Insect Pests Of Agricultural Importance Research Articles

The Mutating Effect of Microwave Irradiation on Spores and Crystal Protein Formation of Iraqi Bacillus thuringiensis kurstaki KS3

Alkhafaji, K.A., F.H. Nahar, S.A. Khlaywi, M.A. Abedallah, A.J. Feaath, A.A. Mezban. and S.A. Saleh. 2023. The Mutating Effect of Microwave Irradiation on Spores and Crystal Protein Formation of Iraqi Bacillus thuringiensis kurstaki KS3. Arab Journal of Plant Protection, 41(3): 285-291. https://doi.org/10.22268/AJPP-041.3.285291 Bacillus thuringiensis is the most important biological control agent that is used in fields and stores against insect pests of agricultural importance. This research was conducted to study the effect of microwave radiation on sporogenesis and crystal protein production by the Iraqi bacterium B. thuringiensis KS3 strain. The bacterium was enriched by Lauria bertani broth (LB) pH 7.0 for spore formation. Spore suspension was microwave irradiated at 1000 Watt for 5, 10 and 15 seconds. Spore inactivation rate for each time period of microwave treatment was calculated and the macroscopic differences were examined. Crystal protein and spore production were estimated for irradiated and nonirradiated bacterial cultures. Viable spores in the control treatment was 3×108 viable spores/ml, and decreased after 5, 10, and 15 s of microwave treatment to 3×107 , 2×106 and 2×104 viable spores/ml, respectively. The reduction of spore viability reached to 49.263% 15 seconds after treatment. The appearance of colonies on the top of nutrient agar (NA) were almost similar with the control, with no differences in color, margin and surface of treated colonies following the three time periods treatment. Colonies with dense color, smaller in size and with straight margin appeared on congo red culture for all treatments in contrast to the control. Microscopic examination showed that treated bacilli were similar regarding their shape, diameter and arrangement, however,smaller bacterial cell size following 15 s irradiation treatment was observed. Control culture after 72 h started to form spores, whereas after 24 h, irradiated spores for 5, 10 and 15 s formed 75, 90 and 90% viable spores, respectively. Crystal protein reached the highest concentration after 72 h in control culture, whereas it varied based on treatment period. The production of viable spores from microwave irradiated isolates increased about one logarithmic cycle compared with the control culture of B. thuringiensis KS3.The peak of the UV spectrum of Crystal protein extracts was recognized at 255-280 nm and the peak of the curve indicated the protein concentration at a given wavelength. Differences were recognized in the UV light wavelength range of 220-235 nm. Keywords: Sporogenesis, Physical effect, Delta toxin.

Insecticidal toxicity of ω-Atypitoxin-Cs1a and its inhibitory effects on insect voltage-gated calcium channels.

Excessive use of chemical insecticides raises concerns about insecticide resistance, urging the development of novel insecticides. Peptide neurotoxins from spider venom are an incredibly rich source of ion channel modulators with potent insecticidal activity. A neurotoxin U1-Atypitoxin-Cs1a from the spider Calommata signata was annotated previously. It was of interest to investigate its insecticidal activity and potential molecular targets. Cs1a was heterologously expressed, purified and pharmacologically characterized here. The recombinant neurotoxin inhibited high-voltage-activated calcium channel currents with an median inhibitory concentration (IC50 ) value of 0.182 ± 0.026 μm on cockroach DUM neurons and thus was designated as ω-Atypitoxin-Cs1a. The recombinant Cs1a was toxic to three insect pests of agricultural importance, Nilaparvata lugens, Spodoptera frugiperda and Plutella xylostella with median lethal concentration (LD50 ) values of 0.121, 0.172 and 0.356 nmol g-1 , respectively, at 24 h postinjection. Cs1a was equivalently toxic to both insecticide-susceptible and -resistant insects. Cs1a exhibited low toxicity to Danio rerio with an LD50 of 2.316 nmol g-1 . Our results suggest that ω-Atypitoxin-Cs1a is a potent CaV channel inhibitor and an attractive candidate reagent for pest control and resistance management. © 2023 Society of Chemical Industry.

