Feeding capacity of Menochilus sexmaculata (Fabricus) (Coleoptera: Coccinellidae) on guava aphid, A. punicae Passerini

Introduction

Aphid are small, minute soft bodied sucking pests and approximately 4000 species of aphids have been observed so far feeding over 250 agricultural and horticultural crops. Aphids cause damage directly by sucking plant juices and secrete honey dew on the leaves and shoots, and indirectly as vector of plant viruses (Raboudi et al., 2002) [1] . Predatory coccinellids play a very important role for control sucking pests. They are sap-sucking insects with piercingsucking mouthparts, having a needle-like stylet that allows the aphid to access and feed on the contents of plant cells causing significant loss of plant's phloem sap, which is essential for plant growth (Dixon, 1998) [2] . Among the predatory Coccinellidae, Menochilus sexmaculata (Fabricius), is one of the potential predators of aphids and is widely distributed in India, Iran, Australia and other parts of the Oriental region (Agarwala and Bardhanroy, 1997) [3] . The lady bird beetle M. sexmaculata is one of the most common predators of sucking and soft bodied insects. All stages of M. sexmaculata eat soft bodied insects such as aphids and mealybugs. The prey are mostly from the order Hemiptera and are predominantly aphids on low growing vegetation. The important features of M. sexmaculata includes its wide geographic distribution and host range, broad habitats, tolerance to certain pesticides, enhanced searching ability, voracious larval feeding capacity and easy rearing in laboratory (Venkatesan et al.) [4] , and has been used in the biological control of insect pest on crops. They are of great economic importance as predators both in their larval and adult stages on various important crop pests such as aphids, coccids and other soft bodied insects (Hippa et al., 1978; Kring et al., 1985) [5] . The present study was undertaken to determine the predatory efficiency in terms of feeding capacity of grubs and adults of M. sexmaculata on host guava aphid, Aphis punicae

Materials and Methods

For testing the feeding capacity of M. sexmaculata at different larval stages, adult male and female beetles and guava aphids, were collected from the field and brought into the Biocontrol laboratory, collage of Agriculture, IGKV, Raipur, (C.G). Newly hatched (neonate) grubs of M. sexmaculata was separated and kept in different petridishes and provided with fresh guava aphids, A. punicae separately daily. Initially ten aphids was provided to each larval instar (grub) ie; 1 st , 2 nd , 3 rd , and 4 th , separately replicated four times and the number of aphids provided as food was increased accordingly. Daily record on the number of aphids consumed was maintained separately till the survival of the adult male and female beetles and then computed for the total number of aphids consumed throughout its larval period. The change in larval instar was confirmed by checking the shed head capsule. The number of aphids fed at each instar was recorded daily and the experiment was continued until death of the beetle.

Results and Discussion

The predatory capacity in terms of feeding capacity of the grub was determined by counting total number of aphids consumed by each larval instar. The data presented in the Table 1 depicts that the rate of consumption increased gradually from the first to fourth instar. Consumption of first instar 13.13±3.76 aphids/day, while predation in 2 nd instar grub was of 25.00±5.09 aphids. Third instar grub showed better predatory activity than first two instars and the fourth and final instar grubs were very active until pupal transformation. They required more food than the previous instar due to bigger size, growth, longer duration and to accumulate nutrient for pupal period. In the 3 rd instar, the mean consumption was estimated to be 42.25±6.57 aphids/day. During 4 th instar, they devoured a maximum number of 58.38±7.71 aphids/day. The result obtained is also in accordance with they also recorded the feeding potential of Lipaphis erysimi as 26.82±0.59 and 47.13±1.75 aphids/days in grub and adult. Duration of all the four instars were found to be of one day in the present studies.

Thus the studies conducted on the feeding potential of Coccinellid predator, M. sexmaculata on guava aphid, A. punicae revealed that the mean maximum number of aphids consumed increased from

Conclusion

The study on the predatory capacity of Menochilus sexmaculatus grubs on Aphis punicae revealed a significant increase in feeding potential across the four larval instars.

The results showed that as the larvae progressed from the first to fourth instar, their aphid consumption rose substantially due to their increasing size and energy requirements. The first instar consumed 13.13 aphids/day, while the fourth instar devoured 58.38 aphids/day. Adult females displayed the highest predatory capacity, consuming 90.69 aphids/day. These findings underscore the importance of M. sexmaculatus as an effective biological control agent against aphids.

Acknowledgement

AcknowledgementThe authors are thankful to Dr. Sunil Joshi, scientist, NBAIR, Bangalore. For identifying the guava aphid as Aphis punicae.

References

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