Perennial Ryegrass

New Zealand Journal of Agriculture, Volume 94, Issue 3, 15 March 1957, Page 273

Perennial Ryegrass

Seed Production in New Zealand

By

E. G. SMITH,

Instructor in Agriculture, Department of Agriculture, Rangiora

ONE of the most useful and popular grasses for New Zealand soils of high fertility, perennial ryegrass [Lolium perenne ) may be sown profitably on a wide range of country provided clovers form a good proportion of the sward. Where vigorous clovers can be grown, so can. perennial ryegrass. Factors contributing to its value are its excellent seed production, its ease and speed of establishment from seed, its high production of good milk-producing and fattening feed (particularly- in spring, when feed is at a premium), its ability to withstand hard grazing, and its permanence under suitable conditions.

PERENNIAL ryegrass is a mediumsized grass with a hairless blade the lower surface of which is shiny. The ligule is short and square cut and. the base of the plant is red. Perennial ryegrass can be distinguished, from Italian ryegrass by its oval sheath in comparison with the round sheath of Italian ryegrass. The strong awning of Italian ryegrass and the absence of awning in perennial ryegrass are obvious differences at the flowering and seeding stages. Place in New Zealand Farming Perennial ryegrass is the basic component of most New Zealand pastures in areas which are intended to remain in grass for more than 3 or 4 years.

It is highly nutritious and supplies useful grazing on a wide range of soil types, its productivity being limited by excessive moisture or by low soil fertility and excessive dryness. Under suitable conditions this grass is quick to establish, tending to smother weed growth and supply early grazing. Perennial ryegrass provides early spring feed and once established thrives under hard grazing. Growth is encouraged by heavy stocking with resultant tramping and building up of soil fertility, this fact being demonstrated by the prolific perennial ryegrass growth round gateways and on camping grounds. However, unless conditions of soil and climate are good, midsummer production is relatively lbw.

A well-drained soil of medium fertility is most favourable for the growth of a perennial ryegrass seed crop. Very high fertility may result in lodged crops, and on the poorer soils plants are unthrifty and of low yield. Strains of Perennial Ryegrass During the farming history of New Zealand a number of widely differing strains of perennial ryegrass have been developed. The system of seed production practised for many years in, districts such as Hawke’s Bay and Poverty Bay, where seed was harvested from old pastures, was conducive to the development of the better strains. In Canterbury and Otago, where •Italian ryegrass was sometimes sown with perennial ryegrass, cross-pollina-tion between the species occurred, and in the absence of any factors which eliminated the poorer types general deterioration took place. Most ,of the seed was harvested from 1-year-old pastures, and the seed crop was therefore taken before the poor strains had died out. That accounts for the old belief, not borne out by fact, that good seed cannot be harvested from young pasture.

Provided no volunteer growth has occurred, there is no reason why seed from a first-year stand of Certified perennial ryegrass should not be of quality equal to that taken at a later harvest.

The certification of seed from naturally developed strains was only a stepping stone to something better. By selection and breeding carried out by the Grasslands Division of the Department of Scientific and Industrial Research at Palmerston North a highly improved strain has been evolved. The ability of this strain to persist and recover quickly after hard grazing, its palatability, and its high leaf production are among its . outstanding characteristics.

Seed Certification

The object of seed certification is the guarantee to the purchaser of trueness to type. The scheme is based on the identification and isolation of a truly perennial and leafy type. The methods used in its identification include field inspection of growing crops, plot testing, and laboratory testing of seed samples.

When inaugurated the certification scheme applied to strains of perennial ryegrass that had developed naturally in districts such as Hawke’s Bay and Poverty Bay. Many of the perennial ryegrass paddocks in those districts had been down for more than 40 years, with the result that the short-lived strains had died out. The scheme was then based on seed from these areas, but now the improved strains raised by the Grasslands Division form the basis. These stocks are grown on contract to the Department of Agricul-

