Author
|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings Publication Acceptance Date: 12/4/2002 Publication Date: 1/1/2005 Citation: Villavaso, E.J. 2005. Sperm production in tarnished plant bugs, lygus lineolaris (palisot de beauvois), following irradiation . National Cotton Council Beltwide Cotton Conference. Interpretive Summary: In 2001 the tarnished plant bugs(TPB)and western plant bugs were the second most damaging pests of cotton in the United States, infesting 55% of the acreage and combining to reduce yields by 0.98% or near 300,000 bales. TPB have developed resistance to several classes of insecticides, and new methods for their control are needed. The advent of an artificial diet and mass-rearing procedures for TPB has opened new possibilities for controlling this pest. Releases of sterilized TPB to suppress native populations is now a possibility. In the Mid South TPB populations often enter cotton fields after leaving the host weeds on which they survive during winter. These pre-cotton hosts tend to occur on very limited acreage, and releasing sterile TPB into them may provide a means of controlling TPB before they attack cotton and with little risk of released insects causing crop damage. Sperm production, shown to be a significant component of competitiveness in sterile boll weevils, can be reduced by irradiation. Before sterile TPB are released into cotton fields, it would be useful to develop an understanding of their sperm production and how natural production is affected by radiation treatments. Our research showed that TPB sperm production is inversely proportional to radiation dosages of 5 to 40 krad, but it is not so severely reduced as in boll weevils. Irradiated TPB appear to produce quantities of sperm adequate for reasonable competitiveness. Technical Abstract: With recent advances that allow their mass rearing, tarnished plant bugs (TPB), Lygus lineolaris (Palisot de Beauvois) are being considered as subjects for mass sterilization and release. Because sperm production in sterile insects has been cited as an important component of competitiveness, it was measured in irradiated and unirradiated TPB. Bugs subjected to dosages of 5, 10, 20, and 40 krad (50, 100, 200, and 400 Gy) of gamma-irradiation at ca. 7 d post-eclosion to adulthood produced less sperm than untreated bugs. Sperm production was inversely related to dosage. Sperm counts exceeded 1 million in the control group and peaked at ca. 600,000 in the 5 krad group at day 14 post-irradiation; at ca. 500,000 for the 10 and 20 krad groups between days 10 and 14 post-irradiation; and never exceeded half of the control for the 40 krad group, which suffered high mortality in all three replications. Sperm was not seen in newly eclosed adults, but accumulations averaged 23,000 in 3-d post-eclosion adults and increased to over 100,000 by day 5. Peak counts of 1.6 million were recorded on day 31 post-eclosion. |
