Effects of soil amendment with poultry manure on carnation Fusarium wilt in greenhouses in southwest Spain

In a search for alternatives to methyl bromide for controlling carnation vascular wilt caused by Fusarium oxysporum f. sp. dianthi (Fod), poultry manure plus soil solarization was studied in soil under greenhouse conditions in four 2-year experiments. These were conducted in naturally infested soil to compare the effects of this treatment with soil solarization alone and methyl bromide. Soil treatments were performed during June 2000 for Experiment 1, from July to mid-August 2002 for Experiment 2, from late July to late August 2006 for Experiment 3 and from late May to late June 2008 for Experiment 4. Additionally, a treatment with commercial poultry manure pellet plus soil solarization was included in the two latter experiments. Poultry manure caused reductions of Fod viability in soil samples at depths of 15 and 30 cm, ranging respectively from 93 to 100% and 89 to 100% for Experiments 1, 2 and 3. Carnations planted in plots treated either with poultry manure, methyl bromide or soil solarization had lower final disease incidences, smaller areas under their disease progress curves and higher yields in comparison with untreated plots in Experiments 2, 3 and 4. In Experiment 1, soil solarization was performed under suboptimal conditions, and it provided disease levels and yields similar to those of the untreated control plots. Nevertheless, under the same conditions, previous amendment of Fod-infested soil with poultry manure increased disease control over soil solarization alone, improved carnation yield and quality and also increased plant vigor, thus providing a satisfactory alternative to methyl bromide. The application of organic amendment to the same plot before every crop cycle is recommended to ensure continuous disease control, but the rates of application could be reduced to half for the third and fourth crop cycles, thereby reducing undesirable environmental effects.     

Improved solarization of containerized medium for the control of Monosporascus collapse in melon

Melon collapse caused by the heat-tolerant soil-borne fungus Monosporascus cannonballus is not controlled by current solarization technology applied to large soil volumes because the temperatures achieved are not high enough to kill the pathogen's ascospores. The efficacy of improved solarization achieved by mulching a shallow layer of growth medium in containers was studied in terms of disease control and yield increase over two growing seasons. Compared to solarization of a regular container, solarization of a shallow layer (5–6 cm) of growth medium resulted in a 3–5°C elevation in maximal temperature at a depth of 3 cm, and in a 7–10°C increases at the bottom of the shallow layer. This led to a higher disease reduction and higher yields in the 1996 experiment. In 1997, both methods of solarization were highly effective. Yield was highly correlated with disease reduction in both experiments. In the 1997 experiment, ascospore viability declined faster in the shallow container treatment than in the regular container. This study demonstrates the potential of an additional approach for improving solarization of containerized plant growth medium and improving its reliability, with the aim of controlling heat-tolerant pathogens.     

Fusarium proliferatum and Fusarium tricinctum as causal agents of pink rot of onion bulbs and the effect of soil solarization combined with compost amendment in controlling their infections in field

Laboratory tests and field trials were conducted in 2010 and 2011 in Salerno province, Southern Italy, to determine the causal agent(s) of pink rot of roots and bulbs of onion and the effects of soil solarization combined with municipal food waste compost amendment in reducing their infections on bulbs of onion. Three fungi were mainly isolated: Fusarium proliferatum and Fusarium tricinctum on bulbs and roots and Pyrenochaeta terrestris exclusively on roots. P. terrestris produce symptoms on roots, but it was not able to cause damage on unwounded bulbs. F. proliferatum and F. tricinctum were able to induce symptoms when inoculated separately and showed no synergistic effects on severity of symptoms on bulbs. They induced symptoms on roots at a lesser extent. Combined inoculations of P. terrestris with both Fusarium species on roots have not increased symptoms severity of pink rot of onion. This is the first report of F. tricinctum as agent of pink rot of onion bulbs. Two years field trials have been carried out from 2009 to 2011 to evaluate the efficacy of soil solarization, applied alone or in combination with municipal food waste compost amendment, for controlling pink rot of onion bulb caused by F. proliferatum and F. tricinctum. For this purpose, soil solarization, alone and combined with compost amendment, were compared with metham sodium and an untreated control. The results of both trials demonstrated that, in presence of pink rot of onion bulbs, compost amendments, applied after solarization, strongly reduced the efficacy of soil solarization from 68.7% to 16.3% in 2010 and from 76.9% to 4.6% in 2011. Organic amendments applied before soil solarization significantly reduced the efficacy of this technique only in 2011. Significant yield increases were detected at the end of both trials in plots treated with solarization alone, metham sodium and compost applied after solarization. The highest incidence of unmarketable infected plants recorded in plots solarized and then amended with compost was compensated by the increase of bulb size and plant weight. These results demonstrated as the benefits achieved with compost amendments in controlling pink rot of onion are not easily predictable and applicable on large scale.     

