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Item Direct and indirect impacts of the Tuberolachnus salignus (Hemiptera: Aphididae) invasion in New Zealand and management alternatives(Published by Oxford University Press on behalf of Entomological Society of America, 2022) Tun KM; Minor M; Jones T; Clavijo-McCormick AC; Joyce AInvasive insects are a serious problem in New Zealand, and their introduction and successful establishment are predicted to increase with global commerce and climate change. A recent introduction to New Zealand is Tuberolachnus salignus (Gmelin), a large aphid that attacks mainly willows but also other plants such as poplars, apples, and pears. It was first reported in 2013 but has since then spread rapidly throughout the country. We conducted a 2-yr study exploring the direct (on the host plant) and indirect (on other organisms) impacts of the aphid, in a field setting including 15 willow clones selected to represent the variety of species and hybrids present in New Zealand. Our research revealed great variation in the level of resistance/susceptibility of different clones and suggested a trade-off between reproduction, growth, and defense. We investigated the indirect effects of the aphid on honeydew foragers and on the soil ecosystem, through honeydew production and deposition, revealing complex cascading effects involving multiple trophic levels. We also explore and discuss management alternatives including the replacement of willows for native species or resistant varieties, the use of biological control agents, and the feasibility of chemical control. This work is one of few studies on the complex ecological effects of invasive phytophagous insects and could serve as a model for future research and to inform pest management. To conclude, we identify gaps in the knowledge and highlight aspects requiring further research.Item Growth, management and nutritive value of willows (Salix spp.) and other browse species in Manawatu, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.) in Plant Science at Massey University, Palmerston North, New Zealand(Massey University, 1998) Oppong, Samuel KingsleyPastoral farming in New Zealand depends mainly on the grazing of ryegrass (Lolium perenne) and white clover (Trifolium repens). These pastures yield less during dry summers and farmers are then faced with feed shortages. This study revealed the potential of deciduous willows, Salix matsudana x alba and Salix kinuyanagi as useful supplementary fodder during dry summers. The species can be managed under cut and carry or in situ browsing systems. The use of the Salix spp. as drought fodder is a viable option for pastoral farmers to assist them to overcome pasture feed shortages while maintaining their role in conserving soil. Three experiments were conducted to determine (1) the effects of cutting height and frequency on browse yield and quality of deciduous Salix spp., compared with Dorycnium rectum, a small leguminous shrub and (2) the effects of planting stocks and fertiliser use on the yield and quality of the Salix species. Experiment 1, conducted at HortResearch, Aokautere (10 km from Palmerston North) demonstrated that edible dry matter (DM) yield of the Salix spp. and D. rectum was uninfluenced by stump height and frequency of harvest. S. matsudana x alba outyielded S. kinuyanagi and D. rectum. The in vitro organic matter digestibility (OMD) and nitrogen (N) concentration of the three species were: S. matsudana x alba (670 g kgDM-1 and 21 g kgDM-1), S. kinuyanagi (613 g kgDM-1 and 18 g kgDM-1) and D. rectum (665 g kgDM-1 and 22 g kgDM-1). Experiments 2 and 3 were conducted at AgResearch Grasslands, Ballantrae (25 km from Palmerston North). Experiment 2 showed that unrooted stem cuttings produced as much foliage as rooted stem cuttings, and the former are recommended due to their cheaper establishment. S. matsudana x alba consistently outyielded S. kinuyanagi even though DM yields were lower than at Aokautere. Experiment 3 revealed that DM yields of the Salix species were unaffected by fertiliser application. The low DM yield at Ballantrae may be due to the effects of strong winds and low temperatures. At both Aokautere and Ballantrae, S. kinuyanagi (255 vs. 289 g kgDM-1) had higher total condensed tannin concentrations than S. matsudana x alba (60 vs. 154 g kg DM-1). Two experiments were conducted at AgResearch Grasslands, Palmerston North to determine (1) the leaf lifespan and effect of leaf maturation on leaf quality of the Salix spp. and the legume Chamaecytisus palmensis, (2) the appropriate time to cut the Salix spp. to optimise regrowth and browse quality