Voracious Feeders Research Articles

Genetic Diversity of Maize (Zea mays L.) Genotypes under Low Level of Nitrogen

Maize (Zea mays L.) is India's second most significant crop, behind rice. As a cross-pollinated crop, hybrid vigour is commonly used to achieve the best production potential. The selection of various genotypes is a primary goal in the maize hybrid breeding programme. Maize is a voracious feeder and requires a lot of fertiliser. The biggest limits on maize production in India are low soil nitrogen and high fertiliser costs. Jharkhand consumes only 82.5 kg of total fertiliser nutrients per acre. In order to discover genetically varied maize genotypes for nitrogen usage efficiency, the current study evaluated 121 maize genotypes in a randomised block design with two replications at low nitrogen levels. Plant height, days to 50% pollen shed, days to 50% silk, anthesis-silking interval (ASI), days to75% maturity, number of leaves per plant, root length, stover yield per plant, grain yield per plant, and harvest index were all recorded. Statistical analysis was performed using the morphological trait data. Analysis of variance revealed substantial (p≤0.05) variations in morphological features between maize genotypes. For statistical analysis, a clustering method was used to locate various genotypes with greater genetic distance in order to develop good heterotic combinations. One hundred twenty one genotypes were divided into six clusters using the dendogram-by-ward minimum variance approach. Cluster III and V had the greatest inter-cluster distance (79.26), followed by cluster III and VI (74.77) and cluster II and III (73.80). The many heterotic combinations developed from these clusters can be employed in subsequent breeding programmes to produce low nitrogen-requiring hybrids with a low yield penalty.

Light and Electron Microscopy Study of Opportunistic Free-Living Nematodes Scavenging and Thriving within Buried Dinosaur Bones

Abstract Nematode worms are the most abundant multicellular organism on Earth. They thrive in every habitat known, and they are voracious feeders within the top 70 cm of soils. Their sturdy cuticle protects them from environmental factors and predators. Nematodes play a significant role in the decomposition of vertebrate remains in soil and serve as indicators of nutrients that enter soils during decomposition. Certain parasitic nematodes have been identified in fossil remains, but reports of fossil worms are rare. We demonstrate the abundant presence of opportunistic nematodes feeding within dinosaur bones from the Hell Creek formation, MT. The presence of visible worm ultrastructure indicates that they were alive when preserved within the dinosaur bones. Our findings are identical to worms characterized as “blood parasites” in a dinosaur bone from Brazil, demonstrating that there is sufficient soft tissue within dinosaur bone canals to sustain large populations of nematodes post-mortem.

Effect of spirulina fortification on the digestive protease, carbohydrases and cocoons economic traits of mulberry silkworm Bombyx mori

Bombyx mori, the silkworm, is a voracious feeder that relies on digestive enzymes for mulberry digestion and its conversion in to silk. In the current study, fifth-instar larvae were given 2% spirulina supplementation with commercially graded spirulina samples, and a few digestive enzymes and cocoon traits were examined. The treatment groups of silkworms T1-control, T2-supplemented with spirulina powder graded for animal dietary consumption, T3- graded for human dietary consumption and T4-spirulina graded for medicinal applications. Spirulina supplementation was tested in silkworms for digestive protease, carbohydrases and cocoon traits. The results shows that the total protein content percentage difference (PD) in the gut wall was increased by 2.79% in T3, 1.96% in T4, and 0.78% in T2 compared to T1 (control). A similar trend was noticed in the gut content, with the PD of 15.81% in T3, 7.51% in T4, and 3.95% in T2. In total carbohydrate content, observed PD of 16.35% in T2, 11.27% in T3, and 9.38% in T4, while the gut content was 13% both in T2 and T3, and 1.22% in T4. The protease activity PD of gut wall tissue has 21.99% in T3, 5.13% in T2, and 4.30% in T4; similarly, the gut content has a PD of 112.38% in T3, 106.12% in T4, and 86.41% in T2. The amylase activity have shown highest PD in T4 (33.43%), T3 (23.37%), and moderate in T2 (19.23%) in the gut wall, and 93.10% in T3, 66.44% in T2, and 14.92% in T4 of gut content. Enzymes such as sucrase, cellulase, and pectinase have also improved with spirulina fortification. The sucrase activity in the gut wall and gut content were, respectively, 7.99% and 80.73% in T3 treatment. Noteworthy, the T2 showed 37.69% in the gut wall and 24.54% in the gut content for the cellulase activity. Unlike cellulase, pectinase activity has been observed with a PD of 93.15% in the gut wall and 64.63% in gut content. The study further confirms that the additional fortification of spirulina will have a beneficial effect on the digestive cells of the silkworm, Bombyx mori, resulting in the highest rate of enzyme activity and in turn, increasing survivability.

