甲氨基阿维菌素苯甲酸盐微乳剂对蔬菜害虫的控制作

甲氨基阿维菌素苯甲酸盐微乳剂对蔬菜害虫的控制作 甲氨基阿维菌素苯甲酸盐微乳剂对蔬菜害虫的控制作用 , 分类: , 作者:钟国华 彭雏燕 陈文团 官 珊 刘晓金 胡美英 , 字数:3531 来源:植物保护 摘要 0(5,甲氨基阿维菌素苯甲酸盐微乳剂以 2药量10mL,667m防治甜菜夜蛾的效果明显优于其2倍使用剂量的乳油，药后3,7 d，对苋菜上甜菜夜蛾的防治效果达到85,以上，显著优于1(8,阿维 2菌素乳油33(33 mL,667m防治效果;施药量8(3 23mL,667m，药后7d，对丝瓜上美洲斑潜蝇(的防治效果达85,以上，与1(8,阿维菌素乳油50mL 2,667m防治效果差异不显著。 关键词 有害生物化学防治;甲氨基阿维菌素苯甲酸盐微乳剂;蔬菜害虫;防治效果 中图分类号 S 481(9 甜菜夜蛾(Spodopteraextgua Htibner)是夜蛾科的重要害虫，食性杂，危害严重，耐药性强，防治难度大，严重影响作物产量和品质，给农业生产特别是蔬菜生产带来极大不利影响。美洲斑潜蝇(Lir, iOInyza sativae Blanchard)则是20世纪90年代小side of road subgrade 2m. Direct-buried cable upper and lower should be covered with not less than 100mm thick layer of soft soil or sand, and affix the protection, the coverage should be wider than 50mm on each side of the cable, cover plate can be used to protect concrete or brick. Direct-buried cable in line every 50-100 meters, cable turns should be appreciable bearing flags or stakes. Direct-buried cable prior to backfill, shall be subject to acceptance of concealed work before they can be filled. 4.1.5 4.1.5.1 factory of making cable terminal cable mainly in the low-voltage cable head, dry Pack, its production should strictly abide by the production process. 4.1.5.2 should check the insulation before the first cable production qualified, low-voltage power cables with 1000V shake table, its insulation value should not be less than the specified value. 4.1.5.3 making cable head, cut from the Strip begins continuous operation until the completion of the cable, reducing insulation exposure time, strip-cut cables, insulation should not damage conductors and reservations. The armored power cable and control cable shield should be connected to a good shall not be interrupted, and ... Correctly positioned, vertical clearance shall be distributed evenly per shell bus and the shell should be concentric, the error shall not exceed 5mm, segments and segment connection, two adjacent bus and enclosure, after connecting bus and enclosure should not be subject to mechanical stress. Short circuit between phases of the shell plate is correctly positioned, good connection between support plates shall be mounted firmly, insulation Grade insulation shell should be made. 4.1.11 the installation of explosion-proof electrical equipment 4.1.11.1 rectisol wash unit area, tank farm and other explosion-proof areas, the electrical installation shall be carried out as explosion-proof requirements. 4.1.11.2 electrical installations 期传人我国的枪疫性害虫，危害多种植物，尤以黄瓜、芸豆、丝瓜、豆角、南瓜等瓜类、豆类蔬菜受害最重。生产上迫切需要经济、安伞、高效、环境相容性良好的新型药剂以控制甜菜夜蛾和美洲斑潜蝇危害。 甲氨基阿维菌素苯甲酸盐是近年来开发的一种高效、广谱、无公害抗牛素类杀虫剂，是阿维菌素的高活性衍牛物，它明显提高了对鳞翅目害虫的活性，对人畜和天敌安全，适宜防治多种重要蔬菜害虫。本文研究比较了甲氨是阿维菌素苯甲酸盐微乳剂与其乳油对甜菜夜蛾和美洲斑潜蝇的田间防效差异，为其科学使用提供依据和参考。 1 材料与方法 1(1 供试药剂和作物 供试药剂:0.5,甲氨基阿维菌素苯甲酸盐微乳剂(Em-B0.5,ME)。0(5,甲氨基阿维菌素苯甲酸盐乳油(Em-B 0(5,EC)，1(8,阿维菌素乳油(齐螨素)均山河北威远牛物化I:股份有限公司提供: 1(5,甲氨基阿维菌素苯甲酸盐乳油(EmB 1.5, EC)山北京华戎生物激素厂提供。 