I agree with Fireboss. A lot of it depends on what area of South Africa you will be hunting. If in Cape region, no worries.
I have hunted Northern South Africa on four occasions (bordering Limpopo) and had no problems myself with mosquitos - and this was in late May/early June. Discuss with your PH or outfitter and see what they recommend.
You will go back! Africa gets into your soul!