Relationships between the lucerne flea, Sminthurus viridis (L.) (Collembola: Sminthuridae), and damage to lucerne

Abstract The effect of lucerne flea, Sminthurus viridis , on plant growth (stem length and leaf number) and damage (percentage of leaves damaged and the percentage reduction in leaf area in the top, mid and lower thirds of stems) was considered at 2-weekly intervals in three consecutive lucerne growth cycles, each with a different mode of attack. The data were analysed to progressively determine relationships leading to a proposal for plant-based thresholds for lucerne flea control. Lucerne flea affected each factor measured, with damage considered more appropriate for making control decisions than plant growth. Damage increased from the base of plants upwards and its effect on yield was carried over into subsequent growth cycles. Damage was significantly related to lucerne flea numbers ( P  < 0.001) in two growth cycles and was higher when large nymphs or adults were dominant in one of these cycles. Yield was closely and best related to the percentage of the total number of leaves damaged ( R ² = 81.3%). The percentage of leaves damaged was also related to loss of final yield estimated at 2 ( R ² = 81.3%), 4 ( R ² = 78.9%) and 6 ( R ² = 66.6%) weeks into the first growth cycle only. Direct damage in the other two cycles did not result in yield loss. The percentage of leaves damaged (± confidence intervals) equating to 5% increments in yield loss were estimated at 2, 4 and 6 weeks into the first growth cycle. These are proposed as damage or treatment thresholds for testing.     

The tolerance of the lucerne flea, Sminthurus viridis (Collembola: Sminthuridae), to currently registered pesticides in Australia

Sminthurus viridis (lucerne flea) is a major crop and pasture pest throughout southern regions of Australia that experience a Mediterranean type climate. It is particularly problematic at the establishment phase, and chemicals are currently the main option available to farmers for their control. Few studies have assessed the currently registered pesticides for the control of S. viridis , and rates of application are generally similar to the frequently co-occurring red-legged earth mite, Halotydeus destructor , despite few comparisons between species for their susceptibility being made. Here, we examine the response of S. viridis to six pesticides (α-cypermethrin, bifenthrin, omethoate, methidathion, chlorpyrifos and phosmet) and then directly compare them with H. destructor . S. viridis displayed similar dose–response curves for bifenthrin, omethoate, chlorpyrifos and phosmet. It had greater sensitivity to methidathion and greater tolerance to α-cypermethrin. S. viridis was found to be significantly more tolerant than H. destructor to all pesticides tested, with the exception of chlorpyrifos. This indicates that rates of application for control of S. viridis should be greater than H. destructor and that the organophosphates are likely to provide the most effective control of this pest.     

Population dynamics and diapause response of the springtail pest Sminthurus viridis (Collembola: Sminthuridae) in southeastern Australia

The springtail, Sminthurus viridis (L.) (Collembola: Sminthuridae), is an important agricultural pest across southern Australia. We investigated the seasonal abundance patterns and summer diapause response of S. viridis in southeastern Australia by using field and shadehouse (a greenhouse that offers seedlings shade) experiments. Seasonal activity patterns of S. viridis were largely consistent with previous studies, with the pest active from autumn to spring. In addition, the timing and pattern of the summer-diapausing egg stage was established, with multiple generations probably producing diapause eggs. A strong relationship between soil moisture and temperature with autumn emergence also was observed. These results suggest that S. viridis autumn pest pressure can be predicted and indicate that late-season spraying strategies currently used for a sympatric agricultural pest are unlikely to be as effective against S. viridis.     

