SPATIAL DISTRIBUTION AND SEQUENTIAL SAMPLING PLAN FOR Tuta absoluta (Meyrick) AND ITS NATURAL ENEMIES IN TOMATO
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Date
2018-11
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UHF, NAUNI
Abstract
ABSTRACT
Tuta absoluta (Meyrick) is one of the most destructive pests of tomato throughout the
world. Present study deals with the spatial distribution and sequential sampling plan for this
pest and the associated predatory bug, Nesidiocoris tenuis (Reuter). The pest and the predator
existed throughout the growing season both in open fields and polyhouse with larval density
varying from 1.01 to 5.44 under open fields and 0.57 to 10.71 under polyhouse conditions,
respectively. In both the situations the pest as well as the predator followed aggregated
distribution and the data fitted well the Taylor’s power law and Iwao patchiness regression.
Within plant T. absoluta larvae were distributed on all the three plant strata with slight
preference to the middle stratum (open field: 33.5-46.8%; polyhouse: 30.3-43.2%) than the
bottom (open field: 22-36.4%; polyhouse: 28.8-36.9%) or the top (open field: 21.7-36.2%;
polyhouse: 21.8 to 34.4%). Mine count was reliably used to estimate larval density and to
predict the possible fruit damage on week later. The optimum sample size decreased with the
increase in density and decrease in precision and vice-versa. Control decision lines for T.
absoluta were developed on the basis of larval and mine density separately for open field and
polyhouse conditions in the presence and absence of N. tenuis. The maximum numbers of
sampling units in case of sequential sampling were less as compared to stratified random
sampling and the presence of the predator pushed the decision lines up in each case. Present
study provides useful information for effective monitoring and taking suitable pest
management decision for the pest.
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