Fertile spikelets are 0.15 to 0.25 inch long, and the smaller sterile spikelets may have bent and twisted awns up to 0.6 inch long. Rhizomes are branching, scaly, and fibrous, 0.5 inch or more in diameter, and reach up to 6 feet long. Rhizomes are usually cream or tan, may have reddish brown streaks, and form a dense sod by the end of the season .Effective management of established infestations can be extremely difficult. Johnsongrass readily colonizes disturbed areas, so field margins, canals, ditches, rights-of-way, and roadsides must be monitored closely if an infestation is suspected. Care must be taken in pasture sown with johnsongrass as forage to prevent its escape. Livestock that may have eaten johnsongrass seed should not be taken to a johnsongrass-free pasture for at least a week, to prevent the spread of seed through feces. Cleaning of equipment, especially shared or rented equipment, prior to relocation is an essential preventative measure against its spread into new areas.Hand-weeding is effective only when the plants are young and when the soil is softened or loose enough to remove all roots and rhizomes without fragmenting them. Caution must be used when pulling or hoeing, as any rhizome fragments left in the soil can sprout new growth. The entire plant should be removed if possible. This is more easily done with smaller seedlings, as their rhizome system is rudimentary. However, sprouts may be attached to a large sod of rhizomes and roots, vertical growing weed in which case removal of the entire plant may be impossible by hand.
For these reasons, weed pullers are generally discouraged.Johnsongrass is known to be unable to tolerate repeated mowing. Mowing should begin when the plants are about 8 to 12 inches tall, before panicle initiation–boot stage, and continue at intervals of 2 to 4 weeks. Mowing can kill seedlings but may not kill all rhizomes, so when used alone it will only suppress established infestations, not control them.Tillage can aid carbohydrate depletion, but it must be used judiciously and only as a part of an integrated management program. Tillage is most effective when the soil is dry, as dried rhizomes are less likely to sprout, and any sprouts will be less vigorous. Summer fallowing can help maximize the effects of tillage, but only where the water table is not too shallow. Johnsongrass rhizomes have buds along their length, but only buds at the tips are active. When fragmented by discing, plowing, or other means, the dormant buds can awaken and send up shoots the current year or the next, depending on the timing of the field operations. A single tillage in spring will most likely result in a more-pronounced infestation. Therefore, early season tillage must be followed by repeated tillage, cultivation, mowing, or herbicide applications every 3 to 4 weeks to control new sprouts. Discing followed by mowing or discing followed by spraying can be effective in reducing an infestation year after year. Use caution when employing deep tillage or plowing, as fragmented rhizomes can send up sprouts from as deep as 12 inches below the soil surface.
Postharvest tillage and fallowing can also be an effective management method, as desiccation can weaken or kill rhizomes. If the harvest is early, desiccation above 85°F for 5 or more days can kill rhizome buds. Late-season tillage can expose some rhizome fragments to killing frost and desiccation, and surviving fragments should produce less-vigorous sprouts the following spring.Propane flaming has been used effectively, but it is usually more expensive than spraying or mowing. It is effective if used biweekly or monthly to manage seedlings and weaken rhizomes. Solarization immediately following harvest may be attempted, as rhizomes do not tolerate high temperatures. Three to five days at above 130°F should kill most rhizomes, but high temperatures will occur in about the first 2 inches of soil depth.Grazing can be used in lieu of mowing to manage seedlings and sprouts, but it will not harm rhizomes. Geese can also be used as a management aid in orchards and broad leaf crops, as they preferentially eat grass seedlings. Food-safety guidelines and best practices must be followed when using livestock as a pest control agent in crops. Grazing and weeder geese can also be used in non-crop areas. In all livestock-management schemes, ingested seed may pass through the animals undamaged, so care should be used when moving animals after grazing. Additionally, many herbicides restrict or forbid grazing of treated areas of certain crops; refer to the herbicide labels for specific details. Caution must be observed when johnsongrass is used as forage or when using grazing as a management method. When stressed by drought, frost, or injury, johnsongrass leaves can build up toxic amounts of hydrocyanic acid , which can be toxic or lethal to livestock. For this reason, grazing is not recommended until plants are 15 to 18 inches tall.
