Effects of different methods to control the parasitic weed Phelipanche ramosa (L.) Pomel in processing tomato crops

The root-parasitic weed Phelipanche ramosa (L.) Pomel represents a major problem for processing tomato crops. The control of this holoparasitic plant is difficult, and better understanding of treatment methods is needed to develop new and specific control strategies. This study investigated 12 agronomic, chemical, biological and biotechnological strategies for the control of this parasitic weed, in comparison with the untreated situation. The trial was carried out in 2014 at the Department of Agriculture, Food and the Environment of the University of Foggia (southern Italy), using processing tomato plants grown in pots filled with soil from a field that was heavily infested with P. ramosa. After transplantation, top dressing was performed with 70 kg ha^–1 nitrogen. A randomised block design with 3 replicates (pots) was adopted. During the growing cycle of the tomato, at 70, 75, 81 and 88 days after transplantation, the number of parasitic shoots (branched plants) that had emerged in each pot was determined, and the leaf chlorophyll of the plants was measured using a soil-plantanalysis- development meter. At harvesting on 8 August 2014, the major quanti-qualitative yield parameters were determined, including marketable yield, mean weight, dry matter, soluble solids, and fruit colour. The results show lower chlorophyll levels in the parasitised tomato plants, compared to healthy plants. None of the treatments provided complete control against P. ramosa. However, among the methods tested, Radicon® biostimulant (Radicon, Inc., Elk Grove Village, IL, USA), compost activated with Fusarium oxysporum, nitrogen and sulphur mineral fertilisers, Enzone^TM soil fumigant (Elliott Chemicals Ltd., Auckland, New Zealand), and a resistant tomato genotype mitigated the virulence of the attacks of this parasite. These effects should be improved by combining some of these treatments, especially for gradual and continued reduction in the seed bank of the parasite in the soil. For the tomato yields across the different treatments, there were no significant differences seen; however, the yields showed an improving trend for treatments with lower presence of the P. ramosa weed.