ture by approved farmers, and from these contract areas Certified Government Stock seed is harvested. This seed is distributed to farmers through merchants each year. Areas sown with Government Stock seed are used primarily for seed production, and from these areas comes Certified Pedigree seed, which in turn is eligible to produce Certified Mother seed. All paddocks sown with Certified Government Stock or Pedigree seed which are entered for certification are inspected during the growing season by officers of the Department of Agriculture to determine whether any contamination of the strain has taken place. All sacks containing the produce of areas passing this inspection are branded and sealed before they leave the paddock for machine dressing of the seed. Machine dressing is supervised, and an official sample of the line is forwarded to the Department of Agriculture’s Seed-testing Station at Palmerston North for purity and germination tests. Areas sown with Mother seed, Permanent Pasture seed, or uncertified seed are not inspected, but the produce may be entered for certification under

a laboratory test. After being machine dressed the seed is held under temporary seal while an official sample is

forwarded to the Seed-testing Station for examination under an ultra-violet light. Under this the germinated seed of poor strains of perennial ryegrass shows a fluorescence which is not evident in good strains. If as a result of this test the seed proves to be of the requisite standard, the sacks are tagged and sealed as Certified Permanent Pasture seed. If it does not reach this standard, the temporary seal is removed.

All lines of Certified perennial ryegrass seed must attain a minimum purity of 97 per cent, before being finally sealed and tagged. A purity and germination certificate covering each line is issued by the Seed-testing Station.

The annual production of Certified perennial ryegrass seed of all classes has amounted in recent years to about half a million bushels. In the 1946-47 season, however, one and a quarter million bushels were produced and in the 1950-51 season one and a half million bushels. The Canterbury Land District accounts for about two-thirds of the total annual production and Hawke’s Bay about a fifth.

Palatability

The importance of sowing grass in association with suitable clovers cannot be over-emphasised. Nitrogen supplied to the soil by vigorous clover plants ensures the growth of succulent perennial ryegrass, which, if well controlled, is relished by stock. For some years Certified perennial ryegrass found little favour in the South Island; farmers claimed that it was extremely unpalatable to stock, and this was attributed to the strain of plant. However, experience has shown that the inclusion in the mixture of a good strain of . white clover,, coupled with judicious stocking and topdressing, will solve the problem of unpalatability.

In the early days of seed certification the sowing of pure stands of perennial ryegrass for seed production was common. This practice is still sometimes adopted on North Island properties, but in the South Island some clover is now always sown. The rapid increase in the use of lime throughout Canterbury has made possible vigorous growth of good strains of white clover where previously acid soil and low fertility limited its growth. Good strains of well-managed perennial ryegrass are not unpalatable to stock. >

Seed Production

About 50,000 acres of perennial ryegrass are harvested for seed each year, the greater portion of this acreage being in the Canterbury Land District.

Seed Mixtures

Though seed production maybe intended, the primary aim in sowing most pastures should be grazing, and

for that reason the method of establishing perennial ryegrass for seed production follows very closely that for ordinary grazing pastures. The rate of seeding and the components of the seed mixtures vary with the requirements of the area. Seedings as low as 101 b. of perennial ryegrass and lib. to 31b. of white clover per acre have given, excellent results on wellprepared land; on the other hand, seeding rates of more than 2 bushels (401 b. per acre with clovers may be warranted, particularly to control weed growth. In . general, 201 b. to

301 b. of perennial ryegrass with 21b. to 31b. of white clover is advocated, the heavier seeding on the better land, Crested dogstail, red clover, or subterranean clover may be included in the mixture if desired.

Where the area is intended for seed production Italian or shortrotation ryegrass must not be included. It is also desirable that dififerent grades of Certified seed should not be sown in one paddock.

