Chlopyralid is especially effective for control of legumes and composites such as Canada thistle , and yellow starthistle. Because it does not control many common broad leaf weeds such as mustards, it must be tank-mixed for complete control of the wide range of broad leaf weeds found in small grains. On wheat, clopyralid should be applied from the 3-leaf stage to early boot stage, complimenting the timing of 2,4-D and MCPA. Carfentrazone is a contact herbicide that controls weeds by disrupting cell membranes. It is effective at very low application rates on coast fiddleneck, little mallow, burning nettle, and other weeds that are difficult to control with other herbicides. Adding surfactants to carfentrazone often causes temporary crop burn. Tank mixing with UN-32 may enhance weed control. Tank-mixing carfentrazone with dicamba provides good control of common chickweed. Combining carfentrazone with phenoxy herbicides broadens the weed spectrum controlled, lowers herbicide application rates, and can reduce the risk of weeds building up herbicide resistance.Preemergent herbicides are not commonly used in small grains in California, but they can be effective in certain situations. Trifluralin is a preemergent herbicide used for wild oat and canarygrass control in wheat and barley. It is applied before or after sowing and must be incorporated no deeper than 2 inches . A double incorporation is more effective than a single incorporation. Small grains must be planted below the 2-inch herbicide zone . Results can be erratic if the zone of treatment does not have adequate moisture. Crop safety is marginal.Diclofop controls wild oat, canarygrass, and Italian ryegrass in wheat and barley.
Diclofop controls wild oat and ryegrass in the 1 to 4 leaf stage and canary grass in the 1 to 2 leaf stage. Avoid applications under saturated soil conditions or cold weather. Fenoxaprop ethyl controls canarygrass, wild oat, rolling benches for growing and several foxtails, including yellow foxtail and green foxtail . It also suppresses mustards. It has a wide window of application, providing effective control when applied between the 1 to 6 leaf stage of grasses. For best control of wild oat, delay application until most wild oat plants have emerged. A tank mixture with bromoxynil allows for a wide range of weed control at an early timing. Fenoxaprop cannot be tank-mixed with phenoxy herbicides since reduced grass control often results when such tank mixtures are used. Mesosulfuron controls most grassy weeds and many broad leaf weeds in wheat. It is especially effective on Italian ryegrass, wild oat, little seed and hood canary grass, and annual bluegrass. It controls ripgut brome and other brome species, depending on weed size at application. Most California wheat cultivars have good tolerance to the herbicide. However, wheat plants will turn a lighter green color for a couple of weeks following application. If soil nitrogen levels are low, this symptom will persist longer, and supplemental nitrogen should be applied. When treated beyond the 1 tiller stage, temporary growth suppression and shortening of the wheat plant will occur. The crop will recover more quickly from these symptoms under good growing conditions. Mesosulfuron is effective on certain broad leaf weeds, including common chickweed, wild radish, and mustards. It also provides partial control of many other broadleaf weeds, including common groundsel , little malva, coast fiddleneck, yellow starthistle, and blessed milkthistle. Mesosulfuron can be tank-mixed with bromoxynil and MCPA and may be applied from the 1 leaf to 1 tiller wheat stage and up to the 2 tiller stage of grasses.
A methylated seed oil or a nonionic surfactant is required; adding ammonium sulfate or low rates of UN-32 enhances weed control on difficult-to-control weeds. Restrictions on crop rotations are greater than with fenoxaprop.Weeds that have germinated can be chemically removed using paraquat and glyphosate before cereal planting or emergence. These non-selective herbicides have no soil-residual effects on germinating small grain plants as long as they are applied before plants emerge through the soil. If the herbicide comes into contact with wheat or barley plants, severe injury will occur. Glyphosate can also suppress perennial weeds such as johnsongrass, nutsedge , bermudagrass , and dandelion when they are growing before grains are planted or emerge.The presence of green weeds late in the season can cause harvest and post harvest problems. Green weeds can slow the progress of combines, raise the moisture content of the harvested crop, and discolor or even cause off-flavors of the harvested grain. Weeds that often cause problems at harvest include field bindweed, Russian thistle, five hook bassia , kochia, common lambs quarters, knot weed, swamp smart weed, and johnson grass. Problems with green weeds at harvest can be avoided by using a preharvest herbicide application or by swathing the crop before combining. In both cases the green weeds should be allowed to dry before the crop is combined. Soil temperature results gathered after steam application in the field were similar to other mobile steamer applicator studies . The premise of this research was to evaluate the pest control efficiency of steam applied in a band prior to planting. We found that weeds, pathogens, and hand weeding times were reduced in steam-treated plots, and yields improved in some cases. In trial 3, for 176 min, steam temperatures were above 70oC were obtained with the Steamy applicator, which used a rototiller as it was incorporating steam on flat ground.
