Determining the efficacy of syringa (Melia azedarach L.) extracts and garlic (Allium sativum L.) extracts in the control of tobacco spider mites (Tetranychus evansi) in tomatoes (Lycopersicum esculentum) under field conditions in Chiredzi District, in Zimbabwe

Abstract

The production of tomatoes is hampered by a variety of pests and diseases despite the importance of tomatoes as a vegetable in everyday life and their economic significance in Zimbabwe. Tobacco spider mites (Tetranychus evansi), is the most troublesome parasite, have significantly reduced the marketable output, quality, and financial loss of tomatoes. The development and widespread use of synthetic pesticides as a quick and more efficient technique of controlling pests and diseases was prompted by the increased high demand for food to feed the expanding world population. Because of their negative impacts on human health, the environment, and the emergence of pest/pathogen strains with resistance, synthetic pesticides should not be used excessively. This, together with rising demand for food grown organically, sparked the development of alternative strategies and botanical insecticides as powerful tools for controlling tobacco spider mites. This sparked interest in research on syringa (a street lining tree) and garlic (grown in abundance for sale and for human consumption at household levels), which are locally available and easily accessible in Chiredzi district of Zimbabwe and led to the study. Botanical pesticides are effective in managing different crop pests, inexpensive easily biodegradable, have different modes of action and their sources are easily accessible and have low toxicity to non target organisms. A field experiment was conducted to ascertain the substantial differences in effectiveness between garlic and syringa in the control of tobacco spider mites. The concentrations of the two plants used were 5%, 25%, 50%, and 75% of each. The research showed that Melia azedarach and Allium sativum have pesticidal effects on tobacco spider mites. Allicin, an active component in minced garlic cloves, and limonoid, a triterpenoid that is an active component in syringa, could be responsible for the pesticidal actions of garlic.