1(2 控制甜菜夜蛾药剂试验 side of road subgrade 2m. Direct-buried cable upper and lower should be covered with not less than 100mm thick layer of soft soil or sand, and affix the protection, the coverage should be wider than 50mm on each side of the cable, cover plate can be used to protect concrete or brick. Direct-buried cable in line every 50-100 meters, cable turns should be appreciable bearing flags or stakes. Direct-buried cable prior to backfill, shall be subject to acceptance of concealed work before they can be filled. 4.1.5 4.1.5.1 factory of making cable terminal cable mainly in the low-voltage cable head, dry Pack, its production should strictly abide by the production process. 4.1.5.2 should check the insulation before the first cable production qualified, low-voltage power cables with 1000V shake table, its insulation value should not be less than the specified value. 4.1.5.3 making cable head, cut from the Strip begins continuous operation until the completion of the cable, reducing insulation exposure time, strip-cut cables, insulation should not damage conductors and reservations. The armored power cable and control cable shield should be connected to a good shall not be interrupted, and ... Correctly positioned, vertical clearance shall be distributed evenly per shell bus and the shell should be concentric, the error shall not exceed 5mm, segments and segment connection, two adjacent bus and enclosure, after connecting bus and enclosure should not be subject to mechanical stress. Short circuit between phases of the shell plate is correctly positioned, good connection between support plates shall be mounted firmly, insulation Grade insulation shell should be made. 4.1.11 the installation of explosion-proof electrical equipment 4.1.11.1 rectisol wash unit area, tank farm and other explosion-proof areas, the electrical installation shall be carried out as explosion-proof requirements. 4.1.11.2 electrical installations 甲氨基阿维菌素苯甲酸盐微乳剂对蔬菜害虫的控制作用 , 分类: , 作者:钟国华 彭雏燕 陈文团 官 珊 刘晓金 胡美英 , 字数:3531 来源:植物保护 , 2 摘要 0(5,甲氨基阿维菌素苯甲酸盐微乳剂以药量10mL,667m防治甜菜夜蛾的效果明显优于其2倍使用剂量的乳油，药后3,7 d，对苋菜上甜菜夜蛾的防治效果达到85,2以上，显著优于1(8,阿维菌素乳油33(33 mL,667m防治效果;施药量8(33mL,6 267m，药后7d，对丝瓜上美洲斑潜蝇(的防治效果达85,以上，与1(8,阿维菌素乳油 250mL,667m防治效果差异不显著。 关键词 有害生物化学防治;甲氨基阿维菌素苯甲酸盐微乳剂;蔬菜害虫;防治效果 中图分类号 S 481(9 甜菜夜蛾(Spodopteraextgua Htibner)是夜蛾科的重要害虫，食性杂，危害严重，耐药性强，防治难度大，严重影响作物产量和品质，给农业生产特别是蔬菜生产带来极大不利影响。美洲斑潜蝇(Lir, iOInyza sativae Blanchard)则是20世纪90年代小期传人我国的枪疫性害虫，危害多种植物，尤以黄瓜、芸豆、丝瓜、豆角、南瓜等瓜类、豆类蔬菜受害最重。生产上迫切需要经济、安伞、高效、环境相容性良好的新型药剂以控制甜菜夜蛾和美洲斑潜蝇危害。 甲氨基阿维菌素苯甲酸盐是近年来开发的一种高效、广谱、无公害抗牛素类杀虫剂，是阿维菌素的高活性衍牛物，它明显提高了对鳞翅目害虫的活性，对人畜和天敌安全，适宜防治多种重要蔬菜害虫。本文研究比较了甲氨是阿维菌素苯甲酸盐微乳剂与其乳油对甜菜夜蛾和美洲斑潜蝇的田间防效差异，为其科学使用提供依据和参考。 1 材料与方法 1(1 供试药剂和作物 供试药剂:0.5,甲氨基阿维菌素苯甲酸盐微乳剂(Em-B0.5,ME)。0(5,甲氨基阿维菌素苯甲酸盐乳油(Em-B 0(5,EC)，1(8,阿维菌素乳油(齐螨素)均山河北威远牛物化I:股份有限公司提供: 1(5,甲氨基阿维菌素苯甲酸盐乳油(EmB 1.5, EC)山北京华戎生物激素厂提供。 