A Detailed Guide to Using Clethodim Herbicide

Clethodim is a foliage herbicide, a highly efficient, safe, and highly selective ACCase inhibitor, with special efficacy against most annual and perennial grass weeds, and it is safe for broadleaf crops. So what is the usage method for clethodim herbicide?

1. Mastering the appropriate application timing is crucial. In mid-November we conducted a clethodim trial in a winter rapeseed field in Wuhan. The results showed that when clethodim was applied to weeds at the 4-5 leaf stage, the leaves turned noticeably yellow 3 days after application, the heart leaves were easily extracted at 7 days, and the base was visibly blackened. After 21 days, the vast majority had died. However, weeds below the 3-leaf stage and above the 5-leaf stage at the time of application showed only slight effects at 5 days and 7 days respectively. At 21 days, the former showed almost no effect at all, while the latter showed obvious leaf yellowing. Our analysis is that when the grass age is too advanced, resistance increases and control becomes difficult; while before the 3-leaf stage of weeds, the leaves are upright, the heart leaves are less exposed, so less herbicide is retained, and at this time a considerable portion of the weeds have not yet emerged. Since clethodim is a foliage herbicide, it has no pre-emergence sealing effect on weeds, and weeds that emerge after application also mask the control efficacy of clethodim. Applying the herbicide when the grass age is at the 3-5 leaf stage and growing vigorously, the herbicide is easily sprayed onto the weed leaf surface, and the weeds absorb and translocate it quickly, so a single application can effectively control most grass weeds.

2. Pay attention to the influence of climatic conditions on efficacy. Weeds absorb the herbicide through the stomata and cuticle of the leaves; under conditions such as drought, high temperature, and low temperature, a large number of stomata close and the cuticle thickens, all of which are unfavorable for weed absorption of the herbicide. When the relative air humidity is above 65%, choose early morning or late evening in summer, and choose midday on sunny days in winter for spraying, which is conducive to herbicide absorption and efficacy. In early July when we conducted a trial in a summer soybean field in Hebei, the temperature was as high as 35°C, and when sprayed at the conventional dosage, after 7 days only some wheat seedlings (the previous crop in the soybean field was wheat) showed yellowing and withering of leaf tips, while when the temperature dropped to 26°C later that day, the effect after spraying was very obvious. When the temperature is too high, weed stomata close, causing slow absorption, and in addition the herbicide sprayed on the leaf surface evaporates quickly, so the efficacy cannot be well exerted.

3. Weed growth vigor and efficacy. In mid-November we simultaneously sprayed clethodim on shortawn foxtail (Alopecurus aequalis) in rapeseed fields in Hubei and Anhui, and two weeks later the former showed obvious control efficacy while the latter showed obvious effects only 1 month after application. We discussed and compared the data and photographic materials observed and recorded at that time for the two locations, including temperature, relative humidity, and the growth vigor of rapeseed and weeds, and found that there was one difference between the two locations. At that time, the shortawn foxtail in both locations was basically at the 3-5 leaf stage, about 12cm tall. But in Hubei the shortawn foxtail leaves were yellowish, spreading and soft, with exposed heart leaves, while in Anhui the shortawn foxtail leaves were deep green and upright. We believe that upright leaves not only make the spray solution roll off easily and adhere poorly, but their cuticle is also thick, which affects the speed of leaf absorption of the spray solution. Therefore, when controlling such weeds, pay attention to the spraying effect, and be sure to spray evenly and thoroughly.

4. Application technique. A good sprayer produces fine droplets of spray solution, which easily adhere to the leaf surface without rolling off, thereby improving the absorption and utilization rate of the herbicide by weeds. We selected a Shandong Weishi brand sprayer and compared it with ordinary sprayers, which confirmed this point. After spraying with a good sprayer, a dense layer of small droplets can be seen adhering to the weed leaf surface.

5. Differences in tillage methods. After the previous crop is harvested, if sowing is done on hard stubble, or if plowing is rough, large soil clods can be seen in the field. Weeds growing in rice stubble or wheat stubble, or hidden among soil clods, cause the spray solution not to reach the weeds, which not only results in poor control efficacy but also wastes manpower and material resources. Therefore, being a bit more meticulous during tillage can save a lot of trouble later.