Use of UV reflective mulch to delay the colonization and reduce the severity of Bemisia argentifolii (Homoptera: Aleyrodidae) infestations in cucurbits

Effectiveness of UV reflective plastic mulch for the management of silverleaf whitefly (Bemisia argentifolii Bellows and Perring) was evaluated in selected cucurbits. The reflective mulch repelled silverleaf whitefly adults in pumpkin (Cucurbita maxima Duchesne), cucumber (Cucumis sativus L.) and zucchini squash (Cucurbita pepo L.). Reduced colonization by B. argentifolii adults resulted in reduced populations of nymphs and a delay and reduction in the incidence of silverleaf in pumpkin and zucchini squash. Reflective mulch was as effective in reducing nymphal B. argentifolii populations as was a pre-plant soil application of imidacloprid. Zucchini squash, pumpkin and cucumber yields were significantly higher in plants grown over reflective mulch than in those grown over unmulched soil. Zucchini squash yields from plants grown over reflective mulch also were higher than from plants grown in plots receiving a pre-plant application of imidacloprid. This study confirmed that UV reflective plastic mulch can be used to manage B. argentifolii and the mulches give protection equal to that provided by imidacloprid.     

Effect of cover crops and mulches on weed control and nitrogen fertilization in tomato (Lycopersicon esculentum Mill.)

Cover crops and mulches are a suitable choice for sustainable agriculture because they improve weed control and crop performance. The aim of this research was to investigate weed control and nitrogen supply by using different winter cover crop species which were converted into mulches in spring. We carried out a 2-year field experiment where a tomato crop was transplanted into four different types of mulches coming from winter cover crops [hairy vetch (Vicia villosa Roth.), subclover (Trifolium subterraneum L.), oat (Avena sativa L.), and a mixture of hairy vetch/oat)] and in conventional treatment (tilled soil without mulch). The mixture of hairy vetch/oat cover crop produced the highest aboveground biomass (7.9 t ha⁻¹ of DM), while the hairy vetch accumulated the highest N in the aboveground biomass (258 kg N ha⁻¹). The oat cover crop was the most effective cover crop for suppressing weeds (on average −93% of weed aboveground biomass compared to other cover crops). After mowing the cover crop aboveground biomass was placed in strips as dead mulch into which the tomato was transplanted in paired rows. Weed density and total weed aboveground biomass were assessed at 15 and 30 days after tomato transplanting to evaluate the effect of mulches on weed control. All mulches suppressed weeds in density and aboveground biomass compared to the conventional system (on average −80% and −35%, respectively). The oat was the best mulch for weed control but also had a negative effect on the marketable tomato yield (−15% compared to the conventional treatment). Amaranthus retroflexus L. and Chenopodium album L. were typical weeds associated with the conventional treatment while a more heterogeneous weed composition was found in mulched tomato. Legume mulches, in particular hairy vetch, gave the best marketable tomato yield 28% higher than the conventional system both with and without nitrogen fertilization. This research shows that winter cover crops converted into dead mulch in spring could be used successfully in integrated weed management programs to reduce weed infestation in tomato crops.     

The use of reflective mulch to reduce the incidence of watermelon mosaic virus in Western Australia

Watermelon mosaic virus has caused losses in cucurbits in the last 8 years in the Gascoyne River district of Western Australia. Neither insecticides nor oil sprays have reduced the incidence of this disease. In three trials, plants mulched with reflective (aluminium) polythene were less infected (by 21%, 30% and 72%) than were those given a control treatment; yield increases of watermelons ranged from 77% to 270%. Black polythene mulch also reduced the incidence of virus and increased yield, but to a lesser degree. In all experiments the disease incidence rose more slowly in the mulch plots: this effect contributed greatly to the observed increase in yield.     

