Viruses are not considered "alive" because they lack many of the properties that scientists associate with living organisms. Primarily, they lack the ability to reproduce without the aid of a host cell, and don't use the typical cell- division approach to replication.
Answer:
<em>1. They effect crop productivity</em>
As weeds start to grow in the area where the crops were destined to grow, the production of the crops gets lowered.
<em>2. They deplete the crops from nutrition</em>
The weeds will compete with the crop plants for resources such as minerals from the soil.
<em>3. They will deplete water resources</em>
The weeds will compete with the crop plants for water.
<em>4. Sun-light will be depleted</em>
The weeds will complete with the crop plants for sun light.
<em>5. The crop quality will be affected</em>
As the crop plants will be in competition with the weeds, hence their quality will be affected.
6. <em>They can reduce the biodiversity of crop plants.</em>
