Effects of Pre-Planting Soaking on Growth and Survival of Black Willow Cuttings

Black willow (Salix nigra) uses periodic flood events for dispersal of vegetative propagules, subjecting them to periods of soaking before their deposition along the streambank. It was hypothesized that this life history trait results in optimal conditions for willow growth and survival. To test this hypothesis, a greenhouse experiment was conducted using 1.2‐m‐long black willow cuttings (posts) with a basal diameter of 5 cm. Cuttings were subjected to three soaking treatments (0, 3, and 10 days) and then grown under four soil moisture regimes (control, drought, permanently flooded, and intermittently flooded). Growth, biomass, and survival were recorded. Results showed that soaking posts for 10 days was most beneficial in the control soil moisture regime, enhancing root, shoot, leaf, and total biomass production. Shoot abundance and growth were also enhanced by 10 days of soaking in the control and permanently flooded moisture regimes. Finally, survival increased significantly in control and drought moisture regimes in response to the 10‐day soaking treatment. Results clearly demonstrated that soaking had significant effects on willow post success when evaluated across all soil moisture regimes. Posts subjected to the 10‐day soaking treatment consistently had greatest growth and biomass and displayed a doubling of the survival rate. Therefore, soaking willow cuttings before planting is a simple, inexpensive technique that may be used to bolster streambank restoration success.     

Partial flooding enhances aeration in adventitious roots of black willow (Salix nigra) cuttings

Black willow (Salix nigra) cuttings are used for streambank stabilization where they are subjected to a range of soil moisture conditions including flooding. Flooding has been shown to adversely impact cutting performance, and improved understanding of natural adaptations to flooding might suggest handling and planting techniques to enhance success. However, data assessing the root aeration in adventitious roots that are developed on cuttings of woody species are scant. In addition, it appears that no data are available regarding aeration of the root system under partially flooded conditions. This experiment was designed to examine the effects of continuous flooding (CF) and partial flooding (PF) on aerenchyma formation and radial oxygen loss (ROL) in black willow cuttings. Photosynthetic and growth responses to these conditions were also investigated. Under laboratory condition, replicated potted cuttings were subjected to three treatments: no flooding (control, C), CF, and PF. Water was maintained above the soil surface in CF and at 10 cm depth in PF. Results indicated that after the 28-d treatments, root porosity ranged between 28.6% and 33.0% for the CF and C plants but was greater for the PF plants (39.2% for the drained and 37.2% for the flooded portions). A similar response pattern was found for ROL. In addition, CF treatment led to decreases in final root biomass and root/shoot ratio. Neither CF nor PF had any detectable adverse effects on plant gas exchange or photosystem II functioning. Our results indicated that S. nigra cuttings exhibited avoidance mechanisms in response to flooding, especially the partially flooded condition which is the most common occurrence in riparian systems.     

Photosynthetic gene expression in black willow under various soil moisture regimes

This study was the first attempt to extract RNA from black willow (Salix nigra Marshall) that contains numerous secondary products and to examine the photosynthetic gene expression of black willow under a wide range of soil moisture regimes. Black willow cuttings were grown under control, continuous flooding, periodic flooding and periodic drought for 42 d. A modified lithium chloride precipitation method was used for RNA extraction. Results of real-time polymerase chain reaction showed reduced gene expression of oxygen evolving complex, large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenasse and ferredoxin on day 7 as well as the latter two on day 14 in response to flooding. Therefore, decreased expression of these three genes may have contributed to the observed reduced photosynthetic capacity in response to flooding.     

Physiological responses of black willow (<Emphasis Type="Italic">Salix nigra</Emphasis>) cuttings to a range of soil moisture regimes

We quantified the physiological responses of black willow to four soil moisture regimes: no flooding (control, C), continuous flooding (CF), periodic flooding (PF), and periodic drought (PD). Stomatal limitation was one of the factors that led to the reduced photosynthetic capacity in CF cuttings. Under PD, stomatal closure, decreased leaf chlorophyll content, and increased dark fluorescence yield contributed to photosynthetic decline. CF cuttings accumulated the lowest shoot biomass while the final height and root growth were most adversely affected by PD. PF cuttings tended to allocate more photoassimilates to root growth than to shoots.     

