DefinePK

Research Objective

To examine the susceptibility of different developmental stages of Lasioderma serricorne F. to various doses of gamma irradiation to develop effective Phytosanitary Irradiation (PI) treatments.

Methodology

Insect culture of L. serricorne was maintained at $30^{\circ}\text{C} \pm 2$ and $50\%\pm 10$ RH. Developmental stages (24-hour eggs, 7-day old larvae, 7-day old pupae, and adults) were exposed to gamma radiation from a $\text{Co}^{60}$ research irradiator (dose rate $4.10 \text{ kGy/hr}$). Doses were verified using Fricke dosimeters. Specific dose ranges were applied to each stage (Eggs: 0-40 Gy; Larvae/Pupae/Adults: 0-100 Gy). Outcomes measured included mortality, inhibition of emergence, developmental period prolongation, growth index, and $\text{F}_1$ sterility. Statistical analysis used ANOVA and LSD test ($P \le 0.05$).

Methodology Flowchart

                        graph TD; A[Culture Preparation: Eggs, 7-day Larvae, 7-day Pupae, Adults] --> B[Gamma Irradiation Treatment]; B --> C[Dose Application0 Gy to 100 Gy]; C --> D[Observation of Developmental Stages]; D --> E[Data Collection: Mortality, Emergence, Development Time, Growth Index]; E --> F[Sterility Testing $\textF_1$ generation]; F --> G[Statistical Analysis ANOVA, LSD]; G --> H[Conclusion: Recommendation of 100 Gy as PI Treatment]; H --> I[Report Findings];                    

Discussion

Gamma irradiation effectively controls L. serricorne across all stages. Eggs are highly sensitive, requiring only 10 Gy for complete hatch inhibition. Larvae and pupae showed dose-dependent increases in developmental periods and mortality, with 100 Gy being highly effective. While pupae showed some radio-tolerance compared to eggs, 80 Gy achieved $\text{F}_1$ sterility. Adult sterility was achieved at 80-100 Gy, although males showed slightly more resistance than females or paired adults. The 100 Gy dose is recommended as an environmentally friendly PI treatment, avoiding hazardous pesticides.

Key Findings

- Eggs were the most radiosensitive stage; no egg hatching occurred at 10 Gy.
- A 100 Gy dose caused maximum mortality in larvae and resulted in the lowest adult emergence (23.3%).
- Pupae exhibited radio-tolerance; 80 Gy sterilized $\text{F}_1$ adults emerging from treated pupae.
- A 100 Gy dose caused complete sterility ($\text{F}_1$ eggs laid = 0, hatched = 0.0%) in adults emerging from irradiated larvae.
- Adults irradiated at 80 Gy or 100 Gy resulted in zero egg hatching, indicating effective sterility induction.
- The maximum dose recommended for effective control of all developmental stages was 100 Gy.

Conclusion

A maximum dose of 100 Gy gamma irradiation is recommended as an effective, residue-free, and environmentally friendly Phytosanitary Irradiation (PI) treatment for controlling all developmental stages of the cigarette beetle, L. serricorne, thereby promoting agricultural trade.

Fact Check

1. No larval emergence was observed when 24-hour eggs were treated at a 10 Gy dose of gamma irradiation. (Confirmed in Abstract and Results: Eggs treated at 10 Gy showed 0.0% hatch.)
2. A 100 Gy dose reduced adult emergence in 7-day old irradiated larvae to 23.3%. (Confirmed in Table 2.)
3. Pupal exposure to 80 Gy resulted in $\text{F}_1$ adults that were sterile (0.0% egg hatching recorded for females crossed with untreated males at 80 Gy in Table 5).

Mind Map