禾谷多黏菌传小麦病毒病的分布及变化动态

为给小麦黄花叶病毒（Wheat yellow mosaic virus,WYMV）和中国小麦花叶病毒（Chinese wheatmosaic virus,CWMV）病的科学防控提供相关技术参考,于2008-2010年采用普查结合ELISA检测和电镜观察等方法,对这两种禾谷多黏菌传小麦病毒病的分布进行了研究。结果表明,WYMV重病区呈现向西、向北扩展的新趋势,发现山东泰安、河南商丘、湖北丹江口、襄樊、随州等新病区,四川省仅在内江发生。江苏省两种病毒复合侵染区正在扩大,浙江病区基本消失。     

Tolerance of parsley varieties to Orobanche

Parasitic plants infest numerous plants throughout the world depleting them of nutrients, minerals and water. Orobanche species are chlorophyll-lacking root holoparasites that cause severe damage to broad-leaved crops. Orobanche aegyptiaca and Orobanche crenata parasitize field, vegetable, fodder, flower and herb crops in the Mediterranean region. Curled parsley (Petroselinum crispum), a major crop in the dry herb industry in Israel, is highly susceptible to O. aegyptiaca and O. crenata and in infested fields suffers severe yield and quality damage. An in vitro study in polyethylene bags, greenhouse experiments in soil-filled pots and trials in a naturally Orobanche-infested field were performed in order to screen and test for differential susceptibility of parsley varieties to O. aegyptiaca and O. crenata. Results revealed that the parsley varieties Garland and Garbo were tolerant to Orobanche compared to the susceptible varieties Darki, Extra Triple and Kaderava.     

Effects of plastic mulch, sowing date and cultivar on the yield and maturity of forage maize grown under marginal climatic conditions in Northern Ireland

The effects of growing forage maize (Zea mays) with or without plastic mulching treatments on the dry‐matter (DM) yield, cob yield, DM content and starch content was investigated in Northern Ireland in 1996 and 1997. Cultivars differing in maturity characteristics were sown in spring at a range of dates in three replicated plot experiments and were used to compare the effects of two plastic mulches and an untreated control: one plastic mulch completely covered the rows (floating); the other had holes punched in the plastic, through which the plants grew (punch). Between April and October in 1996 and 1997, the Ontario heat units (OU) received were above average at 2489 and 2660 respectively; in those years without plastic mulches, the earliest maturing cultivar, Melody, yielded 11·0 and 13·6 t DM ha^–1, with dry‐matter contents of 214 and 215 g kg^–1 respectively. Mean daily increases in soil and air temperature under plastic mulches of up to 6°C and 11°C, respectively, were closely related to solar radiation. Under plastic mulches, 15% fewer OU were required to reach silking, and 33% more OU were available between silking and harvest. Meaned over three experiments, two years and three cultivars, plastic mulches, when compared with the unmulched control, increased maize yield from 12·0 to 14·7 t DM ha^–1, cob yield from 3·7 to 6·8 t DM ha^–1, dry‐matter content from 230 to 270 g kg^–1 and starch content from 198 to 272 g kg^–1. The effect of plastic mulch on the maturation of the crop was greatest at earlier sowings. In 1997, plants from an early sowing date (10 April) that had recently emerged through the punch plastic mulch were damaged by frost, whereas those in the floating plastic mulch plots were unaffected. When the floating plastic mulch was left on after the six‐ to eight‐leaf stage of the first‐early maize cultivar Hudson, the plants were physically damaged and the yield reduced, but DM and starch contents continued to increase. The increases in yield and dry‐matter content under the plastic mulch were greater in Diamant (second‐early cultivar) than in Melody (first‐early cultivar). It was concluded that, under marginal climatic conditions, plastic mulches ought to be used to improve the reliability of early cultivars rather than growing later maturing cultivars.     

The effects of living mulches and weed cover on the dynamics of foliage- and soil-arthropod communities in three crop systems

The effects of vegetation background in the form of living mulches and weed cover on the population dynamics of foliage and soil arthropods were studied in corn, tomato and cauliflower crop systems in California. In Davis (Central Valley site) herbivores (especially aphids and lygaeids) were more abundant in the weed cover than in the clover mulch, whereas leafhoppers were most common in the clover mulch. Higher numbers of natural enemies were observed in the clover plots. Significantly more ground predators (Carabidae, Staphylinidae, spiders) were caught in pitfalls placed in the weedy and clover plots, than in the clean cultivated plots. In Albany (Coastal area), specialized herbivore (cabbage aphids and flea-beetles) densities were significantly reduced in plots with additional vegetation cover. It is not clear if this reduction was due to plant diversity or density effects, to the effects of natural enemies or to the lower quality of plants in the weedy and mulched plots, as crop growth and yields were drastically reduced in these plots at both sites. Further agronomic work is warranted to minimize the competitive effects of legume covers on crops, so that the entomological advantages reported here can be used in a practical way.     