Effects of periodic flooding and root pruning on Quercus nuttallii seedlings

In the southern United States, much of the emphasis in bottomland restoration is placed on establishing an oak-dominated forest. Artificial regeneration is an alternative for restoration on cleared lands and where a desirable seed source is not present. Currently the standard procedure for seedling preparation is to prune the roots prior to transplanting in the field. It is not fully known what effect(s) root pruning has on transplanted seedlings. In addition, bottomland restoration efforts inherently take place on floodplains. The potential interaction between root pruning and flooding on seedling performance is not known. This study consisted of two separate but related laboratory experiments. The purpose of the first experiment was to quantify the effects of various percentages of root removal and varying soil moisture regimes on transplanted Nuttall oak seedlings (Quercus nuttallii Palmer). Root pruning treatments consisted of removal of roots at 0%, 25% and 75% while soil moisture regime was maintained at non-flooded or periodically flooded conditions. Plant gas exchange, growth, and survival were measured. Root pruning alone had adverse effects on height growth during the first 72 days following transplanting. Periodic flooding also produced adverse effects on stomatal conductance (p = 0.0002), height growth (p = 0.005), and survival (p = 0.02). Photosynthetic data indicated that as pruning intensified in the periodically flooded seedlings, photosynthetic rates decreased. In contrast, as pruning intensified in the non-flooded seedlings, photosynthesis increased. This demonstrated that pruning rate had a varying effect on photosynthesis dependent upon soil moisture condition. Experiment 2 focused on the effects of varying degrees of root pruning on new root formation. The seedlings were grown under laboratory conditions, harvested at 0, 10, 20, and 30 days after treatment initiation, and analyzed for new root formation. Results of Experiment 2 indicated no difference in new root formation, root length, or root biomass due to the pruning treatment. Overall, our results from both experiments indicated that root pruning had no detectable long-term adverse effects on growth and survival of seedlings under drained soil conditions; however, as results from Experiment 1 demonstrated, if seedlings were planted in periodically flooded conditions, root pruning produced adverse effects. Thus, in restoration efforts utilizing Nuttall oak seedlings, the planting strategy and pruning rate should be carefully evaluated based on the knowledge of sites' hydrology. Alternatively, on sites with unpredictable flooding both pruned and unpruned seedlings may be utilized to ensure survival.     

Factors governing survival of black willow (Salix nigra) cuttings in a streambank restoration project

A field study was conducted at Little Topashaw Creek in northern Mississippi, aimed at expanding the limited database on the survivorship of Salix nigra (black willow) cuttings planted on riparian restoration sites. We tested the hypothesis that sediment moisture availability (deficit, excess) as mediated by sediment texture and depth to the prevailing water table is a major factor governing black willow survival during the initial stage of establishment following transplanting. Replicated plots were established across elevational gradients and a range of soil texture. Each plot contained 16 planted cuttings (2.5 cm diameter × 2.5 m length). Plot depth to water table, soil texture, and soil redox potential were measured. Plant gas exchange, leaf chlorophyll content, growth, and survival were monitored periodically over two growing seasons. Survival was best at low elevation compared to cuttings planted at mid- and high elevations. Poor survival and growth were noted for cuttings that encountered sediment moisture deficits in plots with coarse texture while the best cutting survival was recorded for intermediate sand content plots. Results indicated that plot location on the bank and soil texture are two important factors that influence riverbank restoration success. Therefore, any riparian restoration plan should include careful assessment of these factors prior to undertaking such efforts.     

Effects of Propagule Phenology (Non-Dormant Versus Dormant) and Planting System (Vertical Versus Horizontal) on Growth Performance of Willow Clones Grown Under Different Weeding Regimes

To assess the effects of propagule phenology and planting system on growth performance of three willow clones grown under different weeding regimes, a field experiment was performed in central Sweden 2014–2016. Freshly harvested (non-dormant) and cold-stored (dormant) cuttings (planted vertically) and billets (planted horizontally) from willow clones Tordis, Tora, and Jorr were planted in weeded and in unweeded plots. Sprouting was significantly higher for willows grown from non-dormant (74%) than dormant (58%) propagules and for cuttings (84%) compared with billets (42%). Survival was higher for willows from non-dormant propagules in weeded (71%) compared with unweeded (63%) plots, willows from dormant propagules in weeded (72%) compared with unweeded (60%) plots, and for willows from cuttings (93%) compared with billets (39%). During 2014–2016, aboveground biomass production was significantly higher for willows from cuttings (11.71 t DW ha^?1) than from billets (6.13 t DW ha^?1), grown in weeded (15.29 t DW ha^?1) than in unweeded (2.55 t DW ha^?1) plots, and differed significantly among willow clones (11.48, 9.27, and 6.01 t DW ha^?1 for Tordis, Tora, and Jorr, respectively). In this study, (i) planting with cold-stored and freshly harvested willow propagules was equally successful and therefore cold storage could be potentially avoided and replaced with planting of freshly harvested propagules in early spring; however, (ii) in terms of measured growth performance parameters, willows grown from cuttings performed better than grown from billets; and (iii) weed competition significantly reduced survival and aboveground biomass production, confirming that weed control during establishment of willow is crucial.     

