The bio-suppression of sugarcane leaf hopper, Pyrilla perpusilla Walker during epidemics in 2007 by its potential nymphal and adult ecto-parasitoid, Epiricania melanoleuca Fletcher in command area of three sugar mills of Uttar Pradesh covering an area of approximately 40,000 ha with commendable success could serve as a model for pest management in other areas also. The sugarcane Pyrilla, which initially appeared on wheat, fodder sorghum, barley and grown up sugarcane, later migrated to autumn, spring plant and ratoon during March-April. The over wintering population of nymphs survived to a great extent due to mild winter which favored the fast multiplication of nymphs into adults. These nymphs developed into adults during March and started breeding profusely and caused the havoc. The population of Pyrilla and its parasitoid was assessed during rapid roving survey. The leaves bearing parasitoids were redistributed in sugarcane fields @ 5000 cocoons + 5 lacs eggs/ha or 10000 cocoons/ha in absence of eggs of Epiricania. The E. melanoleuca played a major role to control the Pyrilla population. The insecticidal spraying operation, which was not recommended, resulted in a saving of about Rs.1600/ha besides avoiding environmental pollution. The splendid control of the Pyrilla epidemic has once again proved that conservation of natural enemies and augmentation through field redistribution could be effective components in bio-suppression of Pyrilla. Hence, it is inferred that if ecto-parasitoid Epiricania melanoleuca cocoon is available in field @1-5/leaf at Pyrilla population level ranging from 20 to 150 nymphs+adults/leaf, the insecticides should not be sprayed at all.

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ABSTRACT:The seasonal variation in the initiation and duration of the I-III generations of the top borer was observed and analysed during five crop cycles from 2002-2003 to 2006-2007 at Lucknow in central Uttar Pradesh. The durations of the I-III generations were significantly correlated with the accumulated thermal time (T base = 10°C). Relatively higher temperature and consequently higher accumulated thermal time shortened the brood duration and early initiation of successive generations and vice versa. Based on these correlations, models were developed for predicting the initiation and duration of these generations. These models were validated for 2007-2008 crop cycle. The differences between observed and predicted duration of the I-III generation of the pest were 3, 1 and 3 days respectively reflecting high precision of the models. As the current management strategy for the chemical control of the pest is based on a calendar week, the shift of III generation initiation due to seasonal fluctuations could lead to escape from insecticide and render the chemical application pointless. The model-based control strategy is more precise and foretells the time of application of chemical against III generation of top borer which is most damaging to sugarcane crop.

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