<p>Citrus species (Rutaceae) serve as important fruits of economic value occupying the second position in world fruit production after grapes. In India more than 250 insect species have been reported to attack citrus hosts throughout the growth period starting right from nursery to maturity of fruit. Of all these, the Asian citrus psylla <italic>Diaphorina citri</italic> Kuwayama is one of the most serious succivorous pests. The use of chemical pesticides for pest control is causing residue problem besides killing the natural enemies of soft-bodied pests in citrus orchard ecosystem. Hence, screening of the available germplasms and development resistant varieties is the most economical and best eco-friendly alternative.</p><p>The study was carried out to assess the susceptibility of available five cultivars of the sweet orange (<italic>Citrus sinensis</italic> Osbeck) against <italic>D. citri</italic> from April to March at Regional Horticultural Research Station, Udheywalla (Jammu). The plants of each cultivar were planted at spacing of 5 x 4 m row in square system, replicated thrice and all the recommended horticultural practices were followed but no plant protection measure was adopted. The age of the orchard under study was about 12 years and the observations in respect of Asian citrus psylla attack were recorded. For the purpose of evaluation the canopy of the selected plants was divided approximately into upper and lower strata and from each stratum, four terminal shoots measuring 10 cm representing four geographical directions were tagged for recording the population of the pest. The data thus, generated was pooled and analysed. <table-wrap id="tab001"><label>Table 1</label><caption><p>Relative susceptibility of important cultivars of sweet orange to <italic>Diaphorina citri</italic></p></caption><table><thead><tr><th rowspan="3">Cultivars</th><th colspan="4" align="center">*Mean population of <italic>D. citri/</italic> 10 cm terminal shoot</th></tr><tr><th colspan="4"><hr /></th></tr><tr><th align="center">Pre-monsoon March-June</th><th align="center">Monsoon July-September</th><th align="center">Post-monsoon October-December</th><th align="center">Winter January February</th></tr></thead><tbody><tr><td colspan="5"><hr /></td></tr><tr><td>Blood red</td><td align="center">3.8</td><td align="center">6.1</td><td align="center">4.1</td><td align="center">0.0</td></tr><tr><td /><td align="center">(2.15)</td><td align="center">(2.62)</td><td align="center">(2.26)</td><td align="center">(1.00)</td></tr><tr><td>Jaffa</td><td align="center">15.2</td><td align="center">15.7</td><td align="center">9.4</td><td align="center">1.4</td></tr><tr><td /><td align="center">(4.01)</td><td align="center">(4.07)</td><td align="center">(3.21)</td><td align="center">(1.57)</td></tr><tr><td>Mosambi</td><td align="center">3.6</td><td align="center">5.3</td><td align="center">0.8</td><td align="center">0.5</td></tr><tr><td /><td align="center">(2.14)</td><td align="center">(2.51)</td><td align="center">(1.33)</td><td align="center">(1.24)</td></tr><tr><td>Valantia</td><td align="center">2.2</td><td align="center">5.3</td><td align="center">0.8</td><td align="center">0.5</td></tr><tr><td>Late</td><td align="center">(1.79)</td><td align="center">(2.51)</td><td align="center">(1.34)</td><td align="center">(1.22)</td></tr><tr><td>Pine</td><td align="center">4.7</td><td align="center">4.0</td><td align="center">1.4</td><td align="center">1.4</td></tr><tr><td>Apple</td><td align="center">(2.39)</td><td align="center">(2.26)</td><td align="center">(1.49)</td><td align="center">(1.53)</td></tr><tr><td>S.Em. ±</td><td align="center">0.24</td><td align="center">0.26</td><td align="center">0.28</td><td align="center">0.12</td></tr><tr><td>CD (P=0.05)</td><td align="center">0.56</td><td align="center">0.60</td><td align="center">0.66</td><td align="center">0.29</td></tr></tbody><tfoot><tr><td colspan="5"><hr /></td></tr><tr><td colspan="5" align="left"><fn id="tab001-fn001"><p>*Mean of 24 observations</p></fn></td></tr><tr><td colspan="5" align="left">The figures in parentheses indicate transformed values (x+1)½</td></tr></tfoot></table></table-wrap></p><p>Seasonwise results revealed that during pre-monsoon (March to June) the cultivars Valantia Late, Mosambi and the Blood Red supported significantly lower population than Pine Apple and Jaffa. The % pest infestation (51.1) was found to be higher in Jaffa but considerably low 7.5% infestation was registered on Valantia Late. The statistical analysis revealed that the maximum population load was recorded on Jaffa (15.2 nymphs/10 cm shoot) followed by Pine Apple on the predetermined sample area of the terminal shoot and the two cultivars differed significantly (<xref ref-type="bibr" rid="bib004">Sharma <italic>et al</italic>., 2002</xref>). During monsoon (July-September) Pine Apple, Valantia Late, Mosambi and Blood Red remained at par in respect of population build up. Pest infestation in case of both Mosambi and Valantia Late was 14.7% whereas it was 16.6% and 10.8% in respect of Blood Red and Pine Apple. The mean population was statistically low on Pine Apple, Valantia Late and Mosambi as compared to Jaffa (15.7 nymphs/10 cm shoot). Rao and Panwar (<xref ref-type="bibr" rid="bib002">2000</xref>), attributed the resistance to the morphological characters of the hosts. However, in post-monsoon season (October-November) peak population (9.4 numbs) occurred on Jaffa followed by Blood Red (4.1 nymphs) and these two cultivars differed significantly. Moreover, Mosambi, Valantia Late and Pine Apple were at par in respect of population load and supported statistically low population as compared to Blood Red and Jaffa. Further, similar trend was observed with regard to % infestation recorded during monsoon season (<xref ref-type="bibr" rid="bib001">Pathak & Rizvi, 2002</xref>). As low as 5.7% infestation was observed on Mosambi and Valantia Late. A quite higher % infestation (56.1) occurred on Jaffa. During winter season (January-February), Blood Red, Mosambi and Valantia Late were at par statistically in terms of population of <italic>D. citri</italic> as compared to Pine Apple and Jaffa again registered higher pest infestation that is 35.2% and 37.5%, respectively during the same season. This preliminary report on the screening of sweet orange varieties against citrus psylla was of great significance could be exploited for integrated management of the pest (<xref ref-type="bibr" rid="bib003">Sharma, 2004</xref>).</p></sec></body><back><ack id="ack001"><title>Acknowledgements