Conserving the efficacy of insecticides against Plutella xylostella (L.) (Lep., Plutellidae)

Abstract:  The diamondback moth (DBM), Plutella xylostella (L.) (Lep., Plutellidae), is one of the most destructive insect pests of crucifers worldwide. It was the first crop insect reported to be resistant to DDT and now in many crucifer-producing regions it has shown significant resistance to almost every insecticide applied in field including biopesticides such as crystal toxins from Bacillus thuringiensis and spinosyns from Saccharopolyspora spinosa . In certain parts of the world, economical production of crucifers has become almost impossible because of its resistance to insecticides and resulting control failure. A coordinated resistance management program needs to be implemented with the involvement of pesticide industry, local pesticide regulatory authorities, scientists and farmers. The judicious use of chemicals in conjunction with other control measures (e.g. biological control agents, resistant varieties, proper fertilization rates) is the best way to manage DBM and other pests of cruciferous crops. Introduction of glucosinolate-sulphatase inhibitors as plant-incorporated-products or sprayable material may also lead to a novel pest management strategy.     

A novel method of self-righting in the springtail Sminthurus viridis (Insecta: Collembola)

Photographic evidence shows that the ventral tube can be used as a tentacle-like mechanical aid for self-righting from an inverted position. It is proposed that the extraordinary length of the vesicles of the ventral tube in globular springtails has been evolved in order to combat postural instabilities resulting from spherical symmetry of body form.     

Control of flea beetles Podagrica spp. (Coleoptera: Chrysomelidae) infestation on okra (Abelmoschus esculentus (L.) Moench) using Piper guineense seed extracts

Crops in the Family Malvaceae are attacked by various insect pests especially Podagria species (Coleoptera: Chrysomelidae) at different stages of their development. The emergence of biodegradable pesticides (botanicals) as safe option has reduced the problems that result from the use of synthetic insecticides, thus creating a renewed interest in their development and use in integrated pest management of crops. Therefore, field experiments were conducted to investigate the control capability of water extracts of Piper guineense seeds and Cypermethrin on flea beetles (Podagrica spp.) infesting okra (Abelmoschus esculentus (L.) Moench). The experiments were conducted in two locations in the rain forest zone of Nigeria. The first experiment was conducted at the Teaching and Research Farm of The Federal University of Technology Akure, Ondo State (2011 Early cropping season), while the second experiment was carried out at the Teaching and Research Farm of Rufus Giwa Polytechnic, Owo, Ondo State (2011 Late cropping season). A synthetic insecticide (Cypermethrin) was included in the treatments as a standard check alongside the untreated (control). The experimental design was laid out in a randomised complete block design with five treatments replicated three times. The effectiveness of the treatments was determined based on reduction in the population of the adult insects. The results showed that water extract of P. guineense seeds and the synthetic insecticide significantly (p?<?0.05) reduced the population of the flea beetles as compared with the control. The synthetic insecticide-treated plots produced the highest standard check, but this was not significantly different from the dried yield recorded in the plots sprayed with aqueous extracts of P. guineense seeds. The results of field trials in both cropping seasons showed that all the treatments significantly suppressed the infestation by the flea beetles throughout the study period. In view of the ability of water extract of P. guineense seeds to control the infestation of Podagrica spp. its use by farmers is therefore recommended.     

印楝素乳油对黄曲条跳甲种群控制作用评价

在生命表方法分析的基础上。建立了害虫累积为害量指标,用以描述和比较某一时间段内害虫动态持续为害力大小．应用该指标分析印楝素乳油对黄曲条跳甲(Phyllotreta striolata(F.))种群控制作用,结果表明,对成虫显著的忌避作用是其对种群控制的主要机理．印楝素0．50ml·L^-1对成虫的忌避率为83．75％,种群趋势指数I值降为0．3354,干扰作用控制指数为0．0863．采用田间试验获得的结果,避免了室内测定的空间限制,因而是评价异源植物次生化合物对害虫忌避作用的主要依据．该指标在以害虫控制为目标的动态研究中具有较好的应用前景．     

Efficacy of some biorational insecticides against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under laboratory and greenhouse conditions in Kuwait

