Preplant Treatments Research Articles

The Effect of Preplant Monoammonium Phosphate Fertilizer and Compost on the Growth and Yield of 'Macoun' Apple Trees

'Macoun'/B.9 apple (Malus ×domestica Borkh.) trees were planted in May 1998 in ± compost or ± monoammonium phosphate (MAP) for a total of four preplant treatments: 1) 90 g phosphorus (P) per tree, 2) 128 kg compost per tree, 3) 90 g P and 128 kg compost per tree, and 4) and an untreated control. MAP did not increase tree growth or yield in any year of the study. Compost increased canopy width into the sixth year after planting, and increased tree height and trunk cross-sectional area (TCA) into the seventh year. Annual yield was increased by compost in the fifth and seventh years, but not fourth or sixth year after planting. Compost increased cumulative yield in the sixth and seventh years.

Effects of AG3 phosphonate formulations on incidence and severity of Pythium damping-off of cucumber seedlings under growth room, microplot, and field conditions

New formulations of phosphonates (AG3) were tested for their efficacy to control Pythium damping-off of cucumber seedlings in peat-based mix (P-mix), muck soil (Mu-soil), and sandy loam soil (SL-soil). Aqueous solutions of various phosphonate formulations (0.035%–0.280% active ingredient (a.i.), v/m) were added to pathogen-infested Pmix or SL- or Mu-soils as a preplanting amendment or postplanting drench treatments. In artificially infested P-mix, preplanting amendment with powder or liquid phosphonate formulation provided control of damping-off and disease suppression that increased with the concentration of phosphonate. Higher rates (0.140% or 0.280% a.i.) provided almost 100% disease control whereas lower rates (0.035% or 0.070% a.i.) had on average 34%–75% healthy plants compared with less than 5% in the control. AG3 liquid formulation as a preplanting treatment also provided effective control in naturally infested Mu-soil and artificially infested SL-soil. Postplanting drench with AG3 was equally effective in all three soil substrates. AG3 applied as an amendment 2 weeks prior to planting in Mu-soil was as effective as that added just prior to planting. Treatments made prior to 2 weeks were less effective. AG3 also provided effective control of Pythium damping-off of cucumber seedlings under microplot and field conditions. The amount and frequency of irrigation and rainfall can affect the disease suppression by AG3 phosphonate in the field.

Ultra‐High Plant Populations and Nitrogen Fertility Effects on Corn in the Mississippi Valley

Populations for high yield and low mycotoxin levels in furrow‐irrigated corn (Zea mays L.) have yet to be firmly established for the Midsouth USA. Preplant N applications compared with a split application and the effects on yield, yield components, and mycotoxin levels were also examined. Experiments were conducted at Site WR (102‐cm‐wide rows, Beulah fine sandy loam) and Site NR (76‐cm‐wide rows, Dundee silty clay). Plant densities of 71760, 82160, 92560, and 102960 plants ha−1 were grown in eight‐row plots, 9.1 m long at both sites. The N fertility treatments were 112 kg N ha−1 preplant, 224 kg N ha−1 preplant, and 112 kg N ha−1 preplant + 112 kg N ha−1 sidedressed at V6 (six leaves). Yields at Site WR did not differ among populations. Maximum yields at Site NR were at 71760 plants ha−1 (10.3 Mg ha−1) and then declined (b = −0.5065). Kernels per ear declined (b = −40.09 and b = −42.69), kernel weights declined (b = −0.4328 and b = −0.8172), and stalk lodging increased (b = 0.0103 and b = 0.0251) with increased populations for Sites WR and NR, respectively. These and previous data place the maximum population for corn in the Midsouth at about 70000 plants ha−1. No differences in yield occurred between the 224 kg N ha−1 preplant treatment and the split application of N. Yields were generally less with 112 kg N ha−1 per‐plant only. Aflatoxin and fumonisin levels at both sites were unaffected by plant population of N fertility.