Feeding ethogram of Antilochus coquebertii F. preying on Dysdercus koenigii

Antilochus coquebertii F. (Hemiptera: Pyrrhocoridae) is one of the most important and voracious feeders of Dysdercus spp. First time, this study explained the feeding ethogram of both male and female A. coquebertii on Dysdercus koenigii adults (both male and female). Female adults of A. coquebertii consumed maximum prey (97.78 %) with respect to male (90.91%). The pre-feeding time was recorded maximum in male adults (12.22 min) as compared to female adults (4.1 min). In case of paralysis time, female adults take more time (0.47 min) as compared to male adults (0.46 min). Both male and female adults of A. coquebertii exhibited different preferences towards different body parts of D. koenigii with variable feeding time and number of feedings. Feeding ethogram showed that both of male and female A. coquebertii adults use their antennae in olfactory and gustatory sense. Based on feeding time, abdomen was more favored by male adults and thorax by female adults. While, in case of number of feedings, male adults of A. coquebertii preferred to feed on head and female on thorax of D. koenigii. Increase in body weight of female adults of A. coquebertii after feeding on its prey was found maximum (0.92 g) as compared to male adult (0.66 g). According to these findings, antennae of A. coquebertii have olfactory and gustatory sense while proboscis kept gustatory sense. Female adults of A. coquebertii is more efficient feeder of D. koenigii than male. Abdomen of D. koenigii was more preferred by male adults, while thorax by female adults of A. coquebertii.

Efficacy of Azadirachta indica and Datura stramonium Extract with Ethanol against Different Life Stages of Tribolium castinium

Tribolium castinium is a devastating stored grain pests of many cereals. Both the larval and adult stages of insect are considered as voracious feeder of cereals. The adult of T. castinium secrete certain type of excretion that give foul smell from grains and make it unfit for consumption. The recent study was conducted in Department of Entomology College of Agriculture Bahauddin Zakariya University, Bahadur sub campus Layyah. Neem (Azadirachta indica)L. and Datura (Datura stramonium)L. ethanol extracts were tested for their repellant and toxicological effects against the larval and adult stages of T. castinium at varying concentrations of 10, 15, and 30ml. The results showed that D. stramonium plant extract recorded highest repellency (86.66%) and the lowest repellency (4.50%) against T. castinium. Minimum mortality was reported at 65% in plant extract of A. indica after an interval of 24 hours at 10ml concentration, and maximum mortality was recorded (90.69%) in plant extract of D. stramonium at 30ml concentration after an interval of 72 hours. The results showed that neem and Datura plant extracts were more effective at repelling and toxicologically acting against T. castinium. The larval stage of T. castinium was also particularly vulnerable to D. stramonium and A. indica ethanol extract.

Effect of prey density on the performance of Eupeodes corollae and its predation rate against the cabbage aphid, Brevicorynae brassicae (L.).