Additionally, johnsongrass can accumulate toxic levels of nitrates when stressed or in soils with high nitrate concentration. Dried johnsongrass cuttings that contain cyanide or high nitrate levels are still unsafe, but well-cured hay should be safe for livestock.Many herbicides are available for controlling johnsongrass, but not every herbicide is equally effective against it, and many can damage desired vegetation. Selection of the correct herbicide for an infested area is critically important. Herbicides that select for broad leaves, e.g., 2,4-D and dicamba, have little to no effect on johnsongrass, and some broad-spectrum and grass-selective herbicides may not be as effective on perennials like johnsongrass as they would be on annual grasses, even at maximum rates.Since the rhizome system of johnsongrass is so large and spreads so rapidly, killing the below-ground tissues or depleting carbohydrate stores is usually the primary goal with herbicide use. Many preemergent and preplant-incorporated herbicides can control seedlings and prevent reseeding, but they are unlikely to be effective against established plants and rhizomes. As such, the use of PRE herbicides may not be a good strategy in early-stage growth unless the target is to control only seedlings and sprouts. However, PRE herbicides such as EPTC, benefin, napropamide, trifluralin, and norflurazon can provide limited suppression of established plants. Contact herbicides, growing rack all postemergent applied to growing plants can prevent the development of seed and new rhizome growth but do not kill existing rhizomes, so new sprouts can be expected in the same season. In order to kill rhizomes, systemic POST herbicides such as glyphosate, fluazifop, clethodim, and sethoxydim are recommended. When applied early in the season these herbicides can prevent flowering but will only have a limited effect on rhizomes. Therefore, systemic POST herbicides are most effective against rhizomes when applied after flowering, when rhizomes are growing vigorously. Grass-selective herbicides like fluazifop, sethoxydim, and clethodim provide their most effective control when plants are 8 to 18 inches tall, though repeat applications may be needed. Glyphosate is most effective on actively growing plants that are 12 to 24 inches tall. Always consult the herbicide’s label for a list of common weeds controlled, as well as the legal limits on application rates and registered crops. Managing johnsongrass in the summer may be most effective in fallow fields, especially if left fallow for multiple summers. During a fallow season, multiple tillage and herbicide operations can maximize carbohydrate depletion and rhizome death. For fields with annual crops, a strategy of early preplant tillage to fragment rhizomes followed by light irrigation to encourage sprouting, mowing to deplete rhizomes, and application of a POST herbicide on actively growing plants can significantly reduce the competitiveness of johnsongrass. In this strategy, sprouts appearing after planting should also be expected and can be handled via cultivation andspot or band herbicide applications. In broadleaf crops, grass herbicides like fluazifop, clethodim, and sethoxydim are good options for controlling johnsongrass without harming crop plants. Perennial field crops will likely need between-row cultivation and spot application of herbicides to minimize damage to crops. In orchards, johnsongrass should be less invasive when canopies are closed and will likely be found only along field margins, so effective management of new infestations may be accomplished with mowing and a spot application of a POST herbicide. Established infestations in smaller tree orchards, such as prunes, may require cultivation between rows to about an 8-inch depth to fragment rhizomes and later a spot application of herbicide to kill new sprouts.
In non-crop areas, herbicides used in conjunction with mowing can be effective in managing or even eradicating johnsongrass, but care must be taken when selecting herbicides, as the desired vegetation may consist of species with different susceptibilities to the chemicals.spot or band herbicide applications. In broadleaf crops, grass herbicides like fluazifop, clethodim, and sethoxydim are good options for controlling johnsongrass without harming crop plants. Perennial field crops will likely need between-row cultivation and spot application of herbicides to minimize damage to crops. In orchards, johnsongrass should be less invasive when canopies are closed and will likely be found only along field margins, so effective management of new infestations may be accomplished with mowing and a spot application of a POST herbicide. Established infestations in smaller tree orchards, such as prunes, may require cultivation between rows to about an 8-inch depth to fragment rhizomes and later a spot application of herbicide to kill new sprouts. In non-crop areas, herbicides used in conjunction with mowing can be effective in managing or even eradicating johnsongrass, but care must be taken when selecting herbicides, as the desired vegetation may consist of species with different susceptibilities to the chemicals.Many herbicides are effective in controlling johnsongrass, but overreliance on one type of herbicide can impose selection pressure on johnsongrass populations to develop herbicide resistance. Herbicide-resistant populations of johnsongrass have been reported in several states, however to date there has been no reported herbicide resistance in California populations of johnsongrass. In general, the most common types of herbicide resistance have been to a more effective and sustainable johnsongrass management strategy should incorporate a variety of herbicide modes of action in order to decrease the possibility of herbicide resistance. Some johnsongrass populations may simply be tolerant to an herbicide, requiring a dosage far higher than usual to kill, while others may be totally resistant, in which case the plant will survive the treatment even if the rate of herbicide is significantly increased . Table 1 summarizes pesticide recommendations from product labels at the time of publication. Always refer to the current product label for complete instructions and restrictions. In addition to the federally required label, many herbicides used for johnsongrass management may have a supplemental Special Local Need label for specific instructions or limitations for handling and use. In addition, some California counties may restrict or forbid the use of certain herbicides. Application rates may must be adjusted based on soil textures and pH, and many herbicides restrict or forbid use on soils that are frozen, compacted, or that have high levels of organic matter. In addition, many herbicides have requirements or restrictions for irrigation before or after application, or when applied to plants under stressed conditions. Management of johnsongrass may be diminished or crop injury may occur if herbicides are applied under nonspecified conditions. Furthermore, many herbicides have postapplication restrictions on reentry, minimum preharvest intervals, crop rotation, replanting, or grazing. Foliar herbicides usually require adjuvants such as nonionic surfactants, crop oil concentrates, or methylated seed oils in the final mixture.In cooler coastal production areas you can plants beans from April through August, and even into September, depending on the potential for early frost. Because production costs are low , growers can risk early or late plantings to have beans in the market when supply is lower and prices are higher. Plant beans grown for harvest as dry beans by mid May on California’s Central Coast. In warmer inland valleys it is best to plant early while daytime temperatures are relatively moderate. Avoid June and July plantings, since fresh market bean quality and quantity will be significantly reduced when daytime temperatures are much above 95ºF . Beans can then be planted again in the late summer to allow for good production until the first frost. On soils with relatively good water holding capacity, large areas can be bedded, pre-irrigated, and then worked with a rolling cultivator following weed seed emergence.