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Biological Study of the Tortoise Beetle. Aspidomorpha Dorsata Fabricius (chrysomelidae : Coleoptera)

G. P. Das
Division of Entomology, Bangladesh Agricultural Research Institute, Joydebpur, Dhaka, Bangladesh

M. A. Islam
Division of Entomology, Bangladesh Agricultural Research Institute, Joydebpur, Dhaka, Bangladesh

Abstract/ Executive Summary:

Aspidomorpha dorsata Fabricius an important pest of sweet potato feeds heavily on the succulent leaves of the plant. The leaf- area consumed by the last instar larva until pupation ranged from 0.80 to 1.20 sq. cm., while that by the adult until death ranged from 3.70 to 4.10 sq. cm. Aside from sweet potato (Ipomoea batatas), it also feeds on "Kangkong" ( I aquetica) and 'Vatkalmi; ( I. crosseiceulis.). The life history of the insect includes an incubation period from 6 to 8 days. The larva undergoes four moultings for a total duration of 12 - 18 days. The pupal period lasts for 5 - 7 days. The longevity of the male and female beetle ranges from 42 to 51 days and 47 to 63 days respectively.

Keywords: Biology, Tortoise beetle, Pest

Location: Central Experimental Station, Bangladesh Agricultural Research Institute, Joydebpur, Dhaka

Start Date: 01-02-1983

End Date: 30-06-1983

Program Area: Pest Management

Commodity: Insects

Objectives:

This study deals only with the nature and extent of damage, life history, seasonal abundance and host range of the pest.

Methodology:

Adult beetles were collected from an infested sweet potato field, located in the campus of the Bangladesh Agricultural Research Institute, Joydebpur, Dhaka and kept in petri dishes. The insects were supplied with fresh tender sweet potato leaves as their diet. Eggs were collected and kept in petri dishes for hatching out. The incubation period was noted. Immediately after hatching out of the eggs the larvae were isolated in plastic pots with porous lids. Each young larva was provided with tender leaves which were replenished twice daily (morning and after noon). With the advancement of the age of the larvae they were supplied with fresh leaves excluding the tender ones. Cotton wads soaked with water was wrapped around the petioles of leaves to supply necessary humidity so that the quick drying off the leaves could be prevented. The time and number of moulting of the larvae were counted and recorded until pupation. Pupae, collected from the pots were isolated in petri dishes for adult emergence. The pupal period was recorded. Ten pairs of newly emerged adults were isolated in petri dishes along with sufficient food for oviposition. Daily counts were made on the total number of egg masses and eggs laid by each female. The total number of egg masses and eggs laid by per female until her death was calculated. The oviposition sites were located under field conditions. The pre- oviposition period, hatchability of eggs and longevity of the adult beetles were noted. The nature of damage caused by both larva and aduIt was observed under both field and laboratory conditions. The extent of damage in terms of leaf area consumed was assessed only for last instar larva and the adult. The damaged leaf area was measured by placing the infested leaf on the graph paper. The damaged area was outlined on the graph paper by pencil markings. Then the total area of the outlined zone was calculated by multiplying the total numbers of small units occupied by the marked zone with the area of each small unit of the graph paper. Seasonal abundance of the pest was determined through the intensive investigation of the pest population in the field. To study the natural host range of the pest regular field investigations were made. Different plants were also supplied to the insect in the laboratory to determine whether they would develop on those hosts. The study was carried out in the laboratory of tbe Division of Entomology during February to June, 1983 as weIl as in the farm of the Central Experimental Station of the Bangladesh Agricultural Research Institute, Joydebpur, Dhaka.

Source of Information: BANGLADESH JOURNAL OF AGRICULTURE Vol. 9 (1), Jan. – Mar. 1984, pp. 48-50, ISSN 0253–5408.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the present study the life history of the insect includes an incubation period from 6 to 8 days. The larva undergoes four moulting for a total duration of 12 - 18 days. The pupal period lasts for 5 - 7 days. The longevity of the male and female beetle ranges from 42 to 51 days and 47 to 63 days respectively.The pest first appeared in the sweet potato field the first week of march. It was most abundant during the months of April and May. Under field condition the pest was found to attack sweet potato and Kangkong. In confinement, the pest initially fed on the succulent leaves of 'Vatkalmi'; but stopped feeding within a few days and ultimately died. Some toxic compounds may be present in the leaves of 'Vatkalmi' which are responsible for the mortality of the pest.

Knowledge Management: Journal