Propagation of Strawberry Plants in Waikato and Coromandel Areas

New Zealand Journal of Agriculture, Volume 87, Issue 1, 15 July 1953, Page 23

Propagation of Strawberry Plants in Waikato and Coromandel Areas

AS the strawberry is a perennial plant which does not breed true from seed, the demand of commercial growers for plants of uniform quality free from disease rests on vegetative propagation by runners. Plants raised in - this manner perpetuate the characteristics, both . good and bad, of the parent plant. Therefore, the value of rogueing so that healthy, disease-free plants are available to growers of strawberries cannot be over-emphasised. Methods of propagation and culture practised in the Cambridge and Tirau (Waikato) and Coromandel districts are discussed in this article by C. E. K. Fuller, Horticultural Instructor, and R. E. Yates, Horticultural Inspector, both of the Department of Agriculture, Hamilton.

FOR maximum, high-quality berry production in the Auckland Province the strawberry is grown as an annual crop, maiden runner plants being set out in May of each year. To meet the demand for plants some 2,500,000 are raised annually in runner plant nurseries near Whitianga (Mercury Bay), Cambridge, and Tirau, areas which receive a fairly high summer rainfall. The runner beds are usually planted on a fresh area of friable, free-draining soil each year. Such conditions, under normal circumstances, favour free production of runners, the resultant plants being made available to growers through various fruit and produce marketing organisations.

Most nurseries are run in conjunction with dairy farming, individual beds ranging in size from less than J acre to 2 acres, the largest producing about 750,000 plants annually. Varieties Captain Cook is the only variety raised on a large scale, as it is virtually the only variety used by northern commercial - strawberry growers. The recently introduced varieties Auchincruive Climax and Perle de Prague have been tried on a limited scale, but runner production has been unsatisfactory in these districts. •

Soil Preparation Preparation. of the nursery bed is begun during autumn, the area to be used generally being ploughed out of pasture and temporarily fenced against livestock. Subsequent cultivation is sufficient to destroy any weed growth before the area is finally brought to a tilth suitable for the planting of the parent or mother plants in early spring. Mother or Parent Plants The mother plants used vary in age from first-year maiden runners to 5year plants. These should be selected for strain and freedom from disease. Careful selection to ensure that the plants are free from virus disease and red core root rot infection is important and, for this reason, it is necessary to rogue mother plants heavily to ensure beds of runners free of disease. Mother plants are normally selected from the grower’s own stock, but sometimes, when beds become degenerated through virus disease, new stock must be brought in. Planting out Planting out of the runner beds begins in early spring (usually September). Plants are spaced - fairly close in the rows, the average planting distance being ' Ift. between plants, but wide spacing (about 3ft.) between rows allows cultivation by machinery

and efficient rogueing of diseased plants up to a fairly late stage. Closer planting is often practised to minimise the reduction in the total number of runners from a given area resulting from rogueing out of diseased plants, but is not recommended. Plants growing too closely together produce such a tangled mass of runners that they cannot be rogued efficiently. Culture . Cultivation after planting, although frequent, is shallow and is aimed at securing good weed control until the developing runners cause it to become impracticable. Flowers are picked off as they appear later in spring so that fruiting is suppressed and the energy of the plant is concentrated on runner production. Some growers hesitate to adopt this practice in the belief that virus diseases may be spread from plant to plant by contaminated hands, but strawberry virus diseases cannot be spread in this manner, the strawberry aphis (Pentatrichopus fragariae) being the only vector. On the cessation of cultivation the beds are left, except for any necessary rogueing, until digging begins. The reason for keeping off the beds at this period is that unnecessary compacting of the surface soil is avoided and thus good rooting conditions for the plants are maintained. ■ Manure is seldom used in the propagating beds, the hardy plants produced without fertiliser normally making good growth when planted into fruiting beds. However, when there is an obvious lack of one of the main elements, a light dressing of the required fertiliser should be applied. Digging and Packing Digging begins during May, plants being lifted and forwarded as required to fruit and produce organisations who supply growers or, sometimes, direct to growers. The forwarding of plants as required, so that rate of digging does not exceed rate of planting, enables growers to receive plants in a relatively fresh condition. Digging on the larger nursery beds is usually carried out by contract Maori labour, the digger loosening the plants with a fork and keeping just ahead of the picker. The latter pulls, places, and ties the plants in bundles of 50, having first discarded the mother and any unthrifty plants. Immediately following is the packer, who puts the bundles in sacks or boxes. Plants awaiting dispatch are placed in the shade, usually beneath a hedge or tree, though a tent is sometimes used if there are no trees handy. Pests and Diseases Strawberry growers are dependent on the plant growers for disease-free plants, which are essential for successful berry production, and all nurseries are registered and inspected by officers of the Department of Agriculture. Unlike England, New Zealand has no plant certification scheme for strawberries. Strawberry plants are subject to attack by a number of pests and diseases and nursery beds are isolated from the main growing areas in an

