Effects of piperonyl butoxide on Bemisia tabaci Genn. (Homoptera: Aleyrodidae): mortality, development, parasitism and predation in Israeli cotton fields

In field trials in Israel, piperonyl butoxide (PB) alone, at concentrations of 2000 and 5000 ppm exerted good control over nymphal Bemisia tabaci populations on cotton. Weekly doses of these concentrations exerted greater control than a recommended oil and were as effective as the standard single application of buprofezin. Cypermethrin caused marked resurgence within the plots, probably as a consequence of its detrimental effects on natural enemies. Neither PB, buprofezin nor the oil reduced the incidence of natural enemies. Treatment with 2000 or 5000 ppm PB resulted in a shift in age structure toward a greater proportion of young instars than in other treatments. There was some evidence that these effects facilitated a greater level of parasitism in PB-treated plots.     

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.     

Sampling and management of Bemisia tabaci (Genn.) biotype B in Australian cotton

Data on seasonal population abundance of Bemisia tabaci biotype B (silverleaf whitefly (SLW)) in Australian cotton fields collected over four consecutive growing seasons (2002/2003–2005/2006) were used to develop and validate a multiple-threshold-based management and sampling plan. Non-linear growth trajectories estimated from the field sampling data were used as benchmarks to classify adult SLW field populations into six density-based management zones with associated control recommendations in the context of peak flowering and open boll crop growth stages. Control options based on application of insect growth regulators (IGRs) are recommended for high-density populations (>2 adults/leaf) whereas conventional (non-IGR) products are recommended for the control of low to moderate population densities. A computerised re-sampling program was used to develop and test a binomial sampling plan. Binomial models with thresholds of T=1, 2 and 3 adults/leaf were tested using the field abundance data. A binomial plan based on a tally threshold of T=2 adults/leaf and a minimum sample of 20 leaves at nodes 3, 4 or 5 below the terminal is recommended as the most parsimonious and practical sampling protocol for Australian cotton fields. A decision support guide with management zone boundaries expressed as binomial counts and control options appropriate for various SLW density situations is presented. Appropriate use of chemical insecticides and tactics for successful field control of whiteflies are discussed.     

中国烟粉虱寄生蜂资源及其区系分布

对中国寄生烟粉虱的寄生蜂种类、寄主类别和分布地区进行了系统论述。根据采集调查和文献记录,目前中国烟粉虱寄生蜂约有27种,占世界记录总数的54%,主要隶属膜翅目(Hymenoptera)蚜小蜂科(Aphelin-idae),其中,恩蚜小蜂属(Encarsia)的21种,桨角蚜小蜂属(Eretmocerus)的6种。主要分布于长江流域以南的福建、广东、广西、台湾和香港等地,台湾种类分布最多。同时,对中国烟粉虱寄生蜂的地理区系分布进行了分析和讨论。     

Investigation of Thrips tabaci Lind. as a cotton pest and the development of strategies for its control in Punjab

Thrips tabaci Lind. migrates from the lower to the upper portion of the cotton plant as the season progresses and plants increase in size. The population level of thrips on seedlings should be determined by visual observations of leaf damage instead of scouting. The crop should be sprayed before the damage level is such that seedling leaflets have a cup-like appearance. Combined attack by thrips (14.6 per leaf) and jassid (4.6 per leaf) caused a 37.6% loss in the yield of seed cotton. Granule application at the seedling stage and foliar sprays at later stages is suggested as a control strategy. Thrips and jassids appear to be mutually exclusive but the exact mechanism is not known.     

Cross-resistance, inheritance and stability of resistance to acetamiprid in cotton whitefly, Bemisia tabaci Genn (Hemiptera: Aleyrodidae)

The cotton whitefly Bemisia tabaci, (Genn.) is an important pest of field crops, vegetables and ornamentals worldwide. Neonicotinoids are considered an important group of insecticides being used against B. tabaci for several years. B. tabaci has developed resistance to some of the compounds of the group. This study was designed to investigate if the selection of B. tabaci with acetamiprid would give a broad-spectrum of cross-resistance and to genetically classify the resistance. At G₁ a low level of resistance to acetamiprid, imidacloprid, thiamethoxam, thiacloprid and nitenpyram was observed with resistance ratios of 3-fold, 8-, 9-, 6- and 5-fold, respectively, compared with a laboratory susceptible population. After selection for eight generations with acetamiprid, resistance to acetamiprid increased to 118-fold compared with the laboratory susceptible population. Selection also increased resistance to imidacloprid, thiamethoxam, thiacloprid, nitenpyram, endosulfan and bifenthrin but no change in susceptibility to fipronil was observed. Furthermore resistance in a field population was stable in the absence of acetamiprid selection pressure. Genetic crosses between resistant and susceptible populations indicated autosomal and incompletely recessive resistance. Further genetic analysis suggested that resistance could be controlled by a single factor. The high level of cross-resistance and stability of incomplete resistance in the field population is of some concern. However, lack of cross-resistance between acetamiprid and fipronil or unstable resistance in the resistant population could provide options to use alternative products which could reduce acetamiprid selection pressure.     

