Instar Larvae Of Diamondback Moth Research Articles

Virulence of entomopathogenic nematode isolate Steinernema bicornutum against diamondback moth (Plutella xylostella L.)

Plutella xylostella L., commonly known as the diamondback moth, is a significant pest of cole crops. It has established resistance to a range of pesticides, including chemical insecticides and Bt toxins. The use of appropriate bio-agents to manage the diamondback moth is a viable alternative to chemical pesticides. The current study was carried out with the goal of using entomopathogenic nematode (EPN) isolate Steinernema bicornutum to manage diamondback moths. Laboratory studies were carried out to know the virulence and reproductive potential of an indigenous population of Steinernema bicornutum at five doses i.e., 2IJs, 5 IJs, 8 IJs, 10 IJs and 12 IJs per third instar larvae of diamondback moth. Percent mortalities were recorded after 24h, 48h and 72h of post inoculation. Maximum percent mortality (81.25) was recorded after 72h with the highest dose i.e., 12 IJs per larva and the LC50 value was 7.99 IJs/100µl. The result of reproduction and recovery of isolates of entomopathogenic nematodes revealed that the highest IJs was yielded (2255.7) from dose of 12 IJs/larva. The overall results strongly suggested that P. xylostella is more susceptible to the entomopathogenic nematode and can be the host for multiplication of entomopathogenic nematodes under laboratory conditions.

Synthesis and screening of kojic acid derivatives for their bio-efficacy against diamondback moth (Plutella xylostella L.)

Kojic acid derivatives containing urea and thiourea linkage has been synthesized and tested against second instar larvae of diamondback moth (Plutella xylostella) under laboratory conditions. Most of the compounds showed ≥ 50% mortality against second instar larvae of P. xylostella. Compound 3b was found more effective against P. xylostella (83.3% mortality at 10,000 ppm) after 96 h of treatment. Other compounds with significant mortality were 4h, 4j (80% mortality at 10,000 ppm), and 3c, 4c, 4m (76.6% mortality at 10,000 ppm). The most promising compounds among the synthesized library could be candidates for further development to obtain lead molecules.

Antifeedant and Insecticidal Effect of Hexane Botanical Extracts on Diamondback moth (DBM), Plutella xylostella L.. (Lepidoptera: Plutellidae)

Diamondback moth (DBM), Plutella xylostella L. (Lepidoptera: Plutellidae) is one of the nefarious pests of cruciferous crops. Crude extracts from six botanicals obtained using hexane by continuous hot percolation process in Soxhlet apparatus were evaluated for their effect on larval mortality, antifeedant, growth and development of second instar larvae of DBM. The results revealed that the antifeedant index of Sesbania grandiflora 5% was 20.82% followed by Swietenia macrophylla 5%, which had 15.61%. The larval mortality and adult emergence exhibited by S. grandiflora was (66.67% and 33.33% respectively) after 72 h of feeding on treated leaf. It was statistically on par with S. macrophylla, which had 63.33% larval mortality and 36.67% adult emergence. With regard to the developmental period of life stages, no significant difference was observed among the treatments. However, all the treatments were significantly superior over untreated check in prolonging the developmental period of DBM. It was concluded that the S. grandiflora and S. macrophylla hexane leaf extract 5% are promising botanicals against P. xylostella, as they possess insecticidal, antifeedant and growth inhibitory activity. These results open up the scope for further isolation of bioactive compounds and validation under field conditions, which would lead to formulation development, ultimately it can be incorporated as ecofriendly component in the integrated pest management strategies.

