Thesis (M. Agric. (Plant Production)) -- University of Limpopo, 2019 / Phytonematicides have allelochemicals as active ingredients and could be highly
phytotoxic on crops being protected against nematode damage. In order to avoid
phytotoxicity, the application concentration, technically referred to as mean
concentration stimulation point (MCSP), along with the application interval, have to be
empirically established. The Curve-fitting Allelochemical Response Data (CARD)
computer-based model was adopted at the Green Biotechnologies Research Centre of
Excellence (GBRCE) for developing the MCSP. The MCSP is computed from the
CARD-generated biological indices and was technically defined as a phytonematicide
concentration that could manage the nematode population densities without causing
phytotoxicity to the test crop and it is plant-specific. The MCSP and application interval
had been empirically established for different crops, but they had not been established
for sweet potatoes. Therefore, the objective of the study was to determine the MCSP for
Nemarioc-AL phytonematicide on Meloidogyne javanica-infected sweet potato cv.
ꞌBopheloꞌ and its application interval. Sweet potato cuttings were planted in 25-cm
diameter plastic bags containing steam-pasteurised loam soil and Hygromix at 3:1 (v/v)
ratio. Each plant was inoculated with 5 000 eggs and second-stage juveniles (J2) of M.
javanica, with seven treatments, namely, 0, 2, 4, 8, 16, 32 and 64% Nemarioc-AL
phytonematicide, arranged in a randomised complete block design, with five replicates.
At 56 days after the initiation of treatment, the MCSP values for plant variables and
plant physiology variables were 1.92 and 3.08% Nemarioc-AL phytonematicide,
respectively. The overall sensitivity values for plant variables and plant physiology
variables were 0 and 1 unit, respectively, showing that the sweet potato cv. ꞌBopheloꞌ
was highly sensitive to the product. Nematode variables with increasing concentrations
of Nemarioc-AL phytonematicide exhibited positive and quadratic relations. The life
cycle of M. javanica and the derived MCSP were used to empirically establish the
application interval. Briefly, the location and most materials and methods were as
outlined above except that ‘weeks-per-month-of-30 days’, with the MCSP being applied
on 0, 7.5, 15, 22.5 and 30 days (0, 1, 2, 3 and 4 weeks) serving as treatments,
replicated eight times. At 56 days after the treatments, plant variables and increasing
application interval exhibited positive quadratic relations with the average of 2.55 ‘week
of-30-day-month’ translating to 19 days (2.55/4 × 30), with nematode variables
exhibiting negative quadratic relationships. In conclusion, when the MCSP of Nemarioc
AL phytonematicide on sweet potato cv. 'Bophelo' at 1.92% was applied every 19 days,
it would not be phytotoxic, but it would be able to suppress nematode population
densities of M. javanica. The MCSP for essential nutrient elements could be reduced to
that of plant growth variables, since the products are not intended for use as fertilisers.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/3080 |
| Date | January 2019 |
| Creators | Sebothoma, Elias Mphashi |
| Contributors | Mashela, P. W. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xvii, 59 leaves |
| Relation |
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