黄绿绿僵菌悬乳剂与低剂量阿维菌素对Q型烟粉虱的联合防治作用

【目的】烟粉虱(Bemisia tabaci)是重要的入侵农业害虫,已对众多常规杀虫剂产生了高度抗性。论文针对烟粉虱的高效治理问题,通过室内和田间联合应用昆虫病原真菌与化学农药,评价其是否对烟粉虱防治具有协同增效作用,为烟粉虱的有效防控提供新的途径。【方法】在前期试验已经筛选到一株对Q型烟粉虱毒力较高的黄绿绿僵菌(Metarhizium flavoviride)菌株Mf96基础上,先于实验室条件下采用喷雾法,在3个浓度梯度(1.0×10~8、1.0×10~7、1.0×10~6个孢子/mL)的黄绿绿僵菌(Mf96)分生孢子悬乳剂中添加1.8%阿维菌素WP,分别配制成含0、15、30、45和60μg·mL~(-1)剂量的1.8%阿维菌素WP溶液,并喷到Q型烟粉虱2龄若虫体表,检测其死亡率。在体视显微镜下记录单位面积内的孢子沉积数量。田间试验中,分别将黄绿绿僵菌Mf96菌株悬乳剂(1.0×10~8个孢子/mL)和1.8%阿维菌素WP(60μg·mL~(-1))单用和混用后喷施于NC95烟草上,评价其对烟粉虱的防治效果。【结果】实验室条件下,Mf96菌株悬乳剂从第4天到第8天对"Q型"烟粉虱2龄若虫的LC50从1 376降至183个孢子/mm~2。Mf96菌株与阿维菌素(60μg·mL~(-1))混合作用7 d后,真菌LC50从378降至46个孢子/mm~2。低剂量的阿维菌素对黄绿绿僵菌Mf96菌株的分生孢子和菌丝生长没有影响。不同浓度黄绿绿僵菌(低、中、高)孢子悬乳剂分别与不同浓度阿维菌素(0、15、30、45和60μg·mL~(-1))复配处理后,Q型烟粉虱2龄若虫有不同僵虫率,其中以阿维菌素30μg·mL~(-1)与黄绿绿僵菌高浓度悬乳剂复配处理Q型烟粉虱2龄若虫产生的僵虫率最高,达86.8%。对照(悬乳剂基础配方)和单独喷施阿维菌素处理中未见到僵虫。田间喷施真菌孢子悬乳剂、药剂和菌药混剂后5 d和10 d,菌药混用的Q型烟粉虱若虫虫口减退率均最高,分别为53.6%和85.7%;5个随机抽查时间得到校正防效变化趋势与虫口减退率趋势一致,25 d菌药混用的校正防效在所有处理中最高,达88.9%;5个随机抽查时间得到的对照组虫口减退率均为负值。【结论】黄绿绿僵菌Mf96菌株与阿维菌素联合在实验室和田间防治Q型烟粉虱均具有协同增效作用。因此,利用黄绿绿僵菌Mf96分生孢子悬乳剂与低剂量1.8%阿维菌素WP联合防治Q型烟粉虱是一项新的有效措施。

Integration of Emulsifiable Formulation Metarhizium flavoviride with Low-Rate Abamectin for Control of Bemisia tabaci Q Biotype

【Objective】 Bemisia tabaci, an important invasion insect pest in agriculture, has displayed a high resistance to many conventional pesticides. The objective of this study is to evaluate the synergistic effect of joint application of entomopathogenic fungi and chemical pesticides against B. tabaci in laboratory and field, and to provide a new approach for effective control of B. tabaci. 【Method】 Based on the previous study that a highly virulent of Metarhizium flavoviride strain (Mf96) was screened for control of B. tabaci Q biotype, three gradient emulsifiable formulation of Mf96 (1.0×10⁸, 1.0×10⁷, 1.0×10⁶ conidia/mL), which were combined with five low doses of abamectin EC (0, 15, 30, 45 and 60 µg·mL^-1) were separately sprayed to the body surface of 2nd instar nymphs of B. tabaci Q biotype in laboratory, and the mortalities were tested. The number of conidia deposited on the unit surface was counted under stereomicroscope. Single agent and their equal volume mixture of the suspension emulsion of Mf96 strain (1.0×10⁸ conidia/mL) and 1.8% abamectin WP (60 µg·mL^-1) were separately sprayed to control B. tabaci Q biotype on tobacco in the field, and the control efficacies were evaluated. 【Result】 LC₅₀ of Mf96 against 2nd instar nymphs of B. tabaci Q biotype decreased from 1 376 to 183 conidia/mm² during 4th to 8th day. After 7 days, LC₅₀ of the fungus combined with abamectin (60 µg·mL^-1) decreased from 378 to 46 conidia/mm². Abamectin had no significant effect on the fungal outgrowths and infection to 2nd instar nymphs of B. tabaci Q biotype at the low spray rates. The mixture suspension of different concentrations of fungus (low, medial and high) with abamectin (15, 30, 45 and 60 µg·mL^-1) resulted in different rates of mycotized cadavers, and high concentration of fungal mixture suspension with 30 µg·mL^-1 of abamectin caused 86.8% mortality of B. tabaci. No cadavers were observed in untreated control and single abamectin spray. Fungal conidia suspension emulsion, abamectin and their mixture were separately sprayed in the field, and the decline rates in nymphae of B. tabaci Q biotype population was the highest (53.6% and 85.7%) when the mixture was sprayed after 5 d and 10 d. Meanwhile, the changing trends of corrected control efficacies and population decline rate of B. tabaci Q biotype were similar at 5 random checks, the corrected control efficacy of the mixture was the highest (88.9%) after 25 d. The population decline rate of B. tabaci Q biotype in untreated control was negative value.【Conclusion】The combined of M. flavoviride with abamectin showed synergistic interaction, with additive effects on Q biotype B. tabaci. Therefore, it is an effective approach to control B. tabaci by combining M. flavoviride with abamectin at low spray rate.