Why you need a mixture of two endoparasitic wasps including Aphidius colemani and Aphidius ervi. they can reduce the crop damage by parasitizing and killing a mixed population of a variety of host species of aphids that are responsible for the crop damage.
In the major cities of the Midwest and Northeast, they found relatively high paying jobs in meatpacking plants, shipyards, and steel mills. The second significant cause of the Great Migration was the desire of black Southerners to escape segregation, known euphemistically as Jim Crow.
There were several major causes of the Great Depression in the United States. 1. Unequal distribution of wealth. There was not a large middle class. While wages were rising foâ¦r the majority of workers, they were not keeping pace with the increase in the cost of living or the wealth in the hands of the industrialists and others in the upper income classes.