jar. Quantitative losses as weight loss, percent damaged grains, progeny development and frass weight was recorded after 90 days of storage at 28oC, 32oC and 35oC. Percentage damage grains, adult emergence and frass weight was significantly high at 32, 28 and 35°C respectively. Maximum infestation in case of percentage damaged grains recorded in course genotype KSK-133(20.58%) and Basmati515(16.90%) followed by Basmati-2006(13.033%), and Super Basmati (12.433%) at 28°C. In a similar way but minimum weight loss (0.5%) was observed in KSK-282 at 35°C and (1%) in Basmati-2006 at 32oC. Overall, low resistance level with highest insect development was counted in KSK-133 (114), (101), (86) and Basmati-515(85), (90), (64.3) at 32, 35 and 28°C respectively. But under similar conditions Basmati-385(53), (43), (42) showed resistance in insect multiplication. Findings should be incorporate in breeding programme and can also be helpful in post-harvest storage.

Studies on Resistance Discrepancy in Seeds of Local and Exotic Lentil (Lens culinarisMedikus) Genotypes AgainstCallosobruchus analisL. (Coleoptera: Bruchidae)

The bruchid, Callosobruchus analis L., is a common storage insect pest of leguminous pulses including lentil (Lens culinaris Medikus). This study was conducted to document relative resistance and susceptibility differences among the eight lentil genotypes against C. analis. Feeding preference, weight lost after feeding, frass weight obtained, reproduction and development time of the bruchid pest, thickness of the outer seed coat and percentage germination were measured to determine the reaction of lentil genotypes. The results showed that none of the genotypes screened was completely free from bruchid infestation. Seeds of genotype AEL-49/20 were least infested and displayed relatively tolerant response; conversely, genotype AEL-23/40 harboured the maximum infestation and was highly susceptible. The remaining six genotypes, Matiary-S, AEL-57/50, M-85, ICARDA-8, AEL-28/40 and M-93 were categorized as intermediate (moderate resistant or moderate susceptible) to the attack of bruchids. Significant (P ≤ 0.05) variations existed among the lentil genotypes with respect to seed coat thickness (from 19 to 39 µm), playing an important role in imparting resistance. Germination test of tolerant genotype AEL-49/20 showed 91 % emergence potential. The results emphasize the importance of resistance development to maximize the protection of L. culinaris against C. analis.

Comparative study on wheat grains produced from plants treated by irradiated sodium alginate and stored in refrigerator with newly planted on vitality, quality, and their resistance to lesser grain borer (Rhyzopertha dominica)

Field experiment was conducted to compare between the wheat grains produced from plants sprayed by 1% solution of irradiated Na- alginate )ISA) stored in refrigerator for 30 months with those planted recently on vitality, quality and resistance to injury by Rhyzopertha dominica invasion. It was observed that untreated stored grains T1 decreased germination percentage about 15% comparing by newly planted control (T) and the depress in the stored treated grains were 7, 2 & 3% in 80 (T2), 120 (T3), and 160 (T4) kGy, respectively. While insignificant changes for the aforementioned treatments in concern to germination rate observed. The best growth characters were observed in T4. The highest soluble sugar, total carbohydrates and total amino acids were detected in T3. In entmology experiment it was noticed that all treatments had a range of resistance to R. dominica injury under laboratory conditions. The resistance cannot be attributed to grain size, but attributed to infestation percentage and frass weight. The most resistance found in stored grains (T3 and T2), respectively, in general non-stored seeds was more resistance to R. dominica than those stored in refrigerator. Moreover, (ISA) treatments had an inhibitory effect on insect amylase which varying from 85.6% - 56.1% and invertase which varying from 67.3% - 6.8%. Except pest tested with stored grains (T4) at low temperature showed an increase 13.5% and 20.6% in amylase and invertase activity, respectively. Irradiated sodium alginate preserved grains survival after long storage period especially T3 followed by T4. Also,using ISA before sowing stimulate the growth and yield.