Post-plant Applications Research Articles

Effects of 2,4-D choline on fruiting in sensitive cotton

AbstractWith the increase in hectares planted to auxin-resistant cotton, the number of preplant, at-plant, and postplant applications of dicamba and 2,4-D choline to aid in the control of troublesome broadleaf weeds, including glyphosate-resistant Palmer amaranth, has increased. More dicamba and 2,4-D choline applications mean an increased risk of off-target movement. Field studies were conducted in 2019 to 2021 at the Texas Tech University New Deal Research Farm to evaluate dicamba-resistant cotton response to various rates of 2,4-D choline when applied at four growth stages (first square [FS] + 2 wk, first bloom [FB], FB + 2 wk, and FB + 4 wk). Applications of 2,4-D choline were applied at 1,060 (1X), 106 (1/10X), 21 (1/50X), 10.6 (1/100X), 2.1 (1/500X), and 1.06 (1/1000X) g ae ha−1 to Deltapine 1822 XF cotton. Relative to the nontreated control, yield losses were observed in all years at FS + 2 wk and FB from rates of 2,4-D choline ≥ 1/100X. At the FB + 4 wk application, only the 1X rate of 2,4-D choline resulted in a yield reduction in all three years. Micronaire, fiber length, and uniformity were negatively influenced by the 1/10X and 1X rates of 2,4-D choline at various timings in 2019, 2020, and 2021. In addition, short fiber content, neps, and seed coat neps increased where micronaire, fiber length, and uniformity were negatively impacted.

Effect of Phosphorus Fertilization on Yield of Chipping Potato Grown on High Legacy Phosphorus Soil

Potato (Solanum tuberosum L.) has low phosphorus (P) use efficiency as compared with other vegetable crops. This study was conducted at two commercial chipping potato farms (A and B) in Northeast Florida to evaluate different P rates for potato production. Plot size was 0.62 and 0.49 hectares for Farms A and B, respectively. The total trial area was 13.32 hectares per growing season for three consecutive years from 2018 to 2020. The randomized complete block design (RCBD) was employed with four replications per P rate. The chipping potato variety, ‘Atlantic’ was cultivated with three P rates: 0, 24.5, and 48.9 kg P ha−1 in 2018, and 12.2, 24.5, and 48.9 kg P ha−1 in 2019 and 2020. The soil of Farm A contained 497 mg kg−1 Mehlich-3 extractable P and 946 mg kg−1 aluminum (Al), and that of Farm B had 220 mg kg−1 Mehlich-3 extractable P and 253 mg kg−1 Al. The results showed that a P rate of 48.9 kg P ha−1 significantly improved tuber yield as compared to 0 in 2018 or 12.2 kg P ha−1 in 2019 and 2020. Application of 48.9 kg P ha−1 fertilizer P significantly increased the soil P level in 2018 and 2020, while the application of 24.5 kg P ha−1 fertilizer P increased the soil P level significantly in 2018 only. Tubers with 48.9 kg P ha−1 showed significantly lower external quality issues than 0 or 12.2 and 24.5 kg P ha−1. However, there were no significant differences in specific gravity, internal tuber quality, and tuber size among the different P rates. The tuber yield data show that potato plants grown on soil with high legacy P still require approximately 50 kg ha−1 P application for sustainable potato production in the area. This high P requirement results from the combination of high concentrations of active metals (Al and iron (Fe)) and a decrease in pH of one unit in the growing season. New P-fertilization programs with post-plant applications rather than with pre-plant application are urgently needed for minimizing P-immobilization by Al and Fe and improving P-use efficiency for potato production in the state.