Physiological responses of black willow (Salix nigra) cuttings to a range of soil moisture regimes

We quantified the physiological responses of black willow to four soil moisture regimes: no flooding (control, C), continuous flooding (CF), periodic flooding (PF), and periodic drought (PD). Stomatal limitation was one of the factors that led to the reduced photosynthetic capacity in CF cuttings. Under PD, stomatal closure, decreased leaf chlorophyll content, and increased dark fluorescence yield contributed to photosynthetic decline. CF cuttings accumulated the lowest shoot biomass while the final height and root growth were most adversely affected by PD. PF cuttings tended to allocate more photoassimilates to root growth than to shoots.This revised version was published online in March 2005 with corrections to the page numbers.     

Effects of Cutting Length,Orientation and Planting Depth on Early Willow Shoot Establishment

To assess the effects of different planting systems on early performance (survival, shoot emergence time, number of shoots, maximum shoot height and biomass shoot production) of willow, cuttings of varying lengths were planted horizontally at different depths and compared with vertically planted cuttings. Cutting lengths of (i) 25–200 cm and (ii) 7–21 cm were studied in a field experiment and in a box experiment, respectively. Shorter cuttings planted deeper had a lower survival rate and emerged a few days later compared to longer cuttings planted shallower. The performance was considerably higher at the apical part of the cuttings, regardless of cutting length. Longer cuttings planted shallow had a higher performance. Vertically planted cuttings produced more biomass and shoots per length unit than horizontally planted cuttings. We conclude that planting systems based on the use of longer horizontally planted cuttings would probably lead to an uneven establishment and gaps in the stand caused by apical dominance. Also, to achieve the same performance, the need of planting material would be considerably higher compared to systems with vertically planted cuttings. To obtain a fast and more even early establishment of willows, we recommend the use of vertically planted cuttings with a length of at least 20 cm. If cuttings are planted horizontally, they should not be planted deeper than 5 cm.     

Effects of Cutting Phenology (Non-dormant Versus Dormant) on Early Growth Performance of Three Willow Clones Grown Under Different Weed Treatments and Planting Dates

To assess the effects of cutting phenology on early growth performance of three willow clones grown under different weed treatments and planting dates, freshly harvested (non-dormant) and cold-stored (dormant) cuttings from willow clone Tora, Jorr, and Olof were planted in bucket experiment outdoors in central Sweden on five planting dates (May–June 2013) with or without a model weed (spring barley). Non-dormant cuttings sprouted faster than dormant cuttings when planted early in the season. For cuttings planted later in the season, bud sprouting was affected only by willow clone. Aboveground biomass production was affected by cutting phenology, planting date, clone, and weed treatment. When planted on May 3 and May 10, biomass produced from non-dormant and dormant cuttings did not differ, while willows grown from dormant cuttings produced 59% more aboveground biomass than willows grown from non-dormant cuttings when planted on May 24–June 16. Tora produced on average 12% more biomass than Jorr and Olof, and weed competition reduced aboveground biomass production on average with 36%. The ability of willow to suppress weeds (WSA) was 26 (non-dormant cuttings) and 12% (dormant cuttings) higher for willows planted on May 3 compared with WSA of willows grown from cuttings planted later in the season. The ability to tolerate competition from weeds (WT) was 51 and 52% lower for willows grown from non-dormant and dormant cuttings planted late in the season compared with WT of willows planted earlier in the season. We conclude that planting with long-term cold storage of willow cuttings can be replaced with planting freshly harvested cuttings when planting is performed in early season, and that weed competition strongly reduces biomass production. Weed control during the establishment phase is crucial in order to maximize willow biomass production.     