for summer use, and (3) the changes in non-structural carbohydrate reserves associated with defoliation. The long leaf lifespan of the Salix spp. (6.5 months) and Chamaecytisus palmensis (5.5 months) indicated that the green standing biomass could be retained until needed in summer. The leaves of the Salix species and Chamaecytisus palmensis declined in N concentration and other nutrients at 3 months, which was longer than for those of most herbaceous species (1-2 months) during most times of the year. Leaf N concentration in all three species at each harvest met the recommended level (17 g kgDM-1) for a diet adequate for a lactating ewe rearing a lamb. S. matsudana x alba yielded 70% more DM than S. kinuyanagi when cut in mid-spring. Sucrose comprised over 90% of the total soluble carbohydrate concentration in the roots of S. matsudana x alba defoliated once and three times in the growing season. Two experiments were also conducted at Massey University to determine (1) the effect of browsing intensity and frequency on the regrowth of the Salix spp. and C. palmensis, and (2) sheep preference for these browse species at different times of the growing season. Regrowth of S. matsudana x alba and C. palmensis was similar under heavy or light browsing whereas heavy browsing in S. kinuyanagi increased regrowth in woody stem and total DM yields. S. matsudana x alba was the preferred species. Sheep biting rate, percent time spent browsing species and preference rating of species were higher in summer than autumn for S. matsudana x alba and similar for C. palmensis in both seasons. For S. kinuyanagi, these variables were higher for autumn and almost zero for summer browsing. The two Salix spp. will complement C. palmensis, when grown in moist sites, where Chamaecytisus trees have low survival. The Salix species under proper management will provide useful supplementary feed for livestock during summer.Item The effect of poplar (Populus spp.) and willow (Salix spp.) supplementation on the reproductive performance of ewes grazing low quality drought pasture during mating : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science in the Institute of Veterinary Animal and Biomedical Science, Massey University(Massey University, 2004) McWilliam, Eileen Lee HafnerA series of grazing experiments was conducted, in the summer/autumn of 2001, 2002 and 2003, to investigate the effects of poplar (Populus spp.) and/or willow (Salix spp.) supplementation, during mating, on ewe production and reproduction when grazing drought pasture. Each experiment involved a rotational grazing system with 300 mixed-age Romney ewes, divided into three groups of 100 ewes each. In each year, all ewes were offered low quality simulated drought pasture, containing more than 60% dead matter, at an allowance sufficient to provide a potential desired intake of 0.70 kg dry matter (DM)/day, for periods of 9 to 12 weeks, including two mating cycles. Mean pre-and post-grazing pasture masses averaged over the three years were 1100 and 600 kg DM/ha. The pasture consumed in all years was typical of pasture available to grazing livestock in a drought; it was high in neutral detergent fibre (NDF; approximately 600 g/kg DM), low in organic matter digestibility (OMD, approximately 0.52) and metabolisable energy (ME; approximately 7.5 MJ/kg DM) and contained approximately 20 g nitrogen (N)/kg DM. The supplementary poplar and willow diets were always superior to drought pasture consumed by the ewes, being higher in OMD (approximately 0.67), ME (approximately 10 MJ/kg DM) and total N (approximately 26 g/kg DM) and lower in NDF (approximately 383 g/kg DM). Tree fodder diets also contained substantial concentrations of the secondary compounds condensed tannin (CT; range 7 to 52 g/kg DM), salicin (approximately 2 g/kg DM) and other phenolic glycosides (approximately 21 g/kg DM), with willow (27 to 52 g/kg DM) containing greater concentrations of CT compared with poplar (7 to 19 g/kg DM). Mean diameter of the tree fodder stem consumed during the series of experiments was approximately 7 mm for poplar and 4 mm for willow with the diameter increasing over the experimental periods in four cases out of live (P<0.05). After the supplementation period, the three groups were joined together and grazed on perennial ryegrass/white clover pasture until the conclusion of each experiment at weaning. In all years, the effect of poplar and/or willow supplementation on ewe live weight (LW) and body condition score (BCS) change; the proportion of lambs (reproductive rate) at pregnancy scanning, lambing, docking and weaning; and wool production and staple length