为什么要装防虫网？
1、能有效防虫。覆盖防虫网后，基本上可免除菜青虫、小菜蛾、蚜虫等多种虫害。农产品覆盖防虫网后可以有效的免除菜青虫、小菜蛾、甘蓝夜蛾、斜纹夜蛾、黄曲跳甲、猿叶虫、蚜虫等多种害虫的为害。据试验，防虫网对白菜菜青虫、小菜蛾、豇豆荚螟、美洲斑潜蝇防效为94-97%，对蚜虫防效为90%。
2、可以防病。病毒传播会给温室大棚种植带来灾难性的后果，特别是蚜虫传毒。但温室大棚安装防虫网后就切断了害虫传毒途径，大大减轻了病毒病的发病率，防效为80%左右。
3、调节气温、土温和湿度。在炎热的季节，用白色防虫网覆盖温室大棚，试验表明：炎热的7-8月，在25目白色防虫网中，早晨和傍晚的气温与露地持平，而晴天中午比露地低1℃左右。早春3-4月，防虫网覆盖棚内比露地气温高1-2℃，5厘米地温比露地高0.5-1℃，能有效地防止霜冻。此外防虫网可阻挡部分雨水落入棚内，降低田间湿度，减少发病，晴天能降低大棚内的水分蒸发量。
4、有遮光效果。夏季光照强度大，强光会抑制蔬菜营养生长，特别是叶菜类蔬菜，而防虫网可起到一定的遮光作用，20-22目银灰色防虫网一般遮光率在20－25%。
防虫网形似窗纱，具有抗拉强度大，抗紫外线、抗热、耐水、耐腐蚀、耐老化等性能，无毒无味，使用寿命一般为4-6年，最高可达10年。它既有遮阳网的优点，又克服了遮阳网的不足之处，因而值得大力推广，那么问题来了：我们应该选用什么样的防虫网？
型号选择
秋季很多害虫开始向棚内转移，尤其是一些蛾类及蝶类害虫，由于这些害虫的体形较大，菜农可以使用目数相对较少的防虫网，如30-60目的防虫网。但是对于棚外杂草较多，粉虱较多的，要根据粉虱的较小体型，防止其从防虫网的孔眼中进入，建议菜农使用较密的防虫网，如40-60目的。
颜色选择
例如，蓟马对蓝色有很强的趋性，使用蓝色防虫网容易将棚外的蓟马吸引到大棚周围，一旦防虫网覆盖不严就会使大量的蓟马进入棚中造成危害；而使用白色防虫网，大棚内就不会发生这种现象，而与遮阳网配合使用时，以选择白色为宜。还一种银灰色防虫网对蚜虫有较好的拒避作用，黑色防虫网遮阴效果显著，冬季、连阴天不适宜使用。
一般春秋季节和夏季相比，温度较低，光照较弱，宜选用白色防虫网；夏季为了兼顾遮阳、降温，宜选用黑色或银灰色防虫网；在蚜虫和病毒病发生严重的地区，为了驱避蚜虫、预防病毒病，宜选用银灰色防虫网。
注意事项
1、在播种或定植前采用高温闷棚或喷施低毒农药杀灭土壤中的寄生虫蛹、幼虫。
2、栽植时秧苗最好带药入棚，并挑选无病虫害的健壮植株。
3、加强日常管理，进出温室大棚要将棚门关严，在进行农事操作前要对有关器
物进行消毒，防止病毒传入，以确保防虫网的使用效果。
4、要经常检查防虫网有无撕裂口，一旦发现应及时修补，确保温室大棚内无害虫侵入。
5、确保覆盖质量。防虫网要全封闭覆盖，四周用土压严实，并用压膜线固定牢固；进出大、中棚和温室的门，必须安装防虫网，并注意进出时随即关好。小拱棚防虫网覆盖栽培，棚架高度要明显高于作物，避免菜叶紧贴防虫网，以防害虫由网外采食或产卵于菜叶。用于放风口封闭的防虫网，与透明覆盖物间不能留有缝隙，以免给害虫留出进出通道。
6、综合配套措施。除防虫网覆盖外，再结合抗病虫良种、耐热良种、无公害套餐肥料、生物农药、无污染水源、微喷微灌等综合配套措施，就可以获得更佳的效果。
7、妥善使用、保管。防虫网田间使用结束后，应及时收下，洗净、吹干、卷好，以延长使用寿命，增加经济效益。
Why install insect net?
1.It can effectively prevent insects.After covered with the net,the pests such as Pieris rapae,Plutella xylostella and aphids can be avoided.Agricultural products covered with insect proof net can effectively avoid the damage of Pieris rapae,Plutella xylostella,cabbage armyworm,Spodoptera litura,scarab beetle,leaf beetle,aphid and other pests.According to the test,the control effect of the net on cabbage caterpillar,Plutella xylostella,cowpea pod borer and Liriomyza sativae was 94-97%and 90%against aphids.