Influence of slitted polyethylene mulch,nitrogen rates,and trickle irrigation on potatoes

In 1974, potatoes(Solanum tuberosum L.) were grown on unmulched, clear, and black slitted polyethylene. Production and tuber specific gravity of the potatoes were determined at four nitrogen rates (0, 75, 150 and 225 lb/A) and with two varieties (Superior and Katahdin). In 1975, potatoes were grown on unmulched and clear slitted polyethylene with and without trickle irrigation. Nitrogen increased marketable yields up to 150 lb/A on the unmulched potatoes. Irrigation increased the marketable yields of potatoes on both unmulched and mulched plots. However, no advantage was found in marketable yields, specific gravities or tuber sizes of the potatoes grown on either clear or black slitted polyethylene mulch over conventional unmulched soil for the ‘Superior’ or ‘Katahdin’ varieties.     

Population dynamics of arthropods associated with early-season tomato plants as influenced by soil surface microenvironment

Two field studies were conducted in the San Joaquin Valley (SJV) of California in order to describe the association of arthropods and possible virus diseases with the plant canopy of early-season, bush-trained, fresh-market tomato (Lycopersicon esculentum L. cv. Shady Lady) over three soil surface microenvironments. The experimental treatments were based on alterations to planting bed surfaces, as follow: 1) soil covered with silver metalized, light-reflective plastic mulch; 2) soil covered with biological mulch consisting of killed, chopped, cool-season cover crop residues [mixture of triticale (X Triticosecale Wittm.), rye (Secale cereale L. cv. Merced), and common vetch (Vicia sativa L.)]; or 3) bare soil (not covered) – the SJV standard tomato production practice. In both studies, the predominant arthropods encountered in all treatments were the aphid species Aphis craccivora Koch, Macrosiphum euphorbiae Thomas, and Myzus persicae Sulzer; the western flower thrips (Frankliniella occidentalis Pergande), and the false chinch bug (Nysius raphanus Howard). These are all considered to be pests of cultivated tomato plants. Spiders were the most prevalent arthropod predator group recovered from foliage samples. All monitored arthropods, except spiders, were most abundant in tomato plants grown over the conventional, bare soil surface, and least abundant (P < 0.05) in plants grown over the silver plastic mulch. Spider numbers were highest in plant foliage over the biological mulch. Other arthropods commonly found on tomato plants in the SJV, including leafhoppers, whiteflies, various caterpillars, and predaceous taxa, were not commonly nor consistently encountered. This was likely due to the early-season timeframe of these studies. Similarly, foliar virus disease symptoms, which were originally targeted for monitoring, were virtually nonexistent. The only arthropod pest species encountered which consistently caused economically important damage to tomato fruit was N. raphanus. In both experiments, tomato fruits grown over the reflective plastic mulch had significantly less (69.5% and 39.7%, respectively) damage due to this pest than those over bare soil. The biological mulch gave inconsistent, intermediate damage reductions. Results from these two field studies showed that reflective plastic bed mulch suppressed populations of a variety of tomato canopy-associated arthropod taxa in early-season plantings, as compared to conventional, bare-soil beds. The biological bed mulch results were more inconsistent, but gave indications that killed cover crop residues, as well as the light-reflective plastic, may be of value in integrated pest management programs for fresh-market tomato production.     

The importance of colonizing and non-colonizing aphid vectors in the spread of cowpea aphid-borne mosaic virus in cowpea

Three species in the genus Aphis (A. craccivora, A. spiraecola and A. gossypii) transmitted cowpea aphid-borne mosaic virus (CAMV) efficiently to and from cowpea, bean and soybean host plants. Rhopalosiphum maidis and Cerataphis palmae also transmitted the virus, but less efficiently. In the field, only Aphis spp. colonized cowpea plants. R. maidis and C. palmae were non-colonizing, but were occasionally found transitory in fields. A. craccivora was the most abundant vector on cowpea both in the first and second growing seasons. Aphids were more abundant and virus disease-infection rate correspondingly faster in the wetter first growing season than in the second one. Although R. maidis and C. palmae may cause primary loci of infection, they may also bring about limited secondary spread, as they alight repeatedly on non-hosts (cowpea plants) during host finding. However, colonizing Aphis spp. would mainly be responsible for secondary spread within the field. It is concluded that both colonizing and non-colonizing aphids are important in the epidemiology of CAMV, and control measures should be directed against both types of vectors.     