Eupeodes corollae (F.) (Diptera: Syrphidae) is the most abundant syrphid fly which is distributed worldwide and is the sole predator of aphids. Therefore, the present study was conducted to evaluate the predation rate and functional response of E. corollae against the cabbage aphid, Brevicoryne brassicae (L.). The experiment was carried out under laboratory conditions at 25 ± 2°C with 60-70% relative humidity. The results revealed that age-specific net predation rate (qx) increased after the 4th day and a peak was recorded on the 10th day of pivotal age in the third larval instar. The stable host kill rate and finite host kill rate of E. corollae were 18.63 and 21.07, respectively, against the B. brassicae and predicted that a mean of 20.78 aphids was needed for E. corollae to produce one offspring. A negative linear coefficient (P < 0) indicated the type II functional response for all larval instars of E. corollae against the B. brassicae. At higher prey density, the prey consumption was significantly at par with second and third instar larvae of E. corollae as the prey consumption was increased with increasing the prey density, which then decreased after attaining the upper asymptote (76.40 and 81.40% consumption, respectively). The Roger's predator random equation for type II functional response was fitted to estimate attack rate (a) and handling time (Th). The maximum prey consumption was recorded for third instar of E. corollae with a higher attack rate (0.336 h-1) and lower handling time (0.514 h) against B. brassicae, followed by the second and first instar. Thus, it is concluded that the third larval instar of E. corollae was the voracious feeder and used as an efficient biocontrol agent in the IPM programme.

Ingestion and excretion dynamics of microplastics by black soldier fly larvae and correlation with mouth opening size

Black soldier fly (BSF) larvae (Hermetia illucens) are voracious feeders that can be reared on food waste streams originating from the food industry and retailers. Because these food waste streams are automatically being unpacked in substantial amounts, they can contain microplastics, potentially jeopardising the larvae’s chemical safety when applied as compound feed ingredients. During this study, the dynamics of ingestion and excretion of microplastics by BSF larvae reared on substrates containing different contents (wMP = 0.00, 0.01, 0.10, 0.50, 1.00, 3.00%) of fluorescent blue-labelled microplastics (median size, Dv(50) = 61.5 µm) were monitored. To correlate the particle size with their uptake, larval mouth opening dimensions were measured during the rearing process. In conclusion, it appeared that ingestion of microplastics by BSF larvae depends on initial particle load, mouth size, and consequently also age. The larvae took up between 131 (wMP = 0.01%) and 4866 (wMP = 3.00%) particles leading to bioaccumulation factors (BAF) between 0.12 (wMP = 3.00%) and 1.07 (wMP = 0.01%). Larvae also appeared to excrete the microplastics, lowering the BAFs to values between 0.01 (wMP = 3.00%) and 0.54 (wMP = 0.01%).

Biology of Khapra Beetle &lt;I&gt;Trogoderma Granarium&lt;/I&gt; on Wheat Varieties

Khapra beetle Trogoderma granarium is a destructive and voracious feeder of several stored products such as wheat, maize and rice, and it is a quarantine pest for wheat producing countries like Pakistan. The present study evaluated its biological and morphological parameters on different wheat varieties. The results revealed that its incubation period was varied from 7.01-8.91 days, being longest on the variety Faisalabad-08, and shortest on Sehar-06. Its total developmental period from egg-adult varied from 48.44- 64.16 days, respectively; male and female longevity was 19.14, and 17.02 days on Sehar-06. The weight of 6th instar larvae ranged from 6.21 to 7.11 mg, while the survival was maximum and minimum on Sehar-06 and Faisalabad-08, respectively. The minimum and maximum weight losses were observed in Faisalabad-08 and Sehar-06, respectively. Thus, Sehar-06 was observed to be the most susceptible variety giving maximum fertility and fecundity.