Combining penthiopyrad with azoxystrobin is an effective alternative to control seedling damping-off caused by Rhizoctonia solani on sugar beet

The soil-borne fungus Rhizoctonia solani causes damping-off on sugar beet seedlings. Growers rely on fungicides to protect sugar beet in fields affected by R. solani. Quinone outside inhibitor (QoI) fungicides, such as azoxystrobin, have been applied as in-furrow and foliar sprays to manage R. solani, but repeated use of QoI fungicides pose risks in fungicide resistance. Penthiopyrad is a novel fungicide with the succinate dehydrogenase inhibitor (SDHI) mode of action. The objectives of this study were to compare the efficacy of penthiopyrad used as a sole seed treatment versus azoxystrobin as an in-furrow or a post-planting application for controlling R. solani; to determine if a penthiopyrad seed treatment combined with azoxystrobin as a post-planting application can improve control of R. solani over sole penthiopyrad seed treatment, azoxystrobin in-furrow or post-planting spray application. Seedling survival rate and area under disease progress curve (AUDPC) for seedling loss rate were used to measure the efficacy of each treatment. A sole penthiopyrad seed treatment at 14 g a. i. kg−1 of seeds, and penthiopyrad seed treatments at 7 and 14 g a. i. kg−1 of seeds combined with one azoxystrobin in-furrow application 14 days after planting resulted in similar seedling survival rate and AUDPC as achieved with the standard azoxystrobin in-furrow application. However, post-planting foliar spray of azoxystrobin alone failed to control seedling damping-off. Our research suggests that penthiopyrad can be used as a seed treatment to provide early protection to vulnerable seedlings while azoxystrobin can be used as a post-planting application to protect the ensuing adult plants.

Control of branched broomrape (Orobanche ramosa L.) in tomato (Lycopersicon esculentum Mill.) by olive cake and olive mill waste water

Effects of olive cake and olive mill waste water on Orobanche ramosa L. infection to tomato (Lycopersicon esculentum Mill.) were investigated in pot experiments conducted under glasshouse conditions during the spring/summer seasons of the 2016 and 2017. Treatments included the use of olive mill cake, cake extracts or mill waste water. In all experiments, treatments were arranged in a randomized complete block design with four replicates. Soil mulching with olive cake slightly affected total parasite shoot number but reduced its shoot dry weight compared with infested-control. Tomato shoot dry weight in all mulch treatments was not significantly different from that of parasite-infested control but greatly reduced compared with Orobanche-free control. Weekly application of olive cake aqueous extract for 3–6 weeks after tomato transplanting reduced tomato shoots dry weight and shoots number and dry weight of O. ramosa. Other extract treatments stimulated or had no effect on tomato growth or Orobanche infection compared with Orobanche-infested control. Soil-incorporated olive cake reduced tomato shoot and root dry weights at the highest (300 and 400 g per pot) rates used in the summer but rates between 50 and 400 g/pot significantly reduced tomato growth during the spring. All treatments significantly reduced Orobanche shoot number (except the lowest rate) and dry weight compared with Orobanche-infested control. Pre- or post-plant application of olive mill waste water and up to 400ml/pot showed no phytotoxicity on tomato; but lower rates in post-plant application increased crop shoot and root dry weights over parasite-free control. Total shoot number and dry weight of O. ramosa at 400 ml per pot were reduced by 70% and 74% for both parameters, respectively. In conclusion, olive mill waste water was more selective and effective against O. ramosa than olive cake and of a high potential use for parasite control in tomato.

Nematicidal activity of fluensulfone compared to that of organophosphate and carbamate nematicides against Xiphinema index and Longidorus vineacola

The nematicidal activity of fluensulfone against Xiphinema index and Longidorus vineacola was compared to that of organophosphate and carbamate nematicides. The number of X. index recovered via Baermann funnel from infested soil treated with fenamiphos or cadusafos at 2.0 and 4.0 mg l−1 soil was higher than that recovered from untreated infested soil. The number of recovered X. index after fluensulfone treatment at these concentrations reflected the same level of that recovered from the control soil; however, a high percentage of the nematodes were immobilized after extraction. In experiments using fig plants in pots, the X. index population was much lower after treatment with fluensulfone vs. fenamiphos. Moreover, the nematode control efficacy of fluensulfone against X. index was much higher by pre-planting vs. post-planting application. Treatment of L. vineacola-infested soil with fluensulfone at 2.0 and 4.0 mg l−1 soil slightly reduced the number of recovered nematodes in one of two trials, whereas fenamiphos and cadusafos did not reduce, and sometimes even increased the number of nematodes recovered from the soil. The nematode control efficacy of fluensulfone against L. vineacola was much higher than that of fenamiphos or oxamyl in pots with pepper plants. Again, pre-planting application of fluensulfone was more effective at reducing the L. vineacola population than post-planting application. The results suggest that fluensulfone can effectively control Xiphinema and Longidorus in the field, especially by pre-planting treatment.