Mpp51Aa1 toxicity to Diaphorina citri nymphs demonstrated using a new, long-term bioassay method

While pesticidal proteins from Bacillus thuringiensis have provided for effective management of several insect pests of agricultural importance, few with toxicity to hemipteran species have been identified. The Asian citrus psyllid, Diaphorina citri transmits Candidatus Liberibacter asiaticus (CLas), the presumed bacterial causative agent of the devastating disease citrus greening. Despite the critical role of D. citri nymphs in the acquisition and inoculation of CLas, the lack of a long-term feeding method impedes the screening of Bt proteins for toxicity against nymphs, which play a key role in CLas transmission. Here, we developed a long-term nymph bioassay and determined the toxicity of the Bt pesticidal protein Mpp51Aa1. The new bioassay method allows nymphs to survive for up to six days when maintained on treated folded wipes. The standard hemipteran membrane feeding assay was used to assess Mpp51Aa1 toxicity against D. citri adults. Mpp51Aa1 was toxic to D. citri nymphs with a median lethal concentration (LC50) of 56.5 µg/ml in wipe feeding assays, and to D. citri adults with an LC50 of 110.4 µg/ml in membrane feeding assays. These results demonstrate the utility of this long-term nymph bioassay method and suggest that Mpp51Aa1 has potential for sustainable use in D. citri management toward mitigation of citrus greening disease.

Insecticidal effect of entomopathogenic nematodes and the cell-free supernatants from their symbiotic bacteria against different larval instars of Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae)

BackgroundEntomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) and their symbiotic bacteria are pathogenic for a wide range of insect pests and have been used successfully as a biological control agent. Although EPNs are well studied against many agricultural insect pests, the efficacy of their symbiotic bacteria still remains unclear for many insect pests of agricultural importance. In the present study, the virulence of native EPN isolates and their cell-free supernatants of symbiotic bacteria were tested against the 3rd and 4th larval instars of Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae) under laboratory conditions (25 ± 1 °C and R.H. 60%).ResultsThe 4th instar larvae were more susceptible to infective juveniles (IJs) and mortalities over (95%) were achieved by all tested EPN isolates at the concentration of 100 IJs/cm2 after 72 hrs of exposure. The cell-free supernatants were more effective against the 3rd instar larvae and the highest mortalities were recorded as 42 and 60% in the contact and leaf disc bioassays, respectively.ConclusionThe results indicated that the cell-free supernatants can be an ideal application for young larval stages of A. segetum. However, further studies are required to test the effectiveness of both EPNs and the cell-free supernatants of their symbiotic bacteria in field conditions.

An Improved Artificial Diet for Rearing Propylea japonica (Coleoptera: Coccinellidae) Larvae

Abstract Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) is an important natural enemy of insect pests of agricultural importance. An artificial diet is needed when insects upon which the predators feed are in limited supply. Larval mortality, duration of larval development, duration of the pupal stage, and adult weight were compared for various concentrations of nine ingredients of an artificial diet in an L9(3)4 multi-index orthogonal array design. A range analysis (“R” method) coupled with an integrated balance method determined that the theoretically optimal diet for P. japonica larvae was 6 g ground powder of Mythimna separata (Walker), 2 g yeast extract, 1 g sucrose, 0.08 g olive oil, and 29.42 g basic diet. After further testing, we found that this diet yielded a higher larval survival rate, longer larval period, longer pupal period, greater adult weight, and higher eclosion rate of P. japonica compared with the eight artificial diets tested.

Effect of methyl jasmonate (MeJA)-induced defenses in rice against the rice leaffolder Cnaphalocrocis medinalis (Guenèe) (Lepidoptera: Pyralidae).

Methyl jasmonate (MeJA) activates host defense mechanisms against insect pests of agricultural importance, and regulates defense responses against living and non-living stresses in various plant species. Rice leaf-folder (Cnaphalocrocis medinalis Guenèe, Lepidoptera: Pyralidae) feeding activity and mortality were evaluated after MeJA treatment of rice plants ASD-16. Rice plant resistance was activated through the topical application of MeJA to rice leaves. Feeding deterrence occurred with application of 2.5 and 5 mm MeJA solution. Feeding activity and consumption rates were significantly different, being reduced compared with controls post MeJA treatment. Significantly greater mortality was seen in second instars post treatment with 2.5 and 5 mm MeJA. Survival was significantly reduced for larvae and adults post treatment. Application of MeJA as a topical spray onto rice plants significantly altered the biology and survival of the leaf-folder, having an effect on all life stages. © 2018 Society of Chemical Industry.

