More info for the terms: competition, cover, fire management, fire suppression, forbs, invasive species, natural, nonnative species, resistance, restoration, rhizome, tree, vines
Impacts: A 1998 review by Lyons [86] indicates that the impact of field bindweed on agricultural lands is well documented, especially in the central U.S., but the threat it poses to rangelands and natural areas is unclear. Almost all research on field bindweed pertains to agriculture. When surveyed in 1982 and 1988, farmers and ranchers in north-central Idaho considered field bindweed to be one of the 3 most serious weeds in their area [27]. The Eastern Region of the U.S. Forest Service ranks field bindweed as a Category 3 plant: often restricted to disturbed ground, and not especially invasive in undisturbed natural habitats [136]. Natural area managers are most likely to find it in moist locations (e.g. riparian corridors and irrigated areas) on tracts once used for agriculture [86].
Field bindweed is found on several of The Nature Conservancy's preserves and may pose a threat to restoration efforts. Stewards at the Phantom Canyon Preserve in Colorado report that field bindweed is most likely to invade and reduce cover of native grasses and forbs in areas that are degraded due to past land use, current human activity, and fire suppression. Stewards at Garden Creek Preserve in northern Idaho report that field bindweed threatens native plant communities by "decreasing biodiversity," and is a direct threat to several species [86]. At the Thousand Springs Preserve in Idaho, field bindweed thrives under cultivated and irrigated conditions, and managers there suggest that field bindweed "outcompetes" native grasses [86,109].
Field bindweed competition for nutrients and water may reduce productivity of native plants, although this has only been studied with crop plants, where yield reductions range from 0 to 100% [128]. Competition from field bindweed for soil moisture may have greater impact in dry years [8].
It has been suggested that field bindweed may be mildly toxic to some grazing animals, and that the amount of field bindweed that can be safely eaten by domestic sheep, cattle, and goats is not known. It is reported to cause distress in domestic pigs that eat it (Callihan and others 1990, as cited by [86]). Field bindweed contains alkaloids that may be toxic to horses [134]. Other authors report a history of using sheep and pigs to eat field bindweed and thereby help control infestations [13,122] (see Biological control).
Control: Field bindweed has a deep, extensive root system that stores carbohydrates and proteins and allows it to sprout repeatedly following removal of aboveground growth. Field bindweed may also produce abundant, long-lived seed. Strategies to control field bindweed infestations must include removing established plants and preventing seed production and seedling establishment. Alcock and others (1974, as cited by [86]) suggest the following as general goals for field bindweed control: 1) reduce seed in soil 2) prevent seedling growth, 3) deplete food reserves in the root system 4) prevent its spread.
Eradication of an established invader is rare, and control efforts vary enormously in their efficacy. Successful control depends more on commitment and continuing diligence than on the efficacy of specific tools themselves. Control of biotic invasions is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders [87]. A long-term perspective is important where total eradication is not a realistic short-term goal. Even with intensive management, field bindweed can persist as seed for several years, and some authors suggest that 3 to 5 growing seasons are required in agricultural settings to eliminate seedlings (Callihan and others 1990, as cited by [86]). The key to implementing a successful control program is to continue treatment even after it appears the infestations are seriously reduced [86].
Successful control of field bindweed is most likely if aboveground biomass is removed multiple times over at least 2 growing seasons (e.g. [13]), or by planting of competitive species following aboveground removal and continuously monitoring for and killing sprouts and seedlings. In agriculture, control has been most successful where tillage is combined with herbicide application, although herbicide application alone may also be effective (see Chemical control) [86].
Prevention: The most efficient and effective method of managing invasive species is to prevent their invasion and spread [116]. Preventing the establishment of weeds in natural areas is achieved by maintaining healthy natural communities and by conducting aggressive monitoring several times each year. Monitoring efforts are best concentrated on the most disturbed areas in a site, particularly along roadsides, parking lots, fencelines, and waterways. When a field bindweed infestation is found, the location can be recorded and the surrounding area surveyed to determine the size and extent of the infestation, so these sites can be revisited on follow-up surveys [67]. It is important to kill any field bindweed plants that are found, followed by some combination of mechanical, chemical and/or biological control. Prevention of new invasions is much less costly than postinvasion control [87].
