Introduction
Weeds steal from farmers every day. It is essential to have access to economically effective and safe weed management tools to control these weedy pests. Our effort to expand the weed management toolbox for farmers through the support of the Georgia Agricultural Commodity Commission for Vegetables has been fruitful. In fact, the number of crops and state herbicide labels (in parentheses) obtained through support of this project include the following: broccoli (5), brussels sprouts (3), cabbage (4), cantaloupe (6), carrots (2), cauliflower (4), celery (1), collards (4), cucumbers (6), eggplants (5), kale (3), lettuce (1), lima beans (2), mustard greens (1), onions (2), okra (3), peppers (6), pumpkins (5), snap beans (2), southern peas (2), spinach (1), summer squash (8), sweet potatoes (2), tomatoes (7), turnips (2), watermelon (9), and winter squash (3).
The goal of this project was to find potential ways to manage wild radish in seeded greens such as mustard, turnips, collards, and others. Wild radish, a member of the mustard family, has historically been recognized as a winter annual weed mainly infesting winter crops grown across the Southeast. Like many other weeds, wild radish aggressively competes with our crops for light, water, nutrients, and space, and it can also harbor problematic pests, including various insects and diseases. For instance, wild radish can shelter and increase issues with diamondback moth caterpillars.
In recent years across our region, there has been a clear and significant change in wild radish, making it even more troublesome for agriculture. What used to be a plant that emerged only in late fall and winter is now actually emerging for at least 11 months during the year across South Georgia. This expanding emergence period is increasing its presence across more fields and in larger populations. The project had two initiatives: 1) applying eight herbicides at numerous rates and documenting the level of radish control and the tolerance of greens, and 2) determining if the LaserWeeder could differentiate wild radish and seeded mustard just after emergence.
Materials and Methods
Herbicide screenings
Command, Dual Magnum, Enversa, Goltix, Torero, Nortron, Prowl H20, and Warrant were all applied immediately after seeding the crop and before wild radish emergence; application rates of each product are found in Table 1. The level of wild radish control and crop injury was determined throughout the season. Wild radish populations exceeded 20 plants per square foot.
LaserWeeder
At the time of seeded mustard and wild radish emergence, the LaserWeeder was evaluated for its potential to distinguish between the weeds and the crop.
Results
Herbicide screenings
The level of weed control was highly correlated with the level of crop injury (Tables 1 and 2). Herbicide treatments that provided some level of radish control significantly injured the crop; treatments that lacked crop injury also did not provide weed control. Ultimately, there were no treatments that provided enough weed control without crop injury to even harvest.
| Herbicide treatment (oz/acre)^ | Application method | % max crop injury (scale 0 to 100%) | % max radish control (scale 0 to 100%) |
|---|---|---|---|
| Control | — | 0 | 0 |
| Goltix 12 oz | Preemerge | 0 | 0 |
| Goltix 16 oz | Preemerge | 0 | 16 |
| Torero 16 oz | Preemerge | 0 | 9 |
| Torero 32 oz | Preemerge | 0 | 34 |
| Torero 48 oz | Preemerge | 35 | 66 |
| Nortron 8 oz | Preemerge | 0 | 0 |
| Nortron 16 oz | Preemerge | 0 | 4 |
| Nortron 24 oz | Preemerge | 0 | 11 |
| Command 8 oz | Preemerge | 77 | 87 |
| Command 16 oz | Preemerge | 84 | 89 |
| LSD | — | 3.13 | 18.58 |
| * Treflan was applied preemerge across all treatments. ^ Herbicides applied in this experiment are not labeled for greens and should not be used to produce greens in Georgia. Follow all pesticide label requirements. | |||
| Herbicide treatment (oz/acre)^ | Application method | % max radish control (scale 0 to 100%) |
|---|---|---|
| Control | — | 0 |
| Enversa 8 oz | Preemerge | 0 |
| Enversa 16 oz | Preemerge | 4 |
| Enversa 32 oz | Preemerge | 15 |
| Warrant 8 oz | Preemerge | 0 |
| Warrant 16 oz | Preemerge | 0 |
| Warrant 32 oz | Preemerge | 18 |
| Dual Magnum 8 oz | Preemerge | 27 |
| Dual Magnum 16 oz | Preemerge | 30 |
| Prowl 16 oz | Preemerge | 0 |
| Prowl 32 oz | Preemerge | 11 |
| LSD | — | 7.1 |
| * Treflan was applied preemerge across all treatments. Crop injury was impossible to evaluate because of the lack of weed control and intense radish population. ^ Herbicides applied in this experiment are not labeled for greens and should not be used to produce greens in Georgia. Follow all pesticide label requirements. | ||
LaserWeeder
The LaserWeeder could not differentiate an emerging wild radish from the seeded mustard crop. Without proper identification, the LaserWeeder is not a solution for removing wild radish from greens.
Conclusion
Managing wild radish in fields planted to seeded greens currently will rely on tillage and hand weeding. Since wild radish emerges from a depth close to the soil surface, deep tillage (soil inversion) can be an effective approach, but it is important to note that researchers have shown seed life longevity can exceed 15 years, making seedbank management rather complex. Thus, the only sustainable approach appears to be prevention, keeping this weedy pest from establishing in fields that will be seeded into greens. Although the LaserWeeder could not identify the difference between wild radish and mustard greens during emergence, the experiment did potentially identify a stage of growth where the two plant species can be differentiated. Additional research will determine if the LaserWeeder can control wild radish at the stage where it becomes identifiable.