Assessment of avoidable losses and economic injury levels for the sorghum head bug, Calocoris angustatus Leth. (Hemiptera:Miridae) in India

Avoidable losses and economic injury levels (EILs) were computed for the sorghum head bug, Calocoris angustatus Leth., on three cultivars during three rainy seasons (1985–1987) at ICRISAT. Grain yield in plots protected with 2–5 insecticide sprays (carbaryl at 500 g a.i./ha) between the half-anthesis and the dough stage was significantly higher than in untreated plots, with cost-benefit ratios > 1. Plots that were not protected at half-anthesis and/or complete-anthesis, and at milk and dough stages, suffered a significant loss in yield. Bug damage spoiled the grain quality in terms of germination, 1000-grain mass, grain hardness and percentage floaters. Three to four sprays between complete-anthesis and the dough stage prevented a significant reduction in grain quality. Head bug density at half-anthesis, complete-anthesis, milk and dough stages was significantly and negatively associated with grain yield. Bug density at different stages explained 43–94% of the variance in yield. Direct effects of bug numbers at the milk stage and the indirect effects of head bug density at other stages through the milk stage contributed towards maximum reduction in yield. Maximum avoidable losses were recorded in cultivar ICSV 1 (88·6%), followed by CSH 1 (69·9%), and CSH 5 (53·9% in 1986 and 55·0% in 1987). Loss in grain yield/ha due to one insect/panicle at half-anthesis and that based on natural increase, were 548 and 232 kg in CSH 5 during 1986 and 1987, respectively, 251 kg in ICSV 1, and 77 kg in CSH 1. EILs based on a cost-benefit ratio of 1:1 ranged from 1·3–1·4 insects/panicle for CSH 1, 0·4 for ICSV 1, and 0·4–0·6 and 0·2–0·4 for CSH 5 during 1986 and 1987, respectively. Simple cost estimates for insecticide sprays and the resultant saving in grain yield are a useful tool for decision-making in pest management.     

CAP Analysis of the Distribution of the Introduced Bemisia tabaci (Hemiptera: Aleyrodidae) Species Complex in Xinjiang,China and the Southerly Expansion of the Mediterranean Species

Bemisia tabaci (Gennadius) cryptic complex has invaded Xinjiang, China, since 1998. The distribution of Mediterranean (MED) and Middle East-Asia Minor 1 (MEAM1) B. tabaci substrains has been gradually identified due to the development of molecular technology. In this study, the distribution of MED and MEAM1 in Xinjiang was determined by cleaved amplified polymorphic sequence (CAPs). Results showed that MED dominated in northern Xinjiang (84%), whereas MEAM1 was dominant in southern Xinjiang (72%). Five pairs of simple sequence repeat (SSR) primers were used to analyze the genetic diversity of B. tabaci among 36 geographic populations. The genetic diversity of MED and MEAM1was low and varied little among populations in Xinjiang (0.09 ± 0.14 and 0.09 ± 0.13, respectively). Based on ∆K statistic, 13 populations of MEAM1 could be classified into two subgroups at K = 2, whereas the 23 populations of MED could be classified into four subgroups at K = 4. However, Mantel t-test demonstrated no correlation between geographical and genetic distances among B. tabaci complex (R = 0.42, P = 1.00). Neighbor-joining and principal coordinate analysis showed that geographical isolation and interspecific differences were the main causes of the genetic variation. Gene flow predicted that MEAM1 was most likely introduced from Urumqi to the southern Xinjiang. Meanwhile, a large proportion of MED in Kashi region came from Changji and Yining. To block ongoing dispersal, strict detection and flower quarantine regulations need to be enforced.     

Modelling the spray deposition and efficacy of two mineral oil-based products for the control of California red scale, Aonidiella aurantii (Maskell)

The pattern and quantity of pesticide deposition may affect the efficacy of pesticide treatments. In this study we evaluated under laboratory conditions the efficacy of two petroleum-derived spray oils (PDSO) (Laincoil^®, an nC21 oil with a content of 83% w/v, Oil A, and Sunspray Ultrafine^®, an nC21 with a content of 85% w/v, Oil B, both with an unsulfonated residue of 92%) applied at 1.5% concentration at five volumes (0.5, 1, 2, 3 and 4 ml) against different stages of Aonidiella aurantii Maskell (Homoptera: Diaspididae). In parallel, we characterized the deposition pattern of treatments resulting from these five volumes and two PDSOs. The objective was to model deposition characteristics and efficacy as a function of the deposited volume in order to determine the optimum volume per unit surface that should be applied to control this pest. Different models that depend on the developmental stage and relate to the efficacy of the treatment as a function of the deposited volume have been obtained for both PDSOs, thus providing a scientific basis for product efficacy comparison. Furthermore, our results are also relevant to find an adequate trade-off between sprayed pesticide volume and expected efficacy.     

