What are the common questions about purchasing and using pesticides?
Pesticides refer to chemical agents used to prevent, eliminate, or control harmful organisms such as diseases, insects, and weeds that harm agriculture and forestry, as well as substances used to purposefully regulate the growth of plants and insects, or substances derived from organisms or other natural materials, or mixtures of several substances and their formulations. Qualified pesticide products must have the "three certificates." The pesticide "three certificates" refer to the pesticide production approval certificate, pesticide standard, and pesticide registration certificate. The "three certificates" are issued per product unit, meaning that each pesticide product, and the same pesticide product produced by different manufacturers, all have their own "three certificates."
The Meaning of Fake Pesticides and Inferior Pesticides
1. The name of the active ingredient contained does not match the approved label;
2. Non-pesticides are passed off as pesticides, or one type of pesticide is passed off as another type of pesticide;
3. Counterfeiting, forging, or transferring pesticide registration certificates or pesticide labels;
4. Pesticides officially announced by the state as prohibited from production or whose registration has been revoked (because they can no longer be used as pesticides).
Inferior pesticides are those that fall under any of the following circumstances:
(1) Product quality seriously fails to meet the requirements of the pesticide product standard;
(2) Those that have exceeded the quality guarantee period and lost their use value; or those with a limited use period but without the expiration time indicated;
(3) Those mixed with harmful components that can cause phytotoxicity or other losses;
(4) Those with seriously damaged packaging or labels.
Shelf Life of Pesticides
The period from the date a pesticide product is manufactured and packaged at the factory to the last date before it degrades in quality or efficacy is called the shelf life. Within the shelf life, the quality of the pesticide product must not fall below the technical indicator values specified in the quality standard, and when users apply it according to the target pests, application methods, use concentration (or dosage), and other provisions on the pesticide label, they should be able to achieve satisfactory control effects without causing phytotoxicity.
Causes of Pesticide Quality Changes During Storage and Transportation
Chemical pesticides are chemical products synthesized from two or more substances through chemical reactions under certain conditions.
Since pesticides are a type of chemical substance, they are naturally also affected by external natural factors such as light, heat, and humidity, which cause their original properties to change, and may even cause them to deteriorate and become ineffective. There are many factors that cause pesticide quality changes during storage and transportation, mainly including:
1. Temperature. The higher the temperature, the greater the impact on pesticide quality. In addition, temperatures below zero degrees Celsius also affect pesticide quality, especially liquid pesticides, which are prone to crystallization or precipitation, reducing emulsifying power and lowering efficacy.
2. Humidity. Excessive humidity in the air can cause changes in pesticide quality and affect efficacy. In particular, powder or wettable powder pesticides, after absorbing moisture from the air, are prone to forming clumps or caking of powder particles, reducing the flowability of powders or the suspension rate of wettable powders, thereby reducing control effectiveness.
3. Light. Light is also a very important factor causing pesticide deterioration and reduced efficacy, as it can promote photochemical reactions in the active ingredients of pesticides, decomposing the active ingredients.
4. Raw material quality. High-quality raw materials produce pesticides with higher content; low-quality raw materials not only result in low active ingredient content in the finished product but also produce many impurities, increasing the toxicity of pesticides to humans and livestock. This is most evident in the synthesis of organophosphate pesticides.
5. Pesticide packaging. In particular, emulsifiable concentrate pesticides must be sealed tightly. If the packaging is not tightly sealed or intact, it can easily cause the product to absorb moisture, decompose, and volatilize, and it can easily come into contact with air, causing oxidative decomposition and quality changes. Omethoate is an example of this situation.
According to some physical and chemical properties of pesticides, in addition to temperature, humidity, sunlight, air, and pressure affecting pesticide quality, acids and bases also have a great impact on pesticide quality. Therefore, the vast majority of pesticides must not come into contact with acidic or alkaline substances during storage.