1(2 控制甜菜夜蛾药剂试验 试验地点设在广州华南农业大学教学试验场， side of road subgrade 2m. Direct-buried cable upper and lower should be covered with not less than 100mm thick layer of soft soil or sand, and affix the protection, the coverage should be wider than 50mm on each side of the cable, cover plate can be used to protect concrete or brick. Direct-buried cable in line every 50-100 meters, cable turns should be appreciable bearing flags or stakes. Direct-buried cable prior to backfill, shall be subject to acceptance of concealed work before they can be filled. 4.1.5 4.1.5.1 factory of making cable terminal cable mainly in the low-voltage cable head, dry Pack, its production should strictly abide by the production process. 4.1.5.2 should check the insulation before the first cable production qualified, low-voltage power cables with 1000V shake table, its insulation value should not be less than the specified value. 4.1.5.3 making cable head, cut from the Strip begins continuous operation until the completion of the cable, reducing insulation exposure time, strip-cut cables, insulation should not damage conductors and reservations. The armored power cable and control cable shield should be connected to a good shall not be interrupted, and ... Correctly positioned, vertical clearance shall be distributed evenly per shell bus and the shell should be concentric, the error shall not exceed 5mm, segments and segment connection, two adjacent bus and enclosure, after connecting bus and enclosure should not be subject to mechanical stress. Short circuit between phases of the shell plate is correctly positioned, good connection between support plates shall be mounted firmly, insulation Grade insulation shell should be made. 4.1.11 the installation of explosion-proof electrical equipment 4.1.11.1 rectisol wash unit area, tank farm and other explosion-proof areas, the electrical installation shall be carried out as explosion-proof requirements. 4.1.11.2 electrical installations 果;药剂使用剂量降低 2到7(14mI,667m时，药后 7 d防治效果与1(8,阿维菌素乳油同期防治效果差异不显著。 2.3 对美洲斑潜蝇的田间控制效果 从表3的试验结果可知，2002年试验中(Em-B 0(5,微乳剂分别以8(33、7(1,21、6(25 mI。,667 m 施用，药后7 d，对美洲斑潜蝇的防治效果分别为 87(94,、85(85,和77(75,，保叶效果分别为 96(06,、83(9S,和57，58,;2003年试验巾，相同处理同期防治效果分别为89(42,、82(84,和 65(96,，保叶效果分别为97(20,、81(37,和 77(03,。对照药剂 1(8,阿维菌素乳油以 50 m1。,667m2处理，药后7 d对美洲斑潜蝇的防治效果亦可达到92,,98,。DMRT统计表明，无论按虫口减退率或保叶效果计算，Em,B 0(5,微乳剂以8(33 mir,667 m2施用，药后7 d对丝 2瓜上美洲斑潜蝇的防治效果均与1(8,阿维菌素乳油 50m1(,667 m的同期防效相当， 2但7(14、6(25mir, 667m的保叶效果则显著低于对照药剂1(8,阿维菌素孔油的同期防效。 3 讨论 side of road subgrade 2m. Direct-buried cable upper and lower should be covered with not less than 100mm thick layer of soft soil or sand, and affix the protection, the coverage should be wider than 50mm on each side of the cable, cover plate can be used to protect concrete or brick. Direct-buried cable in line every 50-100 meters, cable turns should be appreciable bearing flags or stakes. Direct-buried cable prior to backfill, shall be subject to acceptance of concealed work before they can be filled. 