Effects of nitrogen rate on nitrate–nitrogen accumulation in forage kale and rape crops

Nitrogen fertilizer is applied to supplement soil nitrogen supply to maximize forage brassica crop dry-matter production. However, nitrogen fertilizer applications in excess of that required to maximize growth result in potentially toxic nitrate–nitrogen (NO₃–N) concentrations in grazeable plant tissues. Three experiments, two for forage kale at Lincoln (Canterbury) and one for forage rape at Hastings (Hawke's Bay) in New Zealand were grown under different rates of nitrogen (0–500 kg N ha⁻¹) to determine the effect of different rates of nitrogen on NO₃–N content of different plant parts of the crops. One of the kale experiments was grown with either full irrigation or no rain and no irrigation over summer, hereafter referred to as summer drought. The NO₃–N concentration on a whole plant (weighted average) basis increased from 0·1 mg g⁻¹ dry matter for the control plots to 2·30 mg g⁻¹ for the 500 kg N ha⁻¹ plots for forage kale. It increased from 0·99 for the control plots to 3·37 mg g⁻¹ for the 200 kg N ha⁻¹ plots for forage rape crops. However, NO₃–N concentration increased with N supply under the summer-drought plots from an average of 0·33 mg g⁻¹ when ≤120 kg N ha⁻¹ was applied to 2·30 mg g⁻¹ for the 240 kg N ha⁻¹ treatments but was unaffected by N supply under irrigation. The NO₃–N concentrations were higher in the stems and the petiole (which included the midrib of the leaf) than leaves in all three experiments. The NO₃–N concentration was highest at the bottom of the kale stem and decreased towards the top. We recommend N application rates based on soil tests results, and for conditions similar to the current studies up to 300 kg N ha⁻¹ under irrigation and adjusted lower N rates for regions prone to dry summers.     

Effect of pre-emergence herbicides and timing of soil saturation on the control of six major rice weeds and their phytotoxic effects on rice seedlings

The study evaluated the effects of pre-emergence herbicides and their rates [oxadiazon (0.5 and 1 kg ai ha⁻¹), pendimethalin (1 and 2 kg ai ha⁻¹), and pretilachlor with safener (0.6 kg ai ha⁻¹)], and time of soil saturation establishment after herbicide application [1, 3, 5, and 7 days after spray (DAS)] in controlling the six major rice weeds, and their phytotoxic effects on rice seedling growth. All herbicides provided 100% control of Echinochloa colona, Echinochloa crus-galli, Leptochloa chinensis, Cyperus iria, and Amaranthus spinosus. Murdannia nudiflora was 100% controlled by oxadiazon and pretilachlor with safener, but poorly controlled (22–75%) by pendimethalin. Pendimethalin at 2 kg ai ha⁻¹ was more effective than at 1 kg ai ha⁻¹ in reducing the biomass of the stem, leaf, and root of M. nudiflora irrespective of timing of soil saturation. Rice plant height was reduced to a maximum (77–96%) by pendimethalin at 2.0 kg ai ha⁻¹ followed by oxadiazon at 1.0 kg ai ha⁻¹ (38–70%) compared to the non-treated control. In contrast, the tallest rice plants were observed in the non-treated control and those treated with pretilachlor with safener which had 80–100% rice plant survival. The lowest rice plant survival of 0, 6, 7, and 16% was found in the soil applied with pendimethalin at 2 kg ai ha⁻¹ and saturated at 1, 3, 5, and 7 DAS, respectively, which was followed by oxadiazon at 1 kg ai ha⁻¹. All herbicides except pretilachlor with safener reduced SPAD values with early soil saturation, which improved with delay in soil saturation timing. Pendimethalin at 2 kg ai ha⁻¹ reduced the SPAD values of rice plants by 100–164% relative to the non-treated control and produced the highest phytotoxicity symptoms. Pendimethalin also reduced rice shoot biomass more than oxadiazon, which was compounded by early soil saturation after herbicide application. Pretilachlor with safener was the only herbicide that exhibited low phytotoxic symptoms on rice plants and did not reduce leaf, stem, root, and shoot biomass of rice. Percent reduction in rice leaf, stem, root, and shoot biomass by the different herbicides was in the order of pendimethalin 2 > oxadiazon 1 > pendimethalin 1 > oxadiazon 0.5 > pretilachlor with safener 0.6 kg ai ha⁻¹. Each herbicide treatment reduced rice growth parameters as soil saturation was delayed in the order of 1 DAS > 3 DAS > 5 DAS > 7 DAS. The study suggests that soil water content and herbicide rates are important factors in influencing herbicide phytotoxicity in rice. The application of herbicides should be avoided when the soil is too wet, and irrigation should be delayed at least one week after herbicide application.     