Molecular ecology of insect pests of agricultural importance: the case of aphids

1. Ongoing environmental change is predicted to have a strong impact on biodiversity. Studies have already noted a range shift in many species as they track their favoured environments. A key challenge entomologists are facing is to understand how insect pest species are responding to this rapid environmental change, and molecular ecology has a central role to play in this task. In the present paper, I argue that molecular ecology has much relevance in relation to the monitoring of insect pests of agricultural importance, with a focus on aphids.2. First, I examine how the combination of phylogeography and species distribution modelling can be a powerful approach to understanding species responses to climate change and to forecasting future distributions. Despite such a joint approach being increasingly used to understand these questions (e.g. in conservation biology), there are still very few studies that concern pest species of agricultural importance.3. I then discuss how the use of samples from natural history collections represent an opportunity to directly observe the evolution of species, enhancing our knowledge of the evolutionary processes occurring at ecological time scales. I introduce the Rothamsted Insect Survey (RIS) sample archive and the central role it plays in the studies of pest species of agricultural importance.4. Lastly, I assess how the advances in DNA sequencing technologies have allowed us to investigate genetic variation at the genome‐wide level. Thus, they provide us with the opportunity of studying a variety of questions about the dynamics of pest insects that were previously impossible as well as unmanageable.

Baculoviruses: Emerging Frontiers for Viral Biocontrol of Insect Pests of Agricultural Importance

Baculoviruses: Emerging Frontiers for Viral Biocontrol of Insect Pests of Agricultural Importance

Comparative study of medicinal plants on feeding behaviour of seven day old larvae of Tobacco caterpillar, Spodoptera litura (Fab.) and Bihar hairy caterpillar, Spilarctia obliqua (Walk.)

Eight medicinal plants viz., Sinduri, Bixa orellana (Bixaceae); Dalchini, Cinnamomum zelanicum (Lauraceae); Camphora, Cinnamomum camphora (Lauraceae); Gular, Ficus racemosa (Moraceae); Arjun, Terminalia arjuna (Combretaceae); Nagkesar, Messua ferrea (Calophyllaceae); Sarpgandha, Rauwolfia serpentina (Apocynaceae); Putranjeeva, Putranjeeva roxburghii (Euphorbiaceae) at 5% and 10 % concentrations were tested for the feeding against larvae of Spodoptera litura and Spilarctia obliqua. At 10% conc. C.camphora (hexane, diethyl ether, and acetone) was found extremely antifeedant against the larvae of both insects (S.litura and S.obliqua) while C.zeylanicum (hexane, diethyl ether, and acetone) and P.roxbughii (diethyl ether, and acetone), B.orellana (Acetone) showed extremely antifeedant activity only against the larvae of S.litura. At 5% concentration, the same plants were also effective against the larvae but their efficacy was less than at 10% concentration. The observation showed promising results with these plant extracts against the feeding and management of these two insect pests of agricultural importance.

Relative Toxicity of Subspecies of bacillus Thuringiensis against Lepidopterous Insect Pests of Agricultural Importance

The relative toxicity of various subspecies of Bacillus thuringiensis (Bt) against important lepidopterous insect pests was determined. Bt kurstaki HD-1 was toxic against all the five insect pests tested; however, with low toxicity against Spodoptera litura . Larvae of Helicoverpa armigera and Pieris brassicae were five fold more susceptible to Bt kurstaki HD-73 that produces only Cry1Ac toxin. However, Bt kurstaki HD-73 was non-toxic against the larvae of S. litura and Spilarctia obliqua . Bt aizawai HD-137 was equally active against S. litura and Sesamia inferens but non toxic against P. brassicae and S. obliqua . On the other hand Bt tolworthi strain was highly toxic against P. brassicae and S. obliqua . Bt japonensis T23 001was non-toxic to all the insect pests tested. Larval growth of H. armigera was severely inhibitied at extremely low concentration of Bt kurstaki HD-73 (EC50 0.07 ng/ml) and Bt kurstaki HD-1 (EC50 0.16 ng/ml). The toxicity of indigenous Bt strains belonged to subspecies tolworthi and galleriae were also promising against H. armigera .

Diversity of <i>Bacillus thuringiensis</i> strains isolated from coffee plantations infested with the coffee berry borer <i>Hypothenemus hampei</i>

The coffee berry borer Hypothenemus hampei Ferrari (Coleoptera: Scolytidae) was first reported infecting Costa Rican coffee plantations in the year 2000. Due to the impact that this plague has in the economy of the country, we were interested in seeking new alternatives for the biological control of H. hampei, based on the entomopathogenic bacteria Bacillus thuringiensis. A total of 202 B. thuringiensis isolates obtained from Costa Rican coffee plantations infested with H. hampei were analyzed through crystal morphology of the crystal inclusions and SDS-PAGE of 6-endotoxins, while 105 strains were further evaluated by PCR for the presence cry, cyt and vip genes. Most of the Bt strains showed diverse crystal morphologies: pleomorphic (35%), oval (37%), bipyramidal (3%), bipyramidal and oval (12%), bipyramidal, oval and pleomorphic (10%) and bipyramidal, oval and cubic (3%). The SDS-PAGE analyses of the crystal preparations showed five strains with delta-endotoxin from 20 to 40 kDa, six from 40 to 50 kDa, seven from 50 to 60 kDa, 19 from 60 to 70 kDa, 29 from 70 to 100 kDa and 39 from 100-145 kDa. PCR analyses demonstrated that the collection showed diverse cry genes profiles having several genes per strain: 78 strains contained the vip3 gene, 82 the cry2 gene, 45 the cry1 and 29 strains harbored cry3-cry7 genes. A total of 13 strains did not amplified with any of the cry primers used: cry1, cry2, cry3-7, cry5, cry11, cry12 and cry14. Forty-three different genetic profiles were found, mainly due to the combination of cry1A genes with other cry and vip genes. The genetic characterization of the collection provides opportunities for the selection of strains to be tested in bioassays against H. hampei and other insect pests of agricultural importance.