大豆花叶病毒侵染性克隆研究进展

大豆花叶病毒(soybean mosaic virus,SMV)是一种株系复杂且不断变化、并对大豆的产量和质量造成恶劣影响的病毒,其严重的致病性受到学者的普遍关注。大豆花叶病毒侵染性克隆技术是研究其致病机理的行之有效的手段。该技术通过病毒侵染获得侵染性cDNA克隆,进一步分析引起症状的相应基因在植株生长过程中的作用机制,由此为SMV相关领域的研究奠定理论基础。本文就大豆花叶病毒侵染性克隆的构建策略和影响因素,以及其应用状况作一综述,以期为大豆花叶病毒的防治提供新的借鉴和思路。     

Treatment decisions based on egg scouting for tomato fruitworm, Helicoverpa zea (Boddie), reduce insecticide use in tomato

Field experiments were conducted to evaluate the effectiveness of a tomato fruitworm, Helicoverpa zea (Boddie), management program where insecticide application was made only when fruitworm eggs were detected on tomato foliage. Fruit damage and number of insecticide applications were compared between the egg scouting program and a standard fruitworm management program where insecticides were applied on a weekly schedule. On average, 59 and 43% fewer insecticide applications (for esfenvalerate and Bacillus thuringiensis, respectively) were required in the egg scouting program, compared with the weekly spray program, without any reduction in marketable yield. The average seasonal insecticide cost savings associated with the use of the egg scouting program were $US109.33 and $US93.33 per ha for esfenvalerate and B. thuringiensis, respectively. When scouting was used, average net returns, considering machinery and labor costs, were $US146.45 and $US164.33 per ha higher for esfenvalerate and B. thuringiensis, respectively.     

我国木薯花叶病毒病的发生危害及其病原鉴定

为明确国内木薯花叶病毒病（cassava mosaic virus disease）的危害情况、田间症状及其病原类型,本研究于2018—2019年调查了该病在国内的分布情况、症状特征及种质来源等数据,采集了8省（区）19地的384份样品,利用特异性引物检测2种木薯花叶病毒侵染引起的症状类型,并通过序列比对明确其病原特点。结果表明：木薯花叶病毒病已经在我国发生,种茎调运是该病远距离传播的主要原因;国内木薯花叶病毒病病原有斯里兰卡木薯花叶病毒株系（Sri Lankan cassava mosaic virus, SLCMV）和木薯普通花叶病毒（Cassava common mosaic virus, CsCMV）2种病毒,可分为单独感染、复合感染,其中SLCMV的检出率为21.1%,CsCMV的检出率为36.5%,SLCMV-CsCMV复合侵染率为15.1%;检测到的SLVMV与东南亚SLCMV序列同源性为99.4%~99.7%,检测到的CsCMV与拉丁美洲的CsCMV序列相似性为91%~96%。推测国内木薯花叶病毒病主要由2种病毒侵染引起,且普通花叶病毒有产生序列变异的可能性。     

A review of the biology and control of selected weed species in the genus Oxalis: O. stricta L., O. latifolia H.B.K. and O. pes-caprae L.

This review considers the distribution, weed problems, biology and control of Oxalis stricta, O. latifolia and O. pes-caprae. The rhizomatous O. stricta is a persistent seed-producing weed which invades horticultural crops in North America. Chemical control is generally most effective in situations where soil-applied residual herbicides can be used; in turfgrass however, foliage-applied herbicides provide suppression only. O. latifolia is widely distributed in a range of annual and perennial crops growing in temperate and tropical locations. This pernicious perennial weed reproduces exclusively by asexual structures, underground bulbs, stolons and tubers. The complexities of the perennating system have rendered ineffective a wide range of herbicide families as a means of restricting the spread of O. latifolia. Similarly, cultural methods of control have not been successful. O. pes-caprae also grows and perennates from bulbs. This weed is essentially a problem in cereal crops in Southern Australia and Mediterranean fruit orchards. Cultural and chemical control difficulties and inadequacies are similar to those in O. latifolia. Future research strategies involving weed physiology, herbicide action and cultural control including biological control are discussed in relation to obtaining improved control methods for the selected Oxalis species.     

