The results of some greenhouse trials this winter and spring and the results of field studies in this growing season showed that the Palmer Palm vegetable dicamba (DR) resistant. These DR populations have been established in Crockett, Gibson, Madison, Shelby and Warren counties and possibly several other counties.
The level of dicamba resistance is relatively low, about 2.5 times. In any given field, the degree of infestation starts with a small pocket, where a female parent plant is sown in 2019, and an area covers several acres. This can be compared with the first recorded glyphosate-resistant Palmer mar vegetable found in Tennessee in 2006. At that time, most growers still had relatively good control over the glyphosate Palmer mar vegetable, while other plantations The person noticed an escape in his field.
When Xtend crops first appeared on the scene, it was not uncommon for Palmer mar vegetables to escape dicamba, which was stray everywhere. These escapes will grow little or no growth in 2 to 3 weeks. Then, most of the crops will be obscured by the crops and will never be seen again. However, today in certain areas, DR Palmer mar dishes will start to grow again in unprecedented numbers within about 10 days.
Some of the special features of this study are the screening of DR weeds in greenhouses at the University of Tennessee and the University of Arkansas. This study shows that the tolerance of Palmer a vegetable that escaped dicamba from multiple fields in Tennessee in 2019 is that of Palmer a vegetable grown from seeds collected from Arkansas and Tennessee ten years ago. More than 2 times. Subsequent greenhouse tests conducted at Texas Tech University showed that populations collected from Shelby County, Tennessee were 2.4 times more tolerant to dicamba than Parma a in Lubbock, Texas (Figure 1).
Repeated field trials were conducted on some of the suspected Palmer populations in Tennessee. The results of these field trials reflect the screens in the greenhouse, showing that the labeled 1x dicamba application rate (0.5 lb/A) can provide 40-60% Palmer mar vegetable control. In these trials, the subsequent application of dicamba only slightly improved the control (Figures 2, 3).
Finally, many growers report that they need to spray the same Palmer mar vegetable 3 to 4 times to get control. Unfortunately, these reports indicate that the greenhouse and field studies are reflecting what some consultants, retailers and farmers in Tennessee see in the fields.
So, is it time to panic? no. However, it is time to reassess weed management. Now, herbicide management is more important than ever. This is why we emphasize the use of hooded herbicides in cotton, such as paraquat, glufosinate, Valor, diuron, metazox and MSMA.
When we look forward to 2021, it is now necessary to effectively use PRE spray residue on Palmer. In addition, freedom must be used immediately after the use of dicamba to eliminate escape. Finally, preliminary studies have shown that DR Palmer mar will also be more resistant to 2,4-D.
Therefore, this makes Liberty the most important herbicide in the weed management system of Xtend and Enlist crops.
Dr. Larry Steckel is an extension weed expert at the University of Tennessee. View all author stories here.