Synergistic effect of naturally occurring Granulosis virus isolates (PbGV) with phagostimulants against the cabbage butterfly, Pieris brassicae (L.) for its eco-friendly management

Background To manage the cabbage butterfly, Pierisbrassicae (L.) (Lepidoptera: Pieridae), it is not wise to use insecticides on leafy vegetables which are eaten mostly fresh. During the past decades, the efforts to manage the pest, through chemical insecticides have raised serious health. Investigations were carried out to isolate naturally occurring GVs (PbGV) as a potent biopesticide against P.brassicae and to explore their efficacy with the application of phagostimulants. Results Among the four naturally occurring isolates obtained from Northwestern Himalayas, Sudhmahadev isolate was found to be the most promising based on virulence and speed of kill against all the instars tested in the laboratory, showing the natural incidence of PbGV infection in field conditions. In concentration and time–response bioassay, all the isolates of P.brassicae Granulosis virus were found high virulent against second instar larvae of cabbage butterfly. Therefore, for enhanced efficacy of PBGV, its combined application with phagostimulants (Lepidiumsativum + Teepol + jaggery) or sticker (Teepol + jaggery), applied in field trials, resulted into greater mortality of larval instars than the single one. Overall, the results indicated that the introduction of a more isolates PBGV strain into populations of P.brassicae could be of vital importance for eco-friendly suppression of this pest globally with the combination of phagostimulants. The application virus alone with the pre-standardized concentration of 1 × 1012 OBs/ha did not reduce the larval population density to the desirable extent in the greenhouse chamber and therefore was not included in field experiments. Overall, the most promising treatments in reducing the larval population of the pest were PbGV + Teepol + B.thuringiensis (93.49 and 91.39%) and PbGV + Teepol + L.sativum (88.79 and 86.97%) over control in both greenhouse and field trials, respectively. Conclusions In this study, the native isolates of PbGV from different target locations to test their efficacy against different instars of P.brassicae were explored. Using native PBGV isolates with phagostimulant combinations played an important role for regulating the pest effectively. These phagostimulants not only protected the OBs from degradation in the presence of sunlight but also increased the speed of killing. The biocontrol potential of PbGV in both laboratory and field conditions indicated that baculoviruses are sustainable alternative to chemical insecticides.

The Evolution of Host Specialization in an Insect Pathogen

Niche breadth coevolution between biotic partners underpins theories of diversity and co-existence and influences patterns of disease emergence and transmission in host-parasite systems. Despite these broad implications, we still do not fully understand how the breadth of parasites’ infectivity evolves, the nature of any associated costs, or the genetic basis of specialization. Here, we serially passage a granulosis virus on multiple inbred populations of its Plodia interpunctella host to explore the dynamics and outcomes of specialization. In particular, we collect time series of phenotypic and genetic data to explore the dynamics of host genotype specialization throughout the course of experimental evolution and examine two fitness components. We find that the Plodia interpunctella granulosis virus consistently evolves increases in overall specialization, but that our two fitness components evolve independently such that lines specialize in either productivity or infectivity. Furthermore, we find that specialization in our experiment is a highly polygenic trait best explained by a combination of evolutionary mechanisms including conditionally positive fitness asymmetries and mutation accumulation. These results are important for understanding the evolution of specialization in host-parasite interactions and its broader implications for co-existence, diversification, and infectious disease management.

Effects of Larval Density on Plutella xylostella Resistance to Granulosis Virus

It has been reported that some phase-polyphenic insects from high-density conditions are more resistant to pathogens than those from low-density conditions. This phenomenon is termed “density-dependent prophylaxis” (DDP). However, whether non phase-polyphenic insects exhibit DDP has rarely been elucidated. The diamondback moth (DBM), Plutella xylostella, one of the most destructive insect pests affecting cruciferous crops, is non phase-polyphenic. In this study, the resistance of DBM larvae to P. xylostella granulosis virus (Plxy GV) and their immune response to the virus when reared at densities of 1, 2, 5, 10, 15, and 20 larvae per Petri dish were investigated under laboratory conditions. Compared with larvae reared at lower densities, larvae reared at moderate density showed a significantly higher survival rate, but the survival rate significantly decreased with further increases in rearing density. Furthermore, the phenoloxidase, lysozyme and antibacterial activity and total hemocyte count in the hemolymph of the larvae, regardless of whether they were challenged with the virus, from different larval densities corresponded to the observed differences in resistance to Plxy GV. These results demonstrated that P. xylostella larvae exhibited DDP within a certain limited density. This study may help to elucidate the biocontrol effect of different density populations of P. xylostella by granulosis virus and guide improvements in future management strategy.