Effects of relative humidity and high temperature on spore germination and development of tomato powdery mildew (Leveillula taurica)

The effects of relative humidity (RH) and temperature on tomato powdery mildew (Leveillula taurica) were studied in controlled environments to define conditions that affect disease development in fresh market tomatoes in California. Gradients of RH (20–90%) at constant temperatures (20–30°C) were generated in single growth chambers to determine their effect on mildew development on mature tomato plants. Temperatures of 30°C and above were deleterious for spore germination, germ tube elongation, and disease development. Lesion growth and rate of disease progress were significantly higher at 20°C than at 25°C. Low RH levels (20–40%) reduced spore germination and lesion growth, accelerated host tissue death and reduced disease progress. Intermediate RH levels (50–70%) increased spore germination and optimized disease development, provided temperatures were maintained within favorable limits. High RH levels (80–90%) were favorable for spore germination but continued exposure to these conditions led to a limited lesion growth and disease progress. Short daily periods (two or three daily exposures of at least 2 h) of high temperatures (35°C) suppressed disease development by 70–92%.     

Soak conditions and temperature following sowing influence the response of maize (Zea mays L.) seeds to on-farm priming (pre-sowing seed soak)

On-farm seed priming of maize (i.e. soaking seed in water overnight, 17 h) in the semi-arid tropics has been shown to improve crop establishment and yield but the benefits can be variable. In previous work, this variation was thought to result from the interaction between primed seeds and conditions in the seedbed following sowing. To investigate this interaction, experiments were carried out under controlled temperature conditions that represented those of seedbeds in the semi-arid tropics. The conditions during seed priming and during subsequent germination and emergence were investigated as potential causes of variable seedling emergence relative to that of untreated seeds. Priming advanced emergence from moist sand cores at 30 °C/20 °C (day/night), reduced emergence at 35 °C/28 °C and delayed and reduced emergence at 40 °C/28 °C. In drier cores (drained 8 days) at 35 °C/28 °C, priming advanced germination time and did not decrease final percentage emergence. These results confirmed earlier field observations that the effect of priming in maize can vary and lead to positive, neutral or negative effects. Priming decreased the optimum and ceiling temperatures for germination, and unlike untreated seeds, the relationship between germination rate and sub-optimal temperature was not linear in all cases. Pre-humidifying seeds did not enhance the effect of priming, but aerating the soak water did. These results indicate that variable results from priming recorded in the field were not due to imbibitional damage, but may result from the negative effects of hypoxia during soaking exacerbated by moist conditions and high temperatures at sowing. These effects differed between seedlots of different cultivars, indicating the importance of selecting more tolerant maize hybrids to reduce variation in response to priming following sowing in the field. The implications of these findings for the use of primed seeds in the field are discussed.     

Assessment of avoidable losses and economic injury levels for the sorghum head bug, Calocoris angustatus Leth. (Hemiptera:Miridae) in India

Avoidable losses and economic injury levels (EILs) were computed for the sorghum head bug, Calocoris angustatus Leth., on three cultivars during three rainy seasons (1985–1987) at ICRISAT. Grain yield in plots protected with 2–5 insecticide sprays (carbaryl at 500 g a.i./ha) between the half-anthesis and the dough stage was significantly higher than in untreated plots, with cost-benefit ratios > 1. Plots that were not protected at half-anthesis and/or complete-anthesis, and at milk and dough stages, suffered a significant loss in yield. Bug damage spoiled the grain quality in terms of germination, 1000-grain mass, grain hardness and percentage floaters. Three to four sprays between complete-anthesis and the dough stage prevented a significant reduction in grain quality. Head bug density at half-anthesis, complete-anthesis, milk and dough stages was significantly and negatively associated with grain yield. Bug density at different stages explained 43–94% of the variance in yield. Direct effects of bug numbers at the milk stage and the indirect effects of head bug density at other stages through the milk stage contributed towards maximum reduction in yield. Maximum avoidable losses were recorded in cultivar ICSV 1 (88·6%), followed by CSH 1 (69·9%), and CSH 5 (53·9% in 1986 and 55·0% in 1987). Loss in grain yield/ha due to one insect/panicle at half-anthesis and that based on natural increase, were 548 and 232 kg in CSH 5 during 1986 and 1987, respectively, 251 kg in ICSV 1, and 77 kg in CSH 1. EILs based on a cost-benefit ratio of 1:1 ranged from 1·3–1·4 insects/panicle for CSH 1, 0·4 for ICSV 1, and 0·4–0·6 and 0·2–0·4 for CSH 5 during 1986 and 1987, respectively. Simple cost estimates for insecticide sprays and the resultant saving in grain yield are a useful tool for decision-making in pest management.     

