Viability and release of Neonectria ditissima ascospores on apple fruit in Brazil

During European canker monitoring in an apple experimental orchard, 14 mummified fruit (two and three trees with 10 and four positive records in 2018 and 2019, respectively) showed perithecia. Perithecium production on apple fruit, confirmation of pathogenicity of Neonectria ditissima isolated from mummified fruit, and ascospore release from fruit tissues has rarely been reported, and their role in the epidemiology of European canker has been largely overlooked. Thus, the objectives of our study were to (a) prove the presence of both conidia and ascospores of N. ditissima in mummified fruit in an experimental field, confirming pathogenesis in different apple cultivars, and (b) monitor production of the two types of inoculum in infected apple fruit over time. Canker incidence in this orchard was 47% of trees with symptoms in 2018 and 48% in 2019. Molecular and morphological tests confirmed that the fungus detected in the mummified apple fruit was N. ditissima. Apple fruit with sporodochia and perithecia washed immediately after collection from the orchard showed conidia but no ascospores of N. ditissima. However, after 4 days’ incubation, perithecia on mummified fruit showed many ascospore cirri. Koch's postulates were fulfilled on apple plants and mature fruit. Fruit inoculated with N. ditissima released spores for over a year under Brazilian field conditions. The release of both spore types peaked in May (Brazilian leaf fall) and October (spring); release of conidia also peaked in February (early harvest). These results support our hypothesis that fruit can serve as primary inoculum for European canker in Brazilian apple orchards.     

The relative importance of conidia and ascospores as primary inoculum of Venturia inaequalis in a southeast England orchard

Apple scab, caused by Venturia inaequalis, can lead to large losses of marketable fruit if left uncontrolled. The disease appears in orchards during spring as lesions on leaves. These primary lesions are caused by spores released at bud burst from overwintering sources; these spores can be sexually produced ascospores from the leaf litter or asexual conidia from mycelium in wood scab or within buds. The relative importance of conidia and ascospores as primary inoculum were investigated in an orchard in southeast England, UK. Potted trees not previously exposed to apple scab were placed next to (c. 1 m) orchard trees to trap air‐dispersed ascospores. Number and position of scab lesions were assessed on the leaves of shoots from both the potted trees (infection by airborne ascospores) and neighbouring orchard trees (infection by both ascospores and splash‐dispersed, overwintered conidia). The distribution and population similarity of scab lesions were compared in the two tree types by molecular analysis and through modelling of scab incidence and count data. Molecular analysis was inconclusive. Statistical modelling of results suggested that conidia may have contributed approximately 20–50% of the primary inoculum in early spring within this orchard: incidence was estimated to be reduced by 20% on potted trees, and lesion number by 50%. These results indicate that, although conidia are still a minority contributor to primary inoculum, their contribution in this orchard is sufficient to require current management to be reviewed. This might also be true of other orchards with a similar climate.     

苹果园种植覆盖作物对于树上捕食性天敌群落的影响

在苹果园果树行间种植覆盖作物——白花草木樨Melilotus albus Desr.是果园土壤管理制度中的一项措施。它影响到苹果树上捕食性天敌群落的组成。种植覆盖作物后,一些天敌,如拟长毛钝绥螨Amblyseius pseudolongispinosus Xin et Lian和中华草蛉Chrysopa sinica Tjeder等在苹果树上捕食性天敌群落中的个体数量相对百分比有所增加;而另一些,如小花蝽Orius minutus(Linnaeus)、塔六点蓟马Scolothrips takahashii Priesaer和瓢虫类(Coccinellidae)等天敌有所减少;还有一些天敌,由于发生数量较少,不易与免耕法对照区进行比较。当使用广谱性化学杀虫剂进行树上喷雾时,覆盖作物对于受到化学杀虫剂干扰的苹果树上小花蝽O.minutus(Linnaeus)种群的恢复与建立有着促进作用。     