APPS

Annals of Plant Protection Sciences

0971-3573

Society of Plant Protection Sciences

apps-13-1-064

SHORT COMMUNICATION

Screening of Sweet Orange Cultivars Against Asian Citrus Psylla, Diaphorina citri

Bhagat

K.C.

Nehru

R.K.

Division of Entomology, Sher-e-Kashmir Univ. of Agri. Sci. & Tech., Udhaywalla (Jammu) - 180 001, India

1532005

131242243

<p>Citrus species (Rutaceae) serve as important fruits of economic value occupying the second position in world fruit production after grapes. In India more than 250 insect species have been reported to attack citrus hosts throughout the growth period starting right from nursery to maturity of fruit. Of all these, the Asian citrus psylla <italic>Diaphorina citri</italic> Kuwayama is one of the most serious succivorous pests. The use of chemical pesticides for pest control is causing residue problem besides killing the natural enemies of soft-bodied pests in citrus orchard ecosystem. Hence, screening of the available germplasms and development resistant varieties is the most economical and best eco-friendly alternative.</p><p>The study was carried out to assess the susceptibility of available five cultivars of the sweet orange (<italic>Citrus sinensis</italic> Osbeck) against <italic>D. citri</italic> from April to March at Regional Horticultural Research Station, Udheywalla (Jammu). The plants of each cultivar were planted at spacing of 5 x 4 m row in square system, replicated thrice and all the recommended horticultural practices were followed but no plant protection measure was adopted. The age of the orchard under study was about 12 years and the observations in respect of Asian citrus psylla attack were recorded. For the purpose of evaluation the canopy of the selected plants was divided approximately into upper and lower strata and from each stratum, four terminal shoots measuring 10 cm representing four geographical directions were tagged for recording the population of the pest. The data thus, generated was pooled and analysed. <table-wrap id="tab001"><label>Table 1</label><caption><p>Relative susceptibility of important cultivars of sweet orange to <italic>Diaphorina citri</italic></p></caption><table><thead><tr><th rowspan="3">Cultivars</th><th colspan="4" align="center">*Mean population of <italic>D. citri/</italic> 10 cm terminal shoot</th></tr><tr><th colspan="4"><hr /></th></tr><tr><th align="center">Pre-monsoon March-June</th><th align="center">Monsoon July-September</th><th align="center">Post-monsoon October-December</th><th align="center">Winter January February</th></tr></thead><tbody><tr><td colspan="5"><hr /></td></tr><tr><td>Blood red</td><td align="center">3.8</td><td align="center">6.1</td><td align="center">4.1</td><td align="center">0.0</td></tr><tr><td /><td align="center">(2.15)</td><td align="center">(2.62)</td><td align="center">(2.26)</td><td align="center">(1.00)</td></tr><tr><td>Jaffa</td><td align="center">15.2</td><td align="center">15.7</td><td align="center">9.4</td><td align="center">1.4</td></tr><tr><td /><td align="center">(4.01)</td><td align="center">(4.07)</td><td align="center">(3.21)</td><td align="center">(1.57)</td></tr><tr><td>Mosambi</td><td align="center">3.6</td><td align="center">5.3</td><td align="center">0.8</td><td align="center">0.5</td></tr><tr><td /><td align="center">(2.14)</td><td align="center">(2.51)</td><td align="center">(1.33)</td><td align="center">(1.24)</td></tr><tr><td>Valantia</td><td align="center">2.2</td><td align="center">5.3</td><td align="center">0.8</td><td align="center">0.5</td></tr><tr><td>Late</td><td align="center">(1.79)</td><td align="center">(2.51)</td><td align="center">(1.34)</td><td align="center">(1.22)</td></tr><tr><td>Pine</td><td align="center">4.7</td><td align="center">4.0</td><td align="center">1.4</td><td