John Deere, the world’s largest seller of tractors and crop harvesters, has announced another wave of layoffs Friday, telling around 610 production staff at plants in Illinois and Iowa that they will be out of a job by the end of the summer.   The company is slashing around 280 workers from a plant in East Moline, Illinois, while another 230 employees are being let go at a factory in Davenport, Iowa. About 100 production employees at the company’s Dubuque, Iowa, plant will also be impacted. All ...