from ewe fleeces with approximately 11 months growth, were measured. Experiment 1 was designed to determine how much poplar fodder needed to be fed to increase ewe production and reproduction over a 71-day supplementation period. The experiment involved a high supplementation group, offered 1.5 kg fresh poplar/ewe/day; a low supplementation group, offered 0.75 kg fresh poplar/ewe/day; and a control group that was offered no tree fodder. Ewes in the high and low treatments lost less LW (-67 and -71 vs. -82 g/day; P<0.05) and BCS (-0.78 and -1.27 vs. -1.31 units; P<0.05) compared with unsupplemented ewes. Reproductive rate was relatively low in the control group (121 lambs born/100 ewes mated), with poplar supplementation increasing ewe reproductive rate by approximately 20% units (P<0.05) and 30% units (P<0.001) for the low and high treatment groups, respectively, at scanning, lambing, docking and weaning. The increase in reproductive rate in supplemented ewes was due to increases in both conception rate (number of ewes pregnant/100 ewes mated) and fecundity (number of lambs born/100 ewes mated). Experiment 2 was designed to determine if production and reproduction varied between ewes fed poplar versus willow at the same rate of supplementation, 1.4 kg fresh forage/ewe/day, for 87 days. Again, reproductive rate was relatively low in the control group (133 lambs born/100 ewes mated), with willow supplementation reducing L.W loss (-86 g/day vs. -103 g/day; P<0.01) and increasing reproductive rate by 15%, 17% 21% and 20% units at ultrasound scanning (P=0.097), lambing (P=0.087), docking (P<0.05) and weaning (P=0.058), respectively. The increase in reproductive rate was due to an increase in fecundity; supplementation did not affect conception rate in this experiment. Unlike the previous experiment, poplar supplementation showed no effect on reproductive rate, despite the increase in DM intake and the apparent reduction in LW loss of 9 g/day (P-0.11). It is likely that severe contamination of the poplar fodder with Melampsora larici-populina, or poplar leaf rust, confounded the results. Building on the results of the first two grazing trials, the next step was to determine the period (days) of tree fodder supplementation necessary to achieve a response in reproductive rate. Experiment 3 involved ewes fed 1.3 kg fresh willow/ewe/day for a 'long' period, 63 days including 6 weeks of mating, and a 'short' period, 31 days including 3 weeks of mating. The mating period commenced on the same day for all groups and lasted for 6 weeks. Willow supplementation for 63 days reduced ewe LW loss (-96 g/day vs. -147 g/day; P<0.05) and BCS (-0.79 VS. -1.09; P<0.05) loss, compared with unsupplemented ewes; however, it did not increase reproductive rate at scanning and lambing. The lack of response in willow-supplemented ewes was likely to be due to toxic concentrations of zearalenone (1.5 mg/kg DM), an oestrogenic mycotoxin, in the drought pasture during mating, which confounded the results by negating any potential benefits due to increased nutrient intakes. Willow supplementation for 63 days did increase reproductive rate at weaning by 13% units, due to a 9% unit (P<0.05) reduction in post-natal lamb mortality, from 17.1 to 8.4%. Supplementation for 31 days did not appear to influence ewe reproduction and production parameters. Overall, the rate of LW loss was greater in Experiment 3 compared with the first two experiments. Seven indoor in vivo digestibility experiments were conducted at the following times; early April 2001 (poplar), February, March and April 2002 (all poplar), and December, March and April 2003 (all willow). Each 14-day trial involved 6 male cryptorchid lambs, individually fed in metabolism cages. The experiments showed that the digestibility of poplar and willow tree fodder declined from late spring to autumn (P<0.05), but that the decline was much smaller than the decline in digestibility of grass-based pastures in New Zealand over the same time period. The experiments also showed that mean ME and digestibilities were generally higher for willow than for poplar. The seven in vivo digestibility coefficients were then used to develop a standard curve for in vitro prediction of in vivo digestibility, this standard was used to analyse all unknown tree fodder samples from the three grazing experiments. Results from the three grazing experiments showed that supplementing ewes grazing drought pasture during mating with poplar and willow tree fodder consistently increased DM intake by 0.25 to 0.33 kg DM/ewe/day for ewes offered 1.3 to 1.5 kg fresh willow or poplar each day and increased calculated