Effect of soil solarisation and mouldboard ploughing on black dot of potato, caused byColletotrichum coccodes

Summary Preplant soil solarisation and mouldboard ploughing to a depth of 30 and 60 cm respectively were evaluated in two field experiments for the control ofColletotrichum coccodes causing black dot of potato. Solarisation reduced disease incidence by 45% when tarping was done for eight weeks and temperatures reached 56°C in the top 5 cm of soil. With a six week tarping period and lower maximum temperature (50°C) the reduction in disease was a nori-significant 25%. Mouldboard ploughing to a depth of 30 cm reduced black dot by 34% and was twice as effective as ploughing to a depth of 60 cm.     

Effects of combined application of potassium phosphite and fungicide on stem and sheath disease control,yield, and quality of rice

Phosphite has been shown to suppress some diseases in different plant species but disease control in rice has not been investigated. In 2012/13 and 2013/14 potassium phosphite was sprayed at 1775 g ha⁻¹ and 3550 g ha⁻¹ in field plots of rice in Uruguay to determine if phosphite alone or in combination with label rates of a mixed strobilurin and triazole fungicide could be used to effectively control stem rot and aggregate sheath spot in irrigated rice. Six treatments consisting of different combinations of potassium phosphite alone or with a fungicide and an unsprayed control were assayed in one application at late-boot to early-heading. Phosphite alone in single and double rate slightly reduced severity and incidence of stem rot and produced a small yield increase over the unsprayed control. Fungicide at a 50% label rate with phosphite reduced stem rot severity and incidence to a similar level as the fungicide alone applied at the label rate. Disease severity was reduced by approximately 25% and incidence by 17–20% when compared with untreated control. Yield increase was 5% for both treatments over the unsprayed control. Fungicide combined with phosphite at single and double rates reduced stem rot severity by 40–45% and incidence by 34–38% when compared with untreated control, with yield increased by 10% over the unsprayed control and 5% over plots treated with a fungicide. These results indicate that a single application of potassium phosphite combined with fungicide can be used efficiently to manage of rice stem diseases.     

Effects of insecticides applied to control cucumber beetles (Coleoptera: Chrysomelidae) on watermelon yields

Foliar insecticides applied to control the striped and spotted cucumber beetles, Acalymma vittatum (Fab.) and Diabrotica undecimpunctata howardi Barber, on watermelon, Citrullus lanatus, were of little or no value in three studies conducted in two locations over 2 years. However, an at-planting application of the systemic, soil insecticide carbofuran resulted in higher early yields, although the differences were not statistically significant in small plots. In 1991, large plots comparing carbofuran-treated watermelons with untreated watermelons in two commercial fields showed large and statistically significant increases in melon yield when carbofuran was applied, especially in early yield. Studies in 1992 and 1993 showed that the application of carbofuran at planting stimulated root and shoot growth after transplating and increased yields when compared with untreated plots, plots treated with methyl bromide, or another soil insecticide, terbufos. These studies suggest that carbofuran may be acting as a growth stimulant, as well as an insecticide.     

Management of silver scurf (Helminthosporium solani) with fungicide seed treatments and storage practices