Efficacy of azoxystrobin for the control of cucumber downy mildew (Pseudoperonospora cubensis) and fungicide residue analysis

During a five-year trial (2007–2011), the efficacy of azoxystrobin (Quadris, 250 g a.i. L⁻¹, Syngenta) in two doses (187.5 g a.i. ha⁻¹ and 250 g a.i. ha⁻¹) and chlorothalonil (Bravo 720-SC, 720 g a.i. L⁻¹, Syngenta) at a rate of 1.44 kg a.i. ha⁻¹ was tested for the control of cucumber downy mildew (CDM). Cultivars that were susceptible or resistant to CDM (Regal and Haros, respectively) were tested for their response to fungicide applications. Differences in both disease severity and yield of the cultivars among resistance levels and fungicide treatments were observed. A highly significant and negative correlation was obtained between AUDPC and yield. Higher yields can be achieved by planting more resistant cultivars in combination with lower doses of fungicides. This is an indication that CDM contributes significantly to yield losses in cucumber production in Serbia. While monitoring the degradation of azoxystrobin residues, a decrease in residue levels to 1.0 mg kg⁻¹ below the maximum residue level (MRL) was observed at the end of the pre-harvest interval (PHI).     

Herbicide and winter flood treatments for controlling volunteer rice off-season

Field experiments were conducted to study the efficacy of 12 herbicide treatments for volunteer rice control with, or without, winter-flooding in Stuttgart and Rohwer, Arkansas, USA over two years (2012–13 and 2013–14). Herbicides were applied either in the fall or at 35 d prior to planting rice in the spring. Commercially harvested Clearfield™ long-grain inbred rice 'CL152' was used as volunteer rice seed, broadcasted and lightly incorporated in October, 2012 and 2013. 'Jupiter' (medium-grain inbred, conventional rice) was planted in May as the rice crop. Winter-flood was initiated soon after the fall herbicide treatments were applied and terminated in February. Winter-flood reduced volunteer rice germination by 34% in 2013 and by 40% in 2014. Some fall herbicide treatments, without winter flood, generally caused more injury to the rice crop planted in the spring than the winter-flooded treatments. Fall application of pyroxasulfone (0.12 kg ha⁻¹), flumioxazin (0.14 kg ha⁻¹), and sulfentrazone (0.34 kg ha⁻¹) as well as pre-plant application of pyroxasulfone (0.12 kg ha⁻¹) and 2,4-D (2.24 kg ha⁻¹), resulted in lower volunteer rice infestation, averaged over flood treatments. Pre-plant application of 2,4-D (2.24 kg ha⁻¹), sulfentrazone in the fall (0.34 kg ha⁻¹) and pyroxasulfone pre-plant (0.12 kg ha⁻¹) injured the rice crop by 20%, 23%, and 47%, respectively. Fall application of pyroxasulfone (0.12 kg ha⁻¹) followed by a lower rate of 2,4-D (1.12 kg ha⁻¹) 35 d pre-plant caused minimal (6%) crop injury and did not reduce yield. This treatment provided better volunteer rice control (73%) than pyroxasulfone alone at 0.12 kg ha⁻¹ applied in the fall (64%). To evaluate the overwintering potential of hybrid and non-hybrid volunteer seeds, these seed types were planted at three depths (0, 7.5, 15 cm) in flooded and non-flooded conditions in a buried-pot experiment at Stuttgart and Rohwer over 2 years. Winter-flood reduced rice germination by 50% in 2013–14 and 40% in 2014–15 (averaged over seed type and burial depth), after 160 d and 130 d of burial, respectively. After the winter, the viability of hybrid seed (germinable + dormant) was higher (13 and 53%) than that of non-hybrid seed (8 and 27%) in both years.     