Apple Root stocks and Pre-plant Soil Treatments Alter Soil Microbial Community Composition in a New York Orchard

Apple (Malu ×domestica) replant disease (ARD) is a soil-borne disease syndrome of complex etiology that occurs worldwide when establishing new orchards in old fruit-growing sites. Methyl bromide (MB) has been an effective soil fumigant to control ARD, but safer alternatives to MB are needed. We evaluated soil microbial communities, tree growth, and fruit yield for three pre-plant soil treatments (compost amendment, soil treatment with a broad-spectrum fumigant, and untreated controls), and five clonal rootstocks (M7, M26, CG6210, CG30, and G16), in an apple replant site at Ithaca, N.Y. Molecular fingerprinting (PCR-DGGE) techniques were used to study soil microbial community composition of root-zone soil of the different soil treatments and rootstocks. Tree caliper, shoot growth, and yield were measured annually from 2002–04. Among the five rootstocks we compared, trees on CG6210 had the most growth and yield, while trees on M26 had the least growth and yield. Soil treatments altered soil microbial communities during the year after pre-plant treatments, and each treatment was associated with distinct microbial groups in hierarchical cluster analyses. However, those differences among fungal and bacterial communities diminished during the second year after planting, and soil fungal communities equilibrated faster than bacterial communities. Pre-plant soil treatments altered bulk-soil microbial community composition, but those shifts in soil microbial communities had no obvious correlation with tree performance. Rootstock genotypes were the dominant factor in tree performance after 3 years of observations, and different rootstocks were associated with characteristic bacterial, pseudomonad, fungal, and oomycetes communities in root-zone soil.

Evaluation of Thymol as Biofumigant for Control of Bacterial Wilt of Tomato Under Field Conditions.

Volatile plant essential oils thymol and palmarosa oil, used at a concentration of 0.7%, were evaluated under field conditions for control of bacterial wilt of tomato caused by Ralstonia solanacearum. The experimental fields were artificially infested with the bacterial pathogen. Two hours after infestation, the plant essential oils were applied, then the plots were sealed with plastic mulch for 3 or 6 days. Tomato seedlings were transplanted into the field 7 days later. In fall of 2002, 92.5% of tomato plants (cv. Equinox) wilted in the untreated control plots. Both thymol and palmarosa oil soil treatments reduced bacterial wilt incidence significantly. Thymol was more effective than palmarosa oil based on the final assessment, when 33.1 and 48.1% of the plants had wilted in plots treated with thymol and palmarosa oil, respectively. Soil treatment with either thymol or palmarosa oil produced significantly higher yield of tomato than the untreated control. In 2003, only thymol was evaluated. Thymol application significantly reduced bacterial wilt incidence on the susceptible cultivar Solar Set. Disease incidence in untreated plots reached 65.5%, while in thymol treated plots only 12% of plants wilted. Thymol treatment also increased yield of Solar Set significantly compared with the untreated control. This is the first report on the use of thymol for controlling a plant disease under field conditions, which indicated that this compound provided effective control of bacterial wilt on susceptible tomato cultivars when used as preplant treatment of soils. Because of its volatile property and broad-spectrum functions, thymol shows potential to be used as a soil biofumigant for the management of various plant pathogens.

Silage maize emergence is reduced by wheel traffic due to increased soil bulk density and penetration resistance

Effects of wheel traffic on plant emergence in conventional and conservational tillage systems for silage maize have been studied. Compaction parameters investigated were as follows: pre-planting in entire plot area, post-planting in entire plot area, post-planting intra-rows, post-planting inter-rows and a control (no extra compaction); using a conventional tillage system such as mouldboard plough and disc harrow, and conservational tillage such as chisel plough with tooth harrow and rotary tiller. Penetration resistance, bulk density, maize mean emergence dates and percentage of emerged seedlings were measured. Soil bulk density and penetration resistance in pre-planting and post-planting compaction treatments in the entire plot area were higher than the other compaction treatments. Compaction caused by pre-planting resulted in lower silage maize emergence than the other compaction treatments. The mean percentage emergence of seedlings was higher in the rotary tiller conservational tillage system than that of the other tillage systems. The mean percentage emergence of seedlings was higher in control and post-planting intra-rows compaction. In conclusion, the percentage of emerged seedlings was affected negatively by the wheel traffic treatments. Compaction treatments caused by tractor wheel traffic in tillage systems increased soil bulk density and penetration resistance.

