Advertisement

Exochomus Troberti Mulsant (Coleoptera: Coccinellidae): A Predator of Cassava Mealybug, Phenacoccus Manihoti Mat-Ferr (Homoptera: Pseudococcidae) in Southeastern Nigeria

  • Ethel-Doris N. Umeh
Research Article

Abstract

The developmental periods of the immature stages of Exochomus troberti Mulsant were studied in the laboratory at the prevailing temperature range of 26–30°C. That of the second instar larva was the shortest (2.1 days) followed by the third instar larva (3.1 days). The longest developmental period (approximately 5 days) was recorded for the egg, first- and fourth-instar larvae and pupa.

Oviposition commenced after 1 week of adult life and peaked in the 5th week with 37.2 female eggs/female. All ovipositing females survived the first 9 weeks of adult life when 82% of the total eggs were laid. By the 13th week, which was the effective end of reproduction (98 % fecundity) only 40% of the females had died.

Both capacity for increase (rc) and intrinsic rate of increase (rm) were calculated for E. troberti and found to be 0.092/day and 0.105/day, respectively.

Mean daily predation rates in non-choice experiments on the second instar nymphs of P. manihoti by the fourth, third and second instar larvae of E. troberti were 28.3, 15.6 and 8.0, respectively. On the third instar nymphs and fourth instar young adults of P. manihoti the mean daily predation rates by the fourth, third and second instar larvae of E. troberti Were 17.6, 8.3 and 4.5; and 4.0, 3.0 and 1.0, respectively.

The populations of E. troberti, other coccinellid predators and P. manihoti were monitored in two small local farms for three seasons. E. troberti was found to be the dominant coccinella predator in terms of numbers of individuals found in the field during the years of this experiment.

The cyclical population oscillations of P. manihoti were similar in all the experimental years but differed only in the amplitude of oscillations. Those of E. troberti and the other coccinellid predators were lower than those of P. manihoti.

Key Words

Exochomustroberti Phenacoccus manihoti oviposition capacity for increase intrinsicrate of increase predation potential 

Résumé

Les périodes developpement des stades larvaires chez Exochomus troberti Mulsant ont été étudiées dans le laboratoire à la température amblarte comprise entre 26 et 30°C. Celle de la larve du deuxième stade fut la plus courte (2, 1 jours) suivie de la larve de troisième stade (3, 1 jours). La plus longue durée de developpement (environ 5 jours) a été notée pour l’oeuf, la larve du premier et quatrième stade et la pupe.

L’oviposition a commencé après un semaine de vie adulte et le pic a été achévé dans la cinquième semaine avec 37, 2 oeufs femelles/femelle. Toutes les femelles en oviposition ont survecu les neuf premières semaines de vie adulte, alorsque 82 % de la totalité des oeufs ont été pondus. Lors de la 13e semaine qui était la fin effective de la reproduction (98% de fecondité) seulement 40% des femelles étaient mortes.

La capacité d’accroisement (rc) et la taux intrinsèque d’accroisment (rm) ont été calculés chez E. troberti et furent respectivement 0,092/jour et 0,105/jour. La déstruction moyenne quotidienne des nymphs du deuxième stade de P. manihoti par les larves du quatrième, troisième et deuxième stade de E. troberti était respectivement 28, 3, 15,6, et 8,0. Sur les nymphs du troisième, stade et les jeunes adultes du quatrieme stade des P. manihoti, la destruction moyenne quotidienne par les larvesdu quatrième, troisième, et deuxième stade de E. troberti étaient respectivement 17,6,8, 3, et 4,5; et 4,0, 3,0 et 1,0.

Les populations de E. troberti, des autres prédateurs coccinellidés et de P. manihoti ont été observées dans deux petites fermes locales pendant trois saisons. Les souches de E. troberti sont apparus comme les prédateurs dominants en fonction du nombre des individus trouvés sur place pendant la durée de cette experience.

