Medics (McLeod, 1982).

Medicago spp. (Finch & Sharp, 1983).

The genus Medicago includes M. truncatula (barrel medic), M. littoralis (strand medic) M. rugosa (Gama medic), M. tornata(disc medic), M. polymorpha (burr medic), and M. scutellata (snail medic) (Weitkamp and Graves, 1988).

The most common types of medic encountered are bur (Medicago polymorpha), barrel (M. truncatula), strand (M. littoralis), and snail (M. scutellata) (Miller et al., 1989).

Medics produce high percentages of hard seeds, which remain dormant for one or more years before germinating (Weitkamp and Graves, 1988).

Taylor and Ewing (1996) found that buried hard seed of medics was slower to soften in the upper 2 cm of the soil than were seed of 3 cultivars of subclover. Subclover seed remained hard if buried 6-10 cm deep, for 12 years. Softening of subclover seed initially requires high temperature, followed by alternating high and low temperatures.

Per the account by Quinlivan et al. (1986), the medics can differ from the clovers (Trifolium species) in having yellow flowers and trifoliate leaves in which the central leaflet has a longer stalk than the two lateral leaflets. Hop and suckling clovers have yellow flowers, and leaves like medics, but most clovers have white, pink or purple flowers and the leaflets have stalks of equal length. The fruits of medics are distinct from those of all clovers. In medics, the flower petals drop off and a spirally coiled pod forms, whereas in the clovers the dry petals often remain on the fruit, the pod is straight or globular and frequently very short and enclosed in the calyx. Medic cotyledons have a blade which gradually narrows into the stalk; in clovers, the blade of the cotyledon has an abrupt articulation or hinge with its stalk. All Medicago spp. have a distinctive tripping mechanism of the flower. In the freshly opened flower, the ovary and anthers are flung out of the keel and over onto the standard petal. This must occur to allow fertilization and subsequent fruit development.

Medic cotyledons have a blade that gradually narrows into the stalk and are described as appearing like a teardrop.

Medics grow best in cool, fall temperatures (Hofstetter, 1988).

Medics are cool season annuals, but research and experiment in the past 10 years have shown them to grow exceedingly fast in spring-summer plantings in the upper midwest. With long days and warm temperatures, they have grown very vigorously and been used as smother crops in Midwest corn. In California-Oregon, at Klamath experiment station, the medics out-produced all other small seeded legumes in a 90 day period, May-Aug. (Dovel et al., 1991)

Medics will persist over a wide range of rainfall and soil conditions and are considered best for planting where rainfall is less than 15 inches annually and the growing season short; most Trifolium spp. (true clovers) will not survive such conditions (Murphy et al., 1976). Short season Trifolium spp., i.e., 'Dalkeith', 'Nungarin' subclover, and 'Hykon rose clover, will easily survive and establish on less than 10 inches of annual rainfall.

Medics are for the most part restricted to Mediterranean climates with winter rain and long, hot, dry, summers. Unlike some clovers, most medics do not tolerate waterlogged soils, perhaps in part explaining their greater abundance in the drier, more inland regions. In areas of high rainfall, vigorous stands are found only on well-drained sites. Hard seeds enable medics to survive dry seasons (Quinlivan et al., 1986).

The irrigation requirement for medics is 12", less any rainfall (Munoz & Graves, 1988). Medics resemble the annual clovers in that they are adapted to a Mediterranean climate with 250 to 500 mm of predominantly winter rainfall (Quinlivan et al., 1986). However, medics do not tolerate waterlogging and, in areas with high rainfall, vigorous stands are found only where drainage is good (Quinlivan et al., 1986).

When seeding medics with a drill, 100-150 lbs/acre of 0-25-0 fertilizer should be placed with or near the seed, acccording to Weitkamp and Graves (1988).

The formulation 0-25-0 has been unavailable for many years. An alternate blend of 0-36-0-19 is often available, but many people seeding legumes end up with formulas of fertilizer that have some nitrogen in order to get the phosphorous and sulfur they need, even using 16-20-0.

Annual medics, Medicago spp., are best suited for alkaline soils, with the exceptions of M. polymorpha and M. murex, which tolerate acid soils (Reed et al., 1989). Medics grow best on neutral to alkaline soil (Miller, 1988), and some workers have stated that only basic soils will do (Munoz & Graves, 1988). Hofstetter (1988) gave the suitable pH range as 6.5 to 7.0. However, Miller et al. (1989) said that the genus performs best with pH above 7 but will adapt to neutral soil types.

