Biological study of Oxycarenus hyalinipennis Costa as a predominant species of cotton seed Bugs and its effect on physiological characteristics of seed

The most important element in the implementation of cotton IPM is the use of healthy seeds with high vitality. In a few years, cotton seed bugs have significantly increased their population in cotton fields and affect the quantitative and qualitative properties of seeds by feeding on them. Adults and nymphs of Oxycarenus hyalinipennis Costa feed on the contents of cottonseed, resulting in a loss in seed weight, germination rate, oil, protein and nitrogen content. The activity of the genus Oxycarenus on cotton fibers disrupts the ginning process and causes spotting, soiling and reduced quality of cotton fibers. Insect pests are important factors that reduce the yield of cotton crops. Proper control in the field requires adequate knowledge of the species of pest, its biology and the extent of its damage to the cotton plant.Due to the increase in the population of seed bugs in cotton fields in recent years, it was necessary to determine the biological characteristics, the predominant species of these seed bugs and their impact on the quantitative and qualitative characteristics of the seed and was investigated in this study.

For this purpose, a study was conducted in 2016-2017 in which seed bugs were collected from the cotton fields of Hashemabad Cotton Research Station and sent to Insect Classification Research Department of Iranian Plant Protection Research Institute to identify and confirm the genus and species. The insects were cultured under laboratory conditions. Biological factors of the insects such as adult life span, total nymphal life span, pre-oviposition period, oviposition period and total life cycle were evaluated. Morphological characteristics such as length, width and weight of adult male and female insects were also studied. To study the effects of the pest on the physiological characteristics of the seeds during the period of boll opening in the cotton field, 45 bolls were randomly isolated and covered with paper bags, and 45 marked bolls were naturally exposed to the pest. The seeds were sampled in the field in three stages at intervals of ten days. Necessary investigations on quantitative and qualitative characters of the seeds were carried out in the laboratory of the institute.

The seed bugs were identified under the scientific name Oxycarenus hyalinipennis Costa (Hemiptera: Oxycarenidae). Laboratory studies on insect biology revealed that adult longevity, total nymphal duration, pre-oviposition time, oviposition time, and total life cycle Mean (±SE) 32±2.20, 13.6±2.08, 10.69±1.35, 19.16±2.27, and 30±2.47 days, respectively. The results showed that the average weight of cotton seeds was highest in isolated bolls with an average of 10.71 grams. Thus, the average weight was 1.33% and 27.1% higher than plants whose bolls were not isolated and cotton seeds exposed to beetles, respectively. In isolated cotton seeds in the field, 20.5% less soluble carbohydrates and 59.1% less phenols were observed than in seeds exposed to pests.

When the population of cotton seed bugs increases, this pest can significantly damage the cotton crop by reducing the potency and other quantitative and qualitative properties of the seeds.