Gut Endosymbiont Disruption through Antibiotics Influences the Metabolic Homeostasis in Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae

Fall armyworm as a polyphagous voracious feeder reported causing yield losses in most agriculturally important crops. As this insect had developed resistance against most of the insecticides, there is a need for an alternate approach to management. Gut endosymbiotic bacteria play a significant role in host feeding, digestion, and defense response throughout the life stages of insects. In the present study, we have isolated and identified the gut endosymbiotic bacteria of fall armyworm and the larvae were treated with antibiotics. The results showed that the maximum bacterial population was observed in the fourth instar of field-caught larvae and the least population was observed in the fourth instar artificially reared population. Based on the biochemical results the isolated gut endosymbiotic bacteria mainly comprised of Bacillus sp, Enterococcus sp., and Enterobacter sp. Based on the susceptibility of gut bacteria to different antibiotics, 6 antibiotic treatments with one insecticide treatment were administered to an artificial diet reared with third instar larvae and their dietary indices were evaluated. Among the antibiotic treatment, there was a reduction in the dietary indices in the larvae treated with Ciprofloxacin CIP5 (45.33%) and Cefotaxime CTX30 (41.73%) and an increase in dietary indices in the larvae treated with Nalidixin NA30 (31.58%), Doxycycline DO30 (8.82%), Vancomycin VA30 (22.05). Elimination of gut bacteria with a suitable antibiotic will affect the insect’s feeding and dietary indices subsequently decreasing the relative growth rate and insect’s physiology. Hence, gut bacteria-based green control measures might be used as an alternative approach for insecticides for the effective management of fall armyworm.

GUT CONTENT ANALYSIS OF ENDEMIC LARVIVOROUS FISH FROM SUSWA RIVER OF DOON VALLEY, DEHRADUN

Food is the basic prerequisite for growth, development, survival and existence of all organisms. Gut content analysis of fish provides an important insight into feeding patterns and quantitative assessment of feeding habits of fish. The objective of present study is to identify the endemic fish having larvivorous potential in natural condition by gut content analysis. Fish were collected from Suswa river, Doon valley by following the standard techniques of fishing during July 2018 to June 2019. The collected fishes were shorted and identified using standard identification keys and catalogues. Fish were dissected and gut content were examined microscopically and numerical methods was used by calculating percentage composition of food items in total contents of fish stomach. A total of 200 fish of 20 species belonging to 13 genera were dissected for gut content analysis. The contents were classified based on food types and fish were differentiated into herbivorous, omnivorous and carnivorous. Choices of food by fish were based on the availability of food at a particular habitat and the fish species showed omnivorosity habit of feeding. Further, feeding potential of fish were estimated based on the percentage composition of insect content only among animal content and categorized as voracious feeder, moderate feeder and opportunistic feeder.

Predacious activity of Serangium parcesetosum Sicard (Coleoptera: Coccinellidae) on Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) on caged tomato

Tomatoes are the most familiar and the most common greenhouse vegetable crop in Turkey, as well as worldwide. Main whitefly species problematic in the greenhouses, where tomatoes grown primarily, is Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) in Mediterranean Region of Turkey. Serangium parcesetosum Sicard (Coleoptera: Coccinellidae) is proved as a coccinellid predator of B. tabaci and a voracious feeder by several studies. The hypothesis “the outcome of a biological control program is determined by the initial pest to predator ratio” was examined on caged tomato in greenhouses. The current study showed the influence of initial whitefly density on the whitefly population growth rate, which was independent of the absence or presence of S. parcesetosum (P&amp;gt; 0.05) for the whitefly density × predator release interaction). No significant differences in whitefly suppression from S. parcesetosum predation were monitored between the two initial whitefly densities in both years. The density of the pest was reduced by S. parcesetosum in high and moderate initial whitefly density cages 2-3 weeks after releasing the ladybird beetles. During the experiment, copulating adults, larvae, and pupae of the predatory ladybird beetle were observed in both predator-releasing cages. These results indicated that S. parcesetosum can survive and reproduce on tomato plants in greenhouse production during the spring months in Mediterraenean region of Turkey.