PATOGENISITAS Achaea janata GRANULOSIS VIRUS (AjGV) TERHADAP ULAT PEMAKAN DAUN TANAMAN JARAK KEPYAR

<p>ABSTRAK<br />Achaea janata L. adalah hama penting tanaman jarak kepyar<br />(Ricinus communis) yang hingga kini pengendaliannya masih<br />menggunakan insektisida kimia secara intensif. Selain tidak efisien,<br />insektisida kimia juga menimbulkan pencemaran lingkungan. Untuk<br />mengatasi masalah tersebut, maka perlu cara pengendalian alternatif yang<br />selain efektif dan efisien, juga ramah lingkungan, seperti virus yang<br />diisolasi dari ulat A. janata (A. janata Granulosis Virus/AjGV). Penelitian<br />patogenisitas AjGV pada A. janata dilakukan di Laboratorium Patologi<br />Serangga Balai Penelitian Tanaman Pemanis dan Serat (Balittas) mulai<br />Januari - Desember 2012. Perlakuan terdiri atas enam konsentrasi AjGV,<br />yaitu 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 occlusion bodies (OB), dan satu kontrol.<br />Perlakuan disusun dalam Rancangan Acak Kelompok dengan empat kali<br />ulangan. Ulat A. janata yang digunakan adalah instar II, III, IV, dan V<br />masing-masing 90 ekor/perlakuan. Parameter yang diamati adalah<br />mortalitas dan bobot ulat, konsentrasi untuk membunuh 50% ulat (LC 50 ),<br />dan waktu untuk membunuh 50% ulat (LT 50 ). Hasil penelitian<br />menunjukkan bahwa AjGV patogenik terhadap A. janata, terutama ulat<br />instar II dan III dengan mortalitas berturut-turut 90 dan 86,7%. LC 50 AjGV<br />pada ulat instar II dan III masing-masing mencapai 1,0 x 10 3 dan 1,2 x 10 3<br />OB/ml, dengan LT 50 kedua instar sekitar 3,4-4,2 hari. Pengaruh infeksi<br />AjGV pada ulat A. janata efektif menurunkan bobot ulat hidup 57,9 dan<br />57,4% masing-masing pada ulat instar II dan III. Hasil penelitian ini<br />mengindikasikan bahwa sasaran yang tepat untuk pengendalian ulat A.<br />janata dengan AjGV di lapangan adalah pada saat instar II dan III.<br />Kata kunci: Achaea janata L, patogenisitas, instar, mortalitas</p><p>ABSTRACT<br />Achaea janata L. is an important insect pest of castor plant (Ricinus<br />communis L.) that was intensively controlled by chemical insecticide<br />caused inefficiency and an environmental polution. To solve the problems<br />it needs an effective, efficient and environmental friendly of alternative<br />control, especially using Granulosis Virus isolated from A. janata larvae<br />(AjGV). Study on pathogenicity of A. janata virus isolate against castor<br />leaf-eater, A. janata L. was conducted at Insect Pathology Laboratory of<br />Indonesia Sweetener and Fibre Crops Research Institute in Malang from<br />January to December 2012. The objective of study is to test the<br />pathogenicity of AjGV against A. janata larvae. Treatment consists of six<br />concentrations of AjGV, viz. 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 OBs/ml and one<br />control. Four instars of larvae, e.g. second, third, fourth, and fifth were<br />used in this study. Each treatments was arranged in Randomized Block<br />Design with four replications. Parameter recorded were mortality and<br />weight of larvae, LC 50 , and LT 50 . Result showed that AjGV was pathogenic<br />to A. janata larvae, mainly on second and third instar in resulting of 90%<br />and 86.7% of mortality, respectively. The LC 50 of AjGV on the second and<br />third instar was 1.0 x 10 3 and 1.2 x 10 3 OB/ml, respectively and the LT 50<br />was 3.4 and 4.2 days, respectively. Infection of A. janata virus reduced<br />the weight of both instar up to 57.9% and 57.4%, respectively. This result<br />indicated that the second and third was the suitable instars of A. janata<br />larvae for better control of AjGV in field.<br />Key word: Achaea janata L, pathogenicity, instar, mortality</p>

Codling moth (Cydia pomonella) mating disruption outcomes in apple orchards

New Zealand apple growers need to produce crops that satisfy conflicting export market requirements Some markets want pestfree fruit while others demand residuefree fruit Pheromone mating disruption combined with the judicious use of insecticides enables crops to meet both demands This study in 14 Hawkes Bay apple orchards showed that seasonal pheromone trap catch was reduced by 70 from 401 codling moths/trap in the season before mating disruption was introduced to 117 moths/trap over the subsequent five seasons In the same period insecticide use reduced from 59 applications/season in 2006 07 to 23 in 200708 and 37 since 200809 The incidence of larvae in fruit where mating disruption operated averaged 001 which was lower than in orchards using insecticides only Damage increased from 200809 with greater reliance on codling moth granulosis virus over residual insecticides Nevertheless mating disruption with 34 insecticide sprays controlled codling moth to the high standard needed