The tomato leafminer, Tuta absoluta, is one of the most destructive pests of tomato worldwide. Management of the pest is mainly based on chemical insecticides. Reliance on insecticides is difficult to sustain because of unintended long‐term adverse effects on the environment and human health. Consequently, there is a need to develop pest management strategies that ensure the production of high‐quality products, while at the same time ensuring environmental sustainability and maximum consumer protection. We evaluated the efficacy the biopesticides: Azadirachtin, Bacillus thuringiensis, Steinernema feltiae and Beauveria bassiana individually and in combination against T. absoluta under laboratory and greenhouse conditions. When second instar larvae were exposed to tomato leaf discs treated with Azadirachtin (3 g / L), B. thuringiensis (0.5 g/L) or B. bassiana (1.5 g/L), 70%–86%, 55%–65%, and 45.5%–58.5% mortality was observed, respectively. Steinernema feltiae (1,000 IJs/ml) was the least effective biopesticide, with 26%–42% mortality. In the greenhouse trials on tomato, pest infestation (mines/10 leaves/plant) and fruits damaged were significantly lower on plants treated with Azadirachtin  +  B. thuringiensis or Azadirachtin  +  B. bassiana compared to plants treated with Azadirachtin, B. thuringiensi, B. bassiana or S. feltiae alone. Azadirachtin  +  B. thuringiensis and Azadirachtin  +  B. bassiana resulted in 90% and 81% reduction in fruits damaged in the summer experiments, respectively, and 96% and 91% in winter. The most severe pest infestation was observed on plants treated with S. feltia. The results indicate that the biopesticides, except S. feltia, can contribute to T. absoluta control in greenhouse tomato crops. In particular, the combined use of Azadirachtin with B. thuringiensis or B. bassiana provided the highest level of control of the pest. The potential for including these biopesticides in an overall sustainable integrated pest management programme for T. absoluta is discussed.     

Genetics and evolution of resistance to insecticides

The evolution of resistance to insecticides has become a serious problem world-wide. It is important to identify patterns of insecticide use whereby insecticides can be used in integrated pest management programmes to help control insect numbers, but in such a manner that the evolution of resistance to insecticides will be retarded. The principal mechanisms of insecticide action and of resistance to these are reviewed. Some generalizations that can be made about the evolution of resistance are examined. In general, to control resistance it appears better to use an intense dose of non-persistent pesticides over a circumscribed area. Some features of the problem where population genetics and evolutionary theory might contribute to controlling resistance are discussed.     

Processed kaolin as an alternative insecticide against the European pear sucker, Cacopsylla pyri (L.)

Abstract:  Application of processed kaolin particle film (Surround^® WP; Engelhard Corporation, Iselin, NJ, USA) repels insects without lethal effects; hence side effects on beneficial arthropods are low. Processed kaolin may be an alternative to broad-spectrum insecticides used against European pear sucker, Cacopsylla pyri (L.), in organic and conventional pear production. A small-plot field trial was conducted in spring 2003 to assess this hypothesis. Multiple applications of processed kaolin during the first flying period of C. pyri significantly reduced the number of nymphs compared to the untreated control. Processed kaolin protected pear trees at least as good as the standard organic insecticide rotenone. Since the effects on the summer population could not be assessed in this small-plot trial due to the high mobility of the adult C. pyri , a large-plot trial was conducted in 2004. Thereby, the processed kaolin showed a very high efficacy and the population of C. pyri was kept under a damaging level over the whole season. At the end of June the population density of C. pyri in the processed kaolin treated area was lower than in the IPM treated plot. In conclusion, kaolin shows promise as an alternative control for C. pyri in organic and IPM orchards.     