Preliminary studies on predatory potential of Australian ladybird beetle, Cryptolaemus montrouzieri Mulsant against Mealybug, Planococcus lilacinus Cockerell

Mealybug Planococcus lilacinus Cockerell (Hemiptera: Pseudococcidae) damages Cocoa, Guava, Citrus, Cotton and other plant families. Besides causing direct loss to the plants they also reduce the market value of infested fruits. The extent of the damage may go up to 70 percent in a severe infestation. An Australian ladybird beetle, Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) introduced from Australia is a potential bio-control agent and is being utilized on many crops in Southern India. Mealybugs or scale insects constitute the natural food of certain ladybird beetles. The adult beetles as well as their larvae (grubs) seek the pests and feed voraciously on all stages. They often wipe out the entire pest colonies. The ladybird beetles are being used for suppression of mealy bugs in citrus, coffee, grapes, guava, ornamental and a variety of other crops. The feeding potential of different development stages of C. montrouzieri, a biological control agent against mealybugs, was investigated on P. lilacinus. Fourth instar grubs and adults of C. montrouzieri were the most voracious feeders of mealybug. The number of mealybug consumed by 1st, 2nd, 3rd and 4th instar larvae and adult beetles of C. montrouzieri was 20, 33.30, 37.50, 40 and 66.60 percent respectively. The results indicate that C. montrouzieri has the potential to be exploited as a bio-control agent. Inoculative releases of 4th instar larvae and adults may provide instant control of P. lilacinus. Field experiments should be conducted to determine the efficiency of the ladybird beetle on this mealybug.

Life history, nesting behaviour, and social behaviour of Stigmaeopsis spider mites (Acari: Tetranychidae)

ABSTRACT Stigmaeopsis mites are voracious feeders of bamboo plants, Pleioblastus spp., Miscanthus spp., and Sasa spp. Fifteen species of the genus Stigmaeopsis have been reported worldwide. Their life history is affected by temperature and they can have many generations overlap in their nests under favourable conditions. Stigmaeopsis species overwinter as only adult stages in temperate zones. Males kill conspecific males to mate with unmated females. Most Stigmaeopsis mites defaecate at pre-determined sites, which differ among species. Stigmaeopsis mites determine defaecation sites through volatile chemical cues or tactile stimuli. Herein, we discuss advances in the understanding of aspects of Stigmaeopsis mite biology and behaviour, such as life history, life types, reproduction, overwintering, nest building and sizing, defaecation, mating, and defence against predators. We conclude that there is a paucity in the literature concerning the biological traits of Stigmaeopsis. Furthermore, we suggest that additional research be performed on the effects of temperature, geographic distribution, and biological and chemical control on the species of this genus.

Seasonal prey availability and diet composition of Lesser Asiatic Yellow House Bat Scotophilus kuhlii Leach, 1821

Diet is an important factor in understanding bat ecology and conservation. This study assessed seasonal prey availability and diet composition of the Asiatic Lesser Yellow House Bat Scotophilus kuhlii in various districts of Uttar Pradesh between January 2016 to December 2018. Fecal and insect samples were collected seasonally using sweep nets between 1800 and 1900 h. From each location 20 fecal pellets were selected for analysis and searched for taxonomically recognizable remnants. The analysis revealed that S. kuhlii fed on Coleoptera, Diptera, Hymenoptera, Isoptera, Orthoptera, Odonata, Blattodae, Lepidoptera, and Hemiptera, identified from legs, antennae and wings/elytra in fecal pellets. Seasonal variation in the presence of isolated insect remnants and insect abundance at foraging grounds was observed. Thus S. kuhlii is a voracious feeder and plays an important role as a pest control agent.

Proteomics and ultrastructural analysis of Hermetia illucens (Diptera: Stratiomyidae) larval peritrophic matrix