align="center">1.4</td></tr><tr><td>Apple</td><td align="center">(2.39)</td><td align="center">(2.26)</td><td align="center">(1.49)</td><td align="center">(1.53)</td></tr><tr><td>S.Em. ±</td><td align="center">0.24</td><td align="center">0.26</td><td align="center">0.28</td><td align="center">0.12</td></tr><tr><td>CD (P=0.05)</td><td align="center">0.56</td><td align="center">0.60</td><td align="center">0.66</td><td align="center">0.29</td></tr></tbody><tfoot><tr><td colspan="5"><hr /></td></tr><tr><td colspan="5" align="left"><fn id="tab001-fn001"><p>*Mean of 24 observations</p></fn></td></tr><tr><td colspan="5" align="left">The figures in parentheses indicate transformed values (x+1)½</td></tr></tfoot></table></table-wrap></p><p>Seasonwise results revealed that during pre-monsoon (March to June) the cultivars Valantia Late, Mosambi and the Blood Red supported significantly lower population than Pine Apple and Jaffa. The % pest infestation (51.1) was found to be higher in Jaffa but considerably low 7.5% infestation was registered on Valantia Late. The statistical analysis revealed that the maximum population load was recorded on Jaffa (15.2 nymphs/10 cm shoot) followed by Pine Apple on the predetermined sample area of the terminal shoot and the two cultivars differed significantly (<xref ref-type="bibr" rid="bib004">Sharma <italic>et al</italic>., 2002</xref>). During monsoon (July-September) Pine Apple, Valantia Late, Mosambi and Blood Red remained at par in respect of population build up. Pest infestation in case of both Mosambi and Valantia Late was 14.7% whereas it was 16.6% and 10.8% in respect of Blood Red and Pine Apple. The mean population was statistically low on Pine Apple, Valantia Late and Mosambi as compared to Jaffa (15.7 nymphs/10 cm shoot). Rao and Panwar (<xref ref-type="bibr" rid="bib002">2000</xref>), attributed the resistance to the morphological characters of the hosts. However, in post-monsoon season (October-November) peak population (9.4 numbs) occurred on Jaffa followed by Blood Red (4.1 nymphs) and these two cultivars differed significantly. Moreover, Mosambi, Valantia Late and Pine Apple were at par in respect of population load and supported statistically low population as compared to Blood Red and Jaffa. Further, similar trend was observed with regard to % infestation recorded during monsoon season (<xref ref-type="bibr" rid="bib001">Pathak & Rizvi, 2002</xref>). As low as 5.7% infestation was observed on Mosambi and Valantia Late. A quite higher % infestation (56.1) occurred on Jaffa. During winter season (January-February), Blood Red, Mosambi and Valantia Late were at par statistically in terms of population of <italic>D. citri</italic> as compared to Pine Apple and Jaffa again registered higher pest infestation that is 35.2% and 37.5%, respectively during the same season. This preliminary report on the screening of sweet orange varieties against citrus psylla was of great significance could be exploited for integrated management of the pest (<xref ref-type="bibr" rid="bib003">Sharma, 2004</xref>).</p></sec></body><back><ack id="ack001"><title>Acknowledgements

The authors are grateful to Dr. D.R. Kotwal, Head, Division of Entomology, SKUAST, R.S. Pura for encouragement and facilities.

ReferencesPathak

Mahesh

Rizvi

P.Q.

(2002). Age specific life tables of Papilio demoleus on different hosts.Ann. Pl. Protec. Sci.10: 375-376.Rao

C.N.

Panwar

V.P.S.

(2000). Morphological plant characters affecting resistance to Chilo partellus in maize.Ann. Pl. Protec. Sci.8: 145-149.Sharma

D.R.

(2004). Seasonal incidence and control of aphid complex on kinnow.Ann. Pl. Protec. Sci.12: 274-278.Sharma

Batra

R.C.

Sharma

D.R.

(2002). Role of weather factors on the activity of Psorosticha zizyphi on different rootstocks.Ann. Pl. Protec. Sci.10: 378-380.