Les cycles d’oscillations de la population chez P. manihoti étaient similaires lors de chaque année d’expérimentation mais différaient seulement par l’amplitude des oscillations. Ceux de E. troberti et des autres prédateurs coccinellidés étaient plus bas que ceux du P. manihoti.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Akinlosotu, T. A. and Leuschner, K. (1979) Outbreak of the green spider mite Mononychellus tanajoa (Bondar) and the cassava mealybug Phenacoccus manihoti Mat-Ferr. on cassava in southwestern Nigeria. Special Project Report. (IAR & T and UTA).Google Scholar
  2. DeBach, P., Rosen, D., and Kennett, C. E. (1971) Biological control of coccids by introduced natural enemies, in Biological Control (Edited by Huffaker C. B.), pp. 165–194. Plenum Publishing, New York, U.S.A.Google Scholar
  3. Doutt, R. L., and DeBach, P. (1964) Some biological control concepts and questions. In Biological Control of Insect Pests and Weeds (Edited by DeBach P.), pp. 118–142, Stamford, Connecticut, Reinhold Publishing, USA.Google Scholar
  4. Fabres, C. and Kiyindou, A. (1984) Comparative bioecology of two coccinellids, predators of the cassava mealybug in the Congo. In Proceedings of the Second Triennial Symposium of the International Society for Tropical Root Crops—Africa Branch held in Douala, Cameroon, 14–19 August 1983. IDRC, Ottawa, Ontario, pp. 93–96.Google Scholar
  5. Greathead D.J. (1971) Review of biological control in the Ethiopian Region. Technical Communication, London, England, Commonwealth Institute of Biological Control, 5.Google Scholar
  6. Iheagwam, E. U. (1981) The influence of temperature on increase rates of the cassava mealybug Phenacoccus manihoti Mat-Ferr. (Homoptera, Pseudococcidae). Rev. Zool. Afr. 95: 859–967.Google Scholar
  7. UTA (International Institute of Tropical Agriculture) (1980) Research highlights 1980. Ibadan, Nigeria.Google Scholar
  8. Laughlin, R. (1965) Capacity for increase: a useful population statistic. J. Anim. Ecol. 34: 77–91.CrossRefGoogle Scholar
  9. Nwanze, K. F. (1978) Biology of cassava mealybug Phenacoccus manihoti Mat-Ferr. in the Republic of Zaire — pp. 20–28. In Proceedings of the International Workshop on the Cassava Mealybug Phenacoccus manihoti Matt-Ferr. (Pseudococcidae) (Edited by Nwanze, K. F. and Leuschner K.) held at Inera-M’Vuazi, Bas-Zaire. 26–29 June 1977, International Institute of Tropical Agriculture, Ibadan, Nigeria.Google Scholar
  10. Parker, F. D. (1970) Seasonal mortality and survival study of Pieris rapae (L.) in Missouri and introduction of an egg parasite, Trichogramma evanescens Westwood. Ann. Entomol. Soc. Am. 24: 1–27.Google Scholar
  11. Sailer, R. I. (1974) Foreign exploration and importation of exotic arthropod parasites and predators. In Proceedings of the Summer Institute on Biological Control of Plants, Insects and Diseases (Edited by Maxwell, F. G., and Harris F. A.), University Press of Mississippi, Jackson, Mississippi, USA.Google Scholar
  12. Umeh E.-D. N. (1982) Biological studies on Hyperaspis marmottani Fairm. (Coleoptera, Coccinellidae), a predator of the cassava mealybug Phenacoccus manihoti Matt-Ferr. (Homoptera, Pseudococcidae). Z. Angew. Entomol. 94: 530–532.CrossRefGoogle Scholar

Copyright information

© ICIPE-ICIPE Science Press 1990

Authors and Affiliations

  • Ethel-Doris N. Umeh
    • 1
  1. 1.Department of Parasitology and EntomologyAnambra State University of TechnologyAwka CampusNigeria

Personalised recommendations