Green­house straw­ber­ries

New Zealand has a well-de­served rep­u­ta­tion for in­no­va­tion in hor­ti­cul­ture, but is well be­hind other de­vel­oped coun­tries in the pro­duc­tion of all berryfruit in green­houses, and par­tic­u­larly for the ma­jor crop straw­ber­ries.

NZ Grower - - The Final Word - Mike Ni­chols

This is a sur­pris­ing fact in re­la­tion to the un­cer­tainty of New Zealand’s weather, par­tic­u­larly in re­la­tion to rain­fall, where, even in Cen­tral Otago, rain can oc­cur at any time of the year. New Zealand does not have a sta­ble cli­mate like many con­ti­nents. For ex­am­ple Mediter­ranean cli­mates have a very high prob­a­bil­ity of warm dry sum­mers and wet win­ters. New Zealand’s cli­mate can best be de­scribed as mar­itime. Rain and berryfruit are not a good mix, as fruit qual­ity can be se­verely af­fected, ei­ther di­rectly, or in­di­rectly, by dis­ease (such as botry­tis).

Green­house straw­ber­ries were ini­tially grown in the field in the soil, and then in high tun­nels in the floor of the house, and more re­cently in what is known as the ta­ble top sys­tem—in troughs placed about 1m above the ground. Clearly as the pro­duc­tion is above the ground some form of hy­dro­pon­ics is nec­es­sary, and the usual method is by means of a me­dia based sys­tem (rock­wool, coir or peat), al­though liq­uid based sys­tems such as nu­tri­ent film tech­nique (NFT), and even aero­pon­ics have been used. In New Zealand some grow­ers use a triple row sys­tem, with the cen­tral row be­ing a fur­ther 60 cm above the two out­side rows. Pick­ing is sim­pli­fied by this sys­tem, but there is no ev­i­dence to sug­gest that yield is af­fected ei­ther up or down, com­pared with the “tra­di­tional” two row sys­tem. The triple row sys­tem comes with a weak­ness in the dif­fi­culty of pro­vid­ing the op­ti­mum wa­ter­ing. Un­less one is us­ing a re­cir­cu­lat­ing hy­dro­ponic sys­tem it is nec­es­sary to ir­ri­gate to en­sure ad­e­quate leach­ing of ex­cess fer­tiliser. Thus the ir­ri­ga­tion fre­quency of the top row needs to be greater than for the two side rows. A sim­i­lar re­quire­ment (to treat the ir­ri­ga­tion of va­ri­eties in­de­pen­dently), is also nec­es­sary.This is be­cause va­ri­eties do not lose wa­ter at the same rate - for ex­am­ple vig­or­ous/leafy va­ri­eties will tran­spire more wa­ter than smaller va­ri­eties, and thus build up salin­ity (a high con­duc­tiv­ity) in the solid medium. Ob­vi­ously not so im­por­tant for NFT sys­tems, where the nu­tri­ent so­lu­tion is re­cir­cu­lated.

In re­la­tion to me­dia con­duc­tiv­ity, there is an in­ter­est­ing re­port from the UK which sug­gests that me­dia con­duc­tiv­ity not only ef­fects yield, but also that strawberry va­ri­eties per­form dif­fer­ently de­pend­ing on me­dia con­duc­tiv­ity.

Of course, mov­ing into pro­tec­tive cul­ti­va­tion of­fers the op­por­tu­nity to con­sider the po­ten­tial of us­ing in­te­grated pest man­age­ment to min­imise the use of pes­ti­cides. With a “roof” over the crop, and the fruit held well above the ground, the risk of botry­tis fruit rots is min­imised, and the main prob­lem to over­come are pests such as spi­der mite, cy­cla­men mite, thrips, aphis, white fly and, on oc­ca­sions, cater­pil­lars. Bi­o­log­i­cal con­trol of cater­pil­lars is straight­for­ward with BT (Bacil­lus thurin­gen­sis). White fly is con­trolled by En­car­sia for­mosa:

spi­der mite by Ph­to­seiu­lus pes­im­ilis; and thrips by Neo­seiu­lus cu­c­umeris, which also ex­erts some con­trol over cy­cla­men mite, a ma­jor prob­lem with the va­ri­ety Al­bion. Aphis has a range of preda­tors, in­clud­ing Aphid­ius,

and black la­dy­birds. This is not to sug­gest that pes­ti­cides are not nec­es­sary, in fact it is a good idea to en­sure that plant­ing ma­te­rial is kept as free as pos­si­ble from pests with reg­u­lar use of ap­pro­pri­ate pes­ti­cides. It is only dur­ing the fruit­ing pe­riod that some form of in­te­grated pest man­age­ment might be con­sid­ered as a po­ten­tially valu­able pro­duc­tion strat­egy.

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