Effects of water regime,nitrogen fertilization,and rice plant density on growth and reproduction of lowland weed Echinochloa crus-galli

Direct-seeded rice systems are increasing in Asia as farmers respond to the high labor cost and shortage of water. Echinochloa crus-galli is one of the most problematic and competitive weeds in direct-seeded rice systems. Because of concerns about excessive herbicide use, there is an interest in developing cultural weed management strategies. However, the design of such strategies requires a better understanding of the weed response to crop density, nutrition, and water regime. A study was therefore conducted in pots to determine the effect of water (flooded and aerobic), nitrogen (N) fertilization (0, 100, and 200 kg N ha⁻¹), and rice density [0, 4 rice plants (≈20 kg seed ha⁻¹), and 16 rice plants (≈80 kg seed ha⁻¹)] on the growth and reproduction of E. crus-galli. When grown alone, the growth and seed production of E. crus-galli were higher in flooded conditions than in aerobic conditions. However, no such differences were observed when E. crus-galli was grown with rice interference. E. crus-galli growth and seed production increased with increases in N rate. Irrespective of water regime and N rate, the growth and seed production of E. crus-galli declined with increases in rice density. At 100 kg N ha⁻¹, for example, E. crus-galli shoot biomass and seed production decreased by 84–86% and 82–87%, respectively, when grown with 16 rice plants compared with its growth without rice interference. The results suggest that growth and seed production of E. crus-galli can be greatly reduced by increasing rice seeding rate. However, there is a need to involve other weed management strategies to achieve complete control of E. crus-galli and other weed species.     

Effects of nitrogen application rate on productivity,nutritive value and winter tolerance of timothy and meadow fescue cultivars

Finnish N fertilizer application regulations for forage grasses are based on field experiments mainly conducted in the 1960–1970s with cultivars and management practices typical of the time. In order to update the yield response function of N, to make it better suited to current grassland farming, field experiments were conducted at two sites in 2015–2017 with two cultivars of timothy (Phleum pratense L.) and one of meadow fescue (Festuca pratensis Huds.). Dry matter (DM) yield, nutritive value and N balance were evaluated, with N application levels 0, 150, 200, 250, 300, 350, 400 and 450 kg N ha⁻¹ year⁻¹. The grasses were harvested three times per season. The data indicate that the DM yield response was significantly stronger, and N was used more efficiently for DM production than earlier without compromising the nutritive value, especially during the first two years. The third harvest produced on average 23% of the annual yield, utilizing N efficiently. N application rates below 350 kg N ha⁻¹ year⁻¹ did not cause substantial overwintering losses or lodging. The data indicate that with changing climate and improved cultivars and management practices, there is a need to modify the rates and timing of N application. The results suggest that N application levels could be increased by at least 50 kg N ha⁻¹ year⁻¹ from the current maximum accepted rate (250 kg N ha⁻¹ year⁻¹) without too high NO₃^- or CP concentrations in feed, or too high N balance that indicates increasing risk of N leaching.     

Winter cover crops influence Amaranthus palmeri establishment

Winter cover crops were evaluated for their effect on Amaranthus palmeri establishment and growth in cotton production. Cover crops examined included rye and four winter legumes: narrow-leaf lupine, crimson clover, Austrian winter pea, and cahaba vetch. Each legume was evaluated alone and in a mixture with rye. Cover crop biomass in monoculture was greatest for rye and lupine (>6750 kg ha⁻¹), while clover, pea, and vetch were less and ranged from 2810 to 4610 kg ha⁻¹. Cover crop biomass was more than doubled when rye was mixed with clover or vetch relative to the legume monoculture. In early-June, A. palmeri densities were 46 seedlings m⁻² in the non-disturbed areas between cotton rows in the fallow, while populations were <4 seedlings m⁻² with rolled vetch or pea and 18 and 29 seedlings m⁻² in rolled clover and lupine. Rye and legume mixtures reduced A. palmeri densities to <3 seedlings m⁻², while rye monocultures had 8 seedlings m⁻². There were no differences in A. palmeri densities (≥144 plants m⁻²) in the cotton row among cover crop treatments. By late-June, rye and winter pea controlled A. palmeri in the row middle >80% relative to the non-cover crop fallow treatment, while control from clover, vetch and lupine ranged from 64 to 70%. The relationship between A. palmeri control in between cotton rows and cover crop biomass was described by a log-logistic regression model with 4530 kg ha⁻¹ providing median weed control (Bio₅₀); predicted A. palmeri control was 25, 50, and 75% from 2950, 4900, and 8600 kg ha⁻¹ cover crop biomass, respectively. However, A. palmeri plants in the cotton rows prevented yield production in the absence of herbicides. Where A. palmeri was controlled with herbicides, the highest yields occurred following rye, with lower yields following lupin/rye mixture and treatments including pea. Management of herbicide resistant weed species requires diverse management tactics; this may include high-biomass cover crops to reduce weed establishment between crop rows. However, greater research effort is needed to devise weed management options for the crop row that do not rely exclusively on the diminishing array of herbicide tools.     