Thiabendazole insensitive strains ofHelminthosporium solani, the causal agent of silver scurf, make controlling the disease with seed treatment difficult. Potato tuber seed treatments and environmental storage management practices were investigated as means to minimize silver scurf. Fungicide seed treatments were evaluated for control ofH. solani; disease was evaluated during the growing season, at harvest, and after 5 months of storage. Silver scurf was observed on progeny tubers eleven weeks after planting. Fungicides that reduced silver scurf incidence and severity on the seed resulted in reduced incidence and severity of the disease in the progeny tubers at harvest and significantly lower disease ratings after storage. Only small increases in disease incidence (0-8%) were seen after storage. Thiophanate-methyl with mancozeb, Captan with mancozeb, and fludioxonil were among the most effective in reducing the incidence and severity of silver scurf on seed and in progeny tubers (Incidence on progeny tubers at harvest for these three treatments were 3%, 9%, and 8% respectively). Thiophanatemethyl alone was not effective for control of silver scurf (48% incidence compared to 43% incidence for the untreated control). Environmental conditions in storage affected disease development. Reduced humidity (85%) during the curing period (0–3 weeks after harvest) significantly reduced (11%) the surface area of tubers infected with silver scurf. Free moisture on the tuber surfaces during storage significantly increased (15%) tuber surface area infection.H. solani was shown to survive in soil and on some potato storage building materials for up to 9 months. The silver scurf disease of potatoes can be suppressed using effective seed treatment and storage management.     

Relationship between sorghum ergot, sowing dates, and climatic variables in Morelos, Mexico

The importance of sowing dates to the development of sorghum ergot (Claviceps africana) was determined at Tlayca, Morelos, Mexico during the rainy seasons of 1998–2000. Annual variation in ergot incidence occurred, with the highest levels in the year 2000. Sowing dates between June 15 and July 14 had the lowest levels of ergot incidence and severity. Temperatures below 15°C 3 weeks before flowering increased ergot incidence. The optimal weather factors for ergot development were a mean day temperature of 25°C, a maximum relative humidity of 96%, a maximum temperature of 28°C, and nighttime relative humidity of 86%.     

Effect of cultural practices and fungicides on Phytophthora fruit rot of watermelon in the Carolinas

Phytophthora fruit rot of watermelon, caused by Phytophthora capsici, is an important and emerging disease in Southeastern U.S.A. The effects of two cultural practices (raised bare ground and raised plastic mulched beds) used for growing watermelon and different fungicide treatments on development of Phytophthora fruit rot were evaluated. The experiments were conducted over three years (2005-2008) at research stations in North Carolina and South Carolina, U.S.A. Fungicides were applied at weekly intervals on the diploid cv. Mickey Lee for an average of five applications. Fruit rot incidence was recorded at the end of each experiment. Fruit rot incidence in the non-treated plots was 66% across two states and six trials. Overall, the levels of fruit rot on the raised bare ground and raised plastic mulched beds were not significantly different. Based on percent disease reduction relative to the non-treated check plots, the fungicide Captan was the most effective across years and locations (range = 23-70%, mean = 57%), followed by mandipropamid (25-65%, mean = 50%), fluopicolide (24-65%, mean = 43%) and cyazofamid (0-48%, mean = 31%). Mefenoxam, the current standard treatment reduced fruit rot by 8-28% (mean = 18%). The addition of copper hydroxide to the spray mix did not significantly enhance effectiveness of Captan or mandipropamid. The variability in fungicide efficacy observed in these experiments across locations and years demonstrates the importance of environmental conditions in disease development and management. Even when the most effective fungicides are used, heavy losses may occur when conditions are highly favorable for disease development. Ultimately, effective control of Phytophthora fruit rot of watermelon will require an integrated management strategy that includes well-drained fields, water management and crop rotation in addition to fungicides.     

Effects of soil solarization on soil-borne populations ofPythium aphanidermatum andFusarium solani and on the potato crop in Tunisia

Summary Soil solarization by mulching with polyethylene for 60 days during summer in Tunisia, was effective in reducing dramatically to a depth of 30 cm inoculum levels ofFusarium solani (Fs) from 3,000 to 450 propagules gram⁻¹ of dry soil. Population densities ofPythium aphanidermatum (Pa) were reduced from 1,700 and 3,000 to 0.5 and 1 propagule gram⁻¹ of dry soil in the top 15 cm and at 1–30 cm depth, respectively. After a subsequent autumn potato crop, populations ofPa remained very low in the previously solarized soil whereas propagule density in non-solarized soils was similar to the initial density. Also, inoculum level ofFs increased by 40% in nonsolarized soils while it remained unchanged in solarized soils, suggesting microbial processes that prevented soil reinfestation. All the annual weeds were eradicated by solar heating but not the perennial weedConvolvulus arvensis. Potato plant growth and yields were improved in solarized plots.     

