一、害蟲幼齡期　近年來有些農戶反映農藥防治效益不佳。據調查，多數情況還是長期使用某種或某類農藥、引起害蟲的抗藥性增強以及未抓住害蟲的防治適期用藥所致。什麼時期是害蟲的防治適期呢
？一般說來
，害蟲3齡之前的幼齡期是防治適期。此期用藥可收到事半功倍的效果。這是因為害蟲3齡前體壁部很薄，體壁上還長了很多的微毛，微毛著生部位的表皮很薄，藥劑就很容易透過這些薄層。而且此時害蟲休小
、食量小
、危wei害hai輕qing
，活huo動dong範fan圍wei小xiao
，抗kang藥yao力li弱ruo。對dui於yu鑽zuan蛀zhu性xing害hai蟲chong，無wu論lun是shi苗miao穗sui莖jing的de鑽zuan蛀zhu性xing害hai蟲chong，還hai是shi蕾lei花hua果guo的de鑽zuan蛀zhu性xing害hai蟲chong
，初chu孵fu幼you蟲chong尚shang未wei鑽zuan入ru植zhi株zhu，此ci時shi防fang治zhi效xiao果guo自zi然ran較jiao好hao。所suo以yi，確que定ding防fang治zhi適shi期qi
，應ying掌zhang握wo在zai害hai蟲chong3齡以前。當害蟲達到4-6齡時，害蟲食量
、體壁厚度均大大增加，其厚度可達到1齡幼蟲的50-100bei，tibishangweimaoyemeiyoule，zheyangyaojijiuburongyizhanfuzaitibishanghetouguotibi，daodahaichongtineijiubijiaokunnan，congerdadajiangdileshachongxiaoguo。erqiehaichonglingqizengdahou，chongtineidezhifangliangyezengduole，juyoujicunhefenjiexuduonongyaodezuoyong。haichongtineizhifanghanliangyuegao，zhezhongzuoyongjiuyuemingxian，kangyaoxingjiuyueqiang。

    二、危險生育期　對dui農nong作zuo物wu來lai說shuo，易yi感gan病bing和he感gan蟲chong且qie易yi造zao成cheng較jiao大da損sun失shi的de生sheng育yu期qi是shi危wei險xian生sheng育yu期qi。如ru早zao春chun的de蔬shu菜cai作zuo物wu幼you苗miao期qi最zui易yi感gan染ran立li枯ku病bing和he猝cu倒dao病bing

，早zao稻dao旱han育yu秧yang和he拋pao秧yang在zai幼you苗miao期qi則ze易yi感gan染ran立li枯ku病bing和he綿mian腐fu病bing。大da小xiao麥mai抽chou穗sui到dao灌guan漿jiang期qi是shi最zui易yi感gan蚜ya蟲chong的de時shi期qi、而er破po口kou到dao齊qi穗sui開kai花hua期qi是shi最zui易yi感gan染ran赤chi黴mei病bing的de時shi期qi
，所suo以yi此ci二er期qi分fen別bie是shi易yi感gan蚜ya蟲chong和he易yi感gan赤chi黴mei病bing的de危wei險xian生sheng育yu期qi。水shui稻dao二er化hua螟ming和he三san化hua螟ming的de危wei險xian生sheng育yu期qi是shi分fen蘖nie期qi和he孕yun穗sui到dao抽chou穗sui期qi。水shui稻dao感gan穗sui頸jing瘟wen的de危wei險xian生sheng育yu期qi是shi破po口kou到dao抽chou穗sui開kai花hua期qi。因yin此ci，防fang治zhi病bing蟲chong要yao抓zhua住zhu危wei險xian生sheng育yu期qi用yong藥yao，對dui於yu害hai蟲chong防fang治zhi要yao在zai危wei險xian生sheng育yu期qi內nei抓zhua住zhu害hai蟲chong低di齡ling幼you蟲chong的de盛sheng發fa期qi用yong藥yao。

    三
、天敵敏感期　農作物的天敵較多
，大部分天敵也是昆蟲
，如各種瓢蟲
、草蛉、食蚜蠅以及寄生蜂、jishengyingdeng。tiandizhonghaiyouyidalei
，najiushinongtianzhizhu。zaizhexiehaichongtiandiduiyaojifanyingbijiaomingandeshiqinei，yingjinliangshaoyongshajunjihuobuyongshajunji，yibaohutiandi，weichitianjianshengtaipingheng。ruxushiyao，jinkenengxuanzetiandiduinongyaobumingandeshiqishiyao。bifangshuo，luanjishengdetiandi，zaijishengqianshiduinongyaodeminganqi
；erjishengyihou，zeshiduinongyaodebuminganqi。yinweijishengyuhaichongdeluanzhihou，zhexiejishengtiandiyoujizhuhaichongluanmobaohu，shachongjiduitadeduxingjiaoshao。zaiyijingsiwangdeyachonghejiekechongtineifayudetiandi，youyuyoujizhuhoushitibidebaohu，yenanyishoudaonongyaodeduhai，cishishiyongshachongjijihuduitamenbuqizuoyong。xiaocaieyouchongbeijifengjishenghou
，duishachongjizuimingandeshiqishiersanlingjifengjishengdeyouchong，er1齡和4齡ling姬ji蜂feng寄ji生sheng的de幼you蟲chong抗kang藥yao性xing明ming顯xian增zeng強qiang。其qi它ta害hai蟲chong也ye存cun在zai同tong樣yang的de現xian象xiang。寄ji主zhu害hai蟲chong的de抗kang藥yao增zeng強qiang，則ze農nong藥yao對dui寄ji生sheng天tian敵di的de影ying響xiang就jiu越yue小xiao，實shi際ji上shang意yi味wei著zhe天tian敵di受shou到dao了le保bao護hu。

    四
、農藥安全間隔期為了安全起見
，在蔬菜采收前按要求天數停止使用農藥。