Comparison of Straw Mulch,Insecticides, Mineral Oil,and Birch Extract for Control of Transmission of Potato virus Y in Seed Potato Crops

Potato virus Y (PVY) is a major pathogen of potato and transmitted non-persistently by aphids. Aphis fabae is the main vector of PVY in the High Grade Seed Potato Production Area (HG area) in Finland, where the number of aphids and infection pressure with PVY are rather low, but problems with PVY occur in PVY-susceptible cultivars. The aim of the study was to test straw mulch, mineral oil, birch extract, and insecticides for control of PVY in small-scale field experiments and, additionally, at farm level in growers’ fields in the HG area of Finland. The insecticide esfenvalerate reduced the incidence of PVY in the progeny tubers by 29% in one of the 3 years, whereas other chemical treatments or birch extract had no significant effect on PVY incidence. Spraying foliage with mineral oil (Sunoco 11 E/3) reduced the incidence of PVY in 2 years by 43 to 58%, respectively. Straw mulch spread to the field at the time of plant emergence reduced PVY incidence in all 3 years by 50–70%. At farm level, straw mulch reduced the incidence of PVY in the progeny tubers by 25–47%, respectively, in both years tested; however, combining application of straw mulch and mineral oil did not further reduce incidence of PVY. Successful control of PVY in the HG area of Finland using straw mulch may be explained by transmission of PVY early in the growing season at the time of plant emergence and the relatively low number of vector aphids.     

Rate of spread of PVYn by alateMyzus persicae (Sulzer) from infected to healthy plants under laboratory conditions

Summary Alate green peach aphids,Myzus persicae (Sulzer), tested in a flight chamber during their maiden flight period displayed behaviours ranging from repeated trivial flights to settling on the plants. The interaction of alate vector density and PVYⁿ spread was dichotomous, virus spread was significantly related to vector density in some trials but virus spread was nil or limited and not significantly dependent on vector density in others. The green peach aphid colony used in these experiments provided a mixture of active and highly active alate populations. Results suggest that inactive and active vectors came from the active and highly active alate populations, respectively. Therefore, winged aphids within a species cannot all be attributed the same vector efficiency unless known to originate from the same population. At a 15% inoculum level the intercept for the regression model for the spread of PVYⁿ was 5.03% indicating that there is a significant probability of propagation at aphid densities as low as one. However, over the range of aphid densities tested, the rate of spread per aphid was low, 0.08%, suggesting that reinfection of newly infected plants or movement interference between aphid vectors rapidly became important factors negatively affecting virus spread. Although these results cannot be directly transferred to field conditions they provide confirmation that lowM. persicae numbers can transmit unacceptable levels of mosaic and that low inoculum levels are required to decrease the risk of transmission by the small aphid numbers which cannot be realistically controlled.     

Potato (Solanum spp.) in the hot tropics III. Influence of mulch on weed growth,crop development,and yield in contrasting environments

Eighteen experiments at three hot tropical sites (5–12 °S, 180–800 m) within Peru were run with various mulches over a 4-year period.Mulch, although suppressing weed growth, favoured both crop emergence and the stand of tuber-bearing plants at final harvest. Canopy development, crop cover and light interception over the season were almost invariably improved by mulch. Tuber initiation, when measured, was earlier and tuber growth rates greater for mulched plants. Tuber yield was consistently increased by mulch in all but two experiments, averaging 25% over all experiments.Yield improvements due to mulch were less evident at the hottest site, where high soil temperature (> 25 °C) during the night at tuber depth, high natural reflectivity of the soil (0.18), a large sand fraction in the soil, and cloudy days and nights, were considered responsible for inconsistent benefits of mulch on tuber yield.At another site, where mulch was also tested during the rainy season, yield was on average improved by mulch in a proportion similar to that during the dry season at the same site. Mulch was particularly beneficial in improving all measured aspects of crop growth and yield when combined with agronomic treatments that, on their own, predisposed plants to greater heat stress. For example, mulch was more effective in ridge than on the flat plantings, at planting depth less than 7 cm, at lower plant populations and for small-canopied determinate clones.Environmental and biological criteria for the successful use of mulch for potato cultivation in hot climates are discussed.     

