The reason seems to be the lack of produce coming from Latin America due to the bad weather. Incoming volumes are not enough to meet demand, so of course prices go up. "Premium bananas from Ecuador and Colombia have reached €18-18.50 per 18kg box, much closer to Chiquita prices than usual." This also led to a change in purchases - as the price gap is not as great, people have started to buy Chiquita bananas.
But, as demand for Chiquita bananas increase, so did their prices, which had not happened so far. At the moment, the difference in price between the two types of bananas is of around €5 per box.
Bananas are not the only South American product going through a peculiar phase - the same is happening to pineapples. "Usually prices vary a lot because prices go up as consumption increases, but the slightest rise in prices is enough to drive demand down. What is weirdis the fact that prices have not gone down in 2/3 weeks. Costa Rican fruit has even reached €1.10-1.30 per kg."