Effects of growth-promoters on the productivity of <i></i><i>Arundo donax</i><i></i> L. (NileFiber™) grown as a purpose-grown biofuel feedstock in Nova Scotia

Arundo donax L. is a perennial grass species of Mediterranean origin. Its high biomass yield potential in its native climate has contributed to A. donax being an important biofuel feedstock crop. This study investigates the potential of A. donax as a purpose-grown biomass feedstock for advanced biofuel production in Nova Scotia. The effects of nine different growth-promoters (bacterial and fungal species, a seaweed extract, and a lipo-chitooligosaccharide) and two inoculation methods on A. donax biomass productivity were investigated through three experimental trials: one greenhouse and one field trial inoculated by a post-planting application of the supplements around the plant stem (soil drenching) and one greenhouse trial with inoculation by root soaking just prior to planting (2016). The survival of A. donax over the winter was also evaluated over two winter seasons (2014–2015 and 2015–2016). Penicillium bilaiae Chalab. illustrated the most consistent positive effects on biomass productivity across ex...

Environmental fate of terbuthylazine and hexazinone in a planted forest steepland Recent Soil, New Zealand

The use of herbicides for weed control in New Zealand planted forestry is important for primary production. The objective of this study was to assess the environmental fate of terbuthylazine and hexazinone in a Recent Soil following an aerial post-plant herbicide application in a New Zealand planted forest. Soil and forest litter were collected from four plots within a recently harvested and replanted Pinus radiata experimental sub-catchment. Samples were taken before and up to 6 months after the aerial application of terbuthylazine and hexazinone. There was no drainage below 1-m depth in the first month after spray application. On the following month, there were six drainage events ranging from 12 to 36 mm. Both terbuthylazine and hexazinone were located predominantly in the 0–10 cm soil depth, followed by the litter layer with only small amounts detected below 10 cm soil depth. Following a month of drainage events, hexazinone showed an increase at a soil depth of 10–50 cm. Both terbuthylazine and hexazinone rapidly dissipated with time after spray application, and predicted half-lives for both active ingredients were less than 1 day. The first 2 weeks after spray application were found to pose the greatest potential risk of movement off-site, after which the risks were low. Organic matter management practices that influence the amount and distribution of forest floor, litter and harvest residue have an important role in determining the environmental fate of both terbuthylazine and hexazinone.

Growth and early fruit production of ‘Tiben’ blackcurrants fertilised with pre- and post-planting applications of mineral fertilisers and swine manure