Sucking insects damaging jojoba, Simmondsia chinensis (link) Schneider, and their natural enemies, in the North Central and Central regions of Chile

This article reports the results of a periodical survey of sap-sucking insects of jojoba [Simmondsia chinensis (Link) Schneider] at five locations in the North Central and Central regions of Chile and describes their damage to the plants. The diaspidid Aspidiotus nerii Bouché, which was commonly found in two of the locations (Casablanca, near Valparaiso, and Curacaví, near Santiago) was potentially the most severe pest of the crop, as it damages the fruits directly. Next in importance as pests, because of their reproductive potential, were the aphids Aphis craccivora Koch and Myzus persicae Sulzer, which were found on leaves and young shoots, in Casablanca, Curacaví, and Hacienda Camarones (IV region). Other species of certain importance because of their numbers were the pentatomid Acledra albocostata (Spinola) and the cicadellid Balclutha sp. (both common in Casablanca and Curacaví). When ovipositing, the cicadid Tettigades chilensis Arm. & Serv. (collected in Las Cardas, in the IV region), was found to produce deep wounds with the oviscapt on branches, which affected their vascular system. The scelionid micro-hymenopteran Trissolcus scuticarinatus Costa Lima was found parasitizing eggs of hemipterans throughout the locations studied. Except in Casablanca, the predatory activity on aphids of the coccinellids Eriopis connexa Germ., Hippodamia variegata Guer., and Scymmus bicolor Goeze was observed in all locations surveyed, including Agua Amarilla, a southern location in the IV region.     

Impacts of transgenic Bt cotton on a non-target pest, Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae), in northern China

Transgenic Bt (Bacillus thuringiensis) cotton has been effectively used to control the cotton bollworm, Helicoverpa armigera (Hübner) in China. However, in recent years, following the wide commercialization of Bt cotton in northern China there have been frequent outbreaks of the non-target pest Apolygus lucorum (Meyer-Dür). To clarify how transgenic cotton contributes to these outbreaks, a four-year field investigation of population dynamics and laboratory life table studies were carried out from 2007 to 2010 to evaluate the impact of two transgenic cotton cultivars (SGK321 expressing Cry1Ac + CpTI and GK12 expressing Cry1Ac) and their corresponding parental non-transgenic lines (Shiyuan321 and Simian3) on A. lucorum. There were no significant differences in the population densities of A. lucorum found in Bt cotton and non-Bt cotton plots, whether one compared those that had received insecticide treatments or those that had not. However, population densities of A. lucorum were significantly lower in pesticide treated plots than in controls. Furthermore, there were no significant differences in the net reproductive rates, generation times or intrinsic rates of increase of A. lucorum when reared on either Bt or non-Bt cotton cultivars. These results suggest that Bt cotton has no direct positive or negative effects on the biology of A. lucorum, so the most logical explanation for the observed outbreaks is the decrease in pesticide applications following the commercial release of Bt cotton.     

Sucrose avoidance by American robins (Turdus migratorius): Implications for control of bird damage in fruit crops

Altering the relative sugar content in fruit is a potential alternative to chemical, aural and visual repellents to control bird damage to cultivated fruit crops. Some frugivorous birds, such as the American robin (Turdus migratorius), lack the digestive enzyme sucrase, and therefore cannot digest sucrose. It was predicted that robins would avoid consumption of foods that contain sucrose. When offered sweetened agar cubes that contained glucose, fructose, sucrose, or a hexose mixture, total consumption was significantly lower and faecal sugar concentration higher in the sucrose tests. In tests involving two sugars, mean total consumption was reduced when sucrose was eaten. Development of high-sucrose fruits warrants further investigation as a means to mitigate bird damage to certain fruit crops.     

Seasonal abundance of the mirids, Lygus lucorum and Adelphocoris spp. (Hemiptera: Miridae) on Bt cotton in northern China

Lygus lucorum Meyer-Dür, Adelphocoris fasciaticollis Reuter and Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) are important secondary insect pests in cotton fields in northern China. The seasonal dynamics of their mixed populations on a transgenic variety expressing the insecticidal Bt protein Cry1A, and a cotton line expressing proteins of Cry1A and CpTI (cowpea trypsin inhibitor gene) were compared to seasonal dynamics on similar but non-transgenic varieties from 1998 to 2001. No significant differences were detected between population densities of these bugs on unsprayed normal cotton and unsprayed transgenic cotton. However, mirid damage on unsprayed transgenic cotton was significantly higher due to a reduced number of insecticide sprays against Helicoverpa armigera compared with the number of sprays in the normal cotton. This suggests that the mirids have become key insect pests in transgenic cotton fields, and that their damage to cotton could increase further with the expansion of the area planted to transgenic cotton if no additional control measures are adopted.     

Economic implications of herbicide resistance and high labour costs for management of annual barnyardgrass (Echinochloa crus-galli) in Philippine rice farming systems

Implications of increasing labour costs and the development of herbicide resistance for profitable weed management in Philippine rice farming systems are investigated. The study employs RIMPhil (Resistance and Integrated Management in the Philippines), a bioeconomic simulation model developed to provide a comprehensive assessment of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice crops. Results indicate that herbicide