Role of Cylindrosporium-type conidia of Mycosphaerella pomi (Pass.) Lindau: cause of Brooks fruit spot of apple, as an infection source in apple orchards

Ascospores of Mycosphaerella pomi, the pathogen of Brooks fruit spot of apple, were produced in pseudothecia on previously infected and overwintered apple leaves from late April through early August in Aomori Prefecture, Japan. In June 2003, the ascospores were germinating and producing Cylindrosporium-type conidia on apple fruit and leaf surfaces in an orchard. After ascospores were sprayed on apple leaves, Cylindrosporium-type conidia developed on the leaf surfaces. Such Cylindrosporium-type conidia caused typical symptoms of Brooks fruit spot on apple trees after inoculations. These results suggested that the Cylindrosporium-type conidia also serve as an infection source, in addition to the ascospores, for Brooks fruit spot in apple orchards.     

Differentiation in populations of the apple scab fungus Venturia inaequalis on cultivars in a mixed orchard remain over time

The ascomycete Venturia inaequalis causes annual epidemics of apple scab worldwide. Scab development is reduced in mixed cultivar orchards compared with monocultures. In order to use mixtures in commercial production, how the population of scab changes in a mixed orchard needs to be understood, together with how likely a super race, with virulence factors overcoming multiple resistance factors in the mixed orchard, is to emerge and become dominant. This study used simple sequence repeat (SSR) markers to investigate the temporal change of scab populations in two mixed cultivar orchards in the UK to infer the likelihood of emergence of a scab super race. There were no significant differences between the populations at the two sampling times (6 or 7 years apart) in either of the two mixed orchards. In one of the orchards, apple scab populations on different cultivars were significantly different and the differences did not diminish over time. These results suggest that it is not inevitable that a super race of V. inaequalis will become dominant during the lifetime of a commercial apple orchard.     

性信息素迷向丝对不同果树梨小食心虫的防控效果

2017年在宁夏果园开展了性信息素迷向丝(北京中捷四方生物科技公司生产的长效迷向丝,有效成分占30%)对为害不同果树的梨小食心虫的防控效果研究。试验地共5.5 hm~2,栽植有成龄苹果树、梨树和李树。试验区按树种设置3个处理区,3个对照区。处理区在边缘区域每株树平均悬挂3条迷向丝,内部区域隔树悬挂,每树悬挂1条迷向丝,悬挂高度为距离地面2 m。调查各树种全年诱蛾量、诱蛾下降率、蛀果率等指标,研究迷向丝对不同果树上梨小食心虫的防控效果,分析苹果、梨和李树分区域集中栽培下梨小食心虫为害特点。研究结果显示:3个处理区的诱蛾下降率均达96%以上,果实膨大期蛀果下降率均达50%以上,成熟期蛀果下降率均达57%以上,说明性信息素迷向丝对3种果树区域的梨小食心虫防控效果明显且稳定;不同果树区域梨小食心虫发生高峰期一致;梨园中诱捕的梨小食心虫成虫最多,说明其具有寄主选择性;李园蛀果率明显高于苹果园和梨园,李果实成熟采摘后成虫诱捕量减少,同时期苹果园与梨园成虫诱捕量增加,说明梨小食心虫具有迁移为害特性。     

Effect of six sanitation treatments on leaf litter density, ascospore production of Venturia inaequalis and scab incidence in integrated and organic apple orchards