Peanut variety response to postemergence applications of carfentrazone-ethyl and pyraflufen-ethyl

Field experiments were conducted in the south Texas and Texas High Plains area in 2005 and 2006 to evaluate peanut variety tolerance to carfentrazone-ethyl and pyraflufen-ethyl. Lactofen was used as the standard. Carfentrazone-ethyl at 0.03 and 0.04 kg ai/ha, pyraflufen-ethyl at 0.003 and 0.004 kg ai/ha, and lactofen at 0.22 kg ai/ha were applied 35 days after planting (DAP) in south Texas and 51–56 DAP in the High Plains area in weed-free plots. Peanut cultivars selected for evaluation were those normally used in each area. In south Texas, Tamrun 96, Tamrun OL 01, and Tamrun OL 02 were evaluated while in the High Plains area, Flavor Runner 458, GP-1, and Tamrun OL 02 were evaluated. No peanut cultivar by herbicide interaction was observed in south Texas but an interaction did occur in the High Plains. In south Texas, peanut stunting was 10% or less with both herbicides and rates. In 2005, carfentrazone-ethyl at 0.04 kg/ha resulted in a yield reduction when compared with the untreated check while in 2006 both rates of carfentrazone-ethyl and the high rate of pyraflufen-ethyl reduced yield compared to the untreated check. No grade differences were noted among herbicide treatments. In the High Plains area, the high dose of both carfentrazone-ethyl and pyraflufen-ethyl caused the greatest peanut injury (at least 25%) compared with lactofen (6% or less). In 2005, the high dose of pyraflufen-ethyl and lactofen reduced yield compared with the untreated check while in 2006 both carfentrazone-ethyl and pyraflufen-ethyl reduced yield compared with the untreated check.     

The effect of seed-and soilborne inoculum ofColletotrichum coccodes on the incidence of black dot on potatoes

Summary Soil in a potato field naturally infested with black dot (Colletotrichum coccodes) was fumigated with methyl bromide at 126 g m⁻² or left unfumigated. Potato seed tubers (cv. BP1) uninfected, lightly infected (1–25% surface affected), severely infected (26–100% surface affected) and severely infected withC. coccodes but dusted with prochloraz manganese chloride as Octave 2.5% DP at 750 g per 100 kg seed were planted in fumigated and unfumigated soil. When harvested, the incidence of black dot on the progeny of infected seed planted in unfumigated soil was twice that of progeny in fumigated soil, with progeny of uninfected seed having a 68.5 times higher disease incidence in unfumigated soil. Black dot on progeny tubers was reduced by pre-treatment of seed with prochloraz in fumigated soil only. With black dot infested fields, planting disease-free seed or treating seed with fungicides would not decrease disease on progeny tubers.     

Efficacy of metam sodium for controllingVerticillium dahliae prior to potato production in sandy soils

The efficacy of metam sodium (MS) for controlling Verticillium wilt of potato was evaluated in two field experiments conducted in a sandy soil, heavily infested withVerticillium dahliae, and previously treated with MS. Compared to control plots where AUDPC value was 3141 (in 1999) and stem infection was 71.2% (in 2000), in plots treated with 600 L MS/ha AUDPC values were reduced by 57% to 80%, and stem infection was reduced by 49–54%. The incidence of infected dry stems, evaluated at the end of each season, was significantly reduced by all MS treatments, especially by 900 L/ha applied to a 60-cm depth (1999). Disease incidence in daughter tubers was also significantly reduced by all MS treatments. Yields obtained with 600 L/ha MS applied to a 30-cm depth were 32% and 21% higher than in the control in 1999 and 2000, respectively. In plots treated with 600 L/ha MS applied to a 60-cm depth yields were 17% and 28% higher than in the control in 1999 and 2000, respectively. With 900 L/ha MS applied to a 60-cm depth, yield was 21% higher than in the control in 1999. The yield of the low MS dose (300 L/ha), applied only in 2000, was not significantly different from the control. The differences in yield were due to the greater percentage of tubers larger than 45 mm. Yield reduction was highly correlated with disease severity expressed as AUDPC (in 1999 experiment). The net income in the 600 L MS/ha treatments was higher than in the control in both experiments. No indication of enhanced biodegradation was observed in the present study.     

外源信号物质诱导人参抗人参锈腐病的作用研究

探讨外源水杨酸(SA)茉莉酸甲酯(MeJA)诱导人参抗锈腐病的效果,以期通过施入外源物质来提高人参植株的抗性.测定了0～800mg·L-1不同浓度SA和MeJA溶液对人参锈腐病菌的影响,利用筛选的浓度(200 mg· L-1)处理二年生人参移栽苗,接种人参锈腐菌,调查人参锈腐病的发病率和病害严重度.结果表明,浓度为200 mg· L-1的SA和MeJA溶液对人参锈腐病菌无直接毒害作用,而经SA和MeJA处理的人参植株锈腐病发病率和病害严重度显著降低,SA的诱抗效果优于MeJA.     