Nitrate Losses in Subsurface Drainage from a Corn–Soybean Rotation as Affected by Fall and Spring Application of Nitrogen and Nitrapyrin

Substantial amounts of NO3 from agricultural crop production systems on poorly drained soils can be transported to surface water via subsurface drainage. A field study was conducted from the fall of 1993 through 2000 on a tile-drained Canisteo clay loam soil (fine-loamy, mixed, superactive, calcareous, mesic Typic Endoaquoll) to determine the influence of fall vs. spring application of N and nitrapyrin [NP; 2-chloro-6-(trichloromethyl) pyridine] on NO3 losses from a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Four anhydrous ammonia treatments (fall N, fall N + NP, spring preplant N, and spring N + NP) were replicated four times and applied at 135 kg N ha(-1) for corn on individual drainage plots. Drainage occurred in all seven years. Seventy-one percent of the annual drainage and 75% of the annual NO3 loss occurred in April, May, and June. Fifty-four percent of the NO3 lost in the drainage occurred during the corn phase and 46% during the soybean phase. Annual flow-weighted NO3-N concentrations for the fall, fall + NP, spring, and spring + NP treatments averaged 14.3, 11.5, 10.7, and 11.3 mg L(-1) during the corn phase but annual NO3-N concentrations were still > or =10 mg L(-1) in three of six years for the spring preplant treatment. Averaged across the six rotation cycles, flow-normalized NO3-N losses ranked in the order: fall N > spring N + NP > fall N + NP > spring N. Under these conditions, NO3 losses in subsurface drainage from a corn-soybean rotation can be reduced 14% by spring N and 10% by late fall N + NP compared with fall-applied N. Nitrate losses were not appreciably reduced by adding NP to spring preplant N.

Yield, Petiole Nitrate, and Node Development Responses of Cotton to Early Season Nitrogen Fertilization#

Nitrogen (N) fertilization continues to be of primary importance in the economically successful production of cotton (Gossypium hirsutum L.). Profit margins of producers might be expanded by increasing the uptake efficiency of applied N. Recently, N fertilization of crops grown in the Mississippi River Delta has been suspected to impact water quality in the Gulf of Mexico. Improving efficiency of N uptake could alleviate some environmental concerns by increasing the retention of N at the site of application. The objective of this study was to determine the impact of replacing preplant N applications with postemergent N applications on the growth and yield characteristics of cotton. Delayed applications of the recommended rate of N fertilizer (112 kg N ha−1) were tested for four years under irrigated and dry land production conditions. The N rate was applied either preplant, after crop emergence, or at first square. Further, 112 kg N ha−1 was split applied evenly at preplant + first square, and after emergence + first square. The five 112 kg ha−1 N treatments were compared to an unfertilized control. Yield tended to be maximized with N treatments that included a first square application. Yields were usually lowest in the unfertilized control and the 112 kg N ha−1 preplant treatments. Not surprisingly, both yield and plant growth was influenced more by irrigation than N fertilization. Years when drought conditions caused water stress and limited plant growth, dry land cotton had only limited response to the N fertilization treatments. Irrigated cotton responded to N treatments all years with increased growth and yield. Optimizing agronomic considerations, the best N fertilization timing was an after emergence + first square split application. #Approved for publication by the director of the Arkansas Agricultural Experiment Station.

Chemical control of weeds in onion (Allium cepa L.)

SummaryThe effect of pre- or post-planting application of selected herbicides on growth and yield of transplanted onion and weeds was investigated in two field experiments conducted in Jordan during the 1997/1998 growing season. Weed competition throughout the season reduced onion yield by 94% and lowered onion quality. All herbicides [except metribuzin and diphenamid under rain-fed conditions, and linuron + terbutryn (Tempo®) under irrigation] increased onion growth and yield over the weed-infested control. Post-planting application of oxyfluorfen (at 2 l ha–1) at the three-to-four leaf stage resulted in better onion bulb yield than in the hand-weeded, weed-free control at both locations. Pre-planting treatment with oxyfluorfen at 2.5 l ha–1 gave higher yields than the weed-free control in irrigated onion, but not under rain-fed conditions. Oxadiazon (at 4 l ha–1) gave higher yields than in weed-free onion as a post-planting treatment under rain-fed conditions, and was second to oxyfluorfen for bulb production. Pre-planting application of pendimethalin (at 4 l ha–1) was also effective, and increased onion yields compared to weed-infested onion plots or other herbicides used under irrigation. Of all herbicides tested under Jordanian conditions, oxyfluorfen and oxadiazon were the best for yield and weed control in onion, followed by pendimethalin, methabenzthiazuron and linuron as pre-planting treatments, and pendimethalin, linuron and paraquat as post-planting applications.