Evaluation of potential biocides for control of the earthworm Eukerria saltensis (Oligochaeta: Ocnerodrilidae), a pest of rice in southern Australia

The earthworm Eukerria saltensis can cause severe crop establishment problems in aerially sown rice grown on heavy clay soils in southern Australia. Damage occurs indirectly through destabilization of the topsoil, increased water turbidity, and mobilization of soil nutrients into the water column which leads to increased algal growth. We investigated the possibilities for chemical control of E. saltensis using laboratory bioassays and a series of field trials involving either the use of enclosures in flooded crops or soil incorporation of pesticides into rice fields during fallow periods or shortly before flooding. The four most toxic compounds in 7 day soil/water laboratory bioassays were carbofuran, acetamiprid, bendiocarb and lambda-cyhalothrin which provided corrected mortalities of 86–100% at 2 mg a.i. L⁻¹. Other compounds that showed some level of efficacy (corrected mortality >20% at one or more rates) were imidacloprid, esfenvalerate, thiacloprid, niclosamide and alpha-cypermethrin. Twenty-six of the 38 pesticides evaluated failed to produce mean corrected mortalities >6% at application rates of up to 2 mg a.i. L⁻¹. Eight trials were conducted in flooded rice crops using small stainless steel enclosures and carbofuran, thiodicarb, niclosamide and bendiocarb at rates of 1 and 2 kg a.i. ha⁻¹. Trials were assessed 8–14 days after chemical application. None of these treatments produced a statistically significant decrease in Eukerria biomass, although consistent downward trends in response to higher treatment rates were evident in 2 trials (one with carbofuran and one with bendiocarb). Three trials with liquid pesticides watered into fallow rice fields were conducted with carbofuran (0.5, 1.0 and 5.0 kg a.i. ha⁻¹) and thiodicarb (0.94 and 1.87 kg a.i. ha⁻¹) however only the 5.0 kg a.i. ha⁻¹ carbofuran treatment provided significant (P < 0.05) levels of control. Preflood soil applications of liquid carbofuran, thiodicarb and niclosamide (2 kg a.i. ha⁻¹), granular carbofuran and granular ethoprophos (0.5–2 kg a.i. ha⁻¹) also did not provide statistically significant levels of control, although the 2 kg a.i. ha⁻¹ liquid and granular carbofuran treatments did provide moderate levels of suppression (49–84%). Although further field trials with compounds such as acetamiprid and lambda-cyhalothrin may prove valuable, our results suggest chemical control of E. saltensis may be difficult to achieve with environmentally acceptable pesticides applied at economically viable rates. Cultural approaches such as appropriate crop rotations and landforming to ensure uniformly shallow water should continue to form the basis of Eukerria management programs.     

Managing Meloidogyne incognita and Bemisia tabaci with thiacloprid in cucumber crops in China

Field trials were conducted to determine the potential use of thiacloprid for integrated Meloidogyne incognita and Bemisia tabaci B biotype control in cucumber (Cucumis sativus Linn.) in China. The following five treatments were evaluated: three thiacloprid doses (7.5, 15, and 30 kg ha⁻¹), an avermectin treatment (7.5 L ha⁻¹) and an untreated control. All thiacloprid application rates were effective for reducing the M. incognita and B. tabaci B biotype populations. M. incognita was reduced by 51.0%∼86.7% on 60th day and B. tabaci B biotype was reduced by about 37.2%∼95.3% within 21 days, respectively. In addition, greater thiacloprid doses resulted in fewer nematodes and whiteflies. Over two successive years, the cucumber plants that were treated with thiacloprid at a dose of 15 kg ha⁻¹ had the greatest plant height, plant vigor and marketable yield, which were 134.1 cm, 91, 1514.3 g plant⁻¹, respectively in 2010–2011 and 151.9 cm, 93, 1651.4 g plant⁻¹, respectively in 2011–2012. In addition, thiacloprid was superior to avermectin. The results of this study demonstrated that thiacloprid could be used in cucumber production for the integrated control of M. incognita and B. tabaci B biotype. Furthermore, a dose of 15 kg ha⁻¹ of thiacloprid was recommended for controlling nematode and whitefly populations according to the control effect and marketable cucumber yield.     

Effect of neemarin on life table indices of Plutella xylostella (L.)