不同稻草覆盖量和栽培方式对广西冬作马铃薯产量的影响

2009～2010和2010～2011冬季生长季节,布置田间试验研究不同稻草覆盖和栽培方式对冬作马铃薯产量和产量构成的影响。在2009～2010年度,试验设置不同肥料用量,不同种植密度及不同稻草覆盖量3个影响因子。结果表明,种植密度为90 000株/hm(2D2)时,无论是商品薯还是非商品薯的产量均较高;而在施肥量较高的处理中(F2,1.2 t/hm2复合肥),商品薯的产量增加,非商品薯产量显著下降。在稻草覆盖处理M0.5(0.5 kg/m)2和M1(1.0 kg/m)2中,马铃薯的产量和产量构成没有显著差别。D2F2M0.5处理的产量最高,为15.0 t/hm2,其中商品薯的产量为13.0 t/hm2。在2010～2011年度,进一步研究了不同耕作方法(箱式耕作和垄式耕作)及不同稻草覆盖量(5个水平)对马铃薯产量和产量构成的影响。与垄式耕作方式相比,箱式耕作节约了一半的工作强度,但产量并没有下降。结果显示,当覆盖量为0.25 kg/m2时,获得的产量最高,为25.3 t/hm2。但是,非商品薯的产量和绿薯率均随着稻草覆盖量的减少而增加。在中国,每公顷的稻草产量约为5 000 kg。因此,考虑到实际条件的限制,在广西冬作区,选用箱式耕作的同时覆盖0.5 kg/m2的稻草是最为经济和高效的栽培方式。     

番茄斑驳花叶病毒海南分离物全基因组序列分析

本研究采用小RNA深度测序及RT-PCR检测技术鉴定海南省陵水县冬种番茄(圣女果)病株受到烟草花叶病毒属的番茄斑驳花叶病毒(Tomato mottle mosaic virus,ToMMV)侵染。通过机械摩擦接种,将该病原病毒保存于本生烟植株上,命名为番茄斑驳花叶病毒海南分离物(ToMMV-HN)。采用RT-PCR分段扩增获得了该病毒分离物的全基因组序列。测序结果表明,该病毒分离物基因组全长6399 nt,含有4个开放阅读框,编码4种蛋白,与已报道的ToMMV9个分离物核苷酸和编码产物氨基酸序列相似性分别为98.0%～100%和99.2%～100%;与同属的番茄花叶病毒(Tomato mosaic virus,ToMV)、番茄棕色皱果病毒(Tomato brown rugose fruit virus,TBRFV)和烟草花叶病毒(Tobacco mosaic virus,TMV)代表分离物核苷酸序列相似性分别为84.7%、80.7%和79.0%。系统进化分析结果表明,ToMMV-HN与该病毒中国西藏和云南辣椒分离物亲缘关系最近,与美国加州和南卡州番茄分离物次之,与西班牙和巴西番茄分离物亲缘关系相对较远。本研究为我国番茄病毒病诊断和防控,尤其是抗病品种选育提供了基础资料。     

抗花叶病转SrMV-P1基因甘蔗的活性氧代谢分析

转SrMV-P1基因甘蔗经过2个世代的试验,表现出对甘蔗花叶病一定的抗性,但不同转基因无性系中,其抗性呈现出不同程度的分化.本研究以受体材料(FN95-1702)和空转对照P7(未插入外源基因SrMV-P1的载体)为对照,以国家发明专利授权的转基因无性系TF53和T64为试验材料,研究其在不同甘蔗花叶病毒剂量,以及载体效应和外源基因效应作用下的活性氧代谢分析,从代谢水平上解析转基因材料抗性呈现不同分化规律的机理.结果表明:转基因无性系在较高病毒剂量胁迫下,通过活性氧代谢相关指标的变化对病毒侵染起到应激作用;载体效应和外源基因效应对活性氧代谢影响存在一定差异,这段差异时期也主要发生在较高病毒剂量的情况下;外源基因对不同无性系中活性氧代谢的影响,表现在高病毒剂量的作用下,其活性氧代谢相关指标在变化幅度上存在一定差异,导致其对病毒的抵御能力上的不同,这可能是转SrMV-P1基因抗性分化的生理基础.