Why isn't there a significant effect after the medicine is finished?
A brief knowledge sharing, introducing why there is no significant effect after the medicine is finished in terms of plant care. Here are the details for your reference.
Friends who grow roses know that roses are prone to diseases and pests, such as black spot disease, powdery mildew, spider mites, thrips, and aphids, which are common occurrences. Therefore, it is necessary to apply pesticides regularly. However, the question arises: Why do some friends achieve good results with the same medicine, while others feel it has no effect? Have you encountered a situation where the medicine had no effect after application? What could be the reason? Today, I will analyze the common reasons for the lack of effect after applying medicine, hoping it will be helpful to you.
Why isn't there a significant effect after the medicine is finished?
If we purchase pesticides from正规 channels and the effect is not obvious after use, we need to consider the following four reasons. You can check them one by one.
1. -- The medicine is not suitable --
Choosing the right pesticide is important when controlling plant diseases and pests. Although most fungicides and insecticides on the market can treat multiple diseases and pests simultaneously, sometimes, specific treatment is needed for better results.
For example, among diseases, there are fungal diseases and bacterial diseases. Most fungicides that kill fungi can also control bacterial diseases, such as pyraclostrobin and myclobutanil. However, if the medicine name contains a certain "mycin" suffix, it usually can only treat bacterial diseases, and its effect on fungal diseases is not significant.
The same is true for insecticides. There are many insecticides, but remember, lambda-cyhalothrin can kill most insects, whether small or large, from aphids and thrips to cockroaches and centipedes. While insecticides like dinotefuran, acetamiprid, and thiamethoxam generally kill smaller insects like thrips, aphids, and whitefly.
So, if you use a bactericide to treat a fungal disease, the effect will naturally not be ideal. Using dinotefuran to kill large caterpillars may also not yield significant results.
It is important to note that many新手 gardeners use chlorothalonil to kill insects, but diseases and pests are completely different. Don't use fungicides to kill insects; it's ineffective!
Also, remember that spider mites are an exception. They belong to the mite family and require special pesticides.
2. -- Insufficient dosage --
If the medicine selection is correct but the effect is not obvious after use, then we need to consider whether the dosage is sufficient.
Different brands of pesticides have different effective contents and dilution ratios. Many pesticides indicate the dosage per mu, which is not easy to control for home gardening. Often, relying on intuition can lead to insufficient drug concentration, resulting in不明显 effects after spraying, and too high a concentration can burn the leaves.
When preparing the pesticide solution, it's best to use measuring tools to calculate the dilution ratio. For example, if aphids are still not killed after spraying insecticide for a day, you can increase the drug concentration and spray again.
Why isn't there a significant effect after the medicine is finished?
Here's an important reminder: Sometimes when aphids are severe, especially black aphids, their mouthparts can penetrate the plant's tender branches. Even if they are killed by the pesticide, they will not fall off and will remain stuck on the branches, leading to the misconception that the medicine is ineffective. When repeatedly applying medicine doesn't work, observe whether the insects are still moving. If they are not, they have been killed and can be washed off with water.
3. -- Wrong timing for applying medicine --
Besides choosing the right medicine and mixing the right concentration, the timing of applying the medicine can also be important. For example, when killing thrips, spraying the medicine in the evening is much more effective than in the morning because thrips are nocturnal and are most active at night. Many insecticides we use are contact-killing types, which means they are effective only when the insects come into contact with the pesticide solution. Therefore, for pests with obvious activity patterns like thrips, it's best to apply the medicine in the evening for better results.
In April, there's often a lot of rain, which can affect the efficacy of the pesticide. Generally, if it rains within 4 hours after applying the medicine, the effect can still be achieved. If it rains within 2 hours, it's pretty much a waste of effort, and you'll need to find another opportunity to reapply.
4. -- Stubborn diseases and pests --
Some friends may say, "I chose the right medicine, mixed the concentration as per the instructions, and applied the medicine at the right time, but why is the effect still not obvious?"
This brings us to the topic of stubborn diseases and pests, such as powdery mildew, gray mold, spider mites, and thrips.
They are called "stubborn" because they are difficult to control.
Powdery mildew fungi are not easily contaminated by the pesticide solution, so the effect is often not obvious after application. When treating powdery mildew, it is recommended to add a little organic silicon or detergent to the solution to increase adhesion. However, it still requires persistent use and it's not something that can be cured with 1-2 applications.
If roses are severely infected with powdery mildew, Green Plant Enthusiast Network suggests using potassium sulfate solution at a concentration of 600-800 times. This strong alkaline medicine has a relatively obvious effect on powdery mildew. However, because the temperature is high in spring, if the seedlings are tender, potassium sulfate can easily burn the leaves. Therefore, Green Plant Enthusiast Network does not recommend using potassium sulfate unless the powdery mildew is severe, so you need to weigh the pros and cons.
Now there's a lot of rain, high humidity, which is a high-incidence period for powdery mildew. It is recommended that you spray fungicides preventively.
Gray mold may be easier to control than powdery mildew, but its destructiveness is much greater. Gray mold is most likely to infect flower buds when there's a lot of rain, causing the buds to rot before or halfway through flowering. If there isn't much rain, it's treatable, but when it's rainy, it's really difficult, unless you can prevent them from getting wet.
Among pests, the most troublesome are spider mites, which are most likely to occur in poorly ventilated environments and have super reproductive power. Often, when the adult mites are killed, the eggs hatch again, making it difficult to control.
When controlling spider mites, it is first necessary to improve environmental ventilation, then wash the leaves of the rose盆栽 clean with water. The more severe the spider mite infestation, the cleaner the leaves need to be. After the leaves are washed and the water has dried, spray the pesticide for killing spider mites, and the effect will be significant. However, it is necessary to observe the leaves again after 3 days and, if necessary, wash the leaves and apply the medicine again. After a few consecutive treatments, it can be cured.
Why are thrips difficult to treat? In fact, thrips are relatively easy to treat, and a single application of medicine usually yields significant results. Many friends think the medicine is ineffective because they demand too much, expecting to eliminate all pests, which is naturally difficult, as our environment is open, and thrips from other places can fly over.
In spring, roses are particularly prone to diseases and pests, and with continuous rain this year, everyone should do a good job of preventing diseases and pests.
The above sharing on why there is no significant effect after the medicine is finished and detailed explanation of why roses with diseases and pests cannot be treated with medicine are for reference only!