The effects of neemarin at 5, 10, 15 and 20 mg l⁻¹ on the life table indices of Plutella xylostella (L.) were studied on cauliflower in the laboratory. Survivorship was increased with increasing concentrations. A total of 69% eggs hatched at 20 mg l⁻¹ compared 85% in the control. Mortality (d_x) of 1st instars was higher than the other instars in both exposed and unexposed individuals. Life expectancy (e_x) was high in the untreated control and reduced at 20 mg l⁻¹. Development times of immatures were prolonged to 32 days at 20 mg l⁻¹ as compared to 18.6 days in the untreated control. Neemarin significantly reduced the emergence of adults. Potential fecundity (P_f) was 34 females/female/generation at 20 mg l⁻¹ and 92 in the control. The net reproductive rate (R₀) was significantly reduced with the increase in concentration. The intrinsic rate of increase (r_m) and finite rate of increase (λ) were significantly decreased at 20 mg l⁻¹ as compared to other concentrations tested and in the control. Mean generation time (T_c) and corrected generation time (τ) were prolonged at 20 mg l⁻¹ and significantly differed to those of the untreated control. Doubling time (DT) was significantly extended to 28.4 days at 20 mg l⁻¹ as compared to 6.1 days in the control.     

Termite prevalence and crop lodging under conservation agriculture in sub-humid Zimbabwe

Provision of permanent soil cover using crop residues in conservation agriculture (CA) is constrained by livestock grazing and termite consumption in smallholder farming systems of sub Saharan Africa. This study evaluated the effects of surface applied maize (Zea mays L.) crop residues on termite prevalence, crop damage due to termite attack and maize yield over two seasons, 2008/9 and 2009/10. Treatments with residue application rates of 0, 2, 4 and 6 t ha⁻¹ under CA and a conventional mouldboard ploughing (CMP) control were laid out in a randomized complete block design with four replicates on three farm sites in Kadoma, Zimbabwe. Maize residues increased (P < 0.05) termite numbers compared to CMP treatment. Crop lodging at harvest increased (P < 0.05) from 30 to 34% in CMP to 42–48% in CA systems. However, no significant difference was found in crop lodging with increasing residue rates within CA treatments. Significantly higher crop yields were observed under CA (P < 0.05) ranging from 2900 - 3348 kg ha⁻¹ in 2008/9 season compared to CMP with 2117 kg ha⁻¹. Nevertheless, increasing residue cover in CA did not necessarily increase maize crop yield. Thus, increasing crop residue application rates under CA increased termite prevalence while crop lodging was influenced more by soil tillage system than by crop residue application rates.     

Droplet deposition and control effect of insecticides sprayed with an unmanned aerial vehicle against plant hoppers

A small unmanned aerial vehicle (UAV) that can spray pesticide with high efficiency and with no damage to crops is required for the timely and effective spraying of small fields and/or those in hilly mountains. The current study aimed to illuminate the influence of spraying parameters, such as operation height and operation velocity, of the UAV on droplet deposition on the rice canopy and protection efficacy against plant hoppers. Droplets of 480 g l⁻¹ chlorpyrifos·(Regent EC) (at a dose of 432 g a.i. ha⁻¹, spray volume rate of approximately 15 l ha⁻¹) were collected using water-sensitive paper, and the coverage rates of the droplets on the rice canopy and lower layer were statistically analyzed. The deposition and distribution of droplets in the late stage of rice growth were closely related to the operational height and velocity of crop spraying as executed by the UAV, further affecting insect control. The spraying parameters for preventing plant hoppers were then optimized. When the spraying height was 1.5 m and the spraying velocity 5 m s⁻¹, the droplet deposition in the lower layer was maximized, and the droplets exhibited the most uniform distribution (CV = 23%). The insecticidal efficacy was 92%–74% from 3 to 10 days after spraying insecticide. Both the insecticidal efficacy and the persistence period were greater than those achieved with a hand lance operated from a stretcher-mounted sprayer (at dose of 432 g a.i. ha⁻¹, spray volume rate of approximately 750 l ha⁻¹), especially on the 5th day, indicating that UAV had a low-volume and highly concentrated spray pattern to enhance the duration of efficacy. This work offers a basis for the optimized design, improved performance, and rational application of UAV.     