Pesticides Must Not Be Stored in the Same Warehouse as Chemical Fertilizers
There are many varieties of chemical fertilizers, and even more varieties of pesticides, and their properties are all different. For example, chemical fertilizers include volatile ones, explosive ones, acidic ones, and alkaline ones. Pesticides also include easily decomposable, flammable, and explosive ones, and they are toxic. Therefore, they cannot be stored together in the same warehouse.
Identifying Pesticide Quality and Scientifically Purchasing Pesticides
1. Dustable Powder
(1) Appearance. The appearance of dustable powder should be loose fine powder with no lumps.
(2) Hygroscopicity. Before taking out powder to test hygroscopicity, first check whether the outside of the powder packaging paper bag is damp. If it is, that is certainly a sign of high hygroscopicity. Then take out a little powder from the bag and pour it onto a piece of white paper. Pick up the white paper and pinch it through the paper with your thumb and index finger. If it sticks together into a patch, it indicates that the powder has absorbed moisture; if this powder is for dusting, it indicates poor quality; if it is still loose fine powder, it indicates a good dusting pesticide. The hygroscopicity of wettable powders is greater than that of ordinary powders, but since this type of pesticide is used by mixing with water anyway, hygroscopicity has less impact on it than on powders used for dusting. However, absorbing moisture is never a good thing, because pesticides are prone to deterioration after getting damp.
2. Wettable Powder
(1) Appearance. It should be very fine, loose powder with no lumps.
(2) Wettability. Use a wide-mouthed glass bottle, fill it with water, then gently pour a spoonful of wettable powder onto the water surface from above. After 2 minutes, if it can all be wetted through and gradually sink, it is a wettable powder with good wettability; if the powder still floats on the water surface, then it is an agent with poor wettability. This method can also be used to distinguish which is a wettable powder and which is a dusting powder. The one that wets easily is a wettable powder. Ordinary powders are not wetted.
(3) Suspensibility. Plug the mouth of the glass bottle used above for testing wettability, shake it back and forth 30 times, then let it stand for 10 minutes and observe. If the liquid is still turbid and not much powder has settled at the bottom of the bottle, it is a wettable powder with relatively good suspensibility; if more than half has settled or the liquid is nearly clear, the suspensibility is poor; if all the powder has settled to the bottom of the bottle, it is a wettable powder with very poor suspensibility; if the agent has clumped together, it also indicates that it is not a good wettable powder.
3. Emulsifiable Concentrate
(1) Appearance. First check whether the emulsifiable concentrate in the bottle has separated into layers, then check whether it has become turbid and whether crystals have precipitated out. Any emulsifiable concentrate that does not separate into layers, is not turbid, and has no crystals is a good emulsifiable concentrate. However, an emulsifiable concentrate that has separated into layers, become turbid, or has crystals precipitated out has already deteriorated, and its efficacy will be poor when used. Of course, if the emulsifiable concentrate has been stored at a very cold temperature and crystals are found, but they can dissolve again when brought to room temperature, this cannot be considered deterioration.
(2) Emulsifiability. Pour one part by volume of emulsifiable concentrate into 19 parts by volume of water, mix, shake 30 times, then let stand for half an hour and observe whether any oily or paste-like substance floats on the water surface, and also check whether there is any sediment at the bottom. If neither is present, it indicates that the agent has very good emulsifying power. When testing emulsifiability, if the emulsifiable concentrate poured into water can quickly diffuse on its own and turn white, it is the best emulsifiable concentrate. This type of emulsifiable concentrate that can diffuse on its own without stirring is also called an emulsion with strong diffusion power; if obvious sediment appears, or there is floating oil or emulsion paste on the water surface, it is an emulsifiable concentrate with poor emulsifying performance.
4. Suspension Concentrate. A suspension concentrate should be a slightly viscous, flowable suspension with very low viscosity, and uniform. If layering occurs due to long-term storage but can return to a uniform state after shaking by hand, it can still be regarded as a qualified product. If it cannot become a uniform suspension again and the sediment at the bottom cannot be shaken up, the suspensibility is poor.