attempt to avoid disease - infection. Despite this, most . beds require attention to control pests and diseases during the year. Descriptions of the major diseases aifecting nursery beds and of control measures follow. Virus Diseases’ Virus diseases, which cause degeneration, are transmitted by only one species of aphis (Pentatrich opus fragariae) . and are usually introduced into strawberry gardens by the planting of infected runners.. They are the most serious diseases affecting strawberries . in . New Zealand and other countries and probably have been the prime factor in the reduction of areas and yields in this country in the past. Two strains of virus are peculiar to the strawberry, yellow edge and crinkle. Yellow edge: This causes a general dwarfing of the youngest leaves and a shortening of the petioles, together with a yellowing of the leaflets, which is more pronounced at the edges. The plant appears flattened, compared with

a healthy one, owing to the dwarfing of the petioles of the leaves nearest the centre of the plant. Crinkle: This may be as prevalent as yellow edge in some districts. The symptoms consist of a crinkling of the young leaves accompanied by yellow (chlorotic) spots, with 'or without

small, red, necrotic (dead) centres and a dwarfing of tne plants.

Often in mild infections these virus diseases cannot be detected by the symptoms described until autumn, as hot weather tends to mask the disease, but the symptoms usually become visible in autumn, when temperatures are lower. Severe infections, however, can be detected readily by the general dwarfing of the. plant and its failure to develop normal runners.

Control: Infected plants do not recover and should be dug out and destroyed by burning as soon as the infection is detected. The degree of spread may be reduced by the control of the aphis by spraying (see section dealing with insects) . • A practical method of dealing with the trouble is rigorous inspection and rogueing to eliminate all visibly infected . plants and thus the building up of a stock of plants as free from disease as possible. This is a long-term, procedure, but if adopted by all plant growers, would bring about an improvement in planting stock.

Rogueing: Too much emphasis cannot be placed on the value of thorough and frequent rogueing to eradicate virus-infected plants from beds. This is particularly important in virustolerant varieties such as Captain Cook, in which virus cannot be detected until it is so severe that . it induces degeneration and unthrifty plants. In an infected plant the virus permeates the entire plant system, including every runner , plant produced. Thus every one of the progeny of an infected mother plant is a potential source of infection when planted in fruiting beds. This can go on until all existing plants of a variety are infected with virus disease to a greater or less extent. Rogueing should be done when the first signs of infection are seen and in the nursery bed can be carried out at any time. To facilitate this, even wider planting of both the plants and rows would be advantageous. Infected plants should be taken from the nursery beds and burnt.

Insect Pests Strawberry aphis (Pentatrichopus fragariae): This aphis commonly attacks strawberry plants throughout New Zealand, but infestation only occasionally reaches such serious proportions as to devitalise plants by the amount of sap extracted and so cause crop reduction. However, the aphis

