Hops have been grown in various parts of New Zealand in the past, but all commercial plantings are now in the Waimea County of Nelson Province. Hops are grown on the heavier silt loams and clay loams of river valleys. The high annual sunshine plays a large part in producing heavy crops. Moreover, a fairly evenly distributed rainfall of approximately 40 in. a year requires only occasional supplementary irrigation.
There has been a steady change from the European varieties to the Californian. The Californian hop was brought to the district about 40 years ago and is the only one now grown commercially. New varieties bred by the Hop Research Station are now being released and may replace some of the Californian. The new varieties resist root rot (Phytophthora cactorum), are heavy cropping, and are of high alpharesin content. All hops grown are seeded. The area has been steadily decreasing (750 acres in 1948 to 530 in 1963) as export markets for seeded hops become increasingly difficult to find. The yield per acre has been decreasing lately and is now approximately 1,250 lb of dried hops, with a total yield of approximately 660,000 lb.
The rows of hills are 7 ft apart with 1,000 hills to an acre. The overhead wire trellis is generally 14 to 16 ft above the ground with the wires directly over plant rows. Four bines from each hill are selected and trained up double strings from the hill to the wire. The two strings are about 5 ft apart at the wire. Harvesting is spread over four weeks in late February and early March. There are 15 picking machines in the district, but as these belong to the larger growers a fair amount of the total area is picked by machine. It appears that imported machines need improvements in order to pick clean without breaking the hops. Hops are dried in kilns on the farms. Kilns are up to 20 ft square and with a bed depth of up to 2 ft. From five to 10 hours drying is needed, depending on the rate of air flow through the hops. After the time on the cooling floor the dried hops are pressed into bales of about 300 lb. The hops are graded after they are delivered to the brokers' store.
The Hop Marketing Committee, a grower committee with State representation, controls the sale of all hops. This Committee acts under the statutory authority of the Hop Marketing Regulations. One business firm in Nelson is the broker for hops. The representatives of New Zealand Breweries inspect samples and select their needs. The surplus is available for export. Under the regulations New Zealand's needs must be met before any export can be made. No imports are allowed while New Zealand hops are available.
Growers, brewers, and Government together operate a Hop Research Station. The station was originally set up to breed satisfactory hops, resistant to Phytophthora cactorum. This has been done, and other projects in the field of hop breeding and drying are under way.
As red spider rarely builds up to epidemic proportions, no control is practised. Black root rot (Phytophthora cactorum), a soil-born fungus, has caused great losses of plants. Resistant varieties are being used as replacement plants. Two minor outbreaks of Verticillium wilt (V. albo-atrum) have been recorded. Quarantine measures prevented the first outbreak spreading and it is hoped that the second one has been also confined. It does not seem necessary to spray hops to control insect pests or diseases.
by Moore Grant Baumgart, B.SC., Horticultural Division, Department of Agriculture, Nelson.