Comparative efficacy of some bioagents, plant oil and plant aqueous extracts in controlling Meloidogyne incognita on growth and yield of grapevines

Abstract

The current experiment was conducted to control the root-knot nematode; Meloidogyne incognita infecting Thompson seedless grapevines by using eight treatments as follows: some bioagents (Trichoderma harzianum and Arbascular mycorrhizae), some plant oil extracts (orange oil extract and jojoba oil) and plant aqueous extracts (Origanum majorana and Tagetes erecta) in comparison with oxamyl (24% EC) on grapes infected with root-knot nematode to determine its impact on growth and yield of grapevines during two successive seasons (2009 and 2010) under field conditions. The chosen vines were 10-year-old grown in a sandy soil in a private vineyard located in Alexandria-Cairo road, spaced at 1.75×2.75m and irrigated by drip irrigation system where the cane was pruned and trellised by the Y shape system. Bioagents and plant aqueous extracts were added to the soil under the vines three times/week after bud burst. Results showed that all the treatments had a significant effect in reducing the total population and build up of root-knot nematodes, M. incognita in both soil and rots especially after the 3months from the time of application. In addition they had increased the physical characteristics of both clusters and berries, vegetative growth parameters, macro nutrient content and yield of Thompson seedless grapevines during two studied seasons (2009 and 2010) under field conditions. Both jojoba oil and orange oil extract were the most effective treatments in reducing total population and rate of build up of M. incognita in both soil and roots up to the harvesting time. They also increased cluster weight, number of clusters, yield per vine as well as enhancing the physical characteristics of berries, TSS % TSS/acidity ratio whereas, acidity was decreased in berry juice and improved vegetative growth parameters and increased the total surface area/vine, wood ripening coefficient, total chlorophyll and percentages of total nitrogen, phosphorus and potassium of leaves. Data of root growth parameters showed that the extension of fine roots through the vertical direction (root density) expressed as length of the fine roots were significantly higher at (30cm) depth in the soil profile, the horizontal extension of fine roots was more concentrated at the distance of (50cm) from the vine trunk. All treatments recorded the highest values of medium roots and large roots in both horizontal and vertical directions as compared with the control but lower than oxamyl treatment. On the other hand, the treatments with bioagents (T. harzianum and A. mycorrhizae) were in the intermediate rank, whereas, treatments of plant aqueous extracts (O. majorana and T. erecta) were the least effective in both seasons. It can be concluded that jojoba oil and orange oil extract were the best safe treatments compared with oxamyl (24% EC) in reducing total population and rate of build up of root-knot nematodes, M. incognita and improving fruiting of vines yield and quality of the berries of Thompson seedless grapevines.