total DM intakes from 0.67 to 1.03 kg DM/ewe/day in Experiment 1, from 0.59 to 0.86 kg DM/ewe/day in Experiment 2 and from 0.47 to 0.75 kg DM/ewe/day in Experiment 3. Supplementation also consistently reduced LW loss and loss in BCS and substantially increased lambing rate through increased conception rate and fecundity and reduced post-natal lamb mortality. The effects on LW and BCS gradually declined in the post-treatment period and were no longer evident by commencement of lambing. There was no effect of supplementation on wool production or staple length in any of the experiments. One of the unexpected results of the experiments was an average 34% reduction in post-natal lamb mortality over three years, due to willow/poplar supplementation of ewes during mating. Initial results showed that despite significant increases in fecundity in supplemented ewes in 2001 and 2002, post-natal lamb mortality was not increased. This result, combined with a statistically significant reduction in lamb mortality in Experiment 3 (P<0.05), in the absence of any differences in fecundity between the groups, suggested that tree fodder supplementation during mating may have reduced lamb mortality in all three years, but that the effect was masked by the increase in reproductive rate in the first two experiments. Therefore, data from the three field trials were combined and analysed by adjusting all mortality data to equal birth rank and sex; this showed a significant reduction due to supplementation (P<0.05) with no treatment-year interaction. The increase in ewe production and reproduction in supplemented ewes was likely due to increases in nutrient intake, through increased DM, ME and CP intakes, prior to and during mating and to increased outputs of undegradable dietary protein and microbial protein from the rumen, per unit of crude protein consumed, thus increasing amino acid absorption. An increase in ovulation rate of 1.5 % units/MJ of digestible energy consumed (Smith 1985) should result in increases in ovulation rate due to tree fodder supplementation of only 5 and 4% units in 2001 and 2002, respectively; however, the increases in scanning rate were substantially greater at 41 and 16% units. Therefore, it is possible that the majority of the increase in reproductive rate was due to increased essential amino acid absorption, which is consistent with increases found in ewes mated on CT-containing forages such as Lotus corniculatus (Birdsfoot trefoil). Gross margin analyses using actual data from unsupplemented ewes in each of the three grazing trials compared with Riverside Farm's commercial ewes from the same years showed that drought reduced scanning rates by an average of 22.4% and wool production by 20% and that this reduction decreases sheep production income by approximately $14/ewe. Further analysis showed that almost half the cost ($6/ewe) could be recovered by supplementing ewes with tree fodder in a drought. On a whole farm basis this represents $58/hectare cost benefit due to tree fodder supplementation. Fungal contamination was a significant factor in the results obtained in Experiments 2 and 3. In all years, simulated drought pasture contained metabolites of zearalenone and the trichothecenes nivalenol and deoxy-nivalenol, produced by Fusarium fungi, while in Experiment 2 the poplar was severely contaminated with Melampsora larici-populina, or poplar leaf rust. Zearalenone concentrations in pasture were at their greatest in Experiment 3 and increased to over 2 mg/kg DM during the mating period. This may explain the lack of increase in reproductive rate expected in willow-supplemented ewes in Experiment 3, which was a feature of previous experiments; however, it did not explain the much greater loss in ewe LW in Experiment 3. Nivalenol (NIV) and deoxy-nivalenol (DON) are common trichothecene toxins found in New Zealand pasture and were found in pasture samples from all three experiments, however, the concentration in Experiment 3 was three- to four-fold greater than in previous experiments. Reports have suggested that trichothecenes may be partly responsible for the reduced growth of otherwise healthy livestock grazing dry autumn pasture, often referred to as 'ill thrift'. However, based on evidence from dosing experiments, it is unlikely that the quantities of NIV and DON present in pasture in Experiment 3 accounted for all of the greater LW loss seen in this experiment. This suggests that these toxins are likely to be indicators of other more potent fungal toxins, which have a much bigger impact on livestock health and production. It is likely that fungal toxins contribute more to reduced