4.1.5 4.1.5.1 factory of making cable terminal cable mainly in the low-voltage cable head, dry Pack, its production should strictly abide by the production process. 4.1.5.2 should check the insulation before the first cable production qualified, low-voltage power cables with 1000V shake table, its insulation value should not be less than the specified value. 4.1.5.3 making cable head, cut from the Strip begins continuous operation until the completion of the cable, reducing insulation exposure time, strip-cut cables, insulation should not damage conductors and reservations. The armored power cable and control cable shield should be connected to a good shall not be interrupted, and ... Correctly positioned, vertical clearance shall be distributed evenly per shell bus and the shell should be concentric, the error shall not exceed 5mm, segments and segment connection, two adjacent bus and enclosure, after connecting bus and enclosure should not be subject to mechanical stress. Short circuit between phases of the shell plate is correctly positioned, good connection between support plates shall be mounted firmly, insulation Grade insulation shell should be made. 4.1.11 the installation of explosion-proof electrical equipment 4.1.11.1 rectisol wash unit area, tank farm and other explosion-proof areas, the electrical installation shall be carried out as explosion-proof requirements. 4.1.11.2 electrical installations 3(1 甲氨基阿维菌素苯甲酸盐微乳剂防治蔬菜害虫的优越性 2 田间试验结果证明，Em,B0(5,微乳剂以 10mL,667 m施用，药后3、7 d对苋2菜甜菜夜蛾的防治效果达到85,以上，显著优于Em-B 0(5,乳油20 mL,667m同期的防治效果，并且显著优于或相当于Em-B 1.5,乳油10mL,667m2(有效成分含量为Em-Bo(5,微乳剂的3倍)同期的防治效果。这说明Em-B微乳剂在蔬菜害虫防治中具有明显的优越性。阿维菌素类化合物主要是通过触杀和胃毒对害虫发挥作用。微乳剂农药含有一些特殊的表面活性剂，用水稀释时，药液表面张力明显降低，喷雾液滴粒径较小，在到达植物叶面后反弹力较小，使其在植物表面更易粘附、润湿和铺展，有利于药剂发挥触杀作用。此外，微乳剂农药液滴在蒸发时浓缩生成粘度很高的液晶相，农药有效成分能牢固地粘附在植物表面，不易被雨水冲洗掉，增加了药剂与害虫的接触机会。 胃毒作用被认为是积累致死剂量的途径。为了能够杀死害虫，药剂有效成分必须在作物叶面中要有足够量的积累，而这与药剂渗透性关系密切。在表面活性剂的增溶作用下，微乳剂能促进有效成分传递穿过动植物组织半透膜，提高药效uo)。 Em-B微乳剂具有乳油剂型所没有的强渗透性，所以，低含量的微乳剂即使在低浓度时施用，对蔬菜害虫的防治效果仍大大优于高含量的乳油剂型。 3(2 甲氨基阿维菌素苯甲酸盐微乳剂与阿维菌素的比较 Em-B0(5,微乳剂与阿维菌素相比，提高了对鳞翅目害虫的杀虫活性。室内毒力测定结果表明， Em,B对小菜蛾[Plutellaxylostella(1)]、甜菜夜蛾、烟芽夜蛾[Heliothisvtresce ns(F()]、粉纹夜蛾 [Tricoplusia”;(H(ihner)]和草地贪夜蛾[Spo— doptera,rugiperda 2同期防效;(J(E(Smith)]等鳞翅目害虫具有较高的杀虫活性，也可用于防治抗性棉铃虫 药量7.8mL, 667 mf的防治效果则与对照药剂的同期防效处于同一水平，即Em-B0(5,微乳剂对甜菜夜蛾的防治效果显著优于阿维菌素(表1和表2)。与阿维菌素相比，Em-B0(5,微乳剂对双翅目害虫的防治效果没有明显提高，以8，33 m[?667 m2(有效含量0(625 g 2,hm)施用，药后7 d，对丝瓜美洲斑潜蝇的防治效果与1(8,阿维菌素乳油50 mL, 667 m,(13(5 g,hm2)的同期防效处于同一水平 (表3)，但其有效成分含量比阿维菌素降低约 20倍。 Em-B 0(5,微乳剂与阿维菌素相比，降低了对哺乳动物的毒性。据报道，Em—Bo，5%微乳剂对哺乳动物的毒性仅为母体阿维菌素的1,6，大鼠经口毒性比阿维菌素降低5倍以上，对虹鳟鱼(On- corhynchusmykiss Walbaum)毒性比阿维菌素降低 208倍”，可用于防治大西洋鲑鱼[Salmo salar (1)]、虹鳟鱼的鲑疮痂鱼虱[Lepeophtheirussal— monis(Kroyer)]和Caligus spp(等寄生虫。这些特性进一步扩大了其使用范围，提高了其环境友好性。 Em-B 0(5,微乳剂用量少、持效较长、无交互抗性、对人畜和环境安全，但值得注意的是，其速效性不突出，必须注意施药的时机，同时对鱼类、水生生物总体较敏感，对蜜蜂毒性较高，使用时应注意避开蜜蜂采蜜期，不能用于池塘、河流等水面。 