Selectivity of fomesafen based systems for preemergence weed control in cucurbit crops

Experiments at two sites during two years evaluated the selectivity of preemergence fomesafen in cucurbit crops of winter and summer squash, zucchini, cantaloupe, cucumber, and pumpkin. Cucumbers were the most sensitive of the cucurbit crops to fomesafen and produced little or no fruit in two out of three experiments when applied at 0.28 kg ai ha⁻¹. Fomesafen also reduced cantaloupe yield. Visual damage was noted on the other crops tested, but crop yield was not impacted by fomesafen at 0.28–0.35 kg ai ha⁻¹. With the exception of cucumbers, injury caused by fomesafen to cucurbit crops was transitory even when fomesafen-treated soil splashed onto the leaves of emerging cucurbits during a powerful thunderstorm at one of the test sites. Control of redroot pigweed (Amaranthus retroflexus), Powell amaranth (Amaranthus powellii) and other Amaranthus spp., lambsquarters (Chenopodium album), hairy nightshade (Solanum physafolium), common purslane (Portulaca oleraceae), and velvetleaf (Abutilon theophrastii) ranged from 92 to 100% with fomesafen applied at 0.28 kg ai ha⁻¹. The excellent efficacy on these difficult to control weed species suggests that lower rates of fomesafen may be appropriate and improve crop tolerance, particularly if fomesafen is tankmix-applied with other preemergence herbicides such as s-metolachlor or dimethenamid-p. Weed control with these combinations was excellent for all weed species in these experiments.     

Effects of box liner perforation area on methyl bromide diffusion into table grape packages during fumigation

Plastic liners are used inside boxes of table grapes to retard moisture loss from the grapes and to contain sulfur dioxide gas released inside the packages to control postharvest decay. However, to control organisms of quarantine concern, regulators specify exported packages must be fumigated with methyl bromide (MB), and to enable adequate diffusion of the fumigant into the packages they specify the liners must be perforated. The percentage of the area of the liner that is perforated, formerly stipulated to be not less than 0.3%, was recently increased to not less than 0.9%. Two MB fumigation schedules specified for control of the Chilean mite, Brevipalpus chilensis, were applied to grape packages with a high-density polyethylene liners with perforated areas of 0.9% or with a SO₂-releasing liners with perforated areas of 0.3, 0.6, or 0.9%. Package and chamber concentrations were measured repeatedly for up to three hours during MB fumigation at 4.4 or 6.0 °C with a dosage 64 mg L⁻¹ or at 26.7 °C with a dosage 56 mg L⁻¹. Diffusion was similar and rapid into the packages among all perforated areas. MB concentrations inside the packages were not less than 95% of those of the chamber atmosphere within 15 min. After fumigation with an MB dosage 64 mg L⁻¹ at 4.4 °C and subsequent storage at 2.0 °C, mean MB residue content in grapes from most packages 48 h after MB fumigation was below the limit of quantitation of 0.002 mg kg⁻¹. After fumigation with an MB dosage 56 mg L⁻¹ at 26.7 °C and subsequent storage at 2.0 °C, mean MB residue content in grapes from most packages 24 h after MB fumigation was below the limit of quantitation.     

Applications of pre-emergent pyroxasulfone,flufenacet and their mixtures with triallate for the control of Bromus diandrus (ripgut brome) in no-till wheat (Triticum aestivum) crops of southern Australia

Four field experiments were conducted over a three-year period in Victoria and South Australia to investigate the effectiveness of pre-emergence (PRE) applications of pyroxasulfone, flufenacet and their mixtures with triallate for the control of Bromus diandrus in spring wheat. Herbicide mixtures of pyroxasulfone plus triallate and flufenacet plus triallate applied PRE to wheat provided consistently high levels of B. diandrus control (≥85%). In contrast, applications of pyroxasulfone and flufenacet applied alone along with trifluralin plus metribuzin (a common farmer practice in southern Australia) provided more variable control of B. diandrus (33–90%). Pyroxasulfone plus triallate treatments had a much lower (≤47 panicles m⁻²) panicle density of B. diandrus than trifluralin plus metribuzin (42–318 panicles m⁻²) and the non-treated control (118–655 panicles m⁻²). PRE herbicides which were safe to spring wheat and provided the greatest level of control of B. diandrus resulted in significantly (P < 0.05) higher grain yields at Culgoa (120%) and Gama (13%) than non-treated wheat (720 and 1740 kg ha⁻¹). Although flufenacet was effective against B. diandrus, crop phytotoxicity at the higher dose (900 g ai ha⁻¹) reduced spring wheat grain yield. Based on these results, PRE pyroxasulfone plus triallate could play an important role in the management of B. diandrus in spring wheat. However, high cost of these herbicides (AUS$35-$70 ha⁻¹) may limit their adoption in low rainfall and low yielding wheat environments in southern Australia where B. diandrus is most prevalent.     

