Potential of 2,4-dihydroxybenzoic acid as an oviposition stimulant for mass-reared ladybird beetles

Authors: Riddick, Eric; WU, ZHIXIN - Retired ARS Employee; Eller, Fred; Berhow, Mark

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2019
Publication Date: 3/7/2019
Publication URL: http://handle.nal.usda.gov/10113/6471117
Citation: Riddick, E.W., Wu, Z., Eller, F.J., Berhow, M.A. 2019. Potential of 2,4-dihydroxybenzoic acid as an oviposition stimulant for mass-reared ladybird beetles. Journal of Insect Science. 19(2):1-6.

Interpretive Summary: A major challenge to mass-producing natural enemies (predators) in large quantities for augmentative biological control of plant pests is stimulating females to lay their full potential of eggs when reared on alternative foods. Alternative foods often lack the chemical cues that predators need to choose egg-laying sites and stimulate maximum egg laying, i.e., oviposition. In this study, we discovered that an inexpensive plant-based compound, known as 2,4-dihydroxybenzoic acid (DHBA) has potential as an oviposition stimulant for ladybird beetles (Coleomegilla maculata females). In communal cages (housing 10 females), oviposition occurred near DHBA, rather than on the walls of the cage over the 12-day test period. When a tissue substrate was added in cages, some females oviposited on the tissue instead. The number of egg clutches per female per day in communal cages, regardless of oviposition site, was not greater in cages with DHBA only. In solitary cages (housing 1 female), females also preferred to oviposit near DHBA over a 12-day test period. But when females were restricted from contacting or tasting DHBA, the stimulatory response declined dramatically. This study is the first to show that DHBA has some potential value as an inexpensive oviposition stimulant for mass-produced ladybird beetles. Further research is necessary to define the taste (gustatory) and smell (olfactory) responses of ladybird beetles exposed to DHBA and related products.

Technical Abstract: The discovery of inexpensive, readily-available bioflavonoids and their degradation products that boost the reproductive potential of mass-reared predators is the overarching goal of this research. We tested the hypothesis that 2,4-dihydroxybenzoic acid (DHBA), an inexpensive degradation product of morin (a flavonol bioflavonoid), stimulates oviposition by the ladybird beetle Coleomegilla maculata (DeGeer). We also tested the hypothesis that C. maculata females must touch or taste DHBA to stimulate oviposition. We setup bioassays in communal cages (housing 10 females) and solitary cages (housing 1 female). In communal cages, 99% of all egg clutches were found in or near the chemical dish with DHBA. Provisioning cages with a tissue substrate reduced oviposition in the chemical dish. Regardless of oviposition site, egg clutch number and egg number per clutch did not increase in communal cages with DHBA only. The combination of DHBA plus tissue in the same cage did not enhance the production of egg clutches. In solitary cages, 70% of all egg clutches were found in the chemical dish with DHBA. Affixing DHBA to the base of the chemical dish, then covering it with a nylon screen, reduced oviposition to 5%. This study suggests that females must touch or taste DHBA to stimulate oviposition. The importance of gustation (taste) and olfaction (smell), rather than olfaction alone, to oviposition stimulation requires further study. DHBA could potentially serve as a cost-effective oviposition stimulant for predatory ladybird beetles in some mass-rearing systems.