Selection for resistance to acetamiprid and various other insecticides in the diamondback moth, Plutella xylostella (L.) (Lep., Plutellidae)

Abstract:  A diamondback moth (DBM) colony (KOBII) originally collected from cabbage fields of Iwaoka-cho in Kobe City, Japan, where acetamiprid is the primary insecticide for DBM control was selected for studies on resistance to acetamiprid, phenthoate, esfenvalerate and cartap, using the leaf-dipping method. Resistance to acetamiprid was slow to develop in KOBII compared with the other insecticides. Three selection experiments each with phenthoate and esfenvalerate yielded a resistance ratio (RR) of 140 and 222, respectively, in the selected strains compared with a part of KOBII that was not exposed to any insecticide (KOBII-NS). Three selection experiments with cartap also gave an RR of 15. However, six selection experiments with acetamiprid yielded an RR of just 9.5 in the selected strain. When cross-resistance to acetamiprid was evaluated, the cartap-resistant strain showed a moderate level of cross-resistance to acetamiprid. In the case of the phenthoate-resistant strain, a very low cross-resistance to acetamiprid was observed. There was however no discernible cross-resistance to acetamiprid in the esfenvalerate-resistant strain.     

小菜蛾对几种常用药剂的敏感性测定

采用叶片浸溃法,在2001年10月和2002年10月分别测定了福州上街蔬菜基地的小菜蛾,对10种杀虫剂的敏感性。结果表明,上街菜区小菜蛾对灭多威、杀虫双、辛硫磷、毒死蜱、杀灭菊酯和功夫菊酯等农药极不敏感,已不能有效控制小菜蛾的危害。而小菜蛾对氟啶脲、阿维菌素、氟虫腈和虫螨腈比较敏感。通过两次毒力测定比较(2002年10月的LC50;2001年10月的LC50),结果表明,大多数杀虫剂敏感性变化较小。但小菜蛾对阿维菌素敏感性明显下降,毒力倍数达6．65倍,对氟虫腈毒力倍数相差1．48倍。此外,2002年10月小菜蛾对功夫菊酯的LC50为2001年10月的2．02倍。用浸叶法和浸溃法测定多杀菌素、氟虫腈与虫螨腈推荐浓度对小菜蛾幼虫的毒杀作用。结果表明3种药剂浸叶法处理效果均较理想。     

The response of lucerne (Medicago sativa L.) to sodium sulphate and chloride salinity

Sodium and sulphate-dominated salinity is a serious environmental problem occurring in soils and groundwater in many parts of the world. The effect of Na2SO4 and NaCl, at electrical conductivity levels ranging from 2 to 17 dS m-1, on the growth and tissue ion concentrations of 16 lines of lucerne (Medicago sativa L.) was examined in the greenhouse over a 2 month period. Averaged across all lines, plants grown at 17 dS m-1 produced 66% of the dry matter of plants grown at 2 dS m-1. However there were significant differences among lines in relative salt tolerance (as defined by the slope of the reduction in dry matter) versus electrical conductivity. Dry matter production was negatively correlated with shoot concentrations of Na+, Cl- and S2- and generally lines that were more tolerant to salinity had lower concentrations of those ions in the shoots. We conclude that lucerne is moderately tolerant to Na2SO4 -predominated salinity, and that the degree of intraspecific variation that exists within this species will allow more tolerant lines to be selected for establishment in conditions where sulphate salinity is a problem.Collaborator     

Evaluation of CropSyst for studying the effect of mulching with lucerne (Medicago sativa L.) in Austria

Conservation of water under semi-arid conditions is of supreme importance to combat forthcoming water scarcity. Crop residue mulches are the key interventions in this regard. Simulation models are emerging as strong analytical tools to study the effect of agronomic interventions but their use to study effect of mulches in Austria is limited. To bridge this knowledge gap, we planned a study to evaluate the efficacy of CropSyst for studying response of lucerne mulches in succeeding lucerne crop. CropSyst is a user-friendly, conceptually simple but sound multi-year multi-crop daily time step simulation model. Above ground biomass and soil water content from field experiments carried out near the city of Vienna, Austria (2007–2008) were compared with simulated results to determine the suitability of CropSyst in regarding mulch. Adequacy of model to regard mulch is demonstrated while pros and cons of disagreement between experimental and modeling results are discussed with a way forward for future research.