Points to Note When Mixing Pesticides
1. The purpose of mixing pesticides must be clear; do not mix just for the sake of mixing. The mixing of pesticides should achieve the purposes of synergism, simultaneous control, and expanding the control spectrum. If the above purposes cannot be achieved, they should not be mixed. Otherwise, it will cause waste, fail to achieve the desired effect, and may even cause phytotoxicity.
2. After pesticides are mixed, there should be no adverse chemical or physical changes. If the agents are not decomposed after mixing, the emulsifiable concentrate is not destroyed, and the suspension does not produce flocculation or large amounts of sediment, then they can be mixed for use.
3. The mixed liquid (or powder) after mixing should not cause phytotoxicity to crops. If phytotoxicity occurs, they must not be mixed for use.
4. After the agents are mixed, the efficacy of the mixed liquid should be improved, or at least should not be reduced; that is, after mixing, there should be synergism.
5. After the agents are mixed, the acute toxicity of the mixture should generally not be higher than the original toxicity of each; that is, toxicity must not be increased.
Causes of Phytotoxicity
1. Misapplication on sensitive crops. Most pesticides have their corresponding sensitive crops, and misuse must be strictly prevented.
2. Applying pesticides at sensitive stages of crop growth. Crops at different growth and development stages have different resistance to pesticides. Generally speaking, seeds have the strongest tolerance to pesticides. Most crops are prone to phytotoxicity at the seedling and flowering stages. Gramineous crops are relatively sensitive to pesticides at the booting stage, and are less sensitive from the tillering stage to before booting.
3. High temperature, high humidity, and strong sunlight make phytotoxicity more likely. For example, lime sulfur mixture is very likely to cause phytotoxicity when used in high-temperature weather above 32°C. A small number of pesticides are also prone to causing phytotoxicity when used at low temperatures.
4. Excessive dosage, too high concentration, or improper application methods. Crops have a limited tolerance to pesticides. If the dosage is too high or the concentration is too high, it will cause phytotoxicity to crops.
5. Improper mixing. Each pesticide has a certain compatibility. Incorrect mixing often causes phytotoxicity.
Main Symptoms of Crop Phytotoxicity
1. Spots
Spot-type phytotoxicity mainly occurs on leaves, and sometimes also on stems or fruit surfaces. Common ones include brown spots, yellow spots, scorched spots, and net-like spots. Phytotoxic spots differ from spots of physiological diseases: phytotoxic spots are distributed irregularly on the plant, and within the same field the severity varies. Disease spots usually occur widely, and the parts of the plant showing symptoms are relatively consistent. Phytotoxic spots also differ from spots of fungal diseases: phytotoxic spots vary greatly in size and shape, while disease spots have a center of infection and relatively consistent spot shape.
2. Yellowing
Yellowing can occur in the stems and leaves of plants, with leaf yellowing occurring more often. The main cause of yellowing is that the pesticide hinders the normal photosynthesis of chlorophyll. Mild occurrence appears as leaf yellowing, while severe occurrence appears as yellowing of the whole plant. Leaf yellowing can also be divided into yellowing of new leaves and yellowing of basal leaves. Yellowing caused by phytotoxicity differs from yellowing caused by nutrient deficiency: the former often changes from yellow leaves to withered leaves, and yellowing develops quickly on sunny days and slowly on rainy days. The latter is often related to soil fertility, and yellowing seedlings appear uniformly across the whole field. Compared with yellowing caused by viruses, the latter often shows mosaic-like green fragments in yellow leaves, and diseased plants show systemic symptoms, with diseased and healthy plants growing mixed together in the field.
3. Deformity
Deformities caused by phytotoxicity can occur in the stems, leaves, and roots of crops. Common ones include leaf curling, clustering, root swelling, deformed ears, and deformed fruits. Phytotoxic deformities differ from deformities caused by viral diseases: the former occur widely, with local symptoms on the plant, while the latter often occur sporadically, show systemic symptoms, and often have symptoms such as mosaic green veins and wrinkled leaves mixed in the leaves.