Agitating the soil as the steam was incorporated allowed for better steam penetration targeting soil aggregates compared with trials 4 and 5 done by the Yuma Steamer. The Yuma steamer kept a steam temperature above 70oC for 98-105 minutes. The temperature duration time above 70oC for the Yuma steamer was not as long as the temperature duration in the Steamy applicator trial. The Yuma steamer has a bed shaper attached to it to ensure the bed tops stay firm after application and is faster than the Steamy.The results from the weed analysis indicate that steam disinfestation does an excellent job controlling weeds, especially on hairy nightshade, goosefoot, sheperd’s-purse, burning nettle, and common purslane. Another objective in this study was to evaluate steam + hydrogen peroxide applied as a band to determine whether this product improves the pest control efficacy of steam by raising the temperature. Hydrogen peroxide did not have a significant effect on weed and pathogen control, hand weeding time, and yields compared with the steam treatments. Because the trials used soils naturally infested with Pythium spp. and S. minor, we had varying levels of disease in the field trials. Steam + hydrogen peroxide did not significantly reduce the amount of Pythium spp. colonies or S. minor sclerotia compared with steam alone. In trial 2, upon steam application, temperatures stayed above 70 oC for a shorter amount of time compared to the other trials . The steam treatment had a significant effect on reducing S. minor sclerotia by 94% when compared with the control using the Steamy in trial 3, similar to findings in other studies . The steam treatment reduced Pythium spp. colonies by 99% when compared with the control using the Yuma steamer in trial 4, similar to another study that was done . Out of all the trials, trial 4 had the most diseased lettuce plants and the best reduction of Pythium spp. colonies. The lettuce plant size for the steam-treated lettuce was significantly larger with an increase in yield when comparing with the control in trial 4 and 2, cannabis dry racks suggesting pathogen suppression. Gross revenues for the lettuce trials in this research showed the potential steam has to increase lettuce yields. A steam study done in strawberry production by Michuda et al., suggested a maximum soil temperature of 62-63oC should be a standard for growers at a duration of 41-44 mins to maximize net returns and increase fruit yield. In our lettuce steam study we surpassed that reaching temperatures above 70oC which increased yield and gross revenue peracre. Better disease control likely resulted in greater lettuce growth with a gross organic revenue of $5,624 an acre for the steam treated lettuce vs. 4,042 an acre for the non-treated control lettuce. The difference was $1,582 an acre. For the gross conventional revenue, it was 5,066 an acre for the steam treated lettuce vs. $3,640 an acre for the non-treated control lettuce. The difference was $1,426. The cost of field application per acre is $971, which suggests steam treatment maybe economically feasible to use commercially in-field given the great gross revenues per acre, but we believe that there is room for improvement in this cost. Machine operator and worker wage will increase the operating costs of this field applicator as the cost of minimum wage increases in the future, so more research needs to be done to drive the costs of the applicator down.
Research and development should focus on the implementation of a rototiller to agitate the soil to target soil aggregates for better steam penetration. Improvements might include making the machine lighter so that there is less compaction. Ideally, machine development and construction should be done in the United States to reduce the overall price of the applicator. It is important to increase the speed of application, but it needs to be done in a way that the machine still heats the soil and makes adequate dwell time. Currently, it takes 9.07 hours to steam an acre, so if the time of application can be reduced, then the amount of fuel costs can be reduced as well. It will be of great benefit to work with a known industry leader like, TriCal Inc. because they specialize in developing new effective technologies and build products to control soil pests in California. Steam applicator development can be maximized with the help of contractors who have the capabilities of building a steam applicator who can lease out to farmers. Steam is also an option for organic farmers to make an applicator in house that can be of great benefit given the need for non-chemical ways of controlling soil pests.Nevertheless, my results indicate that with a greater reduction of pathogen inoculum and weed seeds in the soil using steam, this will allow more opportunity for the crop to thrive with less pest competition. Even though the hydrogen peroxide treatment was evaluated only in two of five trials, there was no significant advantage when compared to the steam treatment alone. Hydrogen peroxide still has potential to create an exothermic effect in the soil steaming process. As a recommendation for future studies if hydrogen peroxide is more thoroughly incorporated into the soil and the trial is pre-inoculated with soil pathogens, there may be a yield benefit. This work further shows the true potential of band steaming for weed and pathogen control in the field .Surface mulches are widely used in the production of strawberries and certain high value vegetable crops. Polyethylene mulch is used on virtually all tomato and strawberry production in Florida and is also widely used in the production of other crops such as peppers, eggplant, and melons throughout much of the southern United States. Researchers at the University of Florida estimate that more than 100,000 acres of vegetable crops in that state currently use plastic mulches annually, making Florida the national leader in this production system . In California, the majority of strawberry and staked tomato production uses polyethylene mulch. Peppers, eggplant, and melons also use mulches in certain situations, especially when earliness is desired. Field management and research related to plastic mulches in these production regions is now quite developed. Potential benefits as well as drawbacks of polyethylene mulches for vegetable crop production are given in table 1. The use of intercrop cover crop residues as surface mulches is a more recent and far less widely used production practice. It has recently gained considerable interest in a number of commercial vegetable crop production regions in the United States. Potential advantages and disadvantages of this vegetable crop production technique are summarized in table 2. Reflective plastic and some cover crop mulches share similar features relative to crop production: insect and disease management, weed management, fertilizer availability, and water conservation. In order for production practices using either polyethylene or cover crop mulches to be successfully adopted in California, specific production goals must be carefully matched with specialized management know how and experience.Plastic mulches have been commonly used for commercial vegetable crop production for more than 30years.