BackgroundThe black soldier fly (Hermetia illucens) has significant economic potential. The larvae can be used in financially viable waste management systems, as they are voracious feeders able to efficiently convert low-quality waste into valuable biomass. However, most studies on H. illucens in recent decades have focused on optimizing their breeding and bioconversion conditions, while information on their biology is limited.MethodsAbout 200 fifth instar well-fed larvae were sacrificed in this work. The liquid chromatography-tandem mass spectrometry and scanning electron microscopy were employed in this study to perform a proteomic and ultrastructural analysis of the peritrophic matrix (PM) of H. illucens larvae.ResultsA total of 565 proteins were identified in the PM samples of H. illucen, of which 177 proteins were predicted to contain signal peptides, bioinformatics analysis and manual curation determined 88 proteins may be associated with the PM, with functions in digestion, immunity, PM modulation, and others. The ultrastructure of the H. illucens larval PM observed by scanning electron microscopy shows a unique diamond-shaped chitin grid texture.ConclusionsIt is the first and most comprehensive proteomics research about the PM of H. illucens larvae to date. All the proteins identified in this work has been discussed in details, except several unnamed or uncharacterized proteins, which should not be ignored and need further study. A comparison of the ultrastructure between H. illucens larval PM and those of other insects as observed by SEM indicates that the PM displays diverse textures on an ultra-micro scale and we suscept a unique diamond-shaped chitin grid texture may help H. illucens larval to hold more food. This work deepens our understanding of the molecular architecture and ultrastructure of the H. illucens larval PM.

Rice yellow hairy caterpillar, Psalis pennatula Fabricius (Lymantriidae: Lepidoptera) an emerging pest of paddy in Assam

Psalis pennatula Fabricius, rice yellow hairy caterpillar (Lepidoptera: Lymantriidae), earlier recorded as a minor pest from different rice growing areas of Assam, has been observed to increase in severity during recent years. The caterpillar is a voracious feeder and can consume whole leaves of tillers within a day. Keeping in view, an attempt was made to study its biology at the Department of Entomology, Assam Agricultural University, Jorhat under laboratory conditions of 29 ± 1°C and RH 80 ± 5%. The study indicated that the insect completed its life cycle within 51 to 69 days. The incubation period ranged from 4 to 6 days. The larvae passed through six to seven instars. The total fecundity of P. pennatula ranged from 25–108 eggs. The adult male lived for 6.5 to 8 days whereas the female lived for 5 to 7 days.

Feeding Behaviour of Tank Goby, Glossogobius giuris (Hamilton) and Its Rearing Feasibility in Upper Assam

Feeding behaviour and rearing feasibility of a multipurpose wild goby fish, Glossogobius giuris in backyard ponds has been discussed. The fish shows inclination towards animal diet with wide range of food preferences at various trophic levels. Specimens collected from natural habitat and also from rearing pond indicate its preference towards small sized fishes. The fish is a voracious feeder and exhibit somewhat aggressive behaviour when kept in fasting mode for a period of 12 to 24 hour. Further, the fish prefers mostly in live food, be it small fish, earthworm or mosquito larvae but exhibit little interest towards homemade and commercial fish feed.

Incidence and distribution of Lemon butterfly (Papilio demoleus L.) on five alternate Citrus hosts at Sahati region, Sindh-Pakistan

In Sindh province of Pakistan district, Naushahro Feroze is considered as the main hub for citrus fruit productivity. At field conditions research studies were carried out from five different citrus farmlands of the given Sahati region. All life cycle stages of Papilio demoleus were observed from the C. paradisi, C. sinensis, C. limetta, C. reticulata and C. aurantium. During one-year study plan data were taken fortnightly interval basis from the host plants. It was frequently observed that temperature fluctuation relaying the effect on the population of the lemon butterfly during severe cold as well as in intense warmer conditions. The overall mean of the egg population was observed at (2.88 to 5.39), larvae (1.12 to 3.89) pupae (0.56 to 1.00) adult (♂ :♀) male and female (0.45 to 1.04), respectively. During the October month population found high and in December month low on the leaves of five citrus verities i.e., Grape fruit maximum and minimum at (4.71 to 4.79), (1.27 to 1.39), Sweat orange (3.88 to 4.19), (1.12 to 1.38), Mousambi leaves (3.30 to 3.51), (0.91 to 1.03), Mandarian orange leaves (2.86 to 2.96), (0.78 to 0.84) and Bitter orange leaves (2.33 to 2.46), (0.54 to 0.63) respectively. It was concluded that caterpillars' fourth and fifth stages are a voracious feeder of citrus orchard leaves. The main motto of the present work is to take initiative over the lemon butterfly and aware of citrus growers of this region. It is recommended and immediate call to enhance stable integrated pest management eco-friendly techniques to secure the citrus industry for the upcoming period. Keywords: Caterpillars; Citrus orchards; Papilio demoleus; Sahati region; Voracious feeder http://dx.doi.org/10.19045/bspab.2020.90280

Efficiency of the convergent ladybird beetle Hippodamia convergens against the legume aphid Aphis craccivora in laboratory and semi-felid conditions.