Management of herbicide-resistant Phalaris minor in wheat by sequential or tank-mix applications of pre- and post-emergence herbicides in north-western Indo-Gangetic Plains

Development of cross resistance or multiple cross resistance in Phalaris minor in wheat will continue to increase, as the weed develops mechanisms of resistance against new herbicides. This weed is a major threat to wheat productivity in north-western India, and as such needs to be addressed with integrated weed management approaches, including crop and herbicide rotations, herbicide combinations along with cultural and mechanical methods. Three field experiments were conducted during 2008–09 to 2012–13 along with large plot adaptive trials during 2012–13 with the objective to evaluate the efficacy of sequential applications of pendimethalin applied pre-emergent followed by clodinafop, sulfosulfuron, or pinoxaden applied post-emergent and tank-mix applications of metribuzin with these post-emergence herbicides for the management of herbicide-resistant P. minor in wheat. Clodinafop 60 g ha⁻¹ or sulfosulfuron 25 g ha⁻¹ at 35 days after sowing (DAS) and pendimethalin 1000 g ha⁻¹ as pre-emergence did not provide consistently effective control of P. minor in wheat. An increase in the dose of clodinafop from 60 to 75 g ha⁻¹ and of sulfosulfuron from 25 to 30 g ha⁻¹ also did not improve their efficacy to a satisfactory level. However, pinoxaden 50 g ha⁻¹ provided effective control (97–100%) of P. minor but not of broadleaf weeds. The tank-mix application of metribuzin with clodinafop 60 g ha⁻¹ or sulfosulfuron 25 g ha⁻¹ at 35 DAS and the sequential application of pendimethalin 1000 g ha⁻¹ or trifluralin 1000 g ha⁻¹ just after sowing followed by clodinafop 60 g ha⁻¹ or sulfosulfuron 25 g ha⁻¹ at 35 DAS provided 90–100% control of P. minor along with broadleaf weeds in wheat, thus resulting in improved grain yields (4.72–5.75 t ha⁻¹) when compared to clodinafop 60 g ha⁻¹ (3.85–5.60 t ha⁻¹) or sulfosulfuron 25 g ha⁻¹ alone (3.95–5.10 t ha⁻¹). The efficacy of mesosulfuron + iodosulfuron (a commercial mixture) 14.4 g ha⁻¹ against P. minor was not consistent across the experiments and over the years. The ready-mix combination of fenoxaprop + metribuzin (100 + 175 g ha⁻¹) at 35 DAS provided effective control of weeds but its varietal sensitivity needs to be determined before its use in field conditions. The tank-mix or sequential application of herbicides would be a better option than their applications alone to manage the serious problem of herbicide-resistant P. minor in wheat.     

Demographic changes in Helicoverpa armigera after exposure to neemazal (1% EC azadirachtin)

We estimated the effect of 5, 10, 15 and 20 mg l⁻¹ of neemazal (1% EC azadirachtin) on life table parameters of Helicoverpa armigera (Hübner) developing on chickpea (Cicer arietinum L.). The effects were assessed on the survivals emerged from 6th instar larvae that had ingested neemazal-treated chickpea pods. Survivorship (I) and expectancy of life (e_x) were highest with the commencement of age (egg) and decreased gradually with the advancement of age with all the concentrations of neemazal including unexposed cohort. All the eggs hatched in the unexposed group while highest numbers of unhatched eggs (10%) were recorded with 20 mg l⁻¹. Mortality of 1st instars was higher at 20 and 15 mg l⁻¹ than that of other concentration tested. Potential fecundity (pf) was reduced in concentration dependent manner and was lowest with 20 mg l⁻¹ (418 eggs/female/generation) and highest in control (898 eggs/female/generation). Net reproductive rate (R₀) was significantly reduced with the increase in concentration of neemazal. The intrinsic (r_m) and finite rate of increase (λ) were significantly decreased at 20 mg l⁻¹ than that of unexposed population. The mean generation time (T_c) was prolonged at 20 mg l⁻¹ and significantly differed with non-treated individuals. Development of immature stages was prolonged to 38 days with 20 mg l⁻¹ while reduced to 32 days with 15 mg l⁻¹ of neemazal as compared to 37 days in untreated individuals. Doubling time (DT) was significantly extended to 5.02 days with 20 mg l⁻¹ as compared to 3.84 days in the non exposed ones.     