Quantitative sidedress nitrogen recommendations for potatoes based upon crop nutritional indices

The quantification of sidedress N rate from in-season information on crop N nutritional status is extremely important in order to use only the necessary amount of nutrient to achieve maximum yields without significant N losses from soil. During three consecutive years (1996, 1997 and 1998) field N fertilizer experiments with irrigated potato ( Solanum tuberosum L., cv. Désirée) were conducted in Bragança (NE Portugal). Eight preplant treatments (0, 50, 100, 200 and 300 kg urea-N/ha and poultry manure, farmyard manure and municipal solid waste in rates equivalent to 100 kg organic-N/ha) were arranged as main plots and five sidedress N rates (0, 25, 50, 100 and 200 kg urea-N/ha) included as subplots. Petiole nitrate concentration, determined by a laboratory method (PNLab, g NO 3-N kg −1, dry weight basis) and by the portable RQflex reflectometer (PNRQflex, mg NO 3 kg −1, from fresh tissues), and leaf N content (LeafN, g kg −1, dry weight basis) were used as N nutritional indices. From the five sidedress N rates applied over each of the preplant treatments, critical sidedress N rates were estimated for several different crop N nutritional status. This was achieved by establishing exponential asymptotic curves between sidedress N rates and tuber yields and solving the equations for 95% of maximum tuber yield. In a second step, multiple regression equations were established between the estimated critical sidedress N rates (SNrate, kg N/ha), as dependent variable, and each crop N nutritional indices (PNLab, PNRQflex or LeafN) and days after emergence (DAE). The equations obtained are: SNrate = 182.7 − 4.146 × PNLab −1.87 × DAE SNrate = 161.0 − 0.013 × PNRQflex −1.34 × DAE SNrate = 562.2 − 8.416 × LeafN −3.59 × DAE These equations provide quantitative sidedress N rates for any level of crop N nutritional indices and sampling dates from 10 to 48 days after emergence.

Effect of whole seed tuber size and pre-plant storage conditions on yield and tuber size distribution of Russet Burbank

Field experiments were conducted in 1995, 1996, and 1997 at Agriculture and Agri-Food Canada’s Harrington Research Farm to assess the effect of whole seed tuber size and pre-plant seed storage conditions on processing yield (> 51 mm dia.) of potato (Solanum tuberosum L. cv Russet Burbank). Following commercial storage, seed tubers were stored at 4.4 C then subjected to one of three pre-plant treatments: (1) planted directly from storage, (2) held at 10 C for 3 wk before planting, or (3) green-sprouted for 3 wk before planting. Five sizes of whole seed were used (28, 42, 56, 70, and 84 g) with a variable size cut seed treatment added for comparison. Plots were harvested 138,134, and 131 days after planting in 1995, 1996, and 1997, respectively. Cut seed produced a higher yield of tubers > 51 mm diameter in comparison to all whole tuber seed sizes, with the exception of the 28 and 56 g sizes. In terms of total yield, the 28and 42-g whole seed tubers yielded significantly less than all other seed sizes examined. Warming or greensprouting seed tubers prior to planting did not increase tuber yield. The larger whole seed tuber sizes tended to result in greater numbers of stems and tubers per plant. To maximize marketable yield of Russet Burbank planted from whole seed tubers, it is recommended that the seed be between 28 and 42 g in size. Accepted for publication 25 May 2004.

