The efficacy of alternative products to manage tomato (Lycopersicon esculentum) late blight, caused by Phytophthora infestans, was evaluated in three field trials (E) that compared: E1- [chili pepper (Capsicum chinense) + black pepper (Piper nigrum) + clove (Syzygium aromaticum) + turmeric (Curcuma longa) + garlic (Allium sativum) extracts]; (black pepper + clove + garlic extracts); and (clove + turmeric + garlic extracts); E2 - neem (Azadirachta indica) oil (0.5%), crude cow milk diluted in water (20% v/v), and Bordeaux mixture; E3 - homeopathic preparation (from tomato tissue infected with P. infestans - C30), the water-ethanol mixture, and Bordeaux mixture. All experiments had two controls: no sprays and metalaxyl. Severity at halfway through the epidemic (Y50); at the end of the epidemic (Ymax); area under disease progress curve (AUDPC); and disease progress rate (r) were estimated. None of the extracts reduced Y50, Ymax, AUDPC, or r values. Neem oil and Bordeaux mixture resulted in similar Y50 values (3% and 1%, respectively). Ymax (44%) in plots treated with neem was higher than in those treated with Bordeaux mixture (14%). Milk at 20% did not reduce Ymax. Values of r (0.161) and AUDPC (533) were lower with neem oil than in control (r = 0.211 and AUDPC = 1186) and similar to the Bordeaux mixture plots (r = 0.156 and AUDPC = 130). Values of r and AUDPC on plots treated with milk were similar to those in the control plots. There was no significant reduction of Y50, Ymax, AUDPC, or r values when plants were treated with homeopathic product. Bordeaux mixture was the most efficient treatment in controlling late blight. Neem oil is potentially useful. Integrated management must be implemented to keep late blight at acceptable levels on alternative tomato production systems.
Phytophthora infestans; Lycopersicon esculentum; epidemiology; plant extracts; neem oil; homeopathy; Bordeaux mixture