A two-year study was conducted to determine the effect of six sanitation treatments on leaf litter density (LLD), relative ascospore production of Venturia inaequalis and scab incidence on spur-leaf clusters, leaves and harvested fruits, on two cultivars with low and high scab susceptibilities, in Hungarian integrated and organic apple orchards. The following sanitation treatments were used: sprays of lime sulphur in autumn, collecting fallen leaves in autumn, straw mulch cover in late winter, sprays of lime sulphur followed by mulch cover, collecting fallen leaves followed by mulch cover, collecting fallen leaves followed by covering the orchard floor with plastic foil, and non-sanitized control. LLD decreased continuously in all treatment plots by 0–23% by mid-May in both orchards and years; however, LLD reduction was 1.4–4.2 times higher in the organic orchard compared to the integrated one. All treatments, except for the lime sulphur treatment, resulted in significant (P < 0.05) reduction of LLD and ascospore production in both the integrated and organic apple orchards compared to non-sanitized plots. The most efficient treatment was leaf collection combined with plastic foil cover, followed by leaf collection combined with mulch cover, leaf collection alone, mulch cover alone, and lime sulphur spray combined with mulch cover, with a reduction in the ascospore production of >95, 72–92, 56–79, 24–38, and 27–46%, respectively, in the mean of both orchards and years. However, only treatments of leaf collection applied alone, or in combination with mulch or with plastic foil cover reduced significantly (P < 0.05) leaf and/or fruit scab incidence by 18–57% compared to non-sanitized plots. These three leaf collection treatments are recommended in both integrated and organic orchards and the possibilities of successfully incorporating these methods into orchard management practices are interpreted.     

不同种植模式下苹果园土壤氮磷养分的分布特征

为研究不同苹果种植模式下土壤养分变化情况,在陕西省千阳县2种不同种植模式(矮化和乔化种植)的苹果园区采集土样,通过测定0~100 cm土层土壤中的全氮、全磷和有效磷含量,分析和比较其土壤氮磷养分含量差异及剖面分布特征。结果表明：在0~100 cm深度的土层中,除全磷外,矮化苹果园土壤各养分含量显著低于乔化苹果园(P<0.05),矮化富士、嘎啦苹果园和乔化富士苹果园全氮含量分别为0.60、0.63、0.76 g·kg^-1,全磷含量分别为0.58、0.56、0.63 g·kg^-1,有效磷含量分别为6.98、3.48、51.00 mg·kg^-1;矮化苹果园全氮、全磷以及有效磷含量主要在0~10 cm的表层土壤中聚集显著(P<0.05);土壤养分含量与土层深度相关性显著(P<0.05),矮化苹果园和乔化苹果园土壤养分含量与土层深度的变化过程分别符合幂函数和对数函数的变化趋势。     

The effect of the weaver ant,Oecophylla smaragdina (Hymenoptera: Formicidae), on the mango seed weevil,Sternochetus mangiferae (Coleoptera: Curculionidae), in mango orchards in the Northern Territory of Australia

Abstract

The mango seed weevil, Sternochetus mangiferae (Fabricius), is one of the major mango insect pests in northern Australia. A reasonable level of control can be obtained with insecticide sprays together with orchard sanitation, but the only option available for organic growers is the latter. Weaver ants, Oecophylla smaragdina (Fabricius), are effective in controlling the main insect pests in citrus, cashew and mango orchards. To determine whether weaver ants, which are usually abundant in non-sprayed mango orchards, have the potential to control the mango seed weevil, field experiments together with regular monitoring programmes at six orchards in the Northern Territory of Australia were conducted from 2001 to 2003. Data from two conventional orchards showed that the treatment with weaver ants plus soft chemicals produced lower levels of downgraded fruits (<0.5%) compared to the treatment with chemical insecticides (1.4 – 2.1%). In three organic or insecticide-free orchards, fruits were much less damaged on trees with weaver ants (<1%) than on trees without the ants (2.5 – 15.7%). In the sixth orchard, that had much higher mango seed weevil populations than the others, levels of downgraded fruits were lower on trees with abundant weaver ants than on trees with fewer weaver ants. We conclude that weaver ants are efficient biocontrol agents of the mango seed weevil, and that for successful control of the pest it is important both to maintain the ants at high levels and to destroy excess fruits.     