The pH minimum range of the genus from observation of trials in California seems closest to the following for long term sustained reseeding:

M. Polymorpha: 5.5-8.0

M. truncatula: 7.0

M. scutellata: 7.5-8.5

M. rugosa: 7.5-8.5

The symbiotic rhizobia of medics tolerate acid soils less well than do those of clovers. This may be a factor limiting medics to soils with an alkaline-neutral in the profile. Sometimes these soil types are slightly acid in the top few cm., but at lower levels in the main medic root zone they may be neutral and become increasingly alkaline with depth. The acid intolerance of medics may also result from mineral deficiencies or toxicities. Medics have an unusually high Ca requirement compared to most other legumes, and this nutrient is often unavailable in acid soils. Medics are less tolerant than other legumes (including suclover) of high Al concentrations (Quinlivan et al., 1986).

According to Howieson and Ewing (1989), annual species of Medicago differ greatly in their ability to nodulate on acid soils. Failure to nodulate in the second year following sowing is the most important barrier to the wider use of reseeding medics on acid soils. Medicago polymorpha L. and M. murex Willd. have proven more successful in nodulating on nutrient-poor, acid soils than have M. truncatula Gaertn., M. littoralis Rohde, and M. tornata (L.) Mill., which are more widely commercialized. At low densities of rhizobial inoculum in acid soil (pH 4.9), evaluation of percentages of nodulated plants yielded the following gradient:

M. murex > M. soleirolii > M. polymorpha > M. aculeata > M. littoralis/truncatula > M. tornata > M. praecox > M. rugosa > M. arabica > M. shepardii > M. orbicularis > M. minima > M. rotata

Not all of these differences were statistically significant. Medicago murex was significantly better than all other groups (Howieson and Ewing, 1989).

Medicago murex, M. polymorpha, and M. soleirolii are particularly good at nodulating on acid soils, when acid-tolerant rhizobia are used (Rhizobia meliloti strain WSM419). M. tornata, M. truncatula, and M. littoralis did not perform so well (Howieson and Ewing, 1989).

The new acid-tolerant rhizobial strains may render previously inhospitable low-pH sites suitable to medics (Graves, pers. comm.).

Medics do well on sandy to clayey soils, according to Munoz & Graves (1988). Annual medics, Medicago spp., are best suited for alkaline soils, with the exceptions of M. polymorpha and M. murex, which tolerate acid soils (Reed et al., 1989).

Medics appear less tolerant of shade in citrus than are vetches (John France, pers. comm.)

Medics show a tolerance to low doses of 2-4,D-amine and a resistance to 2-4,DB. They also will show tolerance to light doses of glyphosate. (Fred Thomas, pers. comm.)

Annual (Munoz & Graves, 1988).

Medics behave as winter annuals (Miller, 1988) but have also been termed winter-spring annual (Munoz & Graves, 1988). Germination occurs with autumn rains, and the stand develops during winter and early spring (Quinlivan et al.,1986).

For various medics, up to 95% of fully-opened flowers abort, failing to produce mature pods. By contrast, for subterranean clover, the range is from 23-63%. Abortion may be a means of ensuring that the seed that form are sufficiently large to produce viable seedlings (Cocks, 1990).

Seeding rates vary by medic species. For cover crops, M. polymorpha and M. truncatula should be seeded at 15 or more lb./acre. For M. rugosa and M. scutellata the seeding rate should be 20-25 lb./acre.

Suggested seeding rates include 10 lb/acre (Miller, 1988; Hofstetter, 1988) and 15-30 lb/acre (Munoz & Graves, 1988).

To reduce economic risk, 2-6 lbs/acre of a mixture of medic varieties has also been recommended. If clovers and/or grasses are included, the rate may total 6 to 12 lbs/acre (Weitkamp and Graves, 1988).

Seed are small, so shallow seeding is important: 1/4 inch depth (Weitkamp and Graves, 1988).

Seed should be sown using a range or grain drill in stubble or established rangeland, or with a broadcast seeder or drill on prepared seedbeds (Weitkamp and Graves, 1988).

Autumn seeding is generally recommended (Miller, 1988; Munoz & Graves, 1988), generally before the first rains (Miller et al., 1989). Weitkamp and Graves (1988) suggested October.

For cool-season annual medics, inoculation type is Medic Special (Nitragin Co. inoculant types) (Munoz & Graves, 1988); this is also known as Special Culture No. 1 for Medicago (Duke, 1981). Medics usually nodulate and fix nitrogen when inoculated with the standard Australian commercial medic inoculant (rhizobial strains SU47 and U45) (Quinlivan et al.,1986).

