The effect of different host plants on the reproduction and longevity of Nysius natalensis H. du Plessis 1,3 *, M.J. Byrne 2 & J. van den Berg 1 1 Unit for Environmental Sciences and Management, North-West University, Potchefstroom 2520, South Africa, 2 Ecophysiological Studies Research Group, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa, and 3 ARC – Grain Crops Institute, Private Bag X1251, Potchefstroom 2520, South Africa Accepted: 18 July 2012 Key words: adult feeding, cultural control, false chinch bug, fecundity, Hemiptera, insect nutrition, nymphal feeding, Orsillidae, weeds, wild host plants Abstract Nysius natalensis Evans (Hemiptera: Orsillidae) is a pest of sunflower in South Africa. Adults invade sunflower fields from their weedy hosts which occur inside crop fields and on surrounding headlands. The host plant suitability for survival and reproduction as well as the effect of within- generation host switching was studied on different wild host plants and sunflower. Life history parameters used to assess host plant suitability were F 1 adult survival, pre-oviposition period, fecun- dity, and longevity. Nymphs and adults were provided with stems and seeds of five host plants, viz., Amaranthus hybridus L. (Amaranthaceae), Portulaca oleracea L. (Portulacaceae), Chenopodium album L. (Chenopodiaceae), Conyza albida Spreng. (Asteraceae), and sunflower, Helianthus annuus L. (Asteraceae). Nymphs were reared on crushed seed of the five plant species. After completion of the nymphal stage, emerging adults of each host plant group were provided with seed of a different host plant species for food. Adults did not survive long on stems only and very few eggs were laid. Seeds of the host plant species were shown to be an essential source of nutrients for N. natalensis reproduction, whereas the vegetative plant parts were unsuitable. Nymphal food and host-plant switching between the nymphal and adult stages significantly affected the pre-oviposition period. Nymphal and adult food source also affected female longevity. The number of eggs laid was not influ- enced by nymphal food, but was influenced by adult food and the switch between nymphal and adult food. The comparative attractiveness of sunflower and wild host plants for oviposition was also investigated and showed that females preferred to lay eggs on wild host plants, compared with sunflower. These results may explain why N. natalensis will lay their eggs on sunflower after weeds in the vicinity are controlled, or senesce toward the end of the growing season. Introduction Different host plants can play an important role in popula- tion increases and outbreaks of polyphagous insect pests (Singh & Parihar, 1988). Both quality and quantity of food influence the development and fecundity of insects (Kehat & Wyndham, 1972). Components of host plant quality (such as carbon, nitrogen, and defensive metabolites) directly affect potential and achieved herbivore fecundity (Awmack & Leather, 2002). Host plant quality also affects insect reproduction strategies. Egg size and quality, the allocation of resources to eggs, and the choice of oviposi- tion sites may all be influenced by plant quality, as may egg or embryo resorption on poor-quality hosts (Awmack & Leather, 2002). The pre-oviposition period of many penta- tomids is spent on plant species other than their nymphal hosts because newly fledged adults disperse (Panizzi, 1997). The quality of the food source used during the nymph-to-adult host-switching cycle has a positive or neg- ative effect, or no effect at all, on adult performance of these pentatomids (Panizzi, 1997). Some species of the hemipteran subfamily Orsillinae feed on the vegetative parts of plants, but in most cases they utilize unripe or ripe seeds that are either still on the plants or have fallen to the ground (Bo ¨cher, 1972). Wild host plants play an important role in sustaining populations of the false cinch bug, Nysius natalensis Evans (Hemiptera: Orsillidae). Eggs, nymphs, and adults of this pest have been collected from *Correspondence: H. du Plessis, Unit for Environmental Sciences and Management, North-West University, Potchefstroom 2520, South Africa. E-mail: hannalene.duplessis@nwu.ac.za © 2012 The Netherlands Entomological Society Entomologia Experimentalis et Applicata 145: 209–214, 2012 Entomologia Experimentalis et Applicata © 2012 The Netherlands Entomological Society 209 DOI: 10.1111/eea.12001