Effects of fungicides on apple crown rot caused by Phytophthora cactorum

The mycelial growth of Phytophthora cactorum on corn meal agar was completely inhibited by metalaxyl or mancozeb at 50 or 100 μg ml^?1, but not by fosetyl-aluminium at the same concentrations. Soil drenches with metalaxyl, followed by metalaxyl+mancozeb, around the base of naturally infected trees under orchard conditions, prevented the growth of P. cactorum in the infected bark of the tree. Soil drenchs with metalaxyl, followed by metalaxyl+mancozeb, also prevented the infection of apple trees with P. cactorum under orchard conditions. The trunk circumference and spur length were not significantly affected by any of the fungicide treatments in all the trials over 2 years, except in one of the four orchards used in the study. Soil drench with metalaxyl alone, or followed by metalaxyl+mancozeb, may provide an effective control method for crown rot of apple trees.     

Bait twig method for soil detection of <Emphasis Type="Italic">Rosellinia necatrix</Emphasis>, causal agent of white root rot of Japanese pear and apple,at an early stage of tree infection

Mulberry twigs were inserted into the soil as bait to detect Rosellinia necatrix at an early stage of tree infection in the orchard. R. necatrix was frequently trapped on twigs near the trunk base at soil depths of 6–20 cm within 10–20 days in May–July, suggesting that the incubation period was dependent on soil temperature. Subsequently, we inserted twig in the soil around healthy-looking trees in naturally infested orchards. R. necatrix was trapped from 80.0% of Japanese pear and 75.0% of apple trees that later proved to be infected. This bait twig method facilitated quicker diagnosis of white root rot on Japanese pear and apple at early stages of infection and can be used to detect recurrence of the fungus after fungicide treatment.     

陕西省新老苹果产区果园土壤硝态氮累积特性研究

以陕西省新、老果区（分别为洛川及礼泉）为研究对象，调查了两县各15个成龄果园的施肥现状，计算了果园氮素表观平衡，并测定了这15个果园的0~200 cm土壤剖面硝态氮含量，分析了树龄、施氮量与土壤剖面硝态氮累积量的关系。结果表明：新、老果区苹果园均过量施用氮肥，平均施氮量分别高达1 287±244 kg·hm^-2（洛川）和1 193±300 kg·hm^-2（礼泉），导致土壤中盈余了大量的氮素。新、老果区土壤0~200 cm硝态氮累积量分别达2 724 kg·hm^-2和5 226 kg·hm^-2, 老果区土壤剖面硝态氮累积量显著高于新果区。相关分析表明，果园土壤剖面累积的硝态氮与树龄和施氮量呈正相关，与树龄的相关系数为0.641，与洛川、礼泉果园施氮量的相关系数分别为0.402和0.306。因此，建议研究区域采取措施控制果园施氮量，减少果园土壤硝态氮累积带来的资源浪费及环境污染。     

黄色黏虫板在3种果园对蚜虫及其天敌的诱集作用

为减少黄色黏虫板(简称黄板)对果园害虫天敌的影响,明确黄板在果园中的使用方法,于2014年5月4日至9月30日在山西省太谷县的苹果、梨、桃园中进行了黄板诱集蚜虫及其天敌的动态调查。结果表明:在3种果园黄板可以诱集8目32科的昆虫,主要类群为蚜虫、叶蝉、瓢虫、食蚜蝇、草蛉和蚜茧蜂等。在苹果园和桃园中诱蚜量呈双峰谷线状,在梨园中呈三峰状;各果园寄生性天敌的数量变化趋势与蚜虫一致且有跟随效应,但苹果园和梨园诱集的捕食性天敌均在8月下旬至8月底出现高峰期,而桃园中捕食性天敌水平一直较高。3个果园在花期至幼果期即5月4日至6月22日益害比最小,苹果园仅为1:202.8,而在其它时段的益害比均大于1:150,甚至最高可达1:19.4,表明在果园中使用黄板的害处大于益处,建议在果园中慎用黄板诱蚜。     