4. Wilting
Phytotoxic wilting often shows symptoms in the whole plant and is mostly caused by herbicides. Wilting caused by phytotoxicity differs from wilting symptoms caused after plants are infected by disease: the former has no center of infection, and in most cases the process develops relatively slowly, first yellowing, then seedling death, with no browning of the vascular tissue of roots and stems; while the latter mostly involves blockage of the vascular tissue of roots and stems, and when sunlight is strong and evaporation is high, the plant first wilts, then loses green and dies, and the vessels at the base of the plant often turn brown.
5. Stunted Growth
This type of phytotoxicity inhibits the normal growth of crops, causing plants to grow slowly. Herbicide phytotoxicity generally has this phenomenon, only to varying degrees. Compared with stunting caused by physiological diseases and deficiency symptoms, slow growth caused by phytotoxicity is often accompanied by pesticide contact injury or other phytotoxicity symptoms, while stunting due to toxic poisoning is manifested as poor root growth, and stunting due to deficiency symptoms is manifested as yellowing or dark green leaf color.
6. Sterility
Sterility is a phytotoxic reaction caused by improper pesticide use during the reproductive growth period of crops. Phytotoxic sterility differs from sterility caused by climatic factors: the former is whole-plant sterility, and although some seeds may set, other phytotoxicity symptoms are mixed in; while sterility caused by climate has no other symptoms, and whole-plant sterility rarely occurs.
7. Shedding
This type of phytotoxicity mostly appears on fruit trees and some dicotyledonous plants, with symptoms such as leaf drop, flower drop, and fruit drop. Note that leaf drop, flower drop, and fruit drop caused by phytotoxicity differ from those caused by atmospheric or cultivation factors. The former is often accompanied by other phytotoxicity symptoms, such as yellowing and scorching before leaf drop. The latter is often related to disastrous weather, often occurring during strong winds, heavy rain, and high temperatures. Cultivation factors mainly refer to flower and fruit drop caused by fertilizer deficiency or excessive growth.
8. Inferior Fruit
This type of phytotoxicity appears on plant fruits, making the fruit smaller in size, abnormal in appearance, and inferior in quality, affecting edible value. Inferior fruit caused by phytotoxicity differs from inferior fruit caused by disease: the former has only symptoms but no signs, and sometimes is accompanied by other phytotoxicity symptoms; the latter has symptoms and often also signs, while some viral diseases show systemic symptoms or do not show other symptoms.
Points to Note When Purchasing Pesticides
1. Look at the product description. Counterfeit and inferior pesticides often have blurred, abnormal, or incorrect wording, unscientific exaggeration of efficacy, and incomplete content.
2. Look at the registered trademark. First, there should be the words "registered trademark," and second, there should be a "trademark design." Neither can be missing. Counterfeit pesticides often have no trademark or trademark design.
3. Look at the two certificates and one number. The two certificates refer to the "pesticide registration certificate" and the "production license" or "production approval certificate." The one number refers to the "product standard code." You can purchase with confidence any pesticide whose label has all of the two certificates and one number.
4. Look at the expiration date and production batch number. The "expiration date" is the maximum period of validity calculated from the start of production and packaging of that pesticide. The "production batch number" is the year, month, day, and batch number of that day for the pesticide production. Pesticides that have exceeded the expiration date must not be purchased.
5. Look at the factory name and factory address. Legitimate pesticide-producing enterprises have clear factory names and addresses, and some manufacturers also note postal codes, telephone numbers, and telegraph registration numbers. Counterfeit and inferior pesticides cannot clearly mark these on the label.
6. Check whether imported and repackaged pesticides have the two certificates and expiration date. If they do, you can purchase with confidence.
7. Look at the appearance quality. Mainly check whether the pesticide has caking, layering, sediment, or leakage. If any one of these phenomena is present, it is an expired or unqualified pesticide, and it is best not to buy it.
8. Check whether the operating unit is legitimate. When purchasing pesticides, be sure to check whether the seller has a business license and a pesticide operating permit. It is recommended that you buy pesticides from agricultural technology departments with complete certificates, as they can also advise you on when it is most appropriate to use pesticides and which pesticides are most effective.