Improving the efficiency of Beauveria bassiana applications for sustainable management of Plutella xylostella (Lepidoptera: Plutellidae) in West Africa

The effectiveness of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin isolates Bb11, Bb115, Bb116 and Bb362 against the diamondback moth (DBM), Plutella xylostella (L.) population from Cotonou, Benin, was investigated in the laboratory and on station. In the laboratory, six concentrations, 104, 105, 106, 107, 108 and 109 conidia/ml of each isolate were used to assess B. bassiana virulence. Third instar DBM larvae were inoculated with 2 µl of each isolate’s concentrations by topical application method. Control larvae were inoculated with sterilized Tween 80 solution (0.05%). Compared with other isolates, Bb11 was more virulent against DBM with LD50 value estimated to 4.96 × 106 conidia/ml and the highest rates of cadaver sporulation. The effectiveness of Bb11 against DBM on cabbage was subsequently assessed on station and on farm in Benin and Togo, at a low doses of 53 g/ha once or twice a week and a high dose of 315 g/ha weekly. Compared with unsprayed control and deltamethrin treatments, the dose of 53 g/ha of Bb11 applied twice a week at intervals of 4 days was able to reduce on farm the density of DBM by 83% and 93%, respectively. Also, the marketable cabbage yield obtained on farm with this dose was significantly higher compared with the other treatments, with a 199% and 452% increase in Danyi and Cotonou over the unsprayed control, respectively. These results confirm the better performance of Bb11 over other isolates, and also indicate that the newly investigated application dosage and frequency of Bb11 could be an efficient management option to control DBM in Benin and Togo.

Predation on Diamondback Moth Larvae and Aphid by Resistant and Susceptible Lady Beetle, Eriopis connexa.

A successful pest control requires both chemical and biological agents for most commercially grown crops. However, insecticide resistance is increasing worldwide. Cabbage, a widely grown Brassicaceae, hosts the most resistant insect pest to insecticides, the diamondback moth (DBM), Plutella xylostella L. However, insecticide-resistant populations Eriopis connexa (Germar), a lady beetle often found controlling aphids and other soft-bodied pest species sharing brassica fields with DBM. Thus, as a model for integration of insecticide and biological control methods, we evaluated predation by pyrethroid-resistant and pyrethroid-susceptible lady beetles on DBM larvae offered alone and in the presence of a preferred prey, the aphid Lipaphis pseudobrassicae (Davis). During 24-h exposure, resistant and susceptible E. connexa consumed an average of 9.8 and 6.0 second-instar instar DBM larvae, respectively. Resistant beetles showed no significant preferences for prey consumption between untreated and deltamethrin-treated leaf surfaces, at field-recommended rate. As a function of DBM availability, resistant beetles exhibited similar predation on treated and untreated arena and higher predation than susceptible beetles in a treated arena. In greenhouse cages, resistant and susceptible beetles exhibited similar survival after 10days on cabbage treated with deltamethrin and promoted the reduction of DBM to 5.0% and 5.6%, respectively. Both populations fed on a mixed diet of aphids and DBM larvae even under high availability of the preferred aphid prey. Resistant E. connexa survives deltamethrin exposure and do not alter their predatory behavior in response to this insecticide-treated environment.

Larvicidal action of Nux-vomica (Strychnus nux-vomica L.) against Diamond back moth (Plutella xylostella L.)

The present investigation reports on larvicidal efficacy of plant extracts of Nux-vomica, Strychnus nux-vomica against Diamond back moth (DBM). In this investigation shade dried and powdered nux-vomica plant sam-ples (leaves, root bark, stem bark, seed and fruit rind) were extracted with organic solvents ethanol, methanol, ace-tone, hexane and chloroform and also formulated as Emulsifiable Concentrates (EC) using surfactant and solvents. This formulated plant extracts were tested against third instar larvae of DBM for larvicidal efficacy using leaf disc bioassay method under laboratory condition. Among the five solvent extracts tested, hexane extracts of root bark 11.11 EC @ 2 % showed highest larval mortality of 76.66 % followed by seed 14.25 EC, leaf 16.66 EC, stem bark 12.50 EC and fruit rind 12.50 EC extracts exhibited maximum mortality @ 2 % concentration recording 66.66, 63.33, 56.66 and 40.00 per cent mortality respectively. Positive and negative control such as respective solvent and water showed 10.00 and 3.33 % larval mortality respectively. The results of these experiment clearly indicate that nux-vomica plant possess promising larvicidal action against diamond back moth.

