Recent Research Work

New Zealand Journal of Agriculture, Volume 91, Issue 6, 15 December 1955, Page 559

Recent Research Work

j SWEET BRIER CONTROL

"EXPERIMENTS with the use of hormone-type weedkillers •*-' for the control of sweet brier (Rosa eglanteria) were first conducted in the high country tussock grasslands of the upper Waimakariri River area during the 1946 to 1948 seasons. These early trials compared 2,4-D (2,4-dichloro-phenoxyacetic acid) with standard sodium chlorate. A further series employing the later-developed esters of 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) began in 1951 and is still proceeding. More recently newer weedkillers, such as the urea compounds, mixtures of borates and chlorates, 4-C (4-chlorophenoxyacetic acid), and 2,4,5-TP (2,4,5-trichlorophenoxpropionic acid) have also been included. Treatments have included coverage sprays and basal sprays and dustings and have been confined largely to the treatment of large, well-established plants, though some work has been done on regrowth from cut stumps. The treatments have been applied at all the main seasonal stages of growth.

RESULTS: HORMONE WEEDKILLERS

2,4-D proved relatively ineffective against sweet brier and the mixed esters of 2,4-D and 2,4,5-T compounds appear to depend on their 2,4,5-T content for effectiveness. Both

the butyl and butoxy ethanol esters of 2,4,5-T have given better results than the polyethylene glycol ester of 2,4,5-T and have proved moderately efficient

as coverage sprays when applied to well-established bushes, though repeat applications are necessary. For spraying during the full-leaf (flowering to petal fall) period (November-December in the upper Waimakariri) dilution strengths of 1 in 250 to 1 in 500 have proved satisfactory. Spring and autumn sprayings require stronger solutions of about 1 in 100. Coverage sprays must be complete, 3 to 4 pints of spray per plant being required when the solution is applied with knapsack equipment to individual bushes. When well-established, dense stands of large bushes are treated with orthodox high-volume equipment 400 to 500 gallons of solution per acre would be needed for adequate coverage. Very satisfactory results were achieved by applying basal sprays of the esters of 2,4,5-T in diesel fuel (1 in 25) during the plants’ dormant period (June to July) and using 1 pint of solution per plant. Good kill was also achieved when regrowth on cut stumps was sprayed with single applications of 1 in 250 and 1 in 500 solutions of 2,4,5-T esters, provided sheep had access to and browsed the treated shoots. For this treatment 1 to 1| pints of solution per stump was required.

RESULTS: OTHER CHEMICALS

As an over-all application boron-chlorate mixtures appear less satisfactory than 2,4,5-T applied in the same way. On young autumn regrowths in stocked areas a 5 per cent, solu-

tion of sodium chlorate applied at 1 to lj pints per bush has been satisfactory. The urea compounds CMU and PMU show distinct promise. —A. R. DINGWALL

EARTHWORMS

ARISING from the favourable publicity given to the activities of earthworms and their ability to improve unploughable hill

pasture in the Raetihi district of the North Island, a .trial with earthworms was undertaken in the Glenledi district near Milton. Activity of soil organisms, particularly earthworms, has always been looked on as. a sign of good soil fertility. and the experiment confirms this view. Six colonies of 25 worms of the species AUolobophora caliginosa were placed in a field at points a chain apart in August 1945 in an 18-month-old sward that, was mainly browntop and ryegrass with some crested dogstail, timothy, cocksfoot, white clover, and red clover. Weeds and bare bare ground comprised 15 per cent, of the ground cover. Little evidence of worm activity was noted until May 1949, when the worm-implanted area was noted to be greener and fresher than the non-wormed area and worm casts could be found readily in the vicinity of the liberation points. As the worms spread their effect could be noted in the colour, vigour, and density of the sward, and when the field was ploughed in spring 1954, boxwood (Cassinia spp.) and manuka were invading the sward of the non-wormed area. In 9 years the 6 colonies of earthworms had spread over an area of approximately J acre, on land which had been limed fairly heavily, though the phosphate status was low. AUolobophora caliginosa is common in many parts of South Otago, but is not found in the district where the trial was undertaken or in the adjoining districts of Akatore, Bull Creek, and Taieri Beach. Worms of this species may have been present in the past and died out as a result of the rather bad treatment the soils in this area received in the early days, when they were extensively cropped. With the use of lime and phosphates and the utilisation of the land for sheep farming the reintroduction of this species of earthworm into the area appears to be worth while for building up soil fertility.

—J. G. RICHARDS