Novaluron prevents oogenesis and oviposition by inducing ultrastructural changes in ovarian tissue of young adult Lygus lineolaris

Abstract

BACKGROUND: The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has emerged as a major pest of cotton, Gossypium hirsutum L, in the mid-southern USA. In the early 1990s L. lineolaris populations developed resistance to several classes of conventional insecticides, increasing the need for insecticides with alternative modes of action such as insect growth regulators (IGRs) for integrated pest management (IPM). The benzoylphenyl urea (BPU) class of IGRs acts by disrupting the growth and development of immature stages of insects, but little is known about its impact on adult stages. RESULTS: The effect of novaluron (Diamond™ 0.83EC), a BPU with known chitin synthesis inhibitor activity, was investigated on adult females of L. lineolaris. Treatment of 1-day-old adults with 600 ppm of novaluron in the diet prevented oviposition, while treatment of older females had no impact on oviposition. Oral novaluron exposure of adults of all ages reduced the viability of eggs laid. Novaluron treatment caused ultrastructural changes in the ovaries of 1-day-old adults (48 h post exposure), distorting the follicular epithelial cell architecture of developing oocytes. Additionally, novaluron treatment decreased the chitin content in ovarian tissue. CONCLUSION: Our results suggest that chitin or chitin-like components in the developing ovaries of adult L. lineolaris are a target of IGRs such as novaluron, but its activity is specific to a critical time during development. This enhances our understanding of the effects of BPUs on adult insects and could lead to incorporation of IGRs in IPM for controlling adult insect pest populations in the field.

Effect of Insect Growth Regulator Insecticides Novaluron, Teflubenzuron and Lufenuron on the Morphology and Physiology of Euschistus heros

“…Studies performed in the laboratory by Tail et al (2010) with the grasshopper S. gregaria, to verify the influence of the ingestion of diflubenzuron (30 mg/ml), the authors found reduced weight of the ovaries after females of this species ingested this IGRs. In a study with adult of Lygus lineolaris (Palisot Beauvois, 1818) (Heteroptera: Miridae), which ingested a diet incorporated with novaluron (600 ppm), Catchot et al (2020) observed a negative effect on oviposition rate, ovarian maturation, and hatching of eggs laid by this species. These results corroborate those obtained in this work when adults of E. heros were exposed to soybean leaves treated with novaluron at the highest dose tested, for egg viability, although the target species and exposure mode were different.…”

Residual Effects of Novaluron and Efficacy of Subsequent Applications to Control Mid-South Tarnished Plant Bug (Hemiptera: Miridae) Populations

“…The success of this approach is likely due to migrating adults being controlled before economic damage from feeding and extensive egg lay occurs. Control of local nymph populations hatching while there was residual novaluron and the potential reduced fecundity of remaining tarnished plant bug adults by the IGR proved beneficial (Catchot et al 2020). This strategy could prove useful in breaking the initial early season buildup of tarnished plant bugs moving into flowering cotton fields, which are most susceptible to yield loss (Wood et al, 2016).…”

“…Data from Catchot et al (2021) indicated that ingestion of novaluron by tarnished plant bug adults was more effective than contact exposure; however, contact with treated foliage up to one day after application often led to the same result: decreased nymph populations. When adult females of any age were exposed to novaluron, reduced egg viability was observed in addition to ovarian malformation in newly reproducing adults (Catchot et al, 2020). Laboratory studies conducted by Owen et al (2011) showed that novaluron is more active against first instar nymphs as compared to second and fifth instars.…”

Biology, Ecology, and Pest Management of the Tarnished Plant Bug, Lygus lineolaris (Palisot de Beauvois) in Southern Row Crops

“…Novaluron is an insect growth regulator that only affects the immature stages of L. lineolaris [ 164 ]. However, recent research has shown that novaluron can cause ultrastructural changes in the ovarian tissues of adult L. lineolaris that prevent oogenesis and oviposition [ 165 ]. Those sublethal effects have also been shown to reduce L. lineolaris populations in the field [ 166 ].…”