Bishwo Prasad Mainali

Evaluation of Apple and Orange Fruits as Food Sources for the Development of Halyomorpha halys (Hemiptera: Pentatomidae)

Halyomorpha halys (Stl) (Hemiptera: Pentatomidae) is a typical polyphagous stink bug causing losses in several host plants including leguminous crops and fruits. Nutritional status of fruits such as apple and orange for the development of H. halys is not yet clear. We evaluated fruits of apple and orange with or without soybean-peanuts as food sources to investigate development, mortality and fecundity of the stink bug in a controlled condition. Those only fed on water could not develop into third instars. H. halys could not develop into fourth instar on apple only food. However, on an orange only food, 14% of H. halys emerged as adults. Those fed on orange only food had the longest development period (74.2 d). Total mortality of those fed on foods consisting of soybean-peanut ranged from 38 to 44%. In an average a female laid 169~190 eggs in a lifetime and those eggs had 81~83% hatchability. Results indicated that the apple fruit as a solo food source is an incomplete food for H. halys development while orange could support development of only few of the bugs.

Preference of Adult Alfalfa Weevil, Hypera postica (Gyllenhal), (Coleoptera: Curculionidae), to Different Seedlings of Upland Crops

Occurrence of adult alfalfa weevil, Hypera postica Gyllenhal, was observed at Chinese milk vetch field, and host plant preference of its generation adult was observed at greenhouse and Chinese milk vetch field. The over-wintered adult of the weevil appeared from late March and peaked in mid April while the generation adult appeared from late April and peaked in late May. However, the occurrence of over-wintered adult was very low contrary to the generation adult which was very high with some variations among observed years. In greenhouse, host plant preference of adult generation of H. postica was evaluated with 11 different seedlings. H. postica was found to occur in significantly higher number on Chinese cabbage seedling followed by soybean, and kale at 7 days after releasing(DAR). Corn, crown daisy and sorghum were found to be the least preferred with nil occurrence of the weevil. Seedlings damage rate by H. postica feeding at 7DAR was the most severe on Chinese cabbage(60.0%) followed by soybean(50.0%), kale(30.0%), foxtail millet(16.7%), proso millet(13.3%) and lettuce(3.3%) significantly. Also, seedlings damage rate by H. postica at 7DAR in Chinese milk vetch field had shown the similar trend with Chinese cabbage(46.7%), soybean(43.3%), kale(23.3%), foxtail millet(13.3%) and proso millet(13.3%) in greenhouse significantly. Accordingly, results on host plant preference of H. postica from this study can be used as a basic information for safe cultivation of upland crops at near or around green manure crop field.

Detection of Soybean mosaic virus by Reverse Transcription Loop-mediated Isothermal Amplification

Soybean mosaic virus (SMV) is a prevalent pathogen that causes significant yield reduction in soybean production worldwide. SMV belongs to potyvirus and causes typical symptoms such as mild mosaic, mosaic and necrosis. SMV is seed-borne and also transmitted by aphid. Eleven SMV strains, G1 to G7, G5H, G6H, G7H, and G7a were reported in soybean varieties in Korea. A reverse transcription loop-mediated isothermal amplification (RT-LAMP) method allowed one-step detection of gene amplification by simple procedure and needed only a simple incubator for isothermal template. This RT-LAMP method allowed direct detection of RNA from virus-infected plants without thermal cycling and gel electrophoresis. In this study, we designed RT-LAMP primers named SML-F3/B3/FIP/BIP from coat protein gene sequence of SMV. After the reaction of RT-LAMP, products were identified by electrophoresis and with the detective fluorescent dye, SYBR Green I under daylight and UV light. Optimal reaction condition was at 58C for 60 min and the primers of RT-LAMP showed the specificity for nine SMV strains tested in this study.