Larvicidal activity and structure activity relationship of cinnamoyl amides from Zanthoxylum armatum and their synthetic analogues against diamondback moth, Plutella xylostella.

Cinnamoyl amides isolated from Zanthoxylum armatum (Rutaceae) and their synthetic analogues were tested for their insecticidal activity against the second instar larvae of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) to determine the promising structures with insecticidal activity. Most of the test compounds showed promising activity against larvae of P. xylostella. However, the activities of different compounds varied depending on the presence of different substituents at various positions of both the aromatic rings A and B. Among the tested compounds, 8, N-(3-bromo-4-methoxyphenethyl)cinnamamide showed best larvicidal activity with an LC50 = 62.13 mg/L followed by 6, N-(3׳-bromophenethyl)cinnamamide (LC50=128.49 mg/L) and 2 N-(4׳-methoxyphenylethyl)cinnamamide (LC50 = 225.65 mg/L).

Effects of tea saponin on growth and development, nutritional indicators, and hormone titers in diamondback moths feeding on different host plant species

The diamondback moth (DBM) is an important worldwide pest. This insect has been studied for several decades; however, its control remains problematic. Numerous chemical insecticides have become ineffective and chemical residues constitute an important problem. In the present study, we determined the mortality of 3rd instar DBM larvae feeding on three different host plant species and exposed to various concentrations of tea saponin (TS). In addition, we evaluated growth and development parameters, nutritional indicators, and juvenile hormone (JH) and molting hormone (MH) titers in 2nd instar larvae exposed to LC20 and LC50 doses of TS. We found that treatment of DBM larvae with LC20 and LC50 doses of TS led to lower growth rates, decreased feed consumption, reduced frass production, lower pupal weights, reduced percentage pupation, slower adult emergence percentages, and diminished fecundity, but prolonged durations of the larval and pupal periods. The efficiency of conversion of ingested and digested food increased, but the approximate digestibility did not differ significantly between treatments and controls. JH and MH titers were higher after TS treatment; these increases varied according to the host species and TS concentration. Our results indicate that TS represents a potential new alternative insecticide based on its natural origin, low cost, and minimum environmental impact.

Effect of partial plant resistance in brassicas on tolerance of diamondback moth (Plutella xylostella) larvae to cypermethrin

Brassica cultivars with varying degrees of partial plant resistance were fed to larvae (up to 4th instar) of the diamondback moth (DBM), Plutella xylostella, and were bioassayed by topical application of cypermethrin to investigate the interaction of plant resistance with insecticide. Larvae reared on the least preferred brassica, Minicole, showed a significantly higher LD50 value than those on the most preferred brassica, Chinese cabbage. Bioassay of 4th instar DBM larvae fed on artificial diet containing pure compounds of glucosinolates revealed a negative interaction between their susceptibility to cypermethin and certain glucosinolates (in particular sinigrin), suggesting that such compounds induced the production of insecticide-detoxifying enzymes.

Insecticidal potential of Paenibacillus elgii HOA73 and its combination with organic sulfur pesticide on diamondback moth, Plutella xylostella

Diamondback moth, Plutella xylostella, is one of the most destructive insect pests of several crops world-wide. Effects of Paenibacillus elgii HOA73 and its combined application with organic sulfur pesticide on Plutella xylostella were evaluated. Results showed that M3 medium composition indicated the best medium for optimization of bacterial colony growth, hydrolytic enzyme production, and insecticidal activity and was selected for culturing P. elgii HOA73 in further assays. The highest colony growth of P. elgii HOA73 was identified at 5 days after inoculation. Extracted crude enzyme and crude insecticidal compound from P. elgii HOA73 cultured in the optimized medium kill the second instar larvae of Diamondback moth in 40 and 50% at 220mg mL−1 of crude enzyme and 2% crude extract, respectively. Combined application of organic sulfur pesticide with bacterial suspension significantly killed 85% second instar larvae of Diamondback moth, when compared to use of single application: bacterial suspension (65%) and organic sulfur pesticide (38%), suggesting that P. elgii HOA73 combined with organic sulfur pesticide could be used to control P. xylostella.

