Efficiency of diatomaceous earths to control four species of the subfamily Bruchinae (Col.: Bruchidae)
عنوان دوره: اولین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Diatomaceous earths (DEs) as alternative to synthetic insecticides abrade insect cuticle, remove its epicuticular wax and desiccation by body water loss. Easily removing form the products before milling, low toxicity to mammalian and non-target organisms are advantages of DEs application in the control of insects especially in the stores. This research evaluated the insecticidal efficiency of commercial formulations of DE including Dryside®, Silicosec® and Pyrisec® on 5-7 day old adults of bruchid beetles (Callosobracus maculatus F., Bruchus pisorum L., B. rufimanus L., and B. lentis L.) at 31±2 °C and 65±5 % RH in dark. The final doses of DEs (LD20-LD80) were admixed with 100 grams of cowpea bean, green pea, fava bean and brown lentil, respectively. Each admixture was manually shaken for 5 min and placed them for 30 min at ambient temperature for uniform distribution and adherence to the grains. Then 50 grams of each treatment were placed in a glass bottle and 20 adults of bruchid beetles were introduced to experimental bottles. The numbers of dead and alive beetles were assessed during the 1st to the 15th day post-treatments. Results showed that Pyrisec®, (containing 25% pyrethrum, 3.1% pipronylbutaoxide and 97.5% of SilicoSec) caused significantly higher mortality than the other two formulations. All treated adults of C. maculatus, B. pisorum, B. rufimanus, and B. lentis were dead after 8, 7, 2 and 12 days of treatment with Pyrisec® at 4000 mg kg-1 (LD100) which demonstrated the effectiveness of this dose against these pests. LD50 values of Pyrisec®, Dryside® and Silicosec® were estimated (900, 1000, 1200, 700), (1500, 1000, 1200, 900) and (1000, 1000, 1500, 900) mg kg-1 on the bruchid beetles, respectively. As results confirmed mortality of DEs are highly affected by chemical structure of formulations, the type of treated grains (lentis), the insect species, time of exposure and dose (P < 0.001). As a conclusion, DE formulations can be used to protect grains against bruchid adults. The sensitivity of B. lentis could be explained by its body thickness and seed sizes of treated lentil in comparison to others which is needed to study in future. Furthermore, the study of residual effects of the DE formulations on grains is required.
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