Management of root-knot nematodes and weeds using different amendments in greenhouse grown asclepias (Asclepias tuberosa l.)

Abstract

The research tested the potential of Tagetes patula, Lantana camara, Tephrosia vogelii and Azadirachta indica to manage root knot nematodes and weeds on greenhouse grown Asclepias tuberosa. Field trials were conducted at James Finlay’s (K) Flowers-Kericho for two seasons under greenhouse conditions. The experiment was laid in Complete Randomised Block Design replicated three times. Chopped plant materials were applied singly as soil amendment or in combination with nemacur. T. patula was applied at 300 g/m2, A. indica at 150 g/m2, L. camara at 10% w/w, and T. vogelii at 10% w/w. Organic plant materials were applied at half rate in combination with nemacur at 20 g/m2. Nemacur treatment alone was applied at a full rate of 40 g/m2. The chopped plant materials were incorporated in the soil and left to decompose for four weeks. Nematode counts, weed density and biomass were evaluated before and after application of soil amendment treatments. L. camara combined with nemacur reduced root knot nematodes count by between 89.3% and 90.8%, while a single application of the same treatment reduced nematodes by 85.1%. Root galling was reduced by 79.3% when a combination of L. camara with nemacur was applied, while nemacur alone decreased galling by 89.6%. A. indica reduced root knot nematodes count by between 52.3% and 58% when applied singly and by 31.2% in combination with nemacur. T. patula decreased nematodes counts by between 47.7% and 55% in combination with nemacur while it reduced nematodes by 34.8% when applied singly. Nemacur or a combination of L. camara with nemacur led to an increase in plant height by between 22.7 cm and 26.5 cm respectively. L. camara with nemacur increased cumulative flower yield by between 78.6% and 83.6% compared to the untreated control. T. patula with nemacur reduced weed biomass by between 33.6% and 36.6% while L. camara alone decreased the population density of Oxalis cornulata weed by between 14% and 17% compared to untreated control. The improvement of nutrient status of the soil and the control of nematodes and weeds could have led to an improvement of yield characteristic of asclepias. A combination of L. camara with nemacur may be used in place of synthetic nematicides alone to control nematodes, weeds and improve nutrient levels. This treatment combination gave the best control of nematodes, enhanced plant growth and significantly increased flower yield compared to all other treatments. The results from this study give cutflower growers alternative options to manage root-knot nematodes and weeds under greenhouse conditions.