Abstract:
Sugarcane, Saccharum officinarum L. is one of the major commercial crops grown in Eswatini.
However, pest and diseases are pivotal to the decrease in yield output in the country. Sugarcane
white grubs (SWG), Heteronychus licas Klug (Coleoptera: Scarabaeidae) are amongst the
important pests of sugarcane in the country. Entomopathogenic nematodes (EPNs) were found to
be effective in controlling both soil borne as well as above ground insect pests. The current study
determined the effect of different concentrations of Malathion and EPNs on the mortality of
SWG. SWG larvae were dipped in different concentrations (0, 0.625, 1.25, and 2.5 g/L) of
malathion and (0, 200, 400, and 600 IJ/insect) EPNs. SWGs were also exposed to the same
concentrations in soil bioassays. Results obtained in the bioassays showed that Steinernema
yirgalemense at 600 IJs/insect (85.4%) gave the highest mortality which was not significantly
different from S. yirgalemense at 400 IJs/insect (72.9%). The Malathion concentrations gave 0,
79.2, 83.3 and 89.6% mortality for 0, 0.625, 1.25 and 2.5g/L of Malathion, respectively. Results
obtained in the soil bioassays showed that Steinernema yirgalemense, at 600 IJs/insect (80.5%),
provided higher (p < 0.05) mortality of the H. licas larvae which was not significantly different
from S. yirgalemense at 400 IJs/insect (70.2%). The Malathion concentrations gave 0, 83.3, 85.4
and 87.5% mortality for 0, 0.625, 1.25 and 2.5g/L of Malathion, respectively. The results
indicated that both EPN and Malathion were tested were effective against H. licas larvae.
Steinernema yirgalemense at 400 IJs/insect and Malathion at 0.625g/L can effectively H. licas
larvae but large-scale field trials are recommended to demonstrate the potential use of the
biocontrol agent within integrated pest management programs. |