2果;药剂使用剂量降低到7(14mI,667m时，药后 7 d防治效果与1(8,阿维菌素乳油同期防治效果差异不显著。 2.3 对美洲斑潜蝇的田间控制效果 从表3的试验结果可知，2002年试验中(Em-B 0(5,微乳剂分别以8(33、7(1, 21、6(25 mI。,667 m 施用，药后7 d，对美洲斑潜蝇的防治效果分别为 87(94,、85(85,和77(75,，保叶效果分别为 96(06,、83(9S,和57，58,;2003年试验巾，相同处理同期防治效果分别为89(42,、82(84,和 65(96,，保叶效果分别为97(20,、81(37,和 77(03,。对照药剂 1(8,阿维菌素乳油以 50 m1。,667m2处理，side of road subgrade 2m. Direct-buried cable upper and lower should be covered with not less than 100mm thick layer of soft soil or sand, and affix the protection, the coverage should be wider than 50mm on each side of the cable, cover plate can be used to protect concrete or brick. Direct-buried cable in line every 50-100 meters, cable turns should be appreciable bearing flags or stakes. Direct-buried cable prior to backfill, shall be subject to acceptance of concealed work before they can be filled. 4.1.5 4.1.5.1 factory of making cable terminal cable mainly in the low-voltage cable head, dry Pack, its production should strictly abide by the production process. 4.1.5.2 should check the insulation before the first cable production qualified, low-voltage power cables with 1000V shake table, its insulation value should not be less than the specified value. 4.1.5.3 making cable head, cut from the Strip begins continuous operation until the completion of the cable, reducing insulation exposure time, strip-cut cables, insulation should not damage conductors and reservations. The armored power cable and control cable shield should be connected to a good shall not be interrupted, and ... Correctly positioned, vertical clearance shall be distributed evenly per shell bus and the shell should be concentric, the error shall not exceed 5mm, segments and segment connection, two adjacent bus and enclosure, after connecting bus and enclosure should not be subject to mechanical stress. Short circuit between phases of the shell plate is correctly positioned, good connection between support plates shall be mounted firmly, insulation Grade insulation shell should be made. 4.1.11 the installation of explosion-proof electrical equipment 4.1.11.1 rectisol wash unit area, tank farm and other explosion-proof areas, the electrical installation shall be carried out as explosion-proof requirements. 4.1.11.2 electrical installations 药后7 d对美洲斑潜蝇的防治效果亦可达到92,,98,。DMRT统计表明，无论按虫口减退率或保叶效果计算，Em,B 0(5,微乳剂以8(33 mir,667 m2施用，药后7 d对丝 2瓜上美洲斑潜蝇的防治效果均与1(8,阿维菌素乳油 50m1(,667 m的同期防效相当，2但7(14、6(25mir, 667m的保叶效果则显著低于对照药剂1(8,阿维菌素孔油的同期防效。 3 讨论 3(1 甲氨基阿维菌素苯甲酸盐微乳剂防治蔬菜害虫的优越性 2 田间试验结果证明，Em,B0(5,微乳剂以 10mL,667 m施用，药后3、7 d对苋 2菜甜菜夜蛾的防治效果达到85,以上，显著优于Em-B 0(5,乳油20 mL,667m同期的防治效果，并且显著优于或相当于Em-B 1.5,乳油10mL,667m2(有效成分含量为Em-Bo(5,微乳剂的3倍)同期的防治效果。这说明Em-B微乳剂在蔬菜害虫防治中具有明显的优越性。阿维菌素类化合物主要是通过触杀和胃毒对害虫发挥作用。微乳剂农药含有一些特殊的表面活性剂，用水稀释时，药液表面张力明显降低，喷雾液滴粒径较小，在到达植物叶面后反弹力较小，使其在植物表面更易粘附、润湿和铺展，有利于药剂发挥触杀作用。此外，微乳剂农药液滴在蒸发时浓缩生成粘度很高的液晶相，农药有效成分能牢固地粘附在植物表面，不易被雨水冲洗掉，增加了药剂与害虫的接触机会。 胃毒作用被认为是积累致死剂量的途径。为了能够杀死害虫，药剂有效成分必须在作物叶面中要有足够量的积累，而这与药剂渗透性关系密切。