糖醋酒液对桃园和苹果园中桃蛀螟的诱捕效果分析

为研究桃园和苹果园中桃蛀螟Conogethes punctiferalis成虫的发生动态,探讨糖醋酒液对桃蛀螟的诱捕效果,于2015—2016年利用糖醋酒液和性信息素对泰安市郊区桃园和苹果园中桃蛀螟成虫的全年发生动态进行监测,并比较糖醋酒液诱捕器在不同悬挂高度0、1.0、1.5、2.0和2.5 m下对桃蛀螟雌、雄成虫的诱捕效果。结果显示,2015—2016年,泰安市郊区桃园和苹果园中桃蛀螟成虫田间始发期为4月下旬至5月中旬,发生末期均为10月上旬。糖醋酒液和性信息素诱捕器监测结果均显示,桃蛀螟成虫群体数量发生高峰期为9月上旬—10月上旬,且在此期间二者的诱捕量无显著差异。糖醋酒液能够同时诱捕桃蛀螟雌、雄成虫,且以雄成虫为主,在桃园和苹果园中,2016年的雄成虫诱捕量分别占总诱捕量的87.62%和88.29%。糖醋酒液诱捕器在地上0～2.5 m悬挂高度均能诱捕到桃蛀螟成虫,其中诱捕器悬挂于地上2.5 m高度时诱捕量最多,显著高于其它悬挂高度处理。表明糖醋酒液可以通过有效诱捕桃蛀螟成虫来准确监测其群体发生动态。     

Toxicity of the herbicide glufosinate-ammonium to Tetranychus urticae (Acari: Tetranychidae) under laboratory and field conditions

The toxicity of herbicides widely used in apple orchards to the two-spotted spider mite (Tetranychus urticae) was evaluated in laboratory and field studies. In a laboratory study with susceptible T. urticae, glufosinate-ammonium was highly effective against larvae, protonymphs and adults, but non-toxic to eggs. Its efficacy was much greater than that of the commonly used acaricide azocyclotin. The immatures died within 24 h after treatment, suggesting that the nymphicidal action may be attributable to a direct effect rather than an inhibitory action of chitin synthesis. Glufosinate-ammonium showed a positive temperature coefficient of toxicity against T. urticae adults at six temperatures from 10 to 32°C, being more toxic at higher temperatures. Very low levels of resistance to the herbicide were observed in the seven field-collected T. urticae populations resistant to various acaricides. Treatment with glufosinate-ammonium did not cause a repellent response from either adults or immature stages of T. urticae. Paraquat dichloride and glyphosate were ineffective against all stages of T. urticae. In a field study of a population of T. urticae, glufosinate-ammonium when sprayed to weeds caused significant decrease in T. urticae population densities in apple trees for nine weeks after treatment, as compared with the control. Thereafter, a single application of standard acaricides to apple foliage greatly reduced population densities, although there was no difference in the densities between the glufosinate-ammonium-treated and control plots. Based upon laboratory and field data, two single treatments with glufosinate-ammonium to weeds in May and a selective acaricide to apple trees in July may be used to prevent damage by T. urticae. ©1997 SCI     

利用腹管食螨瓢虫控制柑桔全爪螨的研究

本文报道分布于中国东南部的腹管食螨瓢虫Stethorus siphonulus Kapur大面积控制柑桔全爪螨Panonychus citri(McGregor)首获成功;试验示范面积2000多亩,证明保护食螨瓢虫,一般株有瓢虫20—40只者,可无需用药。在春季移殖散放食螨瓢虫,除能控制春季桔全爪螨外,尚可继续控制桔全爪螨的秋季种群,全年无需喷药防治。倘若单独在秋梢期散放食螨瓢虫,秋梢害螨亦可得到显著的控制。移殖散放食螨瓢虫的指标为叶平均有桔全爪螨(包含卵在内各虫态)10只以上,方能建立起瓢虫群落。一般30—40亩果园,只需集中在10株桔树上散放食螨瓢虫200只左右(每株20只),短期内即可繁殖扩散至全园。在大面积桔园,适时进行瓢虫转株再移殖,可以迅速扩大控制范围。     

