There is no evidences for increase of any non-target insect pests/mites after growing Bt transgenic crops (may be cotton,corn etc

In Brazilian agriculture it is often seen that secondary pests may emerge as important pests after some years of use of either GM soybean, maize or cotton. This is to be expected and  means no failure or otherwise unexpected changes in pest dynamics..

Yes, in Pakistan Bt cotton has changed the threshold of insect species to a great extent with the emergence of new pests (minor to major pests) as well. Boll weevils, dusky bugs, red bugs are main examples. 

Dear colleagues, this is to be expected, as Bt plants need less insecticides and effectively kills the target pest. This allows the emergence of secondary pests asn important, "new" pests.

Some... In Spain Bt maize some differences were found in homopteran abundace

Transgenic Bt maize and Rhopalosiphum padi (Hom., Aphididae) performancehttp://onlinelibrary.wiley.com/doi/10.1111/j.0307-6946.2004.00597.x/abstract;jsessionid=F7B1638A042497A3220A8F5BCB6250A1.f04t02?deniedAccessCustomisedMessage=&userIsAuthenticated=false

Abundance of non-target pests in transgenic Bt-maize: A farm scale studyhttp://www.ask-force.org/web/Bt/Pons-Abundance-Non-target-2005.pdf

And check citing articles also!

Agnes and other colleagues.

I have to admit that the observations on the increase of secondary pests in maize and ctton fields are not yet published in peer reviewed papers. The increase was taken as an inevitable, expected event by most farmers and is dealt by the use of integrated pest management, It is mostly an agricultural issue and I fear it will never be published, except in the internal technical reports in the country.

The occurence of secondary pests in Bt crops and the underlying mechanisms were described in the following papers:

Hagenbucher, S., Wäckers, F.L., Wettestein, F.E., Olson, D.M., Ruberson, J.R., and Romeis, J. (2013). Pest tradeoffs in technology: Reduced damage by caterpillars in Bt cotton benefits aphids. Proc. Roy. Soc. B 280: 20130042. http://dx.doi.org/10.1098/rspb.2013.0042  

Faria, C.A., Wäckers, F.L., Turlings, T.C.J. (2007). Increased susceptibility of Bt maize to aphids enhances the performance of parasitoids of lepidopteran pests. PLoS ONE 7

There are many published manuscript  which show increase in pest other than boll worms on Bt cotton. This can be due to many reason, especially in tropical countries where sucking pest does not require any spray before introduction of Bt, but the sprays against sucking pests have increased due to the withdrawal of  sprays against boll worms which used to provide good control of sucking pests during reproductive phase. Since Bt cotton seed is supplied by private sector and they rarely consider resistance to sucking pests as key issue but only show concern for high yield, may be with more use of pesticides against cotton.  The increase in yield with high cost of productivity is not the concern with private seed industry. More problems of sucking pests are likely to come up with change in climate in near future.

Resurgance of the major pest is another associated problem with Pakistani cotton which is mostly due to low level of Bt toxin in the germplasm released and no adoption of genuine technology. Moreover, undescript seeds and lack of updated seed laws and plant breeders rights have further agrravated the situation. We observed severe infestation of Heliothus and Pectinophora in Bt crops last year as the farmers were not expecting that so they did not care of plant protection measures or the sudden damage was so much that it gave no opportunity to farmers to spray the pests. Army worm is also developing itself more vigorously as no technology has yet been adopted against it. Entomoligts have done well to project this issue but still there is a dire need to keep monitor and highlight the threshold of the same and new pests on the existing set of varieties. Development of resistance in target pests in Bt cotton needs to be properly monitored on seasonal basis. Dusky bug (minor pest before) in Pakistan has caused huge damages to seed thus affecting germination power of the seeds and similarly Cotton strain / Red cotton bug cuased devastating damages in patches casuing severe losses to seeds and cotton both. I will stress regional level coordination among experts on this subject. What is more important to keep awaring and informing farmers about all these prevailing issues for an efficient crop management. We noted even shortage of required pesticides to control these minor to major pests when required in emergency.