Acid-tolerant rhizobial strains may enable cool-season medics to grow on sites that were formerly inhospitable (W. Graves, pers. comm.). Medicago murex, M. polymorpha, and M. soleirolii are particularly good at nodulating on acid soils, when acid-tolerant rhizobia are used (Rhizobia meliloti strain WSM419). M. tornata, M. truncatula, and M. littoralis did not perform so well. At low densities of rhizobial inoculum in acid soil (pH 4.9), evaluation of percentages of nodulated plants yielded the following gradient:

M. murex > M. soleirolii > M. polymorpha > M. aculeata > M. littoralis/truncatula > M. tornata > M. praecox > M. rugosa > M. arabica > M. shepardii > M. orbicularis > M. minima > M. rotata

Not all of these differences were statistically significant. Medicago murex was significantly better than all other groups (Howieson and Ewing, 1989).

Proper inoculation just before seeding is important. The Pellinoc-Pelgel method of inoculation, which can be applied to the seed by the rancher, has given good results more consistently than pelleting methods applied by seed companies (Weitkamp and Graves, 1988).

The Pellinoc-Pelgel method with medic special No. 1 may be the best for nodulation, but it has to be ordered two months in advance from Nitragin Co. on a non-returnable basis. Over a 10 year period, 99% of all medic sowed in California was inoculated by Cel Pril using the Rhizokote process because it was convenient, available, and it works. Over that 10 year period, Dr. Walsh, microbiologist, worked to include improved medic strains into the Cel Pril coating process.

Medic seed is readily available in most parts of the U.S., especially California, to satisfy the needs of the dryland range pastures in high-pH soils. (Fred Thomas, pers. comm.)

The species and cultivars vary in length of time to flowering. Approximate dates when flowering begins were given by Quinlivan et al. for Merredin, Australia (Southern Hemisphere), with dates for the Northern Hemisphere projected by the editor (R.L. Bugg):

• Ghor barrel medic - 1st week of August (early March in Northern Hemisphere)
• Cyprus barrel medic - 2nd to 3rd week of August (mid- to late- March in Northern Hemisphere)
• Harbinger strand medic - 3rd week of August (late March in Northern Hemisphere)
• Goldfields medic - 3rd week of August (late March in Northern Hemisphere)
• Burr medic - 3rd week of August (late March in Northern Hemisphere)
• Dwalganup subterranean clover - 3rd week of August (late March in Northern Hemisphere)
• Hannaford barrel medic - 1st week of Sept. (Early April in Northern Hemisphere)
• Cyfield barrel medic - 1st week of Sept. (early April in Northern Hemisphere)
• Tornafield disc medic - 1st week of Sept. (early April in Northern Hemisphere)
• Murrayland disc medic - 1st to 2nd week of Sept. (early to mid April in Northern Hemisphere)
• Jemalong barrel medic - 2nd week of Sept. (mid-April in Northern Hemisphere)

'Harbinger' strand medic matures about the same time as 'Cyprus' barrel medic (Quinlivan et al., 1986).

Medics are good at self-seeding (Munoz & Graves, 1988; Miller, 1988).

All medics produce hard seed. Most seed become hard and remain so through to the following autumn or beyond. Where medic pastures are used in rotation with field crops, hard seededness is an asset. The disadvantage is that second year pasture can be thin, because most seed does not germinate. By the third and fourth years, medic stands tend to improve, if competition from other species is not excessive (Quinlivan et al., 1986).

Annual medics, Medicago rugosa cv 'Paragosa', M scutellata cv 'Robinson', and M. truncatula cvs 'Cyprus' and 'Jemalong' were evaluated in 3 rotational systems. Medicago spp. re-established better under permanent pasture than under any rotational scheme involving tillage. Seed preservation, however, was better in rotations involving tillage. Medicago rugosa cv 'Paragosa' in rotation trials produced a higher seed yield in the year of sowing than did M. scutellata cv 'Robinson', or M. truncatula cvv 'Cyprus' and 'Jemalong'. However, its seed bank persisted only 3 years, and its re-establishment was poor, perhaps due to its higher proportion of permeable seed. Medicago truncatula cv 'Jemalong' maintained higher seed reserves after six years of cropping than M. scutellata cv 'Cyprus' or M. scutellata cv 'Robinson'. Seed banks of all species were exhausted after 7 years (Crawford and Nankivell, 1989).