Points to Note When Using Pesticides
1. Match the pesticide to the problem. There are many types of pesticides with different characteristics, so the most suitable pesticide should be selected according to the target pest.
2. Apply pesticides at the right time so that the control effect is ideal.
3. Strictly control the application dosage and use it according to the recommended dosage. Arbitrarily increasing or decreasing it can easily cause crop phytotoxicity or affect the control effect.
4. Apply pesticides evenly, without repeated spraying or missed spraying, to ensure safety to crops and effective control of diseases, insects, weeds, and rodents.
5. Mix pesticides reasonably. After mixing, they must not increase toxicity to humans and livestock, the active ingredients must not undergo chemical reactions with each other, and the cost of pesticide use must not be increased.
6. Apply and mix pesticides safely to prevent poisoning of humans and livestock.
7. Highly toxic and extremely toxic pesticides are prohibited from use on crops such as melons, fruits, vegetables, fruit trees, and Chinese medicinal materials.
Alternative Pesticides for 5 Prohibited Pesticides in Vegetable Production
"Pollution-free" vegetable production has become the general trend, and the majority of vegetable growers have a deep understanding of this. However, the 5 highly toxic and high-residue pesticides such as methamidophos that vegetable growers have long been accustomed to using have been explicitly prohibited in the technical regulations for pollution-free vegetable production. Here we introduce alternative pesticides for the 5 prohibited pesticides to achieve equivalent control effects.
1. Methamidophos. It is a broad-spectrum insecticide, previously habitually used to kill various pests, but it is highly toxic, with a residual period of more than 30 days, and often causes human and livestock poisoning incidents, making it the primary prohibited pesticide in pollution-free vegetable production. In production, note the following:
(1) For lepidopteran pests such as cabbage caterpillar, diamondback moth, and bean pod borer. There are two types of alternative pesticides: first, biological pesticides, such as Eling Susa, Shiji Juesha, Taoxiaoling, Nongdile, etc.; second, use compound mixed pesticides, commonly mixed as dichlorvos
+BT, dichlorvos + Kungfu, etc. In use, note: ① Spray to control pests at the young larval stage for good results; ② Rotate the use of various insecticides, and use more biological pesticides, so as to prevent pests from developing resistance; ③ Current pesticides mostly have contact-killing action, so spraying during pest foraging periods gives the best effect, for example, bean pod borers mostly crawl out of bean pods to forage from 6:00-8:00 in the morning, and spraying at this time gives the best insect-killing effect.
(2) For migratory pests such as striped flea beetle and yellow squash beetle. Alternative pesticides include dichlorvos, Nongdile, phoxim, etc. In use, note: ① Simultaneous control over a large area gives good results; ② When there are many striped flea beetles, in addition to spray control, root drenching should also be used to kill underground larvae; ③ At intervals of 5-7 days, control continuously 2-3 times.
(3) Aphids, whiteflies, and similar pests. They are relatively easy to kill, and timely control with agents such as imidacloprid and dichlorvos is sufficient.
2. Dicofol. It was previously mainly used to kill red spiders, mites, and similar pests. Alternative pesticides include abamectin, fenbutatin oxide, and avermectin, etc., with obvious effects after use.
3. Omethoate. It was previously mainly used to kill thrips on melons and similar pests. Alternative pesticides include imidacloprid, dimethoate, etc.
4. Carbofuran. It was previously mainly applied to soil to kill nematodes and other soil pests. Alternative pesticides include Miral and Dexon, etc. In addition, methods such as turning and sun-drying the soil and applying lime can also achieve equivalent effects.
5. Methyl 1605. It was previously widely used to kill various vegetable pests, such as tobacco cutworm. The alternative pesticides and methods of use are similar to those for methamidophos.
Vegetable production should strictly comply with pollution-free operating regulations, prohibit highly toxic and high-residue pesticides, and for permitted pesticides, the safety interval regulations must also be strictly observed. By improving the technical level of pesticide application, the requirements of pollution-free vegetable standards can be met while also achieving high yield and high quality.