Genotypic variability and stability of poplars and willows grown onnitrate-contaminated soils

Abstract

Phyto-recurrent selection is an established method for selecting tree genotypes for phytoremediation. To identify promising Populus (poplar) and Salix (willow) genotypes for phytotechnologies, our objectives were to (1) evaluate the genotypic variability in survival, height, and diameter of poplar and willow clones established on soils heavily contaminated with nitrates; and (2) assess the genotypic stability in survival and diameter of selected poplar clones after one and eleven growing seasons. We tested 27 poplar and 10 willow clones planted as unrooted cuttings, along with 15 poplar genotypes planted as rooted cuttings. The trees were tested at an agricultural production facility in the Midwestern, United States. After 11 growing seasons, using phyto-recurrent selection, we surveyed survival and measured the diameter of 27 poplar clones (14 unrooted, 13 rooted) that were selected based on superior survival and growth throughout plantation development. Overall, willow exhibited the greatest survival, while poplar had the greatest height and diameter. At 11 years after planting, superior clones were identified that exhibited above-average diameter growth at the establishment- and rotation-age, most of which had stable genotypic performance over time. Selection of specific clones was favorable to genomic groups, based on the geographic location and soil conditions of the site.     

Leaf dynamics and insect herbivory in a Eucalyptus camaldulensis forest under moisture stress

Abstract The influence of soil moisture content on leaf dynamics and insect herbivory was examined between September 1991 and March 1992 in a river red gum (Eucalyptus camaldulensis) forest in southern central New South Wales. Long-term observations of leaves were made in trees standing either within intermittently flooded waterways or at an average of 37. 5m from the edge of the waterways. The mean soil moisture content was significantly (P≤0.05) greater in the waterways than in the non-flooded areas. Trees in the higher soil moisture regime produced significantly larger basal area increments and increased canopy leaf area. This increase in canopy leaf area was achieved, in part, through a significant increase in leaf longevity and mean leaf size. Although a greater number of leaves was initiated and abscissed per shoot from the non-flooded trees, more leaves were collected from litter traps beneath the denser canopies of the flooded trees. Consumption of foliage by insects on the trees subjected to flooding compared to the non-flooded trees was not significantly different. However, the relative impact of insect herbivory was significantly greater on the non-flooded trees. Leaf chewing was the most common form of damage by insects, particularly Chryso-melidae and Curculionidae. No species was present in outbreak during this study. Leaf survival decreased as the per cent area eaten per leaf increased. In addition, irrespective of the level of herbivory, leaf abscission tended to be higher in E. camaldulensis under moisture deficit. The influence of soil moisture content on the balance between river red gum growth and insect herbivory is discussed.     

Abiotic determinants of the fynbos/succulent karoo boundary,South Africa

This study investigates the influence of texture, soil moisture and nutrient status on the growth and survival of seedlings of two typical fynbos (Leucadendron pubescens and Passerina vulgaris) and succulent karoo (Ruschia spp.) species, which grow in the boundary zone between these two vegetation types. Seedlings of each species were grown in shalederived and sandstone‐derived soils and under xeric and mesic regimes. Under the xeric regime, the shale‐derived and sandstone‐derived soils represented fine and coarse‐textured soils, respectively. Under the mesic regime, the same soils represented nutrient‐rich and nutrient‐poor soils, respectively. The seedlings of both fynbos species died rapidly under the xeric regime, irrespective of soil type. In contrast, the succulent karoo seedlings survived for over 77 days without water. Under mesic conditions, the fynbos seedlings grew faster than the succulent karoo seedlings, irrespective of soil type. Fynbos seedlings appear to be directly limited by the environment (moisture and salinity), whereas succulent karoo seedlings may be limited by interactions with other plants.     

Determining factors of cottonwood planting survival in a desert river restoration project

Planting native riparian trees can help recover wildlife and fish habitat on a local scale, when full recovery of natural processes that sustain riparian ecosystems is infeasible. To help improve planting success, we determined which environmental factors and management practices most influenced survival of planted Populus fremontii (Fremont cottonwood) in a field experiment on the San Rafael River, Utah, U.S.A. We planted 474 approximately 2‐m‐tall trees and tracked survival for 1.25 years. We used logistic regression to evaluate whether tree height, elevation above the river channel, distance to existing cottonwood or Salix exigua (coyote willow), soil conductivity, soil texture, planting depth, planting method (mechanical auger vs. hand‐digging), and provision of natural and commercial supplements affected survival probability. Survival probability decreased with elevation above the river channel bottom and was greater in auger‐dug than hand‐dug holes. Survival probability was lower in soils with the highest salinity levels and was lower in sandy soils than soils with silt and clay. Survival may be improved by planting well above the channel to avoid flooding impacts but within 2 m above the channel in auger‐dug holes to ensure access to soil moisture. Testing soil salinity and texture in areas with suitable elevation could also help improve survival. Approximately 35% of trees survived to the end of the study period, indicating that planting can help recover riparian habitat locally, especially if survival is improved in future planting efforts. However, full recovery of desired riparian habitat throughout the floodplain will require natural flows.     