For various medics, up to 95% of fully-opened flowers abort, failing to produce mature pods. By contrast, for subterranean clover, the range is from 23-63%. Abortion may be a means of ensuring that seed are sufficiently large to produce viable seedlings (Cocks, 1990).

Most medics have a high hard seed content of 30-45% the first year. Seed germination declines slowly and may still be 50% viable after 10 years. (Fred Thomas, pers. comm.)

Growth habits of cool-season annual medics are variable; as given by Duke (1981): Medicago arabica (southern or spotted burclover): branched at crown, spreading or decumbent; Medicago lupulina (black medic or yellow trefoil): prostrate or ascending; Medicago orbicularis (buttonclover or large disc-medic): procumbent, decumbent, or ascending. Medicago polymorpha (California or toothed burclover): semierect or prostrate; Medicago scutellata (snail medic): stems long, slender, and weak.

While generally viny and prostrate as a class, the 'Sava' snail medic when grown with barley can be as tall as the barley heads, or 30-36 inches. (Fred Thomas, pers. comm.)

Because it is prostrate or decumbent burr clover, M. Polymorpha in a solid stand only grows 6-10 inches tall, but in the best of conditions during a burr medic year I have observed runners of burr clover 4 feet long growing from a planted vineyard alley, under the vines, and trailing down the terrace as a solid mat. (Fred Thomas, pers. comm.)

Medics are typically deeper rooted and more drought tolerant than are subclovers (Quinlivan et al., 1986).

Annual medic roots were shown in slant tube growth experiments to grow twice as fast as subclover roots. (Matches et al., 1987).

The seed should be planted one-half-inch deep. Seedlings will respond to phosphate and sulfur fertilizer as a starter. (Fred Thomas, pers. comm.)

After a medic stand has produced seed for one year or more, the reserve of hard seed enables the stand to tolerate grazing pressure during flowering or seed maturation and still regenerate the following year (Weitkamp and Graves, 1988).

In the Palouse region of Washington state, Goldstein and Young (1987) compared conventional winter wheat - spring barley - winter wheat - spring peas rotation to low-input rotation of peas+black medic - medic - wheat rotation. The latter is termed a "perpetuating-alternative-legume-system" (PALS) because the medic will reseed and reestablish. Based on results from field trials, PALS generated higher net returns when market prices were used, but the converse was true when government target prices were employed.

Crawford and Nankivell (1989) used 3 rotational systems under which they evaluated annual medics: Medicago rugosa cv 'Paragosa', M scutellata cv 'Robinson', and M. truncatula cvs 'Cyprus' and 'Jemalong'. Medicago spp. re-established better under permanent pasture than under any rotational scheme involving tillage. Seed preservation, however, was better in rotations involving tillage. Medicago rugosa cv 'Paragosa' in rotation trials produced a higher seed yield in the year of sowing than did M. scutellata cv 'Robinson', or M. truncatula cvv 'Cyprus' and 'Jemalong'. However, its seed bank persisted only 3 years, and its re-establishment was poor, perhaps due to its higher proportion of permeable seed. Medicago truncatula cv 'Jemalong' maintained higher seed reserves after six years of cropping than M. scutellata cv 'Cyprus' or M. scutellata cv 'Robinson'. Seed banks of all species were exhausted after 7 years.

Medicago rugosa, similar to M. scutellata, has very large seeds. There are half as many seeds per pound as in M. truncatula. M. rugosa seedlings are vigorous and upright, allowing them to be easily grazed out early by large and small herbivores. They are also much more demanding of a truly alkaline soil, 7.5 to 9.0 than M. truncatula or M. polymorpha. To maintain a persistant stand of M. rugosa and M. scutellata, they must be planted on alkaline soil, protected from early grazing and lightly incorporated in late summer by disking or harrowing to get the large seed down into the soil every other year.

Medics tolerate mowing or grazing well (Munoz & Graves, 1988) and should be mowed frequently to height of 3-5 inches during their growing season to improve competitiveness against weeds and seed set (Miller et al., 1989).

Medics should be grazed from February to the beginning of flowering, then rested through seed maturation. Thereafter, grazing can resume through the summer and up to the time of cereal planting (in ley rotation system). Grazing stimulates flowering and seed production (Miller et al., 1989).

