Biotechnology refers to use of biological systems for the benefit of humanity. Thus ideally speaking, by definition any thing playing negative role for humanity should not be considered a part of biotechnology. However, people using biotechnology with best intentions can make mistakes that can cause serious unintended damages. In this way biotechnology can play a negative role in agriculture.
Biotechnology is used in agriculture primarily for genetically developing new crops, offering advantages like, higher yields, better quality and ability to survive and grow in relatively adverse condition. However, such genetically modified crops may also promote the development and growth of plant pests and pathogens to pesticides. Such pests pose the risk of affecting other crops also and cause major damage to agriculture. Also genetically modified food pose the risk of causing unforeseen health damages.