Relative toxicity of insecticides against diamondback moth (Plutella xylostellaL.) in cabbage (Brassica oleraceavar.capitata)

An experiment was conducted to evaluate the relative toxicity of some insecticides against 3rd instar larvae of diamondback moth, Plutella xylostella L. on cabbage (Brassica oleracea var. capitata) during 2007–08 and 2008–09. The order of relative toxicity of insecticides on the basis of LC50 values were spinosad > B.t.k. > cartap-hydrochloride > cypermethrin > quinalphos > endosulfan > azadirachtin. Spinosad had maximum relative toxicity (113.95) with lower LC50 values, 0.00038; whereas azadirachtin had lower relative toxicity (0.014) with higher LC50 values, 3.1565.

High-Level Expression of Sporamin in Transgenic Chinese Cabbage Enhances Resistance Against Diamondback Moth

This study introduced the protease inhibitor-encoding gene sporamin from sweet potato together with the wound-responsive promoter pMSPOA into the Chinese cabbage (Brassica campestris ssp. chinensis var. parachinensis) through Agrobacterium tumefaciens-mediated transformation. Transgenic lines were confirmed via PCR detection of both the sporamin and hygromycin gene fragments in the cloning vector. The expression level of sporamin in the different lines was determined using RT-PCR analysis. Leaves from four individual transgenic lines including T0-2, T0-3, T0-4 and T0-5, possessing higher levels of sporamin than control plants, were then used to conduct insect feeding studies. Second instar larvae of diamondback moth (Plutella xylostella L.) were used in feeding assays. All four transgenic lines demonstrated high levels of resistance against diamondback based on average body weight of total incubated larvae following feeding assays and amount of leaf damage.

Effects of Nosema Infection on Ovipositional Preference and Larval Performance of Plutella xylostella (L.) (Lepidoptera: Plutellidae), on Some Brassica Plants

Biological control, using pathogenic microsporidia, may have the potential to be an alternative to chemical control against the diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae). The microsporidium, Nosema bombycis (NB), is one of many disease agents that can be used in the Integrated Pest Management (IPM) of DBM. Nosema bombycis affected DBM fecundity negatively and may affect its preference to lay eggs on particular host plant species. To investigate this, infection was performed on second instar larvae of DBM and the emerged adults were released into cages in greenhouse. A choice experiment with whole plants was conducted with four selected hosts: rape leaves, Brassica juncea, green mustard, B. Chinese, cabbage, B. Oleracea and pak choi, B. Rapa to examine adult oviposition preference for both untreated and N. Bombycis-infected DBM. P. xylostella performance (larvae hatched, pupae developed, adults emerged and developmental time for each stage) parameters were also conducted using mean values for each host plant and the results showed that it varied between plants. For untreated DBM, rape plants were the most preferred for oviposition, and more eggs were laid by DBM on rape than either green mustard or pak choi while oviposition was lowest on cabbage. However, the infected DBM exhibited no significant different in egg laying preference between rape, green mustard and pak choi with low number of egg laid irrespective of host plants. Interestingly, Normal and Nosema-infected DBM adults showed an unattractive egg laying behaviour to cabbage.

The in vitro efficacy of a Zimbabwean isolate of Zoophthora radicans Brefeld (Batko) in the control of Lepidoptera larvae infesting Brassica sp.