The aim of the study was to examine the effects of different fertiliser strategies on the growth and fruit production of ‘Tiben’ blackcurrants (Ribes nigrum L.). The trial was performed under controlled greenhouse conditions from 2007 to 2010 on plants grown in 50-L polyethylene bags filled with a coarse-textured soil that was low in organic matter and available phosphorus (P) and potassium (K). Prior to planting, the soil was mixed with either superphosphate and potassium sulphate fertilisers at rates of 0.7g P and 2.8g K per plant or with solid swine manure at a rate of 300g per plant, which was equivalent to 170kg nitrogen (N) per ha. After planting, the plants were fertilised with either ammonium nitrate at rates of 1.3–2.0g N plant−1 per year or with swine manure each year at the same amount as used prior to planting. Another treatment group was fertilised with manure prior to planting and ammonium nitrate after planting and was fertilised each following year with a complete foliar fertiliser. Plants grown without fertiliser or manure were also included as a control. The control plants had the lowest root dry weight, while the plants fertilised with any combination of mineral fertiliser had a greater root dry weight than those grown with manure only. Plants supplied with mineral fertilisers also had stronger vigour, higher photosynthetic rates, more chlorophyll in the leaves, and greater yields than did those grown with manure only or no fertiliser. Each fertiliser treatment increased the concentration of N, P, K, and magnesium (Mg) in the leaves relative to the control, and all but the concentration of leaf K was highest in the plants supplied with foliar fertiliser. The fertiliser treatments increased the soluble solids concentration and acidity of the fruit each year but resulted in lower berry weights than the control treatment during the fourth year of the study (2010). Fruit anthocyanins were not affected by any fertiliser treatment. Overall, the plants had the strongest growth and highest fruit production when P and K fertilisers or swine manure was applied prior to planting, and N fertiliser was applied each year after planting.

Isolation, characterization, and formulation of antagonistic bacteria for the management of seedlings damping-off and root rot disease of cucumber

Antagonistic bacteria are common soil inhabitants with potential to be developed into biofungicides for the management of seedling damping-off, root rot, and other soil-borne diseases of various crops. In this study, antagonistic bacteria were isolated from a commercial potato field and screened for their growth inhibition of fungal and oomycete pathogens in laboratory tests. The biocontrol potential of the 3 most effective antagonistic bacteria from the in vitro tests was evaluated against seedling damping-off and root rot of cucumber caused by Pythium ultimum. Based on phenotypic characteristics, biochemical tests, and sequence analysis of 16S-23S rDNA gene, the 3 antagonistic bacteria were identified as Pseudomonas fluorescens (isolate 9A-14), Pseudomonas sp. (isolate 8D-45), and Bacillus subtilis (isolate 8B-1). All 3 bacteria promoted plant growth and suppressed Pythium damping-off and root rot of cucumber seedlings in growth-room assays. Both pre- and post-planting application of these bacteria to an infested peat mix significantly increased plant fresh masses by 113%-184% and percentage of healthy seedlings by 100%-290%, and decreased damping-off and root rot severity by 27%-50%. The peat and talc formulations of these antagonistic bacteria applied as seed or amendment treatments to the infested peat mix effectively controlled Pythium damping-off and root rot of cucumber seedlings and enhanced plant growth. The survival of all 3 antagonistic bacteria in peat and talc formulations decreased over time at room temperature, but the populations remained above 10(8) CFU/g during the 180-day storage period. The peat formulation of a mixture of 3 bacteria was the best seed treatment, significantly increasing the plant fresh masses by 245% as compared with the Pythium control, and by 61.4% as compared with the noninfested control. This study suggests that the indigenous bacteria from agricultural soils can be developed and formulated as biofungicides for minimizing the early crop losses caused by seedling damping-off and root rot diseases.

Field Efficacy of Neem Seed Oil and Diazinon in the Management of Sweetpotato Weevil, Cylas puncticollis (Boh.) in South-eastern Nigeria

The efficacy of the pre- and post-planting application of neem seed oil (NSO) or/and diazinon and time of harvest for the control of sweetpotato weevil, Cylas puncticollis (Boh.) was evaluated during the 2009 and 2010 cropping seasons. Forty-eight plots of 3 x 4 m 2 each were demarcated and 240 sweetpotato (var. TIS2532.op.1.13) vine cuttings were dipped into 0, 30 and 50 mls NSO and 30 mls of diazinon mixed in 2 and 10 litre soapy water respectively, and kept for 30 mins before planting. Similar treatment was also basally applied post-planting at 1MAP. In 2009, results showed that treatments (NSO or diazinon or their combinations) did not significantly influence percentage plant stand at harvest in both years, but lower percentage plant stands were obtained at 6 MAP (47.72%) than at 5MAP (56.87%). Significantly higher mean total weights of 34.44 t/ha was obtained in 2009 and 8.99 t/ha in 2010 respectively. Similarly, yield ranged from as high as 53.69 t/ha at 5MAP in 2009 to as low as 5.51t/ha at 6MAP in 2010. Significantly lower C. puncticollis attributes as a pest were obtained in 2009 than in 2010. Treatments significantly suppressed total progeny from 11.07 to 7.08, scores from 3.78 to 2.52 and root damage from 68.59% (Pr0Pt0) to 44.38% (Pr3Pt3), 66.55% to 40.00% at 5 to 6MAP. Time of application was significant as 50 mls of NSO applied pre- and post-planting gave highest (35.30%) control of the pest at harvest.