Avoid management activities that encourage invasion and be prepared to eradicate small infestations that may follow such disturbances. Factors indicated by Nature Conservancy managers as encouraging field bindweed invasion include cultivation and irrigation in Idaho grassland and road grading and haying in Oregon along roadsides and riparian areas [109]. Weed prevention and control can be incorporated into all types of management plans, including logging and site preparation, management of grazing allotments, recreation management, research projects, road building and maintenance, and fire management [137]. See the USDA "Guide to noxious weed prevention practices" [137] for specific guidelines and recommendations for preventing the spread of weed seeds and propagules under different management conditions.
Roads act as dispersal corridors for many invasive species. Avoid road building in nature reserves, and when unavoidable, redeposit original topsoil in roadside ditches. Road construction projects should not be considered complete until native vegetation is fully established. Road construction projects in nature reserves should be treated and funded as 10- to 20-year biological projects rather than 1-2 year engineering projects, with biologists and resource managers consulting on road construction. Roadsides should be actively managed by regular monitoring for establishment of nonnative species, and reseeding roadsides with natives [135].
Integrated management: A combination of complementary control methods may be helpful for effective control of field bindweed. Integrated management includes not only killing the target plant, but establishing desirable species and discouraging nonnative, invasive species over the long term. Components of any integrated weed management program are sustained effort, constant monitoring and evaluation, and the adoption of improved strategies. An integrated management plan includes efforts to place continual stress on undesirable plants.
In agriculture, most effective programs for the control of field bindweed combine cultivation and crop rotation with the use of herbicides. A review by Weaver and Riley [144] summarizes this information as follows: Cultivation at frequent intervals results in a gradual and continuous reduction in the concentration of total available carbohydrates and a decrease in root quantity. However, 1 to 5 years of repeated tillage may be required to exhaust the root reserves and effectively control populations of field bindweed. Competitive crops such as winter wheat or perennial forages are able to reduce field bindweed infestation after 3 to 5 years, particularly when combined with the application of herbicides.
In North Dakota, 2 fields were prepared for planting to native grasses by burning once and summer fallowing for 2 years. Summer fallowing effectively killed all aboveground vegetation. Within 2 months after drill seeding native grasses, perennial weeds, including field bindweed, were very dense. Fields were then sprayed with 2 applications of 2,4-D. Results of these treatments are not given [62].
Managers at Thousand Springs Preserve in Idaho had success controlling field bindweed in an agricultural site undergoing restoration, using a combination of tilling and planting competitive plants. In the 1st year the field was burned and planted with peas and oats. After the crop was harvested in the spring, the field was tilled and irrigated to encourage germination of weeds. Glyphosate was applied in October, although this had little effect because it was quickly followed by a killing frost. Native perennial bunchgrass seeds were no-till drilled in late fall, and seedlings emerged in February and March. The native grasses were irrigated and cheatgrass was suppressed using glyphosate. Annual weeds were controlled by mowing around the bunchgrasses. Mowing and irrigation continued for 1 year. After 5 years the perennial grasses were well established, the annual weeds continued to persist, and the perennial weeds (e.g. field bindweed) were minor components. Field bindweed grows most successfully only where there are irrigation leaks and generally does poorly if not irrigated. See the review by Lyons [86] for more details.
In a greenhouse study on the combined effects of the bindweed gall mite (Aceria malherbae) and herbicide (2,4-DB or glyphosate) on field bindweed height and biomass, mite feeding alone reduced field bindweed shoot biomass 37% to 48% and root biomass 46% to 50%. Herbicide alone reduced field bindweed root biomass 25% to 52%, and combining mite feeding with either 2,4-DB or glyphosate reduced root biomass more than mites or either herbicide alone. Combination of bindweed gall mite with sublethal doses of herbicide may allow for field bindweed suppression while reducing potential herbicide injury to desirable plants and maintaining mite populations. The herbicides did not appear to negatively affect the mites [21].
Physical/mechanical: Removing aboveground parts of field bindweed repeatedly to starve the roots is commonly suggested as a control method in agricultural settings (e.g. [11,13,17]). Common methods for removing top-growth include tillage, hoeing, cutting, or mowing. Tillage is usually not recommended for natural areas, as it may damage desirable vegetation and/or increase soil erosion. On rangelands or natural areas that were previously used for agriculture, tilling may be useful for ridding infestations. For small areas this may be done using hand-held tools, but for large areas machinery is often required [86].
