I prefer a different glib solution: continue to buy their products and get rid of agricultural subsidies.
Sadly, while I like the spirit behind this, it doesn't always have the effect you hope for. Tiko, Cameroon, is surrounded by plantations (think they are Del Monte owned). Instead of employing locals they give the jobs to immigrants from Equatorial Guinea and pay them less, so that even by southern Cameroonian stands Tiko is poor. It was always a bit depressing to pass through. Most of the money seems to go right into the bosses' pockets. I would focus on purchasing "Fair Trade" products from those countries instead of the standard grocery store fruit by the big companies.