In Hawke’s Bay perennial ryegrass is frequently sown pure for seed production, as it has been found that in that district the better types of white clover smother ryegrass plants. In Canterbury the general practice is to sow 201 b. to 251 b. of perennial ryegrass with 21b. to 31b. of white clover and to harvest perennial ryegrass seed in the first season and white clover seed in the second. Establishment Methods of establishing perennial ryegrass vary. In Hawke’s Bay excellent results are obtained by sowing 2 bushels per acre following a crop of either peas or potatoes. The land is ploughed directly after the crop, and then well worked and rolled before the seed is broadcast in late March or

during April. Harrowing and a final rolling complete operations. In Otago and Southland the seed is seldom sown in autumn, the most popular method of establishment being spring and summer sowing with either turnips or rape. . In Canterbury sowing in spring under wheat with rape or turnips or with a spring-sown cereal all have the merit of reducing costs. A common practice is to plough after a cereal crop has been harvested and sow the pasture mixture in late autumn. Though any of these methods of establishment may produce a satisfactory pasture, such practices have certain disadvantages and inferior pastures must often result. When ryegrass is sown under wheat in spring its establishment is poor in a dry season, and in a wet one the wheat crop may be sufficiently heavy to smother grass growth. Even under normal conditions pastures sown under wheat are usually clover dominant. Ryegrass sown with oats or barley is frequently smothered, though reasonable results are usually obtained from a seeding with linseed or mustard. If the pasture mixture is sown with rape, turnips, or chou moellier, the heavy concentration of stock during the feeding of the supplementary crop is likely to result in injury to the young pasture plants; this is particularly noticeable when rape is fed off during a dry period.

Neither perennial ryegrass nor clover plants can make their best growth when they have to compete with other crops for soil moisture and plant nutrients. When land is ploughed after a cereal crop soil fertility is often low, and because of the time of harvest hasty cultivation is necessary. Time is too short to allow full advantage to be taken of weathering of the soil, an important feature in the preparation of the seed-bed. Further, the seed-bed is usually not prepared until late in the season. All these factors combine to retard germination and establishment and thereby increase the risk of frost lift during winter. -> The most reliable method of establishing perennial ryegrass in Canterbury is undoubtedly to sow in January or early February after a summer fallow. During the fallow moisture has been conserved and weed growth checked, and the soil is warm in early autumn, ensuring rapid germination and vigorous growth. Thus, under normal conditions, useful grazing for sheep during winter and early spring can be confidently expected. A practice commonly followed in Canterbury is to sow oats for greenfeed after a cereal crop and to plough in the residue in October. When this method is used the land is rolled on the furrow to conserve soil moisture. Timely working with grubber, roller, and harrows develops the fine, firm, weed-free seed-bed essential to rapid

establishment. Deep working during the final preparation of the land is not desirable, for it not only brings a fresh supply of weed seeds to the surface, but also results in loss of soil moisture. Soil that is well worked retains moisture during a dry period, and if the ground is rolled about a week before the time of sowing, this moisture is brought very close to the surface. Methods of Sowing The method of sowing the seed varies from farm to farm and from paddock to paddock. Under favourable conditions broadcasting gives a good spacing of plants and a quick ground cover, but in dry districts many of the seedlings are likely to die soon after germination. Drilling one way has the distinct disadvantage of slow ground coverage, but it is the safest method of sowing, particularly on the lighter soil types, which dry out quickly. Where fertility is high perennial ryegrass and clovers usually grow quickly and soon fill in the spaces between the drills. A sowing method that finds favour principally on the better land is the drilling of the perennial ryegrass and the broadcasting of the clovers. In many cases cross drilling has proved highly satisfactory. If the work is done efficiently, not only is spacing good, but the seed is placed at a uniform depth in moist soil. Fertiliser is concentrated in the drills with the seed and therefore facilitates

rapid root development. However, with this method care must be taken to avoid an over-deep sowing, particularly in the first drilling. Drill coulters should be set right back, and where possible worn coulter tips should be used. Rolling between the two drillings is necessary for an even depth of seeding. Possibly the greatest danger in cross drilling is a change of weather. If heavy rain follows the first drilling, the paddock may not be sufficiently dry for the sowing to be completed before the first seed sown has germinated.

There are points for and against each method of sowing, and farmers therefore must be guided in their choice by conditions ruling at the time of sowing.

Recently several types of special drill coulters have come on the market. The use of these results in a substantially better ground cover than with the standard grain drill.