The use of microbes in pest control is an important aspect of integrated pest management (IPM). A Zimbabwean isolate of the fungal entomopathogen Zoophthora radicans was tested for efficacy in the control of Brassica infesting lepidopteran larvae. Z. radicanscaused 98.68% mortality on small (1st - 2nd instar) diamondback moth (Plutella xylostellaL.) larvae and 21.34% mortality on large (3rd - 4th instar) diamondback moth (DBM) larvae 6 days after treatment. Z. radicans was not effective against larvae of Helicoverpaarmigera, webworm (Hellula undalis), cabbage moth (Crocidolomia sp.) and cabbage looper (Trichoplusia ni). There was no significant difference (p > 0.05) in adult Cotesia plutellae emergence from cocoons treated with Z. radicans and cocoons sprayed with water. There was 95% emergence of C. plutellae adults from cocoons treated with Dimethoate 40 EC. No adults of C. plutellae emerged from cocoons treated with Carbaryl 75 WP, Malathion 25 WP and Malathion 50 EC. The study showed that Z. radicans was effective against early instar DBM larvae and did not have adverse impacts on the emergence of C. plutellae adults from cocoons and Diaeretiella rapae adults from aphid mummies. Key words: Zimbabwe, Zoophthora radicans, efficacy, in vitro, Lepidoptera, Brassica spp.

Potential of Mammea siamensis as a botanical insecticide: Its efficiency on diamondback moth and side effects on non-target organisms

Nine species of local Thai medicinal plant extracts with known insecticidal properties that is,Acorus calamus, Eugenia caryophyllus, Mammea siamensis and 6 species of Stemona(Stemona curtisii, Stemona tuberosa, Stemona burkillii, Stemona kerrii, Stemona unknown 1 and Stemona unknown 2) were screened for the highest insecticidal activity by the brine shrimp lethality test (BST). M. siamensis showed a very strong toxic effect on brine shrimp with the lowest 24 h LC50 value of 0.072 µgml-1. The purification of its active compound was conducted using chromatographic methods and the BST to select the most effective fraction. The spectroscopic methods were used for the identification of the active compound. Surangin B was finally identified as the active compound. Its insecticidal effectiveness on the 3rd instar larvae of diamondback moth was investigated by topical application and leaf dipping methods in comparison with methomyl. The results indicated that surangin B demonstrated high in both contact and anti-feedant activities than methomyl. According to its side effects on non-target organisms, M. siamensis exhibited no negative impact on earthworm and honeybee. In contrast, it showed a higher toxicity on fish than methomyl. From the results it can be concluded, that M. siamensis might be one of the natural insecticides for the diamondback moth management. Key words: Plutella xylostella Linn., botanical insecticide, surangin B, bioactive compound.

Sub-Lethal Effects of Fenvalerate on the Development, Fecundity, and Juvenile Hormone Esterase Activity of Diamondback Moth, Plutella xylostella (L.)

The toxicities of fenvalerate (20% EC) to the 3rd instar larvae of diamondback moth (DBM), Plutella xylostella (L.), reared on three host plants viz., radish, oilseed rape, and cabbage were tested. The LC 50 values of fenvalerate to the 3rd instar larvae of DBM varied with host plants, however, there wasn't any significant difference among them ( P > 0.05). Similarly, DBM fed on three host plants had same pupal weight, pupal period, pupation rate, adult emergence rate, female ratio, and fecundity. The activity of juvenile hormone esterase (JHE, EC 3.1.1.1) in the 3rd instar larvae of DMB did not significantly vary with host plants, either. These suggested that DBM had similar fitness on the three host plant species. When fed on the host plants pretreated with fenvalerate at the concentrations equivalent to LC 20, LC 50 and LC 80, the pupation rate, pupal weight, adult emergence rate, female ratio, fecundity, and JHE activity of the tested insects were declined as compared with insects in control treatments fed on the same host plant species. Furthermore, the pupal period of the tested insects was extended after fenvalerate treatment. The decrease in JHE activity after fenvalerate treatment in the tested insects could partly explain the changes in the mentioned growth parameters. Whether the role of fenvalerate in the inhibition of JHE activity could serve as a new way to control DBM needs further investigation.

Interaction between Short-Term Heat Pretreatment and Fipronil on 2 Instar Larvae of Diamondback Moth, Plutella Xylostella (Linn).

