that's disappointing. from what i've read most of the pest problems are caused by poor soil structure, lack of minerals, lack of compost, etc and it seems to be true in my experience.
Sounds like you can't get compost there affordably and probably there isn't the equipment there to make any on a larger scale such as grinding up tree branches like the guy in the Back to Eden film so the only thing i could think of is hugulkulture. Seems like it might be a way to add a lot of nutrients to the soil without too much effort if you have access to some trees or logs.