Economics of Neem (Azadirachta indica A. Juss) Seed oil for the Management of Cylas puncticollis (Boheman) (Coleoptera: Brentidae) infesting Sweetpotato in Nigeria

The cost benefits of pre- and post (after one month) planting application of neem seed oil (NSO) on sweetpotato during late season production (August to February in 2009 and 2010) for the management of the sweetpotato weevil, Cylas puncticollis (Bohoman) was determined using the complete costing analysis. Root yield and percentage infestation was determined by ANOVA and significant means separated using SNK test at 5 % probability. The results indicated that 30 mls (4 l/ha) NSO applied pre- and post-planting (Pr2Pt2) had the highest comparative advantage as the income was 457 % (N1,130,800.50) and provided 22.70 % control of C. puncticollis infestation. However, pest control of 33.4 % was obtained when 50 ml (6 l/ha) of NSO was applied pre- and post-planting (Pr3Pt3) and it significantly suppressed root infestation from 64.22 % (Pr0Pt0)to 42.75 %. The sweetpotato pest management tactics developed in this study was discussed.

NOTA TÉCNICA: CUSTOS OPERACIONAIS DO PLANTIO MECANIZADO E SEMIMECANIZADO DE CANA-DEAÇÚCAR

Atualmente, a produção de cana-de-açúcar tem grande importância no agronegócio do Brasil. Por essa razão, este trabalho foi desenvolvido com o objetivo de comparar os custos operacionais dos sistema de plantio mecanizado e semimecanizado de cana-de-açúcar. Foi realizado um levantamento das operações de plantio, considerando todos os aspectos referentes à sulcação da área, distribuição, fracionamento, cobertura, repasse do colmo e uma aplicação de herbicida ao final do plantio. Foram determinados os rendimentos operacionais, custos fixos e variáveis de cada sistema de plantio. Os resultados mostraram que o plantio mecanizado apresentou uma redução de R$ 841,84 por hora, em relação ao custo operacional do plantio semimecanizado. O rendimento operacional do plantio mecanizado foi de 0,66 ha h-1, enquanto o rendimento do plantio semimecanizado foi de 1,31 ha h-1. Em relação aos custos e rendimento operacionais, a adição de um segundo conjunto ao sistema de plantio mecanizado implicaria aumento no rendimento operacional para 1,32 ha h-1, ainda com economia de R$ 297,56 por hora, quando comparado com sistema semimecanizado.

Efficacy of Brassicaceous Seed Meal Formulations for the Control of Apple Replant Disease in Conventional and Organic Production Systems.

