Abstract
The nematicidal activity of crudely milled powders of stems, leaves, and bulbs of Cassia abbreviata, Cissus cactiformis, Euphorbia ingens, Ipomoea kituiensis, Synadenium cupulare, Senna petersiana, Urigenia sanguinea, Maerua angolensis, and Tabernaemontana elegans on eggs and J2 population densities of Meloidogyne incognita race 2 on tomato was examined under glasshouse conditions. These plant species have medicinal properties and are being used in South Africa by traditional healers as so-called “muti.” All plant species showed a suppressive effect. Relative to untreated control, the soil amendments consistently suppressed M. incognita population densities in tomato roots and the reproductive potential (RP) of the nematode. When compared to fenamiphos, a commercial systemic chemical nematicide, the soil amendments performed comparable or better in suppressing nematode populations in the root systems in 2008 and 2009, but fenamiphos performed better than all soil amendments in 2011. The RP of M. incognita was comparable for both soil amendment- and fenamiphos-treated plants. No consistent trend in the effect of the soil amendments on plant root and shoot bioweight was observed, except when plants were treated with T. elegans-based soil amendments and both root and shoot bioweight were consistently higher compared with untreated control plants. Our results show that the plant species examined are potential sources of phytonematicides effective against M. incognita race 2.
Highlights
Tomato (Solanum lycopersicon L.) is one of the most common vegetables grown in South Africa (SA) (FAO, 2017)
Our results show that the plant species examined are potential sources of phytonematicides effective against M. incognita race 2
The suppressive effect of C. cactiformis, E. ingens, S. cupulare, and T. elegans were confirmed in 2011 when soil amendments based on these plant species significantly (P ≤ 0.05) suppressed nematode population densities with 78 to 94% compared to untreated control and, with results of all of the above except for M. angolensis being comparable to results with C. myriocarpus
Summary
Tomato (Solanum lycopersicon L.) is one of the most common vegetables grown in SA (FAO, 2017). Nematicide application is usually effective in reducing plant-parasitic nematode population densities below damage threshold levels (Desaeger et al, 2017) in the short term but resource-poor peri-urban and rural tomato growers do not have the means to purchase nematicides which are often expensive. Many of these chemicals are banned from the market because they are highly toxic to animals and humans, posing a serious threat to the environment and dangerous to handle (Jones, 2017). White (dead-man’s tree), Tabernaemontana elegans Stapf (toad tree), and Urginea sanguinea Shinz. (rooislangkop) on growth of tomato plants and suppression of population densities of M. incognita race 2 under glasshouse conditions
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