Failure of metalaxyl to eradicate late blight on potatoes (cv. Green Mountain)

Eradication of potato late blight with metalaxyl was examined in field studies from 1980 to 1983. In 1980 disease outbreak and subsequent progression were late and moderate. In 1981 and 1983, they were early and moderate to severe, while in 1982 the disease became established later in the season but developed rapidly and resulted in moderate to severe damage to foliage. There were no significant differences in foliar disease severity among metalaxyl treatments. While treated plots generally showed significantly less foliar damage throughout the season than untreated plots, except in 1983, the reduction in foliar damage in September was only 30–50% in 1980, 10–20% in 1981, 20–30% in 1982, and less than 10% in 1983. Sporulation of the pathogen occurred readily on infected leaves of both treated and untreated plants. There were no significant differences in yield, but application of metalaxyl to foliage significantly reduced the incidence of late blight tuber rot.     

A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights. 1. Sward characteristics

Two 1·0 ha plots of a late-heading diploid perennial ryegrass (var. Contender) and a late-heading tetraploid ryegrass (var. Condesa), and two 1·4 ha plots of the tetraploid with Aberystwyth S184 small-leaved white clover, were direct sown in May 1987. Over the three years 1988–90 they were continuously stocked by Mule ewes with Suffolk-cross twin lambs, from early April to the end of August, at a target sward surface height (SSH) of 4–6 cm on one set of plots (constant swards) and, on the other set, al 4–6 cm rising after June to a target 6–8 cm (rising swards). The heights were achieved by variable stocking. Fertilizer N was applied only to the grass plots at the rate of 150- 180kgN ha^-1 annually.
SSH was mainly within the target 4–6 cm, after higher initial heights at turnout in 1988and 1990. Mean heights of the constant swards (April- August) averaged 5·53, 4·43 and 5·04cm in the three years. The rising swards (July-August) increased in height over the constant swards by an average of 0·88, 0·48 and 0·55 cm, in successive years.
Clover content of the herbage mass dry matter in the grass/clover swards increased over each grazing season to average 13·0, 26·5 and 21·2% in the three years, with a high mean stolon density of 130 in m^-2 in August 1990. Ryegrass tiller densities in year 3 were 23% higher in the diploid than in the tetraploid swards, which had 43% more than the 10000 tillers m^-2 of the tetraploid ryegrass/clover swards.
It is concluded that the combination of a densely stoloniferous small-leaved clover with the open growth habit of a tetraploid ryegrass can achieve swards of high clover content under continuous sheep stocking.     

The effects of regrowth and maintenance height on a grass sward with a high density of tillers

A perennial ryegrass sward was grazed by sheep in April 1993 to a target sward surface height (SSH) of 3 cm to create a high density of grass tillers. From 3 May, the sheep were removed and small plots were established on the sward, when the average tiller density (± s.e.) was 35 900 ± 420 live tillers m⁻². Different regrowth treatments were then imposed by allowing plots to regrow to target SSHs of 6 cm (18 g dry matter (DM) M⁻²), 9 cm (78 g DM m⁻²), 12 cm (132 g DM m⁻²) or 15 cm (197 g DM m⁻²). The plots were then maintained by cutting at either 6 or 9 cm SSH until the end of the experiment on 30 September. Live tiller density was reduced by regrowth beyond 8.9 cm (78 g DM m⁻², P <0.001) and leaf-stem ratio and in vitro organic matter digestibility were reduced by regrowth beyond 6.1 cm (18 g DM m⁻², P < 0.05). The effect on live tiller density was sustained through the remainder of the season. From the beginning of June to the end of September, maintenance of SSH at an average of 9.1 cm compared with 6.4 cm also resulted in lower live tiller density, live-dead tiller ratio and leaf-stem ratio and higher herbage mass (at least P < 0. 05). There were significant interactions between regrowth SSH and maintenance SSH, so that leaf-stem ratio, live-dead tiller ratio and live tiller density were reduced by regrowth to a SSH of 16–4 cm followed by maintenance at 9.1 cm, compared with regrowth to 6.1 cm and maintenance at 6.4 cm.