Lime and Fertiliser

No hard-and-fast rules can be laid down for the use of lime and fertiliser, and farmers must be guided by local knowledge. On most South Island farms 1 ton of carbonate of lime per acre should be applied. to the land just before sowing. If lime is not available at that time, it should be topdressed on the area as soon as the plants have established. In some districts, particularly in the North Island, the use of lime is not warranted. In practically all cases phosphatic fertiliser should be sown with the seed.

Lime and phosphate promote healthy growth, and adequate topdressing with a suitable phosphatic fertiliser should be done each year, preferably during autumn or early winter. Lime deficiency of the soil should be corrected either by annual topdressing or by heavier applications every 3 or 4 years. The season for the application of lime is not as important as that for fertiliser, topdressing with which gives best results when done, during autumn.

Where spring growth is not vigorous nitrogenous fertiliser may be applied at the time the paddock is closed for seed or 2 or 3 weeks later. This will promote grass growth, and in spite of the high price of these fertilisers, the increase in seed yield usually will more than compensate for the expense. If clover is threatening to smother the grass, a dressing such as 2cwt. of sulphate of ammonia per acre will depress the clover growth, but this heavy application is not usually warranted.

Areas to be saved for perennial ryegrass seed should not be grazed heavily during winter and early spring. Lenient grazing of the perennial ryegrass-clover pasture tends to

cause shading of the clover plant and thereby inhibit its growth. On the other hand hard winter grazing allows the clovers to make such rapid spring growth that the grass may be smothered.

Time of Closing

The early closing of paddocks for seed production is desirable, but the actual time stock are removed will vary with conditions. The following suggestions can therefore be only a guide.

On land where grass growth is backward because of low soil fertility or late sowing stock should be removed toward the end of September. Under average conditions an area need not be closed from stock until mid-October, and if conditions are favourable for rapid growth, grazing may be carried on into November. On some farms the paddock is required for grazing until it is nearly fit to harvest; stock are then removed and a light seed crop harvested. In some districts sheep are run on the area until harvesting time to keep down such weeds as burr clover.

Harvesting

Hot, dry weather and an absence of strong winds give ideal ripening and harvesting conditions. Rain during the latter period of growth may result in tangled crops with abundant growth of clover and weeds.

Before the advent of the header harvester various harvesting methods were adopted: Some crops were mown and then threshed out of either cock or stack; light crops were handled by the grass seed stripper; and others were reaped and tied before being threshed out of stock or stack. The last method has much to commend it and is still used by some South Island farmers, but most perennial ryegrass crops are now windrowed and picked up with a header harvester. In the North Island this work is generally done by contractors, but in the South Island the farmer usually has his own header harvester.

Light crops may be either direct headed or handled with a grass seed stripper. In such cases the seed is allowed to become fully mature before harvesting is begun, and even then the crop is not in fit condition to be bagged in the usual way. Therefore it is placed in open-meshed sacks, which should be only half filled and then hung on a fence until the seed is thoroughly fit for bagging.

Perennial ryegrass is ready to windrow when it reaches the binderripe stage; that is, when the seed is well developed and has lost all trace of greenness. This stage is indicated when a few seeds have fallen and seed comes away readily into a hat swept lightly through the crop. Earlier

cutting gives a pinched sample, and if the crop is allowed to become fully mature, loss from shedding is experienced. A mower fitted with an inside divider is generally used for windrowing. If the crop is light, windrowing and picking up may be simplified by the use of 2 binders; one taking a 6ft. cut delivers the material from the platform canvas to the ground, and the second, from which the tying apparatus has been removed, takes a 10ft. cut, the material being run over the elevator canvas. Thus the two windrows are placed sufficiently close to enable both to be picked up at one round of the header. Though the header harvester gives best results when fed to reasonable capacity, heavy windrows with consequent overloading of the machine should be avoided. When the cut material is placed in an even, fairly narrow, and not overbulky row it conditions in a few days and threshes easily. Threshing should never be started before the crop is fit. : As perennial ryegrass is easy to thresh, the concave should be right open and the drum speed about half that used for wheat. Inaccurate setting and fast drum speed result in damaged seed.