The efficacy of brassicaceous seed meals for the control of apple replant disease and the effects of such treatments on the causal pathogen complex were examined in conventional and organic production systems. When used in conjunction with a postplant application of mefenoxam, Brassica juncea and Sinapis alba seed meal soil amendments were as effective as preplant fumigation of soil with 1,3-dichloropropene-chloropicrin in terms of disease control, tree growth, and overall fruit yields of Gala/M26. Brassica napus seed meal amendment-mefenoxam soil drench also enhanced yields in a manner comparable to preplant fumigation, but vegetative growth was intermediate between the control and fumigation treatments. When applied alone, seed meal amendments failed to enhance tree growth or control disease to the level attained in response to soil fumigation. Postplant mefenoxam treatments revealed that failure of seed meal amendments to enhance tree growth and yield when used independently was due, at least in part, to increased apple root infection by Pythium spp. in B. napus and S. alba seed meal-amended soils, and by Phytophthora cambivora in B. juncea-amended soil. As mefenoxam treatment is not compatible with organic cropping systems, a seed meal blend was formulated which, based upon biological activity, was predicted to suppress known components of the target pathogen complex without need of additional treatment. Gala/M26 trees planted in soils treated with a 1:1 ratio of B. juncea:B. napus seed meal blend performed as well in terms of disease control and vegetative growth as trees cultivated in fumigated soil at an organic-certified orchard. Because these trials utilized the highly susceptible rootstock M26, the results demonstrate that these amendments are a viable alternative to soil fumigation for the control of apple replant disease in both conventional and organic systems.

Effect of Pre- and Post-Plant Fungicide and Fertilizer Treatments on Infection by Colletotrichum acutatum, Plant Survival, and Yield of Annual Strawberry in Florida

The effects of pre-plant dips and post-plant treatments on the infection by Colletotrichum acutatum, survival, and yields of strawberry plants were evaluated over two seasons in Florida using naturally infected transplants imported from northern nurseries. Handling practices such as washing, refrigerating, and dipping plants in water had no effect on infection, survival, or yield. Pre-plant dips with the fungicide Switch 62.5 WDG (cyprodinil + fludioxonil) and, in some cases, with Abound 2.08F (azoxystrobin), reduced infection and plant mortality, and increased yield. Pre-plant dips with Oxidate (hydrogen peroxide) were ineffective and, in some cases, increased plant mortality and reduced yield. Fertilizer treatments, such as dipping and spraying plants with Brotomax (8-0-0 plus micronutrients) or application of slow-release Osmocote (15-9-12 plus micronutrients) after planting, had no effect or reduced plant survival and yield. Post-plant application of Surround WP, a kaolin clay intended to reduce heat stress and control mites and insects, had little or no effect on infection, survival, or yield. In summary, strawberry transplants infected with C. acutatum can be dipped in Switch or Abound at planting to reduce infection and increase survival and yield, but other treatments and practices examined are unlikely to have beneficial effects. Accepted for publication 6 October 2009. Published 25 January 2010.

Weed Control with Hydrophobic and Hydrous Kaolin Clay Particle Mulches

Three experiments were performed to determine the effect of amending the soil surface layer and mulching with hydrophobic kaolin particle on weeds and blackberry (Rubus subgenus Rubus Watson) plants. In the first study a processed kaolin material (product M-96-018, Engelhard Corporation, Iselin, N.J.), was incorporated in August into the top 3 cm of freshly roto-tilled field that had been in pasture the previous 5 years. The following spring, dry weight of weed vegetation in the control treatment was 219 g·m–2 and was significantly higher (P = 0.05) than the 24 g·m–2 harvested from the treated soil. In two other studies, planting holes for blackberry transplants were either 1) pre- or postplant mulched with a 2- or 4-cm layer of 5% or 10% hydrophobic kaolin in field soil (w/w), or 2) postplant treated with a) napropamide, b) corn gluten meal, c) a product comprised of hydrous kaolin, cotton seed oil, and calcium chloride in water (KOL), d) hand weeded, or e) left untreated. Although untreated plots had 100% weed cover by the end of July, herbicide treatments, 4-cm deposition of hydrophobic kaolin particle/soil mulch, and KOL all suppressed weeds the entire establishment year. Preplant application of hydrophobic kaolin mulch and postplant application of KOL reduced blackberry growth and killed transplants, respectively. In year 2, blackberry plants produced more primocanes that were on average 10-cm taller in weed-free plots (herbicide, 4-cm kaolin soil mulch, and mechanical weeding) than in weedy plots (control and 2-cm kaolin soil mulch). In year 3, yield was significantly lower in control plots (1.5 kg/plant) than in plots that were treated with napropamide and 2- and 4-cm hydrophobic kaolin mulch, or hand weeded during the establishment year (4 kg/plant). The results showed that 4-cm hydrophobic kaolin mulch applied after planting can suppress weeds without affecting blackberry productivity. These kaolin products are excellent additions to the arsenal of tools for managing weeds in horticultural crops.