Management of Aphid-Borne Viruses andBemisia argentifolii(Homoptera: Aleyrodidae) in Zucchini Squash by Using Uv Reflective Plastic and Wheat Straw Mulches

Plastic UV resective mulch (metalized mulch) and wheat straw mulch delayed colo- nization by Bemisia argentifolii Bellows & Perring and the incidence of aphid-borne viruses in zucchini squash. No insecticides were used in either mulch treatment. The mulches were compared with a preplant treatment of imidacloprid and an untreated, unmulched control. In 2000, yield of marketable fruit in the plastic and straw mulched plots was approximately twice that from the imidacloprid plot. In 2001, yield from the straw mulch plots was twice that of the imidacloprid and plastic mulch plots. Yields from both mulched plots and from the imidacloprid plots ranged from 3 to 12 times higher than those from the control plots. The mulches were more effective than a preplant application of imidacloprid in reducing the incidence of both B. argentifolii and aphid-borne viruses. Plants growing over the plastic mulch and the straw mulch grew more rapidly and reached a larger size, as determined by plant dry weight, than did those growing over bare soil, with or without imidacloprid. The spectral quantum sux from the plastic averaged between 80 and 90% of ambient spectral quantum sux values in the UV (300 Ð 400-nm) range. Spectral quantum sux values of wheat straw were similar to those of the resective mulch and ambient near 300 nm but were virtually identical to bare soil beyond 320 nm. The metalized mulch resected 94% of the incoming photosynthetically active radiation (PAR) in the 400 Ð700-nm range compared with ambient, whereas the straw mulch resected 85%. Bare soil resected only 41% of incoming PAR compared with ambient.

The effect of soil fumigants methyl bromide and metham sodium on the microbial degradation of the nematicide Cadusafos

Rapid biodegradation of Cadusafos in a soil from a previously treated greenhouse site from the area of Vasilika in Northern Greece was observed using both incubation and bioassay studies with nematodes. The slow rates of Cadusafos degradation observed in soils from the previously treated site after sterilization with chloroform and also in soils from an adjacent previously untreated site suggested that soil microorganisms adapted to metabolize Cadusafos were responsible for its rapid dissipation. Fumigation of the soil from the previously treated site with methyl bromide (MB) 9 months prior to the experimental addition of Cadusafos (4 μg g −1) only temporarily inhibited degradation of Cadusafos, unlike metham sodium (MS) whose application significantly hampered degradation of the nematicide. However, when the time interval between fumigation of soil from the previously treated greenhouse with MB and MS and the experimental application of Cadusafos was minimized to 20 d, both fumigants halted the rapid degradation of the nematicide. The transient inhibitory effect of MB on the microbial degradation of subsequent Cadusafos applications was attributed to the recovery of the soil microflora within 9 months. In contrast, the persistent inhibitory effect of MS on the microbial degradation of Cadusafos might have been caused by the adverse effects of the fumigant on the microorganisms, which were responsible for the rapid degradation of Cadusafos in the specific soil, although this was not tested in this study. According to these findings, the combined application of MS as a pre-planting treatment with a post-planting application of Cadusafos would maximize the biological efficacy of the non-fumigant nematicide by extending its persistence and preventing the development of enhanced biodegradation for organophosphorus nematicides such Cadusafos.

Reclamation of roads and landings with balsam poplar cuttings

Balsam poplar ( Populus balsamifera L.) can easily be grown when planted as dormant, unrooted cuttings. The first part of this research project consisted of a greenhouse study to identify the best combination of pre-planting treatments to maximize rooting of hardwood cuttings for large-scale greenhouse propagation. Eighty-four treatment combinations were tested on 10 cm-long cuttings, including seven soaking lengths of time (0, 1, 2, 3, 4, 5 and 14 days), three dips (none, powder and liquid rooting hormone), two collection dates (fall and spring), and two cutting selections (average trees and a superior clone). Secondly, we tested the performance of unrooted cuttings on typical forestry sites lacking natural regeneration, using 30 cm-long cuttings and full-length whips (>60 cm). Three pre-planting treatment combinations were used (soaking for 1 or 3 days, or 3 days with a dip in rooting hormone). Other factors tested were two collection dates (fall and spring), two cutting selections (average trees and a superior clone), two storage methods (stored as full whips or cut to size), and two cutting locations (basal or top 30 cm of stools).