Fireblight in Békés County (Hungary) in 1996/20021

Fireblight (Erwinia amylovora) appeared in Hungary in 1996. Most damage occurred on apple, pear, quince and medlar, and also on the ornamentals Pyracantha, Sorbus, Cotoneaster and Crataegus. In 1996–2006, an official programme for elimination of infected parts of plants started in Békés county. This mainly concerned trees in towns and villages, since there are few pome‐fruit orchards in the county. Work teams under official direction pruned back or cut down trees. In total, some 13 000 trees were pruned back and nearly 11 000 were cut down. In addition, 21 villages were subjected to special phytosanitary measures. Infection decreased considerably between 1996 and 2002, but over 90% of the inhabited areas in the county remained subject to special measures, because of the very dispersed occurrence of fireblight.     

Monitoring conidial density of <Emphasis Type="Italic">Monilinia fructigena</Emphasis> in the air in relation to brown rot development in integrated and organic apple orchards

In a three-year Hungarian study, conidial density of Monilinia fructigena in the air determined from mid-May until harvest was related to brown rot disease progress in integrated and organic apple orchards. Conidia of M. fructigena were first trapped in late May in both orchards in all years. Number of conidial density greatly increased after the appearance of first infected fruit, from early July in the organic and from early August in the integrated orchard. Conidial number continuously increased until harvest in both orchards. Final brown rot incidence reached 4.3–6.6% and 19.8–24.5% in the integrated and organic orchards, respectively. Disease incidence showed a significant relationship with corresponding cumulative numbers of trapped conidia both in integrated and organic orchards, and was described by separate three-parameter Gompertz functions for the two orchards. Time series analyses, using autoregressive integrated moving average (ARIMA) models, revealed that the temporal patterns of the number of airborne conidia was similar in all years in both integrated and organic orchards. Conidia caught over a 24-h period showed distinct diurnal periodicity, with peak spore density occurring in the afternoon between 13.00 and 18.00. Percent viability of M. fructigena conidia ranged from 48.8 to 70.1% with lower viability in dry compared to wet days in both orchards and all years. Temperature and relative humidity correlated best with mean hourly conidial catches in both integrated and organic apple orchards in each year. Correlations between aerial spore density and wind speed were significant only in the organic orchard over the 3-year period. Mean hourly rainfall was negatively but poorly correlated with mean hourly conidial catches. Results were compared and discussed with previous observations.     

Implementing wood ants in biocontrol: Suppression of apple scab and reduced aphid tending

BACKGROUND

Ants can become efficient biocontrol agents in plantation crops as they prey on pest insects and may inhibit plant pathogens by excreting broad-spectrum antibiotics. However, ants also provide a disservice by augmenting attended honeydew producing homopterans. This disservice may be avoided by offering ants artificial sugar as an alternative to honeydew. Here we tested the effect of artificial sugar feeding on aphid abundance in an apple plot with wood ants (Formica polyctena, Förster), and tested the effect of ant presence on apple scab (Venturia inaequalis, Cooke) disease incidence.

RESULTS

Over a 2-year period, sugar feeding eliminated ant-attended aphid populations on the apple trees. Furthermore, scab symptoms on both leaves and apples were reduced considerably on ant trees compared to control trees without ants. The presence of ants on the trees reduced leaf scab infections by 34%, whereas spot numbers on fruits were reduced by between 53 and 81%, depending on apple variety. In addition, the spots were 56% smaller.

CONCLUSION

This shows that problems with wood ant-attended homopterans can be solved and that ants can control both insect pests and plant pathogens. We therefore propose wood ants as a new effective biocontrol agent suitable for implementation in apple orchards and possibly other plantation crops. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.