Population dynamics, distribution and rind disorder of mites and thrips on citrus in Punjab
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Date
2018
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Punjab Agricultural University, Ludhiana
Abstract
The studies on “Population dynamics, distribution and rind disorder of mites and thrips on citrus
in Punjab” were conducted at three locations namely Fruit Research Farm, Punjab Agricultural
University, Ludhiana; Regional Research Station, Abohar and Department of Horticulture
(Punjab), Hoshiarpur (Bhunga). During the present study eight mite species namely Brevipalpus
phoenicis (Geijskes), B. californicus (Banks), Tetranychus urticae Koch, Eutetranychus orientalis
(Klein), Polyphagotarsonemus latus (Banks), Amblyseius (Euseius) alstoniae Gupta, A. (Euseius)
finlandicus (Oudemans) and Cunaxa setirostris (Hermann) were observed on leaves, B. phoenicis
was also observed on fruits from May onwards with maximum population in November -
December. There was a negative correlation between mite abundance and rainfall at all locations.
The mite families viz. Tenuipalpidae, Tarsonemidae and Cunaxidae had negative correlation with
temperature and positive correlation with maximum R.H. but Tetranychidae had positive
correlation with temperature and negative with maximum relative humidity. Citrus thrips,
Scirtothrips citri (Moulton), started appearing in first week of March with the initiation of
flowering and their attack continued up to last week of May. The population of citrus thrips
increased progressively with increase in temperature and decrease in relative humidity. Maximum
population of citrus thrips and mite species was observed in the arid zone (Abohar) followed by
central zone (Ludhiana) and submontane zone (Hoshiarpur) of Punjab. Among all the mite
species, E. orientalis and Amblyseius spp. were found to be widely distributed and recorded on all
sampled fruit crops in Kinnow orchards. The study of alpha diversity indices showed that
diversity and evenness indices were highest in Hoshiarpur (H’ = 1.32, Dmg = 1.42, E = 0.83),
followed by Ludhiana (H’ = 1.27, Dmg = 1.32, E = 0.77) whereas lowest were observed in
Abohar (H’ = 1.23, Dmg = 1.22, E = 0.73). The highest dominance indices were observed in
Abohar (Simpson index = 0.37, d = 0.54). Results also indicated the dominance of B. phoenicis
during November month at all the three locations. The experiments to study the impacts of rind
disorder caused by mites, thrips and wind on various quality and biochemical parameters were
conducted in the laboratory of Punjab Horticultural Postharvest Technology Center (PHPTC),
Punjab Agricultural University, Ludhiana. The results showed that damaged fruits (rind scarring
by mites and thrips) had less fruit firmness and lesser amount of ascorbic acid, phenols, pectin and
carotenoids. But acidity, reducing sugar, total sugar and non reducing sugars were not affected due
to rind scarring. However, TSS was higher in fruits having 50 per cent rind scarring as compared
to healthy fruits but fully damaged fruits (75 - 100%) had less TSS. Wind damaged fruits had
nonsignificant results or negligible differences between values of all physiochemical parameters
of healthy fruits and wind scarred fruits. So it was concluded that these losses might be due to
deterioration caused by only thrips and mites but not wind.
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