Behle Robert W, Tamez-Guerra Patricia, McGuire Michael R
Crop Bioprotection Research Unit, USDA-ARS-NCAUR, 1815 N. University, Peoria, IL 61604, USA.
J Econ Entomol. 2003 Aug;96(4):1066-75. doi: 10.1603/0022-0493-96.4.1066.
A multiple-embedded nucleopolyhedrovirus isolated from Anagrapha falcifera (Kirby) (AfMNPV) has potential to be developed into a microbial bioinsecticide because the host range includes several economic pests. We tested spray-dried AfMNPV formulations after storage for insecticidal activity based on bioassays with neonate Trichoplusia ni (Hübner). Eight experimental lignin-based spray-dried formulations, a glycerin-based formulation, and an unformulated sample were made with virus stock from three commercial production lots. Samples of these formulations were stored at 30 degrees C in individually sealed sample containers for destructive sampling after 1, 3, and 6 mo whereas the remaining product was stored in glass jars under refrigeration for up to 30 mo. Spray drying did not significantly reduce the initial LC50s of AfMNPV in experimental formulations compared with unformulated virus that was not spray dried. Refrigerated storage for 6 mo did not significantly lower virus activity of formulated samples compared with the unformulated AfMNPV stored frozen, while samples stored for 30 mo had higher LC50 values determined by both droplet and leaf feeding assays. When stored at 30 degrees C, most formulations (22 of 24) maintained insecticidal activity for 3 mo, but most (21 of 24) lost significant activity after 6 mo of storage. The glycerin-based formulation also lost activity within 6 mo of storage at 30 degrees C when compared with frozen unformulated virus, but did not lose activity when stored refrigerated for up to 30 mo. These formulations were evaluated after 7 mo at 4 degrees C for residual insecticidal activity when applied to field grown cabbage. Insecticidal activity was determined against T. ni neonates for treated leaf samples collected at 3, 7, 27, and 51 h after application of 2.5 x 10(12) obs/ha. Field tests showed no differences in activity among samples of stored formulations and one freshly made formulation. Spray-dried formulations had significantly higher insecticidal activity (67.5% mortality) compared with the unformulated treatment (30% mortality) sampled 3 h after application. At 3, 7, and 27 h after application, the spray-dried formulations had higher residual activity (67%, 59%, and 42% mortality, respectively), compared with the commercial glycerin-based formulation (61%, 38%, and 23% mortality, respectively). These experiments demonstrated that AfMNPV in lignin-based spray-dried formulations had a shelf-life of up to 3 mo at 30 degrees C and up to 30 mo at 4 degrees C, and with longer residual insecticidal activity in the field compared with unformulated or a glycerin formulation.
从苜蓿绿夜蛾（Kirby）中分离出的一种多重包埋核型多角体病毒（AfMNPV）有潜力被开发成一种微生物生物杀虫剂，因为其宿主范围包括几种经济害虫。我们基于对初孵小菜蛾（Hübner）的生物测定，测试了储存后的喷雾干燥AfMNPV制剂的杀虫活性。用来自三个商业生产批次的病毒原液制备了八种基于木质素的实验性喷雾干燥制剂、一种基于甘油的制剂和一个未配制的样品。这些制剂的样品在30℃下分别密封于样品容器中储存，在1、3和6个月后进行破坏性取样，而其余产品则储存在玻璃罐中冷藏长达30个月。与未喷雾干燥的未配制病毒相比，喷雾干燥并未显著降低实验制剂中AfMNPV的初始半数致死浓度（LC50）。与冷冻储存的未配制AfMNPV相比，冷藏6个月并未显著降低配制样品的病毒活性，而储存30个月的样品通过点滴法和叶片饲喂法测定的LC50值更高。当在30℃下储存时，大多数制剂（24种中的22种）在3个月内保持杀虫活性，但大多数（24种中的21种）在储存6个月后失去显著活性。与冷冻的未配制病毒相比，基于甘油的制剂在30℃下储存6个月内也失去了活性，但在冷藏长达30个月时并未失去活性。在4℃下储存7个月后，对田间种植的卷心菜施用这些制剂，评估其残留杀虫活性。在施用2.5×10¹²个包涵体/公顷后3、7、27和51小时收集处理过的叶片样品，测定对小菜蛾初孵幼虫的杀虫活性。田间试验表明，储存制剂的样品与一种新配制的制剂之间在活性上没有差异。与施用后3小时取样的未配制处理（死亡率30%）相比，喷雾干燥制剂具有显著更高的杀虫活性（死亡率67.5%）。在施用后3、7和27小时，喷雾干燥制剂具有更高的残留活性（分别为死亡率67%、59%和42%），相比之下，商业基于甘油的制剂（分别为死亡率61%、38%和23%）。这些实验表明，基于木质素的喷雾干燥制剂中的AfMNPV在30℃下的保质期长达3个月，在4℃下长达30个月，并且与未配制或甘油制剂相比，在田间具有更长的残留杀虫活性。
