Bioefficacy of three promising predators on Myzus nicotianae Blackman (Homoptera: Aphididae).
Notice bibliographique
Résumé
Coccinella transversalis Fab., Cheilomenes sexmaculata (Fab.) and Chrysoperla carnea Stephens were evaluated for their bio-efficacy against the tobacco aphid, Myzus nicotianae Blackman under field conditions. Based on the results of a feeler trial under greenhouse conditions, the predators were tested at two dosages of release (i.e., 8 and 16 larvae/plant) and three schedules of release (i.e one release @5 weeks after planting (WAP), two releases @ at 5 & 7 WAP and three releases @ 5, 7 & 9 WAP. The efficacy of the predators was measured in terms of the density of the aphid, both before and after the release of the predators, besides estimating the reduction in the density of the aphid at 6, 8 and 10 WAP. Among the three predators evaluated, C. transversalis gave the significantly highest reduction in aphid density at 6 WAP (54.38%), 8 WAP (60.42%) and 10 WAP (59.96%), thus indicating that C.transversalis was relatively more superior then the other two predators in the suppression of the aphid population under field conditions. INTRODUCTION The current total global production of tobacco is 6 billion kg. Nearly one-third of India’s total tobacco production comprises of Virginia flue-cured (VFC) tobacco which is utilized in the manufacture of cigarettes. It is the principal export-oriented variety of tobacco and as much as 50 per cent of India‘s total production of VFC tobacco is exported to foreign countries. India produces about 300 million kg. of VFC tobacco and occupies third place after China and USA (Anonymous, 2009). Among the tobacco growing states Andhra Pradesh, Karnataka and Gujarat are important. In Karnataka, VFC Tobacco production is mainly concentrated in the districts of Mysore, Shimoga and Hassan. However, tobacco is plagued by several insect pests throughout its growth and developmental stages, of which the tobacco aphid, Myzus nicotianae Blackman (Homoptera : Aphididae) assumes significance, particularly since it not only feeds on the plant sap but also produces honeydew on which sooty mould grows and spoils the leaf quality (McPherson et al., 1989), the aphid activity also hinders the curing process of VFC Tobacco and it is also known to transmit several viral diseases. This pest has got serious implications on VFC Tobacco production, particularly considering the fact that India is one of the top twelve flue-cured tobacco producers in the world. India occupies second place in area, third place in production and eighth place in exports of VFC Tobacco (Chari, 1995). The aphid, M. nicotianae has been reported to be most serious in USA during 1987 and 1988 and also in south eastern Canada (Lampert, 1989). This pest broke out in epidemic form in Andhra Pradesh during 1990-91 and 1991-92 seasons, during which the economic threshold level (ETL) has been estimated to be around 2 per cent or lesser (Anon, 199293). In this context, feeler studies conducted under laboratory and green house proved the usefulness of 3 predators, viz., C. transversalis, C. sexmaculata and C. carnea in the suppression of the aphid . Therefore, the present investigation was conducted to evaluate their performance in actual field situation so as to develop suitable bio-control strategies for the management of this pest in VFC tobacco. MATERIALS AND METHODS Bioefficacy of C. transversalis, C. sexmaculata and C. carnea of these predators were tested at the following dosages and schedules, which was decided based on the results of the feeler study conducted earlier under green house conditions in two doses like D1 [8 larvae/plant (early second instar larvae)] and D2 [16 larvae/plant (early second instar larvae)] with three release schedules viz., S1 [one release/spray at 5 week after planting (WAP)], S2 [two release/sprays, one each at 5 & 7 WAP)] and S3 [three release/sprays, one each at 5, 7 & 9 WAP)]. Monocrotophos (@ 2 ml/litre) was used as the standard recommended check. The design of the experiment followed was three factor RCBD with three replications. Each treatment plot was separated from the neighboring treatments by a distance of 1 metre all around the plot. One observation on aphid density was recorded one day © JBiopest. 96 Predators on Myzus nicotianae
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
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