Based on the cooperative virulence index (c.f.) and LC(50) of fipronil, the interaction effect between short-term heat pretreatment and fipronil on 2(nd) instar larvae of diamondback moth (DBM), Plutella xylostella (Linnaeus), was assessed. The results suggested that pretreatment of the tested insects at 30 °C for 2, 4 and 8h could somewhat decrease the toxicity of fipronil at all set concentrations. The LC(50) values of fipronil increased after heat pretreatment and c.f. values in all these treatments were below zero. These results indicated that real mortalities were less than theoretical ones and antagonism was found in the treatments of fipronil at 0.39 and 0.78 mg/L after heat pretreatment at 30 °C at 2, 4 and 8 h. However, pretreatment at 30 °C for 12h could increase the toxicity of fipronil at all set concentrations, the LC(50) of fipronil decreased after heat pretreatment and c.f. values in all these treatments were above zero, which indicated real mortalities were higher than theoretical ones. Pretreatment of the tested insects at 35 °C for 2, 4, 8 and 12h was found to increase the toxicity of fipronil at all set concentrations which resulted in the decrease of LC(50) values of fipronil and c.f. above zero in all treatments with only one exception. Most interactions were assessed as synergism. The results indicated that cooperative virulence index (c.f.) may be adopted in hormetic effect assessment.

Interaction between short-term heat pretreatment and avermectin on 2nd instar larvae of diamondback moth, Plutella xylostella (Linn).

Based on the cooperative virulence index (c.f.), the interaction effect between short-term heat pretreatment and avermectin on 2(nd) instar larvae of diamondback moth (DBM), Plutella xylostella (Linnaeus), was assessed. The results suggested that the interaction results between short-term heat pretreatment and avermectin on the tested insects varied with temperature level as well as its duration and avermectin concentration. Interaction between heat pretreatment at 30 degrees C and avermectin mainly resulted in addition. Meanwhile, pretreatment at 35 degrees C for 2 or 4 h could antagonize the toxicity of avermectin at lower concentrations, which indicated a hormetic effect occurred. The results indicate that cooperative virulence index (c.f.) may be adopted in hormetic effect assessment.

Persistence of the pesticidal Bacillus thuringiensis protein expressed in Bt maize plant materials in two soils of the Central Eastern Cape, South Africa

Environmental effects of genetically modified plants are not yet fully understood. Experiments were conducted to determine relative amounts of the bioactive Bt protein in roots, leaves and stems of Bt maize and persistence of the protein in two soil forms (Shortlands and Oakleaf). The Bt protein activity was bioassayed using 2nd to 3rd instar larvae of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). Bioassay results showed that the extracts from different parts of Bt maize plants were equally toxic and caused overall larval motility of over 70%. It was also found that two years' storage of dried Bt maize material at room temperature, did not reduce the pesticidal activity of the protein toxin. When Bt maize plant materials were incubated'in soils for two weeks under glasshouse conditions, the extracted toxin caused 20% larval mortality and within 7 weeks of incubation in both soils, the extracts obtained caused <10% larval mortality. However, extracts obtained from Bt maize plant materials incubated in the field showed decreased larval mortality, from 60% to 30% in two weeks and remained >25% after 12 weeks of incubation in the Shortlands soil and from 55% to 15% within four weeks and eventually down to 10% in 23 weeks of incubation in the Oakleaf soil. The findings suggest that Bt maize plant parts contribute comparable amounts of Bt protein toxin to the soil, and toxin persistence in the soil appears to depend on soil type, and temperature and moisture conditions.

Storage Proteins of Diamondback Moth, Plutella xylostella: Purification and Expression Profile

Storage proteins (SPs) were significantly detected in the hemolymph during the late instar larvae of diamondback moth, Plutella xylostella. These SPs were resolved into three proteins (SP1, SP2, and SP3) at 7% SDS-PAGE. Their apparent molecular sizes were around 80 kDa. SP1 was synthesized later than SP2 and SP3 during the development of the last instar. Total soluble proteins of last instar larvae were extracted and fractionated sequentially with ammonium sulfate, size-exclusion chromatography, and ion-exchange chromatography. The SPs were purified and their developmental expression was discussed.