2.It can prevent disease.Virus transmission will bring disastrous consequences to greenhouse planting,especially aphid transmission.However,the installation of insect proof nets in greenhouse can cut off the transmission route of pests,greatly reducing the incidence rate of viral diseases,and the control effect is about 80%.
3.Adjust air temperature,soil temperature and humidity.In the hot season,the greenhouse was covered with white insect proof net.The test showed that the temperature in the morning and evening was the same as that in the open field in the 25 mesh white insect proof net from July to August in the hot season,but it was about 1℃lower at noon than that in the open field on a sunny day.From March to April in early spring,the air temperature in the shed covered with insect proof net was 1-2℃higher than that in open field,and the ground temperature of 5cm was 0.5-1℃higher than that in open field,which could effectively prevent frost.In addition,the insect net can prevent some rainwater from falling into the shed,reduce the field humidity,reduce the incidence of disease,and reduce the water evaporation in the greenhouse on sunny days.
4.It has shading effect.The light intensity is high in summer,and the strong light will inhibit the vegetative growth of vegetables,especially leafy vegetables.The insect proof net can play a certain role in shading.The shading rate of 20-22 mesh silver gray insect proof net is 20-25%.
The insect proof net is shaped like a window screen.It has high tensile strength,ultraviolet resistance,heat resistance,water resistance,corrosion resistance and aging resistance.It is non-toxic and tasteless.Its service life is generally 4-6 years,up to 10 years.It not only has the advantages of the sunshade net,but also overcomes the shortcomings of the sunshade net,so it is worth promoting.So the question comes:what kind of insect proof net should we choose?
Model selection
In autumn,many pests begin to move to the shed,especially some moths and butterflies.Due to the large size of these pests,vegetable farmers can use relatively small mesh nets,such as 30-60 mesh nets.However,if there are more weeds and whiteflies outside the shed,the smaller size of whiteflies should be taken to prevent them from entering through the holes of the nets.It is suggested that vegetable farmers should use dense nets,such as 40-60 mesh.
Color selection
For example,thrips have a strong tendency to blue,the use of blue insect net will easily attract thrips outside the shed to the surrounding of the greenhouse,once the insect net is not covered tightly,a large number of thrips will enter the shed and cause harm;while using white insect net,this phenomenon will not occur in the greenhouse,and when used with sunshade net,white should be selected.In addition,a silver grey insect net has a good repellent effect on aphids.The black net has a significant shading effect,and is not suitable for use in winter or even cloudy days.
Generally,in spring and autumn,compared with summer,the temperature is lower and the light is weaker,so the white insect prevention net should be selected;in summer,in order to take into account the shading and cooling,the black or silver gray insect prevention net should be selected;in the areas where aphids and virus diseases occur seriously,silver grey insect prevention net should be used in order to drive away aphids and prevent virus diseases.
matters needing attention
1.Before sowing or planting,the pupae and larvae of parasites in the soil were killed by high-temperature airtight shed or spraying low-toxic pesticides.
2.When planting seedlings,it is best to bring medicine into the shed,and select healthy plants without diseases and insect pests.
3.Strengthen the daily management,close the door of the greenhouse when entering and leaving the greenhouse,and check the relevant equipment before agricultural operation
In order to ensure the use effect of the anti insect net,disinfection is carried out to prevent the introduction of virus.
4.It is necessary to regularly check whether there is tearing crack in the insect proof net.Once found,it should be repaired in time to ensure that there is no insect invasion in the greenhouse.
5.Ensure coverage quality.The insect proof net should be completely closed and covered,the soil should be pressed tightly around,and the film pressing line should be used to fix it firmly;the doors of large and medium-sized sheds and greenhouses must be installed with insect proof nets,and attention should be paid to close them when entering and leaving.The height of the trellis should be significantly higher than that of the crops in the small arched shed,so as to prevent the pests from eating or laying eggs on the leaves of the plants.There should be no gap between the insect proof net used for sealing the vent and the transparent cover,so as to avoid leaving passage for the pest.
6.Comprehensive supporting measures.In addition to the coverage of insect prevention net,combined with the comprehensive supporting measures such as disease resistant and insect resistant varieties,heat-resistant varieties,pollution-free fertilizer,biological pesticides,pollution-free water source,micro spray and micro irrigation and other comprehensive supporting measures can achieve better results.
7.Proper use and storage.After the use of the net in the field,it should be collected in time,cleaned,dried and rolled up in order to prolong its service life and increase its economic benefits.