reproduction in breeding ewes and to ill thrift in young stock grazing dry autumn pastures in East Coast regions than is currently acknowledgedItem Effects of willow (Salix spp.) browse upon ewe reproduction and rumen microbiology under drought feeding conditions : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2007) Pitta, Dipti WilhelminaA series of grazing experiments were conducted in the summer/autumn of 2003 and 2004 at Massey University's Riverside dryland farm near Masterton in Wairarapa on the East Coast of NZ, to study the effects of grazing willow fodder blocks (6,000 stems/ha) upon the production and reproductive performance of ewes relative to ewes grazing drought pastures. Drought pastures were simulated in this study and included short drought pasture and long drought pasture. Pasture with a low pre-grazing mass of approximately 1500 kg OM/ha, a dead matter content of >50 % and a sward height of 5-7 cm was defined as short drought pasture typical of drought conditions. Long drought pasture was similar to pasture growing in the willow fodder blocks, with a pre-grazing pasture mass of >4000 kg OM/ha, a sward height of > 30cm and a dead matter content of 30-60 % . Willow fodder blocks were established on low-lying wet, marshy areas of the farm that had very low or zero productivity in the undeveloped state. Pasture development in the fodder blocks was noticed with the growth of unsown grasses and legumes, as the areas dried up following the planting of willow stakes, due to evapotranspiration from the trees. Forage in the willow fodder blocks included both trees and pasture that was grown under the trees. The nutritive value of short drought pasture was low with an ME of 8 MJ/kg O M ; long drought pasture ranged between 8- 1 0 MJ ME/kg DM; willow pasture contained 8 MJ M Elkg DM in 2003 and 1 0 MJ ME/kg OM in 2004. The nutritive value of edible willow tree (<5 mm diameter) was superior to drought pasture with an ME of > 10 MJ/kg OM. The concentrations of the secondary compounds such as condensed tannins (CT ; 30- 40 glkg OM) and phenolicglycosides ( PG ; 1 5-35 g/kg DM) were higher in willow trees compared to their concentrations (CT ; 2-3 g/kg DM) and (PG; 2-9 g/kg OM) in control drought pastures. Experiments involving short drought pasture, long drought pasture and willow fodder blocks as treatment groups were grazed by ewes for 10 weeks in regular breaks from mid February to early May. Ewes were mated during this period and were joined together after mating and grazed on normal pasture until weaning. Live weight (LW) change and body condition score (BCS) were recorded throughout the experiments, whilst reproductive performance of ewes was measured as the number of lambs recorded at ultrasound pregnancy scanning, lambing, docking and weaning. Measurements on wool production were also recorded at weaning. In 2003, experimental ewes grazed control drought pastures (short and long) and willow fodder blocks (restricted and full access) as treatment groups (n= 1 00 ewes/group; Chapter 2). Ewes grazing short drought pasture had an allowance of 0.8 k g DM/ewe/d whilst ewes with restricted access had an allowance of 0.8 kg DM/ewe/d from drought pasture and 0 .4 kg OM/ewe/d from willow fodder blocks. Ewes in full access treatment group had no access to pasture but were confined to willow fodder blocks at an allowance of 2.0 kg OM/ewe/d, which was the same allowance given to long drought pasture ewes. Ewes grazing short drought pasture lost weight at approximately 1 00g/d and recorded a low reproductive rate (90 lambs weaned/100 ewes mated) with a high proportion of single lamb births. Live weight loss was significantly reduced to 40 g/d in ewes grazing willow fodder blocks (full access) with a 20% units increase in reproductive rate due to more multiple births (P <0. 05). Ewes grazing long drought pasture performed intermediate to ewes with full access to fodder blocks and ewes grazing short drought pasture, whilst ewes with restricted access performed similar to ewes grazing short drought pasture. In 2004 (Chapter 3), the restricted access to willow fodder blocks treatment was eliminated from the study and the number of ewes was increased to 165 ewes per treatment group. Performance of ewes grazing short drought pasture was similar to that of ewes grazing short drought pasture in 2003 , with ewes loosing live weight (40g/d) and a low reproductive rate (90 lambs weaned/l00 ewes mated) whilst ewes grazing long drought pasture gained L W (54 g/d) and had a higher reproductive rate (P<0.05). Ewes grazing willow fodder blocks performed better than ewes grazing short drought pasture