must be considered a serious pest even when present in small numbers, because it is the sole means of transmitting the virus diseases of strawberries in New Zealand. The aphides transmit virus by feeding on the sap of infected plants and injecting virus into healthy plants when they transfer to feed on them. In this way a considerable reduction of crop can be brought about in one season. As aphides multiply very rapidly, control measures should be adopted as soon as they appear. Control: Beds should be sprayed periodically, as necessary, with one of the following: 1. One per cent, of summer oil plus nicotine sulphate 1: 800: To make 100 gallons use 1 gallon of summer oil, 1 pint of nicotine sulphate, and 100 gallons of water. To make 4 gallons use 6-j fl. oz. of summer oil, 4/5 fl. oz. of nicotine sulphate, and 4 gallons of water. 2. Hexaethyl tetraphosphate (H.E.T.P.) 1 :1600: To make 100 gallons use J pint of H.E.T.P. and 100 gallons of water. To make 4 gallons use 2/5 fl. oz. of H.E.T.P. and 4 gallons of water. 3. Tetraethyl pyrophosphate (T.E.P.P.) 1: 1600: To make 100 gallons use | pint of T.E.P.P. and 100 gallons of water. To make 4 gallons use 2/5 fl. oz. of T.E.P.P. and 4 gallons of water. Fungous Diseases Leaf spot (Mycosphaerella fragariae): Leaf spot is probably the most common fungous disease affecting strawberries in New Zealand. Attacks

are usually confined to the foliage, where the symptoms show as small, circular spots, at first reddish brown but later becoming greyish from the centre outward with a reddish margin, The spots enlarge and may run ther / W thl Ch lP*f UCe thn? e area of the leaf thus restricting growth of the plant. Control: A Bordeaux 5 : 4 : 50 spray should be applied in spring, after which routine spraying of Bordeaux 3 : 4 : 50 should be carried out throughout the season to ensure that the young, plants will start off free from To Sea makf e so Pl gallons lll 5 4 -To use 51b 'bluestone (copper Idlho+al lib nf hvHrftod hrnA 4 f water h T d o make l 4 gallons use g 6ilz <S bluestone 51fz of hydrated lime and gallons of water To make 50 gallons of Bordeaux 3 ? 4™0 use 31b g of bluestone 41b of ? j x Ji- ci /jiuesione, “tio. oi hydrated lime and 50 gallons of water. To make 4 gallons use 4oz of bluestone, stoz. of hydrated lime, and 4 gallons of water. Red core root rot: Investigations have revealed that red core root rot (Phytophthora fragariae) of strawberries is due mainly to a parasitic fungus which invades the root tips and grows into the core, which becomes reddened Roots become infected from autumn to spring, and m late spring and early summer the fungus causes debilitation and gradual dwarfing, wilting, and often death of the

plant. The intensity of the disease depends on soil moisture, being most severe when the water content is high « has been established that root rot disease was introduced into fruiting beds on runners previously infected in a plant nursery. stunted strawberry plants susnected of being infected bv root rot dingus should be lifted with the root S y Sem intact for inspection. If there i s an abundance of small white feedin § + roots and no rotting of the larger roots, stunting is probably due to some other cause - If the all, fibrous roots ar< i decoloured or are absent, leaving only the rat \ s tail ; h large roots, and « the central P art of th large roots la dark ed > stung ls due to the red core fungus. The red colour of the central portion of an infected root may extend throughout its length or the colour may show only a short distance above the dead tin This reddening of the root interior is best demonstrated by splitting the root with a knife or by stripping off the outer portion of the root with the thumbnail. The dark red colour of the central part of affected roots is not known to be associated with any other strawberry disease and the symptom is considered the most reliable one for recognising the disease in the field. , The fungus causing root rot disease is not. known to invade the crown or

stem, and any discoloration of those tissues should be attributed to some other cause. Control: As the fungus can remain alive in the soil for several years, strawberry nurseries should not be replanted in soil where infection has occurred previously. Heavy, poorly drained soils should be avoided. Greater care in the selection of runners for planting will reduce the incidence in the field. Runners free from the fungus when planted in soil no previously used for strawberry growing should remain free, but a sma percentage of infected plants can spread the infection rapidly where wet conditions prevail. Infected plants should be removed from the nursery beds and destroyed by - burning. ' „ „ ~ The success of the strawberry crop depends largely on the quality of the planting material used. It is essential that preparation and after treatment of the runner bed should be such that the production of vigorous, well-rooted, disease-free plants is encouraged. References NT „ , . . . „ . . B S e o ala 32l , s ? rawberr t y g f LlIt k f j C n u Nel Zealand”, by J. H. Watt. United States Department of Agriculture Farmers’ Bulletin 1891, ‘‘Diseases of Strawberries”, by J. B. Demaree.