Medics can be mowed close early but after they reach a height of 6-8 inches the mowing should be raised to 3-4 inches to keep from shocking the plant and cutting off the new growth points. When medics are 12 inches tall, the cutting height should be 6 inches or they will have trouble regrowing. This contrasts with subclover which has a prostrate habit; so in a cover crop mixture, close mowing favors subclover while moderate mowing favors medics.

Grazing reduces competition from grasses and other plants. Stock moderately to heavily during the winter and early spring growth periods, then rest to allow flowering and seed maturation (Weitkamp and Graves, 1988).

For Californian vineyards, French plowing would leave a narrow strip of cover crops in each alley and would permit use of early-maturing species like burr medic. Dates for plowing down cover crops depend on the maturation dates; for medics, the date should be in mid-May (Christensen, 1971).

Medics are harvested the same as subclover. The overburden of plant material is removed, then the seed pods are vacuum harvested and threshed in the field (Fred Thomas, pers. comm.).

The standard machine for medic harvesting is a Horwood-Bagshaw vacuum harvester. Recently, Revellseeds of Dimboola, Australia, developed a custom vacuum harvester that is substantially faster. In California burr medic, M. Polymorpha, is occasionally harvested as a containment in wheat, barley and even peas. The pods can be separated and resold. Every 2 or 3 years some of the product will come into the market place or the grower reapplies the by-product to his rangeland.

Any equipment that puts seed at the proper depth (one-fourth to one-half inch) will work (broadcast, drill, etc.) (Fred Thomas, pers. comm.)

Medics can be used as green manure (Hofstetter, 1988), orchard cover crops (Miller, 1988), forage (Munoz & Graves, 1988), hay, or compost (Munoz & Graves, 1988).

As observed by Glatzle (1989), ley-farming (cereal grain production alternating with pasture) with annual, self-regenerating legumes is increasingly used in areas with Mediterranean climate. In particular, practices in southern and southwestern Australia involve the use of self-regenerating stands of annual medics (Medicago polymorpha, M. truncatula, M. littoralis, M tornata, M scutellata, and M. rugosa) and subterranean clovers (Trifolium subterraneum L., ssp. subterraneum, brachycalycinum, and yanninicum). Advantages include production of high-quality forage, need to sow pasture but once, increased yield of cereal in response to nitrogen added by pasture legumes, soil protection and improvement, and stabilization of farmers' incomes.

Medics are well suited for close rotations such as annual legume (livestock) - cereal rotation (ley farming system) (Miller et al., 1989), as is practiced in Australia and Northern Africa (Weitkamp and Graves, 1988).

Seed pods make excellent high-protein dry feed (Weitkamp and Graves, 1988).

Miller et al. (1989) suggested seeding mixtures of medic varieties, in lieu of area-specific information on varietal adaptation. Medics can be seeded alone or with subterranean and rose clovers, depending on soil and climate (Weitkamp and Graves, 1988).

Christensen (1971) suggested using winter cover crops in Californian vineyards, with the aim of producing a sod-like condition. Cover crops would be low growing, require little or no mowing, and be self re-seeding. Their functions would be to reduce tillage and dust, provide habitat for predators that attack spider mites, improve water penetration, and provide nitrogen. Annual grasses suggested include barley, 'Blando' brome, or rye. Subterranean clovers recommended include cv 'Geraldton', Dwalganup', 'Howard', and 'Mt. Barker'. Rose clovers included cv 'Kondinin' and 'Hykon'. Medics suggested were California bur clover (Burr Medic), 'Cyprus' barrel medic, and ''Harbinger' barrel medic. Mixtures of subterranean clovers were suggested so that better-adapted varieties will reseed.

Subterranean clovers recommended include 'Dalkeith', 'Junee', 'Trikkala', 'Koala', 'Clare', 'Karridale'. Other new varieties include Rosedale, Gosse, Denmark, and Losa.

Estimated biomass production by barrel medic was 7.8 +/- 0.8 Mg/ha and by burr medic, 8.3 +/- 1.8 Mg/ha (mean +/- S.E.M.), based on a study in an organic wine vineyard in Hopland, Mendocino County, California (Bugg et al., 1996).

M. polymorpha (burr medic) yields 5,000-7,500 kg/ha of hay (Duke, 1981).

Munoz and Graves (1988) estimated that, as an orchard or vineyard cover crop, medics could contain 50-100 lb N/a, and 50-200 lb/a as living mulch for vegetable or field crops.