The disposal of straw after the header harvesting of perennial ryegrass seed is too often neglected. It is of particular importance if the crop has been fairly bulky. Apart from its smothering effect, straw left lying on the paddock gives shelter to such pests as grass-grub, porina (.Oxycanus), and slugs, and many good pastures have been ruined by carelessness in this direction. This straw makes quite x useful hay if baled directly after heading. Machine Dressing Modern seed-cleaning machinery is very efficient, and provided threshing has been done carefully, machine dressing presents no great difficulty. If seed has been harvested before it is fit, it will heat and suffer not only germination injury but also loss of appearance. Goosegrass is probably the most serious impurity in perennial ryegrass seed. If through hard threshing this seed is shelled or the awns are removed from it or such species as Italian ryegrass, their separation from perennial ryegrass by machine dressing is not practicable. Losses in machine dressing vary from line to line and may range from negligible quantities in seed from very clean paddocks to up to 50 per

cent, or more in seed from dirty, weed-infested areas. The average loss over all lines is about 35 per cent., including any white clover seed which may be separated and later recleaned.

Yields

Crops yielding 40 to 50 bushels of machine-dressed seed per acre are by no means uncommon, though the average yield is about 18 bushels.

The possible number of remunerative seed crops depends very largely on management. In Hawke’s Bay some pastures have been harvested periodically for up to 80 years and their yields are still high. On the mixed farms of Canterbury the general practice is to harvest perennial ryegrass up to the third and even fourth seasons. From that time it is usual to graze the area until it is again ploughed for supplementary feed or an annual cash crop.

An analysis of the yields in Canterbury for the 1946-47 season shows that areas harvested in the first season average 19.6 bushels per acre; areas which had been grazed right through the first season and harvested in the second season returned the same average yield, but areas which were harvested in both the first and second seasons averaged only 8.4 bushels in the second harvest. Many of these areas may have been treated primarily as white clover seed areas. All areas in their third harvest season averaged 13.2 bushels, these also probably including some handled primarily for white clover seed. As the age of the pastures increased so did the yields, those in their fourth harvest season averaging 14.8 bushels, in their fifth harvest season 16.8 bushels, and areas older than this (a very small proportion) 20.9 bushels per acre.

The bulk of the seed is harvested from young areas, the first crop giving the highest yield. The effect of successive crops is very marked and probably many areas in the second and third seasons are harvested chiefly for the white clover seed they produce.

From this stage onward yields, tend to increase and this may be accounted for by the harvesting of seed only from those areas where the perennial ryegrass has had every opportunity to become firmly established. Such areas can produce very satisfactory seed crops.

Subsequent Management

Because of the harvesting of successive seed crops without sufficient spelling perennial ryegrass thins out in many pastures and an invasion of such species as goosegrass and hairgrass occurs. It may be found uneconomic to close such areas for seed, though with suitable management they may be brought back to a highly profitable state.

Both goosegrass and hairgrass are annuals and may be eliminated or at

least reduced to harmless proportions in the pasture. The aim should be to prevent their reseeding, and this may be accomplished by grazing and mowing. In summer the seed heads which will appear despite heavy grazing must be cut with a mower before they reach maturity. A spell under grazing permits the perennial ryegrass and clover plants to stool and cover the ground previously occupied by the weed species.

If this grazing and mowing are carried out before the weed infes-

tation becomes too great, recovery to- a high-producing state is rapid, but if it is delayed too long, ploughing the pasture will be the only satisfactory alternative.

Diseases and Pests

Blind Seed Disease

Blind seed disease, which in damp seasons causes low germination in ryegrass seed, has presented a serious problem not only to farmers and seed merchants ' but also to research workers. The trouble is by no means new, but has been brought to notice since the cause was first discovered by Neill and Hyde in 1932. Since then the disease has been isolated in numerous countries.

As perennial ryegrass forms the basis of most New Zealand pastures and is also the main seed exported, blind seed disease, which unfortunately is more prevalent in the better strains, is of considerable economic importance to the country as well as to the seed producer.

