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Helicoverpa punctigera (Wallengren) larvae have been recorded on native non-crop hosts in the inland regions of Australia. However, there are few records of their survival on these non-crop hosts, especially on plants with the C4 photosynthetic pathway. We investigated larval survival on four C4 plant species (Atriplex numularia Lindl. Atriplex vesicaria Heward ex Benth., Portulaca oleraceae L. and Tribulus terrestris L.) and two C3 plant species (Medicago polymorpha L. and Cullen cinereum (Lindl.)) under glasshouse conditions. Larvae fed on all C4 plants, although performance varied among these plants being higher (32.2 ± 6.9 and 31.7 ± 6.9% survival) on the Atriplex plant species and lowest (15.9 ± 7.9% survival) on P. oleraceae. Larval survival was similar between the two Atriplex species. A direct comparison of larval performance between the C4 plant A. nummularia and the known H. punctigera C3 host plants C. cinereum or M. polymorpha suggested that this C4 plant might be a suitable food source in the field, particularly in situations where it is growing nearby to C3 plants as is common in inland Australia.

Temperature is a crucial driver of insect activity and physiological processes throughout their life-history, and heat stress may impact life stages (larvae, pupae and adult) in different ways. Using thermolimit respirometry, we assessed the critical thermal maxima (CTmax-temperature at which an organism loses neuromuscular control), CO2 emission rate (V́CO2) and Q10 (a measure of V́CO2 temperature sensitivity) of three different life stages of Helicoverpa punctigera (Wallengren) by increasing their temperature exposure from 25 °C to 55 °C at a rate of 0.25 °C min−1. We found that the CTmax of larvae (49.1 °C ± 0.3 °C) was higher than pupae (47.4 °C ± 0.2 °C) and adults (46.9 °C ± 0.2 °C). The mean mass-specific CO2 emission rate (ml V́CO2 h−1) of larvae (0.26 ± 0.03 ml V́CO2 h−1) was also higher than adults (0.24 ± 0.04 ml V́CO2 h−1) and pupae (0.06 ± 0.02 ml V́CO2 h−1). The Q10: 25–35 °C for adults (2.01 ± 0.22) was significantly higher compared to larvae (1.40 ± 0.06) and Q10: 35–45 °C for adults (3.42 ± 0.24) was significantly higher compared to larvae (1.95 ± 0.08) and pupae (1.42 ± 0.98) respectively. We have established the upper thermal tolerance of H. punctigera, which will lead to a better understanding of the thermal physiology of this species both in its native range, and as a pest species in agricultural systems.

The native budworm, Helicoverpa punctigera (Wallengren), is an important economic insect pest of cotton and other crops. It is widely distributed in Australia and has been recorded on a range of host plants including native, non-crop hosts in inland regions. To date, there are few records of its occurrence on plants with the C4 photosynthetic pathway. Here, we assessed the oviposition preferences of H. punctigera for naturally occurring C3 and C4 plants under glasshouse conditions, to establish their potential as hosts. We conducted bioassays on two C4 plants, saltbushes Atriplex nummularia Lindl. and Atriplex vesicaria Heward ex Benth.; and two C3 plants, legumes Medicago polymorpha L. (burr medic) and Cullen cinereum (Lindl.) J.W.Grimes (annual verbine). The two C4 plants attract egg laying in the field; however, C3 plants are the preferred hosts. Ovipositing females showed a preference for the C3 over the C4 plants but oviposition occurred on both. Of the C4 plants, females preferred to oviposit on A. nummularia (77%) over A. vesicaria (24%) in both a multi- and two-choice test. In addition, ovipositing females preferred the upper leaf surface of A. nummularia (68%) and the under leaf surface of A. vesicaria (64%) as their oviposition site. Our findings suggest that under field conditions, when C4 plants such as saltbushes grow near C3 plants, as occurs in inland regions, the C4 plants could receive eggs along with the C3 plants, enabling the initial stages of larval recruitment to occur in C3 plants.

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