Willow genotype, but not drought treatment, affects foliar phenolic concentrations and leaf-beetle resistance

In a greenhouse experiment we examined the effect of willow genotype and irrigation regime (moderate drought and well‐watered) on plant growth parameters, foliar nitrogen, and phenolic concentrations, as well as on the preference and performance of the blue leaf beetle, Phratora vulgatissima (L.) (Coleoptera: Chrysomelidae). The 10 vegetatively propagated willow genotypes in the experiments were F2 full‐sibling hybrids, originated from a cross between Salix viminalis (L.) (Salicaceae) (high in condensed tannins) and Salix dasyclados (L.) (Salicaceae) (rich in phenolic glycosides). Insect bioassays were conducted on detached leaves in Petri dishes as well as with free‐living insects on intact potted plants. The 10‐week long irrigation treatments caused statistically significant phenotypic differences in the potted willow saplings. Total biomass was somewhat higher in the well‐watered treatment. The root to total biomass ratio was higher in the drought‐treatment plants. There was significant genotypic variation in foliar nitrogen concentrations, and they were higher in the drought‐treatment plants. There was also a strong genotypic variation in each of the phenolic substances analyzed. Condensed tannins, which accounted for the greatest proportion of total phenolic mass, were higher in the well‐watered treatment. There was, however, no difference in levels of the other phenolics (salicylates, cinnamic acid, flavonoids, and chlorogenic acid) between irrigation treatments. The sum of these phenolics was higher in the well‐watered treatment. There was a strong variation in P. vulgatissima larval development on different willow genotypes, and larval performance was negatively correlated with levels of salicylates and cinnamic acid. There was, however, no effect of irrigation treatment on larval performance. Phratora vulgatissima preferred to feed on well‐watered plants, and we found a preference for oviposition there, but neither feeding nor oviposition site preference was affected by willow genotype. Adult feeding and oviposition preferences were not correlated with larval performance.     

Effects of Flooding Regime and Seedling Treatment on Early Survival and Growth of Nuttall Oak

Effects of flooding on survival and growth of three different types of Nuttall oak (Quercus texana Buckl.) seedlings were observed at the end of third and fifth growing seasons at Yazoo National Wildlife Refuge, Mississippi, U.S.A. Three types of seedlings were planted in January 1995 in a split‐plot design, with four replications at each of two elevations on floodprone, former cropland in Sharkey clay soil. The lower of the two planting elevations was inundated for 21 days during the first growing season, whereas the higher elevation did not flood during the 5‐year period of this study. The three types of 1‐0 seedlings were bareroot seedlings, seedlings grown in containers (3.8 × 21–cm plastic seedling cones), and container‐grown seedlings inoculated with vegetative mycelia of Pisolithus tinctorius (Pers.) Coker. Survival of all the three seedling types was greatest at the lower, intermittently flooded elevation, indicating that drought and related effects on plant competition were more limiting to seedling survival than flooding. At the lower elevation, survival of mycorrhizal‐inoculated container seedlings was greater than that of noninoculated container seedlings. Survival among bareroot seedlings and inoculated container seedlings was not significantly different at either elevation. At the higher, nonflooded elevation, however, bareroot seedling survival was greater than the survival of container seedlings without inoculation. Differences were significant among the inoculated and the noninoculated container seedlings, with higher survival of inoculated seedlings at both elevations, though differences were only significant in year 3. At the end of the fifth year, height of bareroot seedlings was significantly greater than the heights of both types of container‐grown seedlings at both planting elevations. Because seedlings grown in the plastic seedlings cones did not survive better than the bareroot seedlings at either planting elevation, the bareroot stock appear to be the economically superior choice for regeneration in Sharkey soil.     

