Thesis (M. Agric. (Plant Protection)) -- University of Limpopo, 2019 / Damage and significant losses of potato cultivar due to Meloidogyne incognita has
become a serious challenge, after the withdrawal of synthetic chemical nematicides
due to their environment-unfriendliness. Various alternatives have been investigated
each with a wide range of drawbacks. Most phytonematicides were highly phytotoxic
to crops, while their effects on nematode suppression were highly variable. The use
of Nemarioc-AG phytonematicide at pre- and post-emergence would help in
determining the level that is effective in supressing M. incognita without being
phytotoxic. The objective of this study was to determine whether Nemarioc-AG
phytonematicide could serve as pre- and post-emergent phytonematicide without
inducing phytotoxicity while suppressing population densities of M. incognita. For
achieving this objective, treatments, namely, 0, 2, 4, 8 and 16 g of Nemarioc-AG
phytonematicide, were arranged in a randomised complete block design (RCBD),
with 7 replicates. Potato seed tubers were sown into 20 cm pots, Nemarioc-AG
phytonematicide placed above the tubers and covered with soil, after initiation of
treatments 5 000 eggs and second stage juveniles (J2) of M. incognita per plant
were inoculated. For post-emergent, treatments, replications and design were the
same as in pre-emergent. Potato seed tubers were sown and inoculated with 5000
eggs and second-stage juveniles (J2) of M. incognita per plant after 100%
emergence. Nemarioc-AG phytonematicide were applied 7 days after inoculation.
Trials were conducted in autumn (February-April) 2017 (Experiment 1) and repeated
in autumn 2018 (Experiment 2). Plant growth variables and selected nutrient
elements were collected and analysed using the Curve Fitting Allelochemical
Response Data (CARD) model and lines of best fit, respectively. In pre-emergent
application, Experiment 1, MCSP was established at 1.95 g, with the overall
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sensitivity (∑k) being equal to zero. Therefore, in Experiment 1 and Experiment 2, all
nutrient elements to increasing concentration of Nemarioc-AG phytonematicide
exhibited negative quadratic relations. In both Experiments, nematode variables over
increasing concentration of Nemarioc-AG phytonematicide on potato exhibited
negative quadratic relations, except in Experiment 1, where J2 in roots exhibited
positive quadratic relations, with models ranging between 72 to 99%. In post
emergent, Experiment 1, MCSP was established at 1.57 g, with the overall sensitivity
(∑k) being equal to 2. In Experiment 1 and Experiment 2, nutrient elements over
increasing concentration of Nemarioc-AG phytonematicide exhibited positive and
negative quadratic relations, with models ranging from 89 to 97%. In Experiment 1,
nematode variables over increasing concentration of Nemarioc-AG phytonematicide
exhibited negative quadratic relations, with models ranging between 92 and 98%.
Positive and negative relations suggested that the product stimulated and inhibited
plant growth or accumulation of selected essential nutrient elements, respectively.
Increasing concentration of Nemarioc-AG phytonematicide had stimulated certain
plant variables and inhibited population densities of M. incognita in pre- and post
emergent application; therefore, this product was suitable for use as pre- and post
emergent in management of nematodes on the test crop.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/3072 |
| Date | January 2019 |
| Creators | Sefefe, Selaelo Khutso |
| Contributors | Mashela, P. W., Pofu, K. M. |
| Publisher | University of Limpopo |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xii, 45 leaves |
| Relation |
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