by maintaining L W and their reproductive rate was intermediate to ewes grazing short and long drought pasture. In 2005, a short grazing trial with rumen fistulated sheep was conducted to study the effect of supplementing willow to ewes grazing drought pastures upon plasma amino acid concentrations (Chapter 4) and upon the microbiology of the rumen (Chapter 5 and 6). Grazing occurred during summer/autumn for 10 weeks with two treatment groups; control (short drought pasture; n=7) at an allowance of 0.8 kg DM/ewe/d and ewes grazing short drought pasture at 0.8 kg DM/ewe/d plus a supplement of fresh willow at 1.4 kg fresh willow/ewe/d (n=7) . Blood samples for the quantification of plasma amino acids were collected at week 5 and 10, with L W and BCS measured at fortnightly intervals. Short drought pasture in this experiment had a low pasture mass (2000 k g DM/ha) and a low nutritive value (8 MJ/kg DM), whilst willow had a higher M E of 10 MJ/kg OM. Both groups of ewes lost live weight at the rate of 50 g/d. Plasma concentration of 3 methylhistidine (3-MTH; 88 vs 127μ mole/L) at week 5 and non essential amino acids (NEAA; 1082 vs 1417μ mo1e/L) at week 5 and ( 1155 vs 1324 μ mole/L) at week 10, were substantially lower (P<0 .05) in w illow supplemented ewes than control ewes. It was concluded that the increased reproductive rate from willow supplementation in ewes grazing drought pasture might be partly explained by reduced body protein catabolism, besides also increasing plasma branched chain amino acids CBCAA) and essential amino acids (EAA) concentrations. To investigate the effects of willow supplementation on rumen microbes, rumen samples were collected during the 2005 experiment with fistulated ewes over a 10 week period. The study involved the use of a molecular technique ( Chapter 5), denaturing gradient gel electrophoresis (DGGE), to compare the rumen microbial populations between the control and supplemented ewes and a cultivation technique (Chapter 6) to study the effect on rumen bacteria of ewes grazing drought pastures with and with out willow supplementation. DGGE analysis of the V3 region of 16S ribosomal RNA genes in DNA extracted from samples of rumen contents taken fortnightly over a 10 week feeding period showed a distinct difference in banding patterns between treatment groups which progressively developed over time, showing rumen microbial adaptation to willow supplementation. However, phylogenetic analysis of the DNA sequences retrieved from the DGGE bands from willow-supplemented and control ewes did not cluster by treatment group. It was deduced that willow supplementation induced a change in rumen bacterial populations through selecting sub-populations of organisms already present in the rumen. The changes in the rumen bacterial populations is attributed to the ability of these bacteria to metabolise secondary compounds in willow such as phenolicglycosides and flavanoid monomers and their ability to resist the inhibitory effects of condensed tannins. The cultivation study involved enumeration, isolation and purification of bacterial colonies on Complete Carbohydrate, Salicin, Xylan, Cellulose and Willow media followed by full characterisation of a representative set of pure bacterial cultures. Total bacterial counts on the above media at week 5 and week 10 were generally lower in willow-supplemented ewes compared to control ewes and the 16S rRNA gene sequences of the majority of iso lates characterised from both Salicin and Xylan media, were most closely related to species from the Pseudobutyrivibrio genus. Isolates from Willow medium clustered as two distinct groups. One group (mostly isolated from control ewes) was made up of mainly of organisms not usually associated with the rumen and probably represent non-resident organisms that are passing through the rumen. The other group of bacteria were mainly retrieved from willow-supplemented ewes and were most closely related to species of the Ofsenella genus. Compared to bacteria isolated on Salicin and Xylan media, isolates on Willow medium showed little ability to ferment various carbohydrates or trypticase (hydrolysed protein) but were able to utilise secondary compounds from willow. It was concluded that willow fodder blocks are useful sources of supplementary fodder for mating ewes during drought situations. Both the field and m icrobiological studies showed adaptation to the willow supplementary diet, including the detection of Olsenelfa-like bacteria for the first time in the rumen. It is suggested that the principal purpose of the rumen investigation is the degradation of secondary compounds present in willow.