Laboratory and semi-field studies were conducted to investigate some biological parameters, feeding capacity and releasing efficiency of Hippodamia convergens on legume aphid, Aphis craccivora. At 25±2˚C and 65±5 R.H., durations of the eggs' incubation period, the four larval instars and pupae were 4.48, 2.11, 2.23, 2.23, 2.68 and 4.39 days, respectively. The average feeding of the 4th instar larvae fed on 84.47 aphids of 4th nymphal instar, being the highest voracious feeder compared to the first three larval instars which consumed the means of 14.4, 21.3 and 32.87 individuals, respectively. When fed on A. craccivora nymphs, female survived longer (50.83 days) than male (34.73days), a single H. convergens female deposited average total of 455.13eggs. The semi-field studies evaluated the controlling capacity against infestation by A. craccivora on faba bean seedlings by H. convergens released under greenhouse conditions, as; only adults, only 3rd instar larvae and both stages. Either of the three treatments for releasing Hippodamia caused reductions of aphid densities than control. In experiment one; 3, 9 and 15 adults/plot were released only one time. Ten days after release, the treatment receiving 15 adults/plot showed the highest reduction rate in aphids (100.00%) compared to that received 3adults (86.78 %) or 9 adults (95.41%) /plot. In the second treatment; 3, 9 and 15 larvae/plot were released one week after infestation, reduction rate of 96.93% occurred 10 days after releasing of15 larvae/plot. In the third experiment; both stages altogether were released at 3 ratios, i.e., 1adult:2 larvae, 3 adults:6 larvae and 5adults: 10larvae/plot. The highest reduction rate (99.14%) of A. craccivora occurred by the third treatment (5A:10L/plot) after 13 days from the releasing date. Treatment receiving only adults showed the highest reduction rate of A. craccivora densities compared to the two other treatments. Accordingly, releasing H. convergens adults only was better than the other two treatments for control of A. craccivora infestations.

Biology, predatory potential and functional response of Mallada desjardinsi (Navas) on melon aphid, Aphis gossypii glover

This study evaluated the developmental biology, predatory potential, and functional response of Mallada desjardinsi (Neuroptera:Chrysopidae) larval instars fed on melon aphid, Aphis gossypii Glover. The experiment was carried out under laboratory conditions at 25 ± 1 °C, with 70 ± 5% R.H and 12:12 L:D photoperiod. The freshly emerged larvae were reared individually in the Petri plates containing moist blotting paper and cucumber leaves (6 × 6 cm) infested with assorted population of second and third instars of A. gossypii. The results showed that incubation, total larval, pre pupal and pupal periods of M. desjardinsi were 2.90, 12.50, 1.40 and 9.10 days, respectively. Pre oviposition, oviposition and post oviposition period of M. desjardinsi was 11.80, 32.40 and 2.76 days, respectively and each female laid an average of 128.58 eggs. The 1st, 2nd and 3rd instars of M. desjardinsi on an average consumed 30.98, 107.80 and 265.40 aphids, whereas total consumption during life cycle was 298.50 aphids/predator. All the three larval stages of the predator exhibited Type II functional response to the aphid. Based on Rogers’s random predator equation, the predator’s attack rate was the lowest (0.092) in the first instar, while the 3rd instar recorded the highest rate (0.118). Functional response parameters indicate that attack rate increased and handling time decreased with the advancement of the predator stage. From biological control point of view, our data suggest the successful use of M. desjardinsi third instar larvae as voracious feeders in IPM programmes against melon aphid.