Mechanical versus herbicidal strategies for killing a hairy vetch cover crop and controlling weeds in minimum-tillage corn production

AbstractThe development of production systems that provide the benefits of reduced tillage and also reduce or eliminate herbicide inputs presents a challenge to practitioners of sustainable agriculture. This research was conducted to evaluate management approaches for minimum-tillage corn production in a hairy vetch cover crop, specifically, mechanical versus herbicidal methods for pre-plant cover-crop kill and for post-emergence control of emerged weeds. Pre-plant treatments included 2,4-D [(2,4-dichlorophenoxy)acetic acid] plus residual herbicides, 2,4-D alone, flail mower, corn stalk chopper, light disk and heavy disk. The pre-plant herbicide treatments were followed by a post-emergence treatment of dicamba, whereas the pre-plant mechanical treatments were followed by post-emergence cultivation, as needed, for weed control. The mechanical treatments that kept residue on the soil surface (mower, stalk chopper and light disk) killed hairy vetch when it was flowering, but not when vegetative. The herbicide treatment with pre-plant 2,4-D alone, followed by dicamba post-emergence, controlled annual broadleaf weeds (the dominant species in these experiments) similarly to treatment with 2,4-D plus residual herbicides, suggesting that residual herbicides may be eliminated in cover-crop-based no-tillage systems. The pre-plant mechanical treatments followed by cultivation did not control annual broadleaf weeds as well as herbicide treatments, but did maintain final populations below threshold levels in two of four experiments. The stalk chopper and light disk left high levels of vetch residue on the soil surface, and reduced initial broadleaf weed populations compared with the heavy disk that incorporated residue. However, broadleaf weed populations were reduced with less efficiency by cultivation of unfilled soil following the stalk chopper or light disk (38–69%) than by cultivation of tilled soil following the heavy disk (87–95%). Thus, although maintaining surface cover-crop residue without tillage initially reduced weed emergence, it also reduced the efficiency of cultivation, leading to similar final weed populations in all mechanical-based, pre-plant treatments.

Preplant Monoammonium Phosphate Fertilizer and Compost Affects the Growth of Newly Planted 'Macoun' Apple Trees

'Macoun'/Budagovsky 9 apple (Malus ×domestica Borkh.) trees were planted in May 1998 in one of four preplant treatments that were soil incorporation of: 1) control, no phosphorus (P); 2) 90 g P per tree; 3) 128 kg compost per tree; and 4) 90 g P and 128 kg compost per tree. Preplant addition of P had no effect on soil organic matter, P, magnesium (Mg), and calcium (Ca) in the first three seasons after planting, but lowered soil potassium (K) in the second season. Foliar nutrients, tree growth and flowering were also not affected by P. The addition of compost increased soil organic matter and P in the first season after planting, and pH, K, Mg, and Ca in the first three seasons. The addition of compost increased foliar nitrogen and K in all three seasons, and decreased foliar Mg in the first season. Compost incorporation increased shoot length in the first season, trunk cross-sectional area in the first two seasons, tree height and the number of growing points in third season, and flowering in the third and fourth seasons. Compost addition was more effective than P fertilization for increasing tree growth during the establishment years.

A comparison of pre-planting treatments on hardwood cuttings of four hybrid poplar clones

Rooting and early growth of four hybrid poplar clones (Populus spp.) planted in a greenhouse were examined after applying 40 pre-rooting treatment combinations to dormant cuttings. Treatments included 2 cutting lengths (5 and 10 cm), 5 soaking times (0, 2, 4, 8, and 12 days), and 4 dips (chitosan, rooting hormone powder, liquid rooting hormone added to the soaking water, and none). Significant differences in both rooting percentages and growth were shown between clones after 7 weeks of growth. Ten cm cuttings had 29% greater rooting success, 28% more above-ground growth, and 12% lower root/shoot ratios than 5 cm cuttings. Cuttings planted without soaking had the lowest rooting success, at less than 45% on average. Commercial rooting hormones decreased the number of rooted cuttings but increased root/shoot ratios. For optimal rooting, we recommend using 10 cm cuttings, soaked for 2 days in water (4 days for the Jackii10 clone) without any additional dipping/hormone substance.

Detection and Management of Downy Mildew in Rose Rootstock.