Evaluation of calcium cyanamide and liming for control of clubroot disease in cauliflower

The effects of six control strategies involving calcitic lime, hydrated lime, calcitic limestone dust and a granular form of calcium cyanamide were evaluated on a cauliflower crop during a 2-year field study. Prior to the first growing season, fall applications of 5 and 25 t ha −1 of calcitic lime broadcast were made. In the first growing season, only pre-planting application of hydrated lime and calcium cyanamide successfully reduced disease indices and increased yields. Post-planting application of calcium cyanamide, and post-harvest application of calcitic lime the preceding year were ineffective. In the second growing season, the best clubroot control results were obtained with the finest lime materials (hydrated lime, calcitic limestone dust) and the preceding post-harvest intensive liming treatment. Successful treatments raised pH from 5.7 to 7.0 in the first season and from 6.7 to 7.4 in the second season. The high cost of using calcium cyanamide was reduced by means of band application along the transplant rows.

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.

Forestry herbicide influences on biodiversity and wildlife habitat in southern forests

In the southern United States, herbicide use continues to increase for timber management in commercial pine (Pinus spp.) plantations, for modifying wildlife habitats, and for invasive plant control. Several studies have reported that single applications of forestry herbicides at stand initiation have minor and temporary impacts on plant communities and wildlife habitat conditions, with some reports of enhanced habitat conditions for both game and nongame species. Due to the high resiliency of floral communities, plant species richness and diversity rebound rapidly after single herbicide treatments, with short- and long-term compositional shifts according to the selectivity and efficacy of the herbicide used. Recently, however, a shift to the Southeast in North American timber supplies has resulted in increased forest management intensity. Current site-preparation techniques rely on herbicide combinations, often coupled with mechanical treatments and ≥1 years of post-planting applications to enhance the spectrum and duration of vegetation control. This near-total control of associated vegetation at establishment and more rapid pine canopy closure, coupled with shortened and repeated rotations, likely will affect plant diversity and wildlife habitat quality. Development of mitigation methods at the stand and landscape levels will be required to minimize vegetative and wildlife impacts while allowing continued improvement in pine productivity. More uncertain are long-term impacts of increasing invasive plant occupation and the projected increase in herbicide use that will be needed to reverse this worsening situation. In addition, the potential of herbicides to meet wildlife management objectives in areas where traditional techniques have high social costs (e.g., prescribed fire) should be fully explored.

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.

Pre- and post-plant applications of copper-based compounds to control Erwinia soft rot of calla lilies

Erwinia carotovora subsp. carotovora is a plant pathogen responsible for producing soft rots in many vegetable and floricultural crops, particularly calla lilies, Zantedeschia spp. In this study, the efficacy of various copper-based compounds, such as Phyton-27, Champ 2, fixed copper, and analytical copper, was compared under laboratory and greenhouse conditions. Copper-based compounds suppressed bacterial growth at various cupric ion concentrations in vitro, but the efficacy of some products was reduced by the presence of phosphate ions in fertilizer solutions used in commercial greenhouses. Under greenhouse conditions, the compounds were applied as a preplant or a postplant treatment to tubers of calla lilies. Postplant applications were made either as an overhead drench or through subirrigation, and the applications were carried out at different stages of plant development. Preplant application of Champ 2 or Phyton-27 did not reduce the number of diseased plants compared with the controls. In contrast, postplanting applications of Champ 2 or fixed copper were effective in reducing soft rot; however, these two compounds also reduced overall plant growth. Poor root development and reduced plant growth occurred when these products were applied during the early stages of plant development and when the products were applied overhead rather than through subirrigation.