Presence and significance of Bacillus thuringiensis Cry proteins associated with the Andean weevil Premnotrypes vorax (Coleoptera: Curculionidae)

The Andean weevil Premnotrypes vorax represents an important cause of damage to Colombian potato crops. Due to the impact of this plague on the economy of the country, we searched for new alternatives for its biological control, based on the entomopathogenic bacteria Bacillus thuringiensis. A total of 300 B. thuringiensis strains obtained from potato plantations infested with P. vorax were analyzed through crystal morphology, SDS-PAGE, PCR and bioassays. We used site-directed mutagenesis to modify the Cry3Aa protein. Most of the B. thuringiensis isolates had a bipyramidal crystal morphology. SDS-PAGE analyses had seven strains groups with delta-endotoxins from 35 to 135 kDa. The genes cry 2 and cry 1 were significantly more frequent in the P. vorax habitat (PCR analyses). Three mutant toxins, 1 (D354E), 2 (R345A, DeltaY350, DeltaY351), and 3 (Q482A, S484A, R485A), were analyzed to assess their activity against P. vorax larvae. Toxicity was low, or absent, against P. vorax for isolates, wild type cry 3Aa and cry 3Aa mutants. The genetic characterization of the collection provides opportunities for the selection of strains to be tested in bioassays against other insect pests of agricultural importance, and for designing Cry proteins with improved insecticidal toxicity.

Effect of temperature on survival of Steinernema seemae, S. masoodi and S. carpocapsae (Rhabditida: Steinernematidae) and their subsequent infectivity to prepupa of Helicoverpa armigera (Hübner)

The survival and infectivity of three indigenous entomopathogenic nematodes, Steinernema seemae, S. masoodi and S. carpocapsae at different temperatures (15, 20, 25, 30, 35, 40 and 45°C) were studied against prepupa of Helicoverpa armigera (Hübner). Percent survival of nematodes decreased with increases in temperature. However, 46.6% of the populations were able to survive and tolerate the sub-lethal temperature (45°C) treatment for 6 h. Out of the populations that survived, 43.3% infectivity was observed against H. armigera prepupa. The survivors did not infect at 25 and 30°C, rather their activity was found optimum. These heat tolerant isolates could play a vital role in the management of susceptible stages of H. armigera at high temperature regimes and for the management of other insect pests of agricultural importance, which pupate in the soil.

Aliphatic amino diacid Asu functions as an effective mimic of Tyr(SO 3H) in sulfakinins for myotropic and food intake-inhibition activity in insects

The aliphatic amino diacid α-aminosuberic acid can function as an effective, stable mimic of the hydrolysis-susceptible Tyr(SO 3H) group in sulfakinin neuropeptide analogs for both hindgut contractile activity in cockroach and food intake-inhibition activity in the desert locust. In the analog, the acidic sulfate group is replaced with an acidic carboxyl group. The degree of activity of sulfakinin analogs is correlated with the carboxyl/α-carbon distance in the cockroach hindgut contractile assay. The results represent an important step in the design and synthesis of biostable, sulfakinin analogs that could potentially suppress the feeding behavior of destructive insect pests of agricultural importance.

Efeito da ausência de hospedeiro e de alimento sobre aspectos biológicos de Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)

The use potential of Trichogramma genus parasitoids is huge for several insect-pests of agricultural importance. However, some biological aspects, such as parasitism capacity, viability and sexual ratio are dependent of the host availability and of food supply. This work evaluated the effect of food absence and of alternative host Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae), absence, in different time intervals, over biological aspects of three Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) strains. The fed strains sponged up to 96 hours, and when the strains were not fed one, two and three of T. pretiosum sponged for 60, 84 and 72 hours, respectively. The results indicate that alimentary stress affects the parasitism capacity of T. pretiosum, after a period of host absence