The blind seed fungus is carried over from year to year on infected seeds of either ryegrass or other susceptible species, the outward appearance of which may not differ from that of healthy ones. Infected seeds lie dormant in the ground during winter, but with a rise in temperature the fungus revives and small fungous cups (apothecia) develop. In an infected area an examination of the soil surface during November and December will disclose these minute, mush-room-like growths. The fungous cups produce spores which are ejected into the air and carried by wind during the flowering period of the ryegrass plant. Those that alight on open florets may, if suitable damp conditions exist, set up a fungous growth which penetrates the young seed and produces a fresh batch of spores enveloped in a slime which is soluble in water and is further spread by either dew or rain.

Development of the seed depends on the time that infection takes place. Early infection results in light seed, which usually is removed during machine dressing, but with a later infection the seed may appear quite normal and its removal be impossible.

These blind seeds which remain in the machine-dressed sample or fall to the ground at or before harvest complete the life cycle.

The incidence of the disease varies from year to year and district to district and its severity is increased by showery weather between flowering and time of harvest. The incidence is usually less in seed harvested from lodged crops than in seed from standing and open crops.

Since the disease was first recognised research work has been carried out in an endeavour to control it either by treatment of the existing strains. or by the breeding of types resistant to it and still having the desirable characteristics of the present pedigree strain. This work is still only in the experimental stage and no recommendations can be made yet. However, some evidence suggests that seed harvested from vigorous stands of perennial ryegrass or from crops which have lodged is of higher germination than that taken from weaker crops.

During recent years a pre-harvest testing service for ryegrass seed crops has been made available to farmers in the main seed-producing districts. This service enables the farmer to know the probable germination of his ryegrass crop before harvesting is begun. Where poor germination is indicated threshing costs may be saved and the crop used for hay. Ergot Ergot (Claviceps purpurea) in perennial ryegrass is important chiefly because of the seed losses it causes. The disease is easily recognised by the hard black sclerotia which take the place of seed in infected plants. Infection occurs at the flowering stage, when the fungous spores are blown to the ryegrass flowers, where they germinate and exude a honeylike substance. This substance produces other spores, which are spread by insects to infect further flowers. The ovaries of infected flowers become enlarged and the black sclerotia develop during summer and either are harvested or fall to the ground. In this stage ergot overwinters before germinating in spring, when ascospores are liberated to cause reinfection of the new generation of flowers. Measures to control this disease are the use of clean seed, destruction of seed grasses which act as hosts, and prevention of affected plants from seeding. Rust Though both stem and leaf rust are relatively common, they are not usually so severe as to reduce germination of the seed, but when infection is severe the yield is affected

detrimentally because of the lighter weight of the seed.

Grass-grub

Grass-grub (Costelytra zealandica) is responsible for the destruction ,of a large area of pasture. The brown beetle, the adult stage of the grub, lays its eggs chiefly in November and December, about a month later than does the porina moth.

The grass-grub feeds entirely on the roots of the plants, leaving the foliage untouched. As a result of the root damage the plants die off and the soil is left spongy because of the activities of the grub under the surface. The damage is usually evident by early April, and the grub is recognisable by its whitish body, brown head, and horseshoe shape.

Grass-grub can be effectively controlled by DDT or lindane. The following are the suggested treatments: lib. of 100 per cent. DDT or lindane in 1000 gallons of water or 141 b. to 341 b. of 100 per cent. DDT or lindane per acre in topdressing or dry soil. Porina In contrast to the common grassgrub, the porina (Oxycanus) or subterranean grass caterpillar is a surface feeder affecting only the foliage or crowns of the plants. This pest, which is up to 2|in. long when fully grown, lives in single vertical burrows 6in. to 9in. below the surface of the soil, emerging at night to feed on the surface. Its colour is usually a greyish green and it has not the distinctive curving of the body which is characteristic of the grass-grub. The soil of an area infested with porina is not made spongy, but remains firm. Though grass-grub damage is most marked on light, friable soils, porina will cause trouble on quite heavy land.

Early recognition, of the cause of damage is important. The presence of caterpillars may be recognised by soil casts on the surface which are distinguishable from worm castings by their fine web.