Bohlen et al. (1997) in Ohio conducted a replicated factorial field study entailing these main plot factors: 1) granular NH4NO3 fertilization; 2) cow manure and straw; and 3) winter cover crops of cereal rye and hairy vetch supplemented by alfalfa hay. The split-plot treatment entailed the following levels: a) augmented earthworm densities; b) reduced earthworm densities; and c) incumbent earthworm densities (unmanipulated). Enclosures of polyvinyl chloride were used and intended to limit earthworm dispersal among the different split plots. Electroshock and removal were used to reduce earthworm densities; field-collected specimens were added to increase densities. Earthworm densities were manipulated in the spring and fall for three successive years. Corn was the warm-season crop. The main plot (nutrient) treatment did not significantly affect earthworm biomass or density. Large nightcrawler (Lumbricus terrestris ) was the earthworm type most markedly affected by the split-plot (population) treatment, and for the augmented split-plots, earthworm biomass was increased by a factor of 1.5 from the value observed in unmodified populations. The latter value, in turn was 3 times that observed in the split-plots with decreased earthworm densities. Mean densities of L. terrestris middens were 20.5, 48.8, and 67.5 per m2 for decreased, unmodified and increased populations. Surface litter in middens had a lower C/N ratio and greater microbial activity than litter found outside middens.

McCartney et al. (1997) reported on additional measurements made on the experiment described above, indicating that total soil organic matter was greatest in with reduced earthworm populations, as was organic matter in the diameter categories 0.25-2m and <0.053 mm.

Habben and Blevins (1989) showed in laboratory studies using double-tube apparatus that transfer of rubidium-86 (potassium) occurred from deeply-rooted alfalfa (Medicago sativa L.) to associated, shallow rooted maize (Zea mays L.) or grain sorghum (Sorghum vulgare Pers.). This may explain previous observations of higher concentrations of potassium and other cationic nutrients for grasses grown in association with legumes than for grasses grown alone. Legumes are typically deeper rooted than the associated grasses and may access deeper sources of nutrients. Possible mechanisms for the transfer are root-to-root contact, transfer via the soil solution, or transfer by mycorrhizal connections. None of these processes were actually demonstrated in this study.

The oestrogenic potency of medics is low. However, the leaves and pods of several cultivars of barrel medic (i.e., 'Cyprus,' 'Jemalong,' and 'Hannaford') sometimes contain substantial amounts of coumestan (especially 4 methoxy coumestrol). The possibility of adverse effects on ewe performance especially on dry pastures needs to be kept in mind. Other cultivars and species (e.g. Tornafield and Paragosa medic) have low coumestan contents (Quinlivan et al.,1986).

Medic species, especially M. polymorpha, cause bloat in cattle when grazed on solid stands. The effect is the same as turning the cattle into straight alfalfa.

Newer medic cultivars show improved resistance to the Egyptian alfalfa weevil. Tolerances are as follows (Weitkamp and Graves, 1988):

Barrel Medic:

• Good tolerance - Sephi
• Fair tolerance - Jemalong, Ghor, Ascot, Paraggio
• Poor tolerance - Hannaford, Cyprus, Cyfield, Borung, Akbar

Strand Medic:

• Poor tolerance - Harbinger

Gama Medics (M. rugosa):

• Fair tolerance - Paragosa, Paraponto, Sapo

Disc Medic (M. tornata):

• Fair tolerance - Murrayland
• Poor tolerance - Tournafield, Swani

Burr Medic (M. polymorpha):

• Fair tolerance - Serena, Circle Valley

Snail Medic (M. scutellata):

• Fair tolerance - Sava
• Poor tolerance - Robinson, Sair

In an unreplicated observation, Lygus lineolaris (Palisot de Beauvois) (tarnished plant bug) attained extremely-high densities on Medicago polymorpha ssp. subspina cv 'Circle Valley', placing it well above the 95% confidence interval for densities observed on 11 varieties of subterranean clover (Bugg et al., 1990). Subsequent observations in northern California suggest that Lygus is abundant on burr and barrel medics in California as well (Bugg, pers. comm.).

In Australia, medic pastures can sustain severe damage by red legged earth mite (Halotydeus destructor) and lucerne flea (Sminthuris viridus), especially early in the season. In south Australia, sitona weevil (Sitona humeralis) is abundant and damaging. Adults feed on foliage, whereas larvae attack nodules of all species. This weevil does not occur in Western Australia (Quinlivan et al.,1986).

Medics have been very effective as smother crops with considerable experimentation as understory plantings in Midwest corn.

Cattle and sheep readily eat medics.

Rabbits can damage thin stands of medics on rangeland.