The study and use of tillage or cultivation for control of field bindweed has a long history, particularly in the midwestern United States, as reviewed by Bell [13]. The biological basis of this research was that field bindweed could be killed if the roots were starved by cutting off the leaves on a regular routine. Food reserves in the surface roots (upper 12 inches (30 cm)) are rapidly depleted by cultivation, but in deep roots (6 to 8 feet (1.8-2.4 m) deep), reserves are exhausted only after long continued cultivation at the emergence of new sprouts. Only a small quantity of reserves is necessary to regenerate new growth [10].
Recommendations of intensive, repeated cultivation for control of field bindweed are common. One recommendation was to cut off field bindweed plants about 3 inches (8 cm) below soil surface "for the whole season" (15-27 cultivations, every 8-10 days, through the spring, summer, and early fall (until frost), and another dozen cultivations the next year). Cultivations should extend 16.5 feet (5 m) from the population boundary because of invasive roots. Another recommendation was to cultivate 8 days after the weed re-emerges, based upon careful studies of the rhizome system that showed that the emerging shoots relied upon food stored in the root system for 8 days before photosynthesis started to replenish the root. For a cultivation tool, a duckfoot sweep was the desired implement [13].
Shallow hoeing and deeper cultivations were equally effective when made every time the 1st shoots of field bindweed emerged. Hoeing at regular 14-day intervals was just as effective as hoeing every 7 or 10 days. All 3 techniques eradicated field bindweed in 2 seasons (Sherwood and Fuelkeman 1948, and Timmons and Bruns 1951, as cited by [6]). The percentage of total sugars, carbohydrates, polysaccharides, starch, and readily available carbohydrates in field bindweed roots cultivated at 3-week intervals was markedly lower than that found in the roots of undisturbed plants. Additional decreases were observed in the roots in the top 12 inches (30 cm) of plants cultivated bi-weekly and weekly [12]. The relative depletion of food reserves, supplied by underground parts of the plant, by cultivation every 7th day as compared with cultivation every 14th day, was calculated. From this it appears that cultivation every 14 days would destroy a 5th more of the readily available carbohydrates and more than double the loss of protein nitrogen in the 2 parts as compared with 2 cultivations at intervals of 7 days in the same unit of time [46]. Caution must be used with cultivation, because much of the root system is concentrated near the surface of the soil [34,133,144], and mechanical tillage may cut and disseminate root fragments [78].
At the Bosque del Apache National Wildlife Refuge on the Rio Grande in New Mexico, 3 techniques were employed in an effort to increase native chufa (Cyperus esculentus) tuber production: 1) mowing early in the growing season; 2) shallow disking 30 days after wetland drawdown; and 3) periodic sustained flooding during the growing season. There was no control in this study. Field bindweed mass (g/m2) appeared unaffected by mowing, and appears to have decreased slightly but not significantly (p<0.10) after disking or flooding treatments [131].
Even under cultivation, field bindweed seedlings may continue to emerge for many seasons. After 6 weeks, a new seedling has a root system large enough to regenerate stems if it is cut [13]. Studies by Swan [129] indicate that field bindweed seedlings can be killed by tillage or cutting at a depth of 4 inches (10 cm) if done within 3 weeks of emergence.
Mulches are effective for controlling field bindweed if no light reaches the soil surface. Black plastic is recommended. Complete death of field bindweed plants under mulch takes about 3 to 5 years [13]. Similarly, 6 to 9 weeks of solarization in California field plots reduced the number of field bindweed seedlings, and regrowth from established field bindweed plants was suppressed for 6 weeks after treatment [41].
Fire: See Fire Management Considerations.
Biological: Several natural enemies of field bindweed have been identified in its home range and several tested for host-specificity. Unfortunately, nearly all of the biocontrol agents tested so far also eat native morning-glories in California, some of which are rare or not abundant [13]. According to Rees and Rosenthal [108], 2 biological control agents have been released in the U.S.:
Agent Locations released or established References bindweed gall mite MT, TX, AB [90,108] bindweed moth (Tyta luctuosa) released in AZ, IA, MO, OK, and TX; not recovered (i.e. not established) [108]
Larvae and adults of the Argus tortoise beetle (Chelymorpha casidea) feed on the leaves of members of the morning-glory family. The Argus tortoise beetle is native to the U.S. and also occurs in Canada. In New York, it has been observed to defoliate infestations of field bindweed and false bindweed (Calystegia sepium) completely, while leaving the associated rye and corn crops untouched. It was being investigated as a potential biological control agent in 1979 (Selleck 1979, as cited by [144]); the outcome of these investigations is unknown.