For some years poison baits of either paris green or arsenate of lead gave some control of the pest, but this treatment is less effective than applications of either DDT or lindane. Satisfactory treatments are: 3|lb. of 13 per cent, lindane in lewt. of superphosphate per acre or lib. of 13 per cent, lindane in 501 b. of bran per acre. (The use of double strength for highreturn crops is recommended.) The pest can also be controlled by 21b. of paris green in 251 b. to 301 b. of bran for populations of under 6 to the square foot.

Areas closed for seed production

are particularly subject to attack by either grass-grub or porina.

Army Worms

Attack by the caterpillar known as the army worm may ruin a perennial ryegrass seed crop. This pest derives its common name from its habit of

moving in large numbers in definite directions. It often does substantial damage in one paddock while another close by is untouched.

The caterpillar feeds on the foliage and seed heads of the plant, and a crop may be ruined almost overnight if infestation is severe.

An application of 21b. per acre of 100 per cent. DDT has given good control. When this pest attacks ryegrass seed crops the most satisfactory method of application is by lowvolume spraying with either aircraft or a ground plant.

Wheat Sheath Miner

Ryegrass is attacked by a fly (Cerodonta denticornis) commonly known as the wheat sheath miner because it also damages wheat. Injury to ryegrass is caused by the maggot or immature stage of the fly sucking the sap from the flowering stem, which results in a premature whitening and loss of the seed head.

The female flies of the wheat sheath miner, which are about l/12in. long and greyish, emerge in early spring and within 3 days start laying their eggs in the blades of ryegrass. The fly punctures the blade and lays a single egg within the tissue. The egglaying period lasts about 3 weeks, during which about nine eggs per day are produced. The young maggot hatches in a week and immediately begins to mine in the leaf tissue. As the insect grows its tunnels can be seen with the naked eye as zig-zagging white lines. When the damage is extensive the sap supply is cut off and the leaf wilts, turns brown, and dies. The maggot may then enter the developing flower stem and cut off the sap supply to the seed head, causing the whitening and loss of seed.

The maggot reaches maturity in 9 to 24 days, according to the season. At this period it comes to rest between the sheath and the flowering stem, where it turns into the puparium or resting stage. This puparium, especially when it is present in wheat, is sometimes confused with the “flax seed” stage of the hessian fly, which it resembles superficially. At this time the white straws are observable in the field, so that puparium is the stage in the pest’s life history which is usually noticed. The time spent as a puparium is usually 2 weeks or less during summer, but autumn broods overwinter in old straw and grass and the flies emerge from the puparia in spring. Under suitable conditions the time taken from egg to adult is only a few weeks, and there are at least three generations in a season.

The wheat sheath miner is usually present in a ryegrass crop, but only periodically appears in sufficient numbers to be of any significance. A severe outbreak occurred in 1944 in

North Canterbury, where in some severely damaged areas there were as many as seven and eight white straws per square foot, whereas other paddocks showed very few damaged straws. However, during the past 3 seasons no significant outbreaks have been reported.

This insect has been introduced into New Zealand and is now found throughout the country. For many years it has appeared periodically in isolated areas, but so far it has not been regarded as a serious pest of perennial ryegrass.

Seed Markets

About half a million acres of land is sown to pasture each year in New Zealand, and if a conservative figure of a bushel of perennial ryegrass seed to the acre is taken as the rate of seeding ovex' the whole area, local consumption of seed is about 5000 tons a year. This figure is probably fairly constant, in contrast with the fluctuating quantities exported from year to year.

New Zealand exports about £250,000 worth of perennial ryegrass seed each year, principally to the United Kingdom and Australia. The bulk of the seed exported is certified, there being no great demand overseas for uncertified seed.

Importance of High Yields On most farms the saving of perennial ryegrass seed is secondary to the growing of pasture for stock feeding. However, the fact that more than 25,000 acres must be harvested each year to meet local requirements alone indicates that the practice is important in suitable districts.

High prices for seed have encouraged seed harvesting in some districts and under types of management not really suitable. Though reasonable returns may have been received under these conditions, the importance of producing high yields of good seed must not be overlooked. By the application of those practices which will lead to high yields of seed and consequent lower unit costs the grower is at the same time encouraging higher consumption locally and making easier the finding of an overseas outlet for surplus supplies.

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