The use of maleic hydrazide as a means of controlling runner production in first-year plantations of strawberries was investigated, together with its effect on subsequent cropping.
Preliminary experiments in the glasshouse showed that the level of maleic hydrazide required for inhibition of runner growth increased with maturity of the runner. They also suggested that at the optimum level one application of maleic hydrazide could be expected to prevent the successful development of two emerged and four unemerged runners, without seriously checking the growth of the parent plant.
Plants of the varieties Redgauntlet and Talisman growing in the field were sprayed at 500, 1,000, 2,000 and 3,000 ppm. on 8th July. On 12th August a second spray at 1,000 p.p.m. was applied to some of the plants treated previously.
Runners rooted before treatment were resistant to inhibition and reduced the effectiveness of the treatment on runners emerging later. Because of this a high level of control was achieved in Talisman only by spraying at 3,000 ppm. In Redgauntlet, runners were adequately controlled at all levels except 1,000 p.p.m. as a single spray and 500 ppm. either as a single application or followed after a month by 1,000 p.p.m.
Cropping in the following year was proportional to the degree of runner control achieved. All treated plants cropped better than controls in which runners had been allowed to grow unchecked and, at the higher levels, cropped as well as controls from which all runners had been removed by hand at intervals throughout the season.
Treatment with maleic hydrazide in the glasshouse resulted in the formation of some branch crowns in place of runners. An increase in cropping of treated Royal Sovereign plants growing in the field was due to an increase in the number of branch crowns rather than to an increase in the number of inflorescences on each branch crown.