Effects of soil moisture regimes on photosynthesis and growth in cattail (Typha latifolia)

Both waterlogging and water deficiency are major environmental factors affecting plant growth and functioning in many wetland and floodplain ecosystems across North America. Wetland plants possess various characteristics that enable them to survive and function in the intermittently flooded wetland environments, while their sensitivity to drought has received less attention. The present study quantified the photosynthetic and growth responses of cattail (Typha latifolia), an important species of freshwater wetlands, to a wide range of soil moisture regimes. In addition, changes in the efficiency of photosynthetic apparatus following initiation of the treatments were investigated. Under greenhouse conditions, seedlings were subjected to four soil moisture regimes: (1) drained (control), (2) continuous flooding, (3) periodic flooding, and (4) periodic drought. Results indicated that dark fluorescence yield was increased in response to periodic drought, while it showed decreases under continuous flooding. Net photosynthesis and stomatal conductance were enhanced by continuous flooding and periodic flooding. In contrast, these parameters exhibited reduction under periodic drought. In addition, leaf chlorophyll content was adversely affected by periodic drought. Recovery of net photosynthesis was noted, along with enhanced height growth, in both continuously and periodically flooded plants. Meanwhile, continuous flooding enhanced biomass production while periodic drought led to biomass reduction. Periodic drought also contributed to substantial reduction in root growth compared with shoot growth. Therefore, the combined photosynthetic performance and growth responses of cattail are likely to contribute to the ability of this species to thrive in flooded condition but be susceptive to periodic drought.     

Iron toxicity to rice in an acid sulfate soil as influenced by water regimes

Summary The effects of two water regimes: Continuous flooding and flooding with soil drying on iron toxicity to rice in an acid sulfate soil was studied by continuously growing 7 crops of IR-32 rice in pots under the two water treatments. There was no plant growth upto the second crop under both water treatments due to iron toxicity. But there was good growth of rice under the continuous water regime from third cropping onwards, however, there was no growth of rice in the flooding with soil drying treatment even upto the seventh crop due to iron toxicity.The results of the study bring out that keeping an acid sulfate soil flooded for a few weeks and then planting rice when iron in soil solution has dropped below toxicity level may be a possible management practice for lowland rice culture on such soils. Drying and reflooding an acid sulfate soil on the other hand aggravates soil acidity and keeps iron in solution in high amounts to be toxic to rice plant.     

The effect of waterlogging on nitrogen fixation and nodule morphology in soil-grown white clover (Trifolium repens L.)

Nodulated, pot-grown plants of white clover (Trifolium repenscv. Katrina) were subjected to different soil moisture regimesand the effect of these treatments on dry matter production,nitrogenase activity, aerenchyma formation, and bacteroid distributionwas determined. In the first experiment, after 9 weeks growthshoots were significantly (P<0.01) heavier for clover plantswhich were flooded from germination compared with those subjectedto normal watering, indicating that clover can adapt to long-termwaterlogging. In the second experiment, time-courses of acetylenereduction showed a lag phase of only 10 min for waterloggedplants, suggesting that gas exchange was occurring through aerationpathways rather than the water. Flooded plants that were drained24 h prior to acetylene reduction assays had substantially greaternitrogenase activity than normally watered or continually floodedplants. However, there was a marked decrease in nitrogenaseactivity when plants which had been watered normally were flooded,suggesting a sensitivity of white clover to sudden changes inmoisture conditions. Morphological studies of nodules from plantsgrown in normally watered and continually flooded soil showedincreased aerenchyma production around roots and nodules ofwaterlogged plants. In addition, the infected cells of submergednodules were larger and had larger vacuoles than those fromnodules of normally watered plants. This increase in vacuolevolume to protoplast volume in infected cells may play a rolein the tolerance of white clover nodules to waterlogging. Key words: White clover, waterlogging, hypoxia, nitrogen fixation, root nodule morphology.     

The Effect of Temperature and Moisture on the Survival of Heterodera glycines in the Absence of a Host

Soybean-cyst nematode larvae survived in water up to 630 days, depending on incubation temperature. Most larvae were killed when ice crystals formed in water, and all died after 1 day at 40 C. At temperatures of 0, 4, 8 and 12 C, larvae survived for the duration of the experiments (630 days). From 16 to 36 C, survival was inversely correlated with temperature. In naturally infested soil, nematode survival was similax but more extended and related to moisture level. Larvae survived 7-19 months in flooded soil, 29-38 months in dry soil, and for 90 months in soil maintained near its field capacity.