When travelling in areas with malaria it is advisable to wear loose-fitting clothes with long trousers and long tunics and sleeves in the evenings. Travellers to areas with a risk of dengue fever infection should cover up during the day if possible, as the Aedes spp. mosquitoes that transmit dengue fever bite during the day.
In tick-infested areas, trousers should be tucked into socks to prevent ticks from crawling up the legs. Avoid dark blue clothing when travelling in Africa in areas where tsetse flies exist.
Clothing can be treated with an insecticide (e.g. permethrin), which kills insects, including ticks, on contact. Permethrin is available in formulations designed to be sprayed on to clothing. (Source: https://www.nathnac.org/pro/factsheets/iba.htm) Moreover loose fitting clothes will provide additional protection from the sun. (Source: http://www.who.int/uv/sun_protection/en/)