M. Mani

Evaluation of the indigenous parasitoid Encarsia transvena (Hymenoptera: Aphelinidae) for biological control of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) in greenhouses in India

The efficiency of the native parasitoid, Encarsia transvena Timberlake for the management of greenhouse whitefly, Bemisia tabaci (Gennadius) was studied in cages and a greenhouse in India. Parasitism by Enc. transvena of B. tabaci on Lycopersicon esculentum L. (tomato), Solanum melongena L. (eggplant) and Nicotiana tabacum L. (tobacco) was evaluated in cages to compare the utility of each species as potential banker plants. B. tabaci populations were consistently present on all three host plant species for almost two months providing sufficient hosts for parasitoid multiplication. Significantly more B. tabaci nymphs/unit leaf area were found on N. tabacum (77.7) and on S. melongena (76.5) than L. esculentum (45.9) in the initial growing period of the plants, that increased more on L. esculentum as the crops grew older. A greater proportion of B. tabaci were parasitised by Enc. transvena on L. esculentum than on N. tabacum and S. melongena. Rate of parasitism on L. esculentum was 25.19 and on N. tabacum was 24.70 in greenhouse. Parasitism, although occurring throughout greenhouses, was greatest on plants within 3 metres of introduced banker plants. The results suggest the utility of the three plant species as potential banker plants for the management of whiteflies in greenhouses.

Role of Coccophagus sp. in the suppression of the soft green scale Coccus viridis (Green) (Hompoptera: Coccidae) on sapota

Abstract The soft green scale Coccus viridis (Green) (Homoptera: Coccidae) has become a major pest of sapota, Manilkara achras (Mill.) Forberg in India. A field study was conducted on the population dynamics of soft green scale Coccus viridis (Green) for 2 years (2004–2006) on sapota at the Indian Institute of Horticultural Research (IIHR) farm, Bangalore, India. The population of green scale declined from 30.72 per leaf in May 2004 to 1.62 per leaf in March 2006. Two coccinellid predators Chilocorus nigrita (Fab.) and Cryptolaemus montrouzieri (Muls.) and one aphelinid parasitoid Coccophagus sp. were recorded on C. viridis. Both the predators played a minor role in the population fluctuation of C. viridis. The parasitoid Coccophagus sp. was the dominant natural enemy observed throughout the study recording a mean of 10.24–94.67% parasitism. A significant positive correlation of the scale population with minimum temperature (r=0.54) and negative relationship with the parasitism by Coccophagus sp. (r=0.81) was recorded. Multiple regression analysis revealed that 75.7% of the variation present in the green scale population could be predicted by abiotic factors and parasitism by Coccophagus sp. Further, step-wise regression procedure employed to arrive at a multiple regression model showed that about 65.60% of the scale population could be predicted by one factor namely, parasitism by Coccophagus sp. These results showed that parasitism by Coccophagus sp. played a major role in regulating the population of the soft green scale infesting sapota.

Egg Parasitoids in Vegetable Crops Ecosystem: Research Status and Scope for Utilisation

In vegetable ecosystem, the egg parasitoids are mainly trichogrammatids (Trichogramma, Trichogrammatoidea) on Lepidoptera and scelionids (Telenomus, Trissolcus) on Lepidoptera and Heteroptera, besides mymarids on leafhopper and thrips. Trichogramma chilonis is found promising as natural and augmentation control agent for several lepidopteran pests. Considerable progress has been made on utilising kairomones for improving the performance of T. chilonis. Release systems could be refined to match with host abundance pattern, while a novel method of spraying parasitised eggs has been found promising. Inundative releases of T. chilonis, T. brasiliensis and T. pretosium for Helicoverpa control in tomato, okra and chilli, besides T. chilonis for Leucinodes orbonalis on brinjal, have been demonstrated as effective. Similar promising results have been obtained from T. bactrae release in controlling Plutella xylostella on cabbage. Integration of egg parasitoid release with NVP, neem and pheromone trap has been shown possible in IPM modules. The scope of mass rearing of Telenomus remus on Corcyra cephalonica has been demonstrated, while further improvements in their efficiency are required. The present constraint in mass production and storage of T. achaeae may merit attention. Further research may focus also on strains collection for stress adaptation, on host searching and also on field dispersal and utilisation of semiochemicals for improving the field performance of mass-released parasitoids.