A technique utilizing the polymerase chain reaction (PCR) was developed to investigate the occurrence and location of Peronospora sparsain dormant, woody rose tissues. PCR primers were designed to amplify the internal transcribed spacer region of the ribosomal DNA of the pathogen. Inhibition of the reaction by plant compounds was minimized by optimizing the reagents used in the extraction of DNA from roses and in the amplification reaction. The PCR assay was capable of detecting as little as 2 pg of DNA from P. sparsa against a background of 4 ng of DNA from rose cane cortex. With this method, DNA of P. sparsa was detected in the cortex of stem and root tissues of symptomatic plants. Pathogen DNA also was detected in the cortex of crown tissues of asymptomatic mother plants used as a source of propagation materials. Epifluorescent and differential interference contrast microscopy were used to confirm the presence of abundant hyphae and oospores within the stem cortex of infected canes. Preplant treatments of dormant rootstock cuttings in fungicides or hot water were evaluated during natural outbreaks of the disease in commercial rose nurseries. In three trials conducted over 2 years, a 10-min preplant dip in the systemic fungicides metalaxyl or mefenoxam at rates of 100 to 10,000 mg a.i./liter reduced the area under the disease progress curve by 63 to 76% relative to nontreated plots. The evidence from PCR assays, microscopy, and fungicide trials all support the occurrence of perennating infections of P. sparsa within rose. A technique utilizing the polymerase chain reaction (PCR) was developed to investigate the occurrence and location of Peronospora sparsain dormant, woody rose tissues. PCR primers were designed to amplify the internal transcribed spacer region of the ribosomal DNA of the pathogen. Inhibition of the reaction by plant compounds was minimized by optimizing the reagents used in the extraction of DNA from roses and in the amplification reaction. The PCR assay was capable of detecting as little as 2 pg of DNA from P. sparsa against a background of 4 ng of DNA from rose cane cortex. With this method, DNA of P. sparsa was detected in the cortex of stem and root tissues of symptomatic plants. Pathogen DNA also was detected in the cortex of crown tissues of asymptomatic mother plants used as a source of propagation materials. Epifluorescent and differential interference contrast microscopy were used to confirm the presence of abundant hyphae and oospores within the stem cortex of infected canes. Preplant treatments of dormant rootstock cuttings in fungicides or hot water were evaluated during natural outbreaks of the disease in commercial rose nurseries. In three trials conducted over 2 years, a 10-min preplant dip in the systemic fungicides metalaxyl or mefenoxam at rates of 100 to 10,000 mg a.i./liter reduced the area under the disease progress curve by 63 to 76% relative to nontreated plots. The evidence from PCR assays, microscopy, and fungicide trials all support the occurrence of perennating infections of P. sparsa within rose.

Biological Approaches for Control of Root Pathogens of Strawberry

ABSTRACT Soil fumigation with methyl bromide plus chloropicrin is used as a preplant treatment to control a broad range of pathogens in high-value annual crop production systems. In California, fumigation is used on approximately 10,125 ha of strawberry production to control pathogens ranging from Verticillium dahliae to root pruning pathogens such as Pythium, Rhizoctonia, or Cylindrocarpon spp. In addition to pathogen control, fumigation also causes an enhanced growth response of the plant and reduces weed pressure. The development of successful, long-term cost effective biocontrol strategies most likely will require the development of an integrated systems approach that incorporates diverse aspects of the crop production system. Although application of single microbial inoculants may provide some level of control for specific production problems, it will be a challenge to provide the broad spectrum of activity needed in production fields.

Effects of pre-planting treatments on the initial establishment success of indigenous grass seedlings planted into a degraded Aristida junciformis-dominated grassland

The effects of various manipulations to facilitate the establishment of indigenous grasses planted into degraded Aristida junciformis subsp. junciformis -dominated grassland were investigated. Four treatments — complete clearing, a single spring burn, applications of Roundup®, and undisturbed (control) — were applied to replicated plots, with half of each plot mown before planting. Themeda triandra and Tristachya leucothrix seedlings were planted into each plot. Post-planting survival of the planted seedlings was uniformly high (> 80%), except in the poisoned, unmown plots where residual herbicide appears to have significantly lowered seedling survival (< 35%). Seedling mortality over the remainder of the growing season and through winter was low (< 10%). Seedlings planted into swards killed with herbicide had a greater basal area and more tillers than did those planted amongst living adult plants. However, basal cover of the sward in the poisoned plots a year after planting was significantly lower (< 6%) than in other treatments (14–19%). The cost of implementing pre-planting treatments and planting the seedlings was high and the method is labour-intensive. It is therefore recommended that a pre-planting burn, which temporarily reduces the vigour of the surrounding sward and is economically viable, be applied before planting, and that the cost and effectiveness of strip-planting be investigated.