Changes in the concentration of avenanthramides in response to salinity stress in CBF3 transgenic oat

Oat avenanthramides have long been known to possess potential nutraceutical and therapeutical properties. The change in avenanthramides 2p, 2c and 2f concentration in four salinity tolerant transgenic oat plants containing CBF₃ gene and non-transgenic control exposed to different levels of salinity stress was investigated. Determination of oat avenanthramides at the nano-scale level was performed using a well-optimized and highly sensitive sequential injection chemiluminescence (SIA-CL) method enhanced by eco-friendly gold nanoparticles biosynthesized from oat biomass extract. Under the conditions of this study, the predominant avenanthramide, which also exhibited the strongest scavenging capacity, was 2c followed by 2p and 2f. At no stress, there was no significant (p ≤ 0.05) difference between the transgenic lines and control regarding the concentrations of the three determined avenanthramides. After exposure to 250 mmol L⁻¹ NaCl, avenanthramide 2c dramatically increased by 170.9%, 580%, 353.6%, 457.6% and 229.1% in the control and the four transgenic lines, respectively. Among the transgenic lines, Agrogle-1 maintained the highest avenanthramides concentration under all salinity levels with maximum values of 71.5 mg kg⁻¹ for 2p, 221.0 mg kg⁻¹ for 2c and 62.0 mg kg⁻¹ for 2f detected at 250 mmol L⁻¹NaCl. The results of this study demonstrated that oat avenanthramides might have a potential role in enhancing abiotic stress tolerance in oats.     

Effectiveness of 1,3-dichloropropene as an alternative to methyl bromide in rotations of tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) in China

Replicated field trials were conducted to determine the effect of 1,3-dichloropropene (1,3-D) as a potential alternative for methyl bromide (MeBr) in tomato–cucumber rotations in two successive cropping seasons in China. Fumigation with MeBr (400 kg ha⁻¹), three 1,3-D doses (180, 120 and 90 l ha⁻¹), an avermectin dose (187.5 g ha⁻¹) and an untreated control were compared. Tomato data revealed that MeBr was generally superior to the treatments involving 1,3-D and avermectin, which in turn were superior to the control, for improving tomato crop yield and inhibiting Meloidogyne incognita, weeds and mortality caused by plant disease. In a successive cucumber crop, all fumigants tested except avermectin, showed significant continual influence in the same plots. In most cases, the highest 1,3-D dose was comparable to MeBr. Overall, in both growth seasons, 1,3-D at the dose of 180 l ha⁻¹ was as effective as MeBr in increasing plant height, yield and in reducing the incidence of soil borne disease, especially in maintaining excellent M. incognita control, but it provided only moderate control of weeds. On the basis of these results, combining 1,3-D with other alternatives to MeBr, is recommended for satisfactory control of soil pests in tomato–cucumber rotations in China.     

Evaluation of chemical disinfestants in reducing Verticillium dahliae conidia in irrigation water

Irrigation water disinfestation is an unexplored option for reducing Verticillium dahliae inoculum in water and consequently for more efficiently managing Verticillium wilts in Andalusia. We assessed Suppressive Efficacy (SE; water was infested and subsequently treated) and Preventive Efficacy (PE; previously treated water was subsequently inoculated) of OX-VIRIN^®, OX-AGUA AL 25^® and Deccoklor^® in reducing water infestations by V. dahliae conidia. Five concentrations of each disinfestant, the lowest three being recommended by the manufacturer, were tested in vitro against six V. dahliae isolates. Validation assays were carried out in experiments under natural environmental conditions in spring. The four highest concentrations of OX-VIRIN^® (0.8–51.2 mL L⁻¹), the three highest of OX-AGUA AL 25^® (46.4–417.5 μL L⁻¹) and the two highest of Deccoklor^® (0.375 and 3.75 mL L⁻¹), showed an in vitro-efficacy (SE and PE) of 96.2, 80.0 and 100.0% after 30, 5 to 30 and 15 days respectively. Therefore, recommended concentrations for OX-VIRIN^® and OX-AGUA AL 25^® showed a greater in vitro-effectiveness than those recommended for Deccoklor^®. Assays in natural environmental conditions proved that OX-VIRIN^® at the recommended concentration of 3.2-mL L⁻¹, applied every 28 days to water, was the most effective treatment (SE and PE), with a 100% reduction of the average relative viability after 56 days. Other chemical treatments showing high in vitro-efficacy, such as OX-VIRIN^® at 0.8 mL L⁻¹ and OX-AGUA AL 25^® at 46.4 μL L⁻¹ showed an SE of 99.9% after 14 and 28 days when applied every 28 and 14 days, respectively. However, PE of OX-AGUA AL 25^® at 46.4 μL L⁻¹ was only 59 and 38% after 28 and 14 days respectively, depending on the experiment.