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.
The causes of IMMIGRATION: social reasons, politic reasons and economic reasons. The immigration, as a decision maked by a person is an act that occurs, because of some factors especially in the under developed countries and the most importants causes or reasons are mainly social reasons, politic reasons and economic reasons.