UC Riverside

The cotton seed bug (CSB), Oxycarenus hyalinipennis (Costa) (Hemiptera: Oxycarenidae), is seed-feeding insect that may become a significant pest of cotton, valued at $135.2 million in California. CSB feeding can reduce the cotton seed weight by up to 15 percent, germination rates by as much as 88 percent, and cotton lint may be stained if CSB are crushed during the ginning process. While CSB is not yet found on cotton in California, CSB is found on ornamental plants such as cow-itch trees, Lagunaria patersonia (Andrews) G. Don (Malvales: Malvaceae). Lagunaria patersonia is a good host plant because seed pods present year-round provide food and shelter for CSB feeding swarms. However, minimal studies have analyzed the population dynamics of CSB on L. patersonia, documented natural enemies, or described the developmental biology of CSB. Phenological sampling found that L. patersonia blooms once per year around May/June and pods reach maturity in early September. Pod sampling determined that CSB populations reached their peak in November and December. Population pyramids demonstrated that adult CSB made up most of the population and were significantly more abundant that nymphs. Generalized Linear Mixed-effects Models (GLMM) found that for Adult CSB in 2024 pods, month was a significant predictor, pod width, length, and number of seeds were positively associated with number of CSB adults, and temperature was negatively associated. For Adult CSB in 2025 pods, month was a significant predictor, pod width, and number of seeds were positively associated with number of CSB adults, and pod length was negatively associated. Month and number of seeds per pod were significant predictors, the latter of which had a positive effect on CSB nymphs in 2024 and 2025 pods. Sentinel egg cards placed on L. patesonia and Sphaeralcea ambigua (A. Gray) (Malvales: Malvaceae) did not detect parasitoids but detected a whirligig mite, Anystis sp. (von Heyden) (Trombidiformes: Anystidae), and Argentine ants, Linepithema humile (Mayr) (Hymenoptera: Formicidae). Retrieval and hatch rates on L. patersonia were significantly greater than on S. ambigua. A significant annual effect, where the retrieval rate for eggs in 2025 was consistently lower than the retrieval rate in 2024, was observed on both plants. There was no significant annual effect on hatch rates for either plant. Predator bioassays revealed that long-legged sac-spiders, Cheiracanthium sp. (C. L. Koch) (Araneae: Cheiricanthiidae buttonhook leafbeetle jumping spiders, Sassacus vitis (Cockerell), (Araneae: Salticidae), green lacewing larvae, Chrysoperla Comanche (Banks) (Neuroptera: Chrysopidae), pirate bugs, Buchananiella continua (White), (Hemiptera: Anthocoridae), leafhopper assassin bug, Zelus renardii (Kolenati), (Hemiptera: Reduviidae), ground sac spider, Trachelas sp. (L. Koch) (Araneae: Trachelidae), and plant bug nymphs, Phytocoris sp. (Fallén) (Hemiptera: Miridae) all fed on at least one stage of CSB. However, this feeding provided little to no natural control of CSB. At a fluctuating 27 °C, CSB reared on L. patersonia seeds developed faster, had a higher probability of surviving to adulthood, and lived longer as adults than CSB reared on upland cotton seeds. Fecundity of females on a diet of L. patersonia or upland cotton seeds was not significantly different. Furthermore, females on both seeds exhibited two peaks for egg production. On L. patersonia seeds, unmated males and females lived significantly longer than their mated counter parts of the same sex and the opposite result was found on upland cotton seeds. Life table analysis predicted that CSB populations on a diet of both seeds would increase. Generation and doubling times were much lower for CSB on a diet of L. patersonia seeds.