在表面活性剂的增溶作用下，微乳剂能促进有效成分传递穿过动植物组织半透膜，提高药效uo)。 Em-B微乳剂具有乳油剂型所没有的强渗透性，所以，低含量的微乳剂即使在低浓度时施用，对蔬菜害虫的防治效果仍大大优于高含量的乳油剂型。 3(2 甲氨基阿维菌素苯甲酸盐微乳剂与阿维菌素的比较 Em-B0(5,微乳剂与阿维菌素相比，提高了对鳞翅目害虫的杀虫活性。室内毒力测定结果表明， Em,B对小菜蛾[Plutellaxylostella(1)]、甜菜夜蛾、烟芽夜蛾[Heliothisvtrescens(F()]、粉纹夜蛾 [Tricoplusia”;(H(ihner)]和草地贪夜蛾[Spo— doptera,rugiperda 2(J(E(Smith)]等鳞翅目害虫具有较高的杀虫活性，也可用于防治抗性棉铃虫 同期防效;药量7.8mL, 667 mf的防治效果则与对照药剂的同期防效处于同一水平，即Em-B0(5,微乳剂对甜菜夜蛾的防治效果显著优于阿维菌素(表1和表2)。与阿维菌素相比，Em-B0(5,微乳剂对双翅目害虫的防治效果没有明显提高，以8，33 m[?667 m2(有效含量0(625 g 2,hm)施用，药后7 d，对丝瓜美洲斑潜蝇的防治效果与1(8,阿维菌素乳油50 mL, 667 m,(13(5 g,hm2)的同期防效处于同一水平 (表3)，但其有效成分含量比阿维菌素降低约 20倍。 Em-B 0(5,微乳剂与阿维菌素相比，降低了对哺乳动物的毒性。据报道，Em—Bo，5%微乳剂对哺乳动物的毒性仅为母体阿维菌素的1,6，大鼠经口毒性比阿维菌素降低5倍以上，对虹鳟鱼(On- corhynchusmykiss Walbaum)毒性比阿维菌素降低 208倍”，可用于防治大西洋鲑鱼[Salmo salar (1)]、虹鳟鱼的鲑疮痂鱼虱[Lepeophtheirussal— monis(Kroyer)]和Caligus spp(等寄生虫。这些特性进一步扩大了其使用范围，提高了其环境友好性。 Em-B 0(5,微乳剂用量少、持效较长、无交互抗性、对人畜和环境安全，但值得注意的是，其速效性不突出，必须注意施药的时机，同时对鱼类、水生生物总体较敏感，对蜜蜂毒性较高，使用时应注意避开蜜蜂采蜜期，不能用于池塘、河流等水面。 side of road subgrade 2m. Direct-buried cable upper and lower should be covered with not less than 100mm thick layer of soft soil or sand, and affix the protection, the coverage should be wider than 50mm on each side of the cable, cover plate can be used to protect concrete or brick. Direct-buried cable in line every 50-100 meters, cable turns should be appreciable bearing flags or stakes. Direct-buried cable prior to backfill, shall be subject to acceptance of concealed work before they can be filled. 4.1.5 4.1.5.1 factory of making cable terminal cable mainly in the low-voltage cable head, dry Pack, its production should strictly abide by the production process. 4.1.5.2 should check the insulation before the first cable production qualified, low-voltage power cables with 1000V shake table, its insulation value should not be less than the specified value. 4.1.5.3 making cable head, cut from the Strip begins continuous operation until the completion of the cable, reducing insulation exposure time, strip-cut cables, insulation should not damage conductors and reservations. The armored power cable and control cable shield should be connected to a good shall not be interrupted, and ... Correctly positioned, vertical clearance shall be distributed evenly per shell bus and the shell should be concentric, the error shall not exceed 5mm, segments and segment connection, two adjacent bus and enclosure, after connecting bus and enclosure should not be subject to mechanical stress. Short circuit between phases of the shell plate is correctly positioned, good connection between support plates shall be mounted firmly, insulation Grade insulation shell should be made. 4.1.11 the installation of explosion-proof electrical equipment 4.1.11.1 rectisol wash unit area, tank farm and other explosion-proof areas, the electrical installation shall be carried out as explosion-proof requirements. 4.1.11.2 electrical installations