This study used a light-trap to investigate jassids on cotton http://krishikosh.egranth.ac.in/bitstream/1/2033695/1/1073.pdf

This one's different as it investigates jassid parasitoids and eggs are collected by collecting the leaves of host plants (again cotton)

https://www.icac.org/tis/regional_networks/asian_network/meeting_5/documents/papers/PapSahitoHA-et_al.pdf

Here, jassid nymph are sampled by visual counting

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7303056

Lastly, this article is listed on ResearchGate

https://www.researchgate.net/publication/39015106_Sampling_for_cotton_insects_5._Sampling_for_monitoring_of_cotton_jassid_populations_based_on_within-plant_distribution

I hope that's helpful - and good luck with the sampling!

Dave

Article Sampling for cotton insects: 5. Sampling for monitoring of c...