Grazing: In Minnesota, domestic sheep grazing on field bindweed infested land sown to several crops (wheat, rye, and Sudan grass) consistently eliminated bindweed in 2 seasons, while grazing of perennial pasture mixtures consisting of alfalfa and brome grass or reed canary grass did not eliminate bindweed in any of 3 experiments. Grazing of pure bindweed reduced the stand somewhat, but was much less effective than was the grazing of infested land on which crops were being grown [122]. According to a review by Bell [13], cattle do not eat field bindweed, sheep will eat it but do not prefer it, and pigs are the field bindweed gourmands. Pigs will eat the whole plant, given a chance. Pigs are said to nearly eradicate the root system of bindweed if the field is plowed before they are let into the field. However, their snouts must be free of nose rings or slits.
Chemical: Herbicides commonly recommended for the control of field bindweed include 2,4-D (alone and in combination), glyphosate, dicamba, picloram, quinclorac, and paraquat. See the Weed control methods handbook or the field bindweed Element Stewardship Abstract for more information on specific chemicals, their efficacy, and recommendations for use in controlling field bindweed.
In general, herbicides should be applied when they will be most effectively absorbed and translocated to field bindweed roots, but before plants produce seed and new buds. The optimum time for the application of foliar-applied herbicides is the bud to full-bloom stage which coincides with the maximum translocation of assimilates downward and root metabolic activity. However, the application of herbicides in late summer, if the vines are actively growing, may also be effective [86,144].
Moisture availability may impact the effectiveness of chemicals applied for field bindweed control. A laboratory test indicated that field bindweed is more resistant to glyphosate action when plants are drought stressed [33]. Similarly, a review by Meyer [93] indicates that field bindweed growing in semiarid conditions (rainfall of 11 to 20 inches (280-500 mm)) may be more resistant to weed control efforts (herbicides and cultural control) than field bindweed growing in more humid conditions (rainfall >25 inches (640 mm)). This is especially apparent for foliar-applied herbicides, possibly due to lower leaf area, thicker cuticle with higher wax content, slower biological processes, and smaller leaf:root ratios under semiarid conditions. But it may also be due, in part, to different cropping and cultural practices employed in the different areas.
According to a review by Lyons [86], repeated use of the same or similar herbicides can result in herbicide-resistant strains of field bindweed. Investigators have unsuccessfully tried to correlate the morphology of field bindweed strains with their herbicide resistance. When planning on using herbicides to control field bindweed, it is useful to know whether field bindweed strains in the area have demonstrated any herbicide resistance [86]. Evidence of resistance of field bindweed to 2,4-D isooctylester after 3 consecutive years of spraying is suggested by Zengin [157]. Field bindweed 1st demonstrated resistance to 2,4-D in Kansas in 1964, and apparently, research has shown that these particular biotypes may be resistant to other synthetic auxin herbicides. See the International Survey of Herbicide Resistant Weeds for more information.
Cultural: In agricultural systems, smother crops are often used to control invasive species such as field bindweed. Competition for light reduces field bindweed vigor [9,13]. According to a review by Lyons [86], light reaching field bindweed plants must be reduced to about 50% shade or more for 3 years to control field bindweed growth.
In agricultural systems suggested smother crops include millet, sorghum, Sudan grass, or alfalfa [66,86]. Winter wheat is often a good competitor with field bindweed because it grows rapidly during the early spring when bindweed is not using soil moisture (Wiese and Rea 1959, as cited by [144]). Summer-planted crops that grow vigorously and provide early shade offer competition to field bindweed at a time when it is normally making its best growth [66].
It may be difficult to find native species that can compete effectively with field bindweed. The outcome of competition between species can be complicated and unpredictable. Managers at Phantom Canyon Preserve were unable to establish native species to compete with field bindweed, while those at Thousand Springs Preserve successfully established perennial grasses [86].
A review by Lyons [86] suggests that, in general, species that grow vigorously during the winter and early spring may offer the best competition to field bindweed, because they force field bindweed plants to compete for light later in the season. Competitive crops may be most effective in humid/shady areas where solar radiation is diminished and shading has larger consequences (Wilson and others 1955, as cited by [86]). Therefore competitive planting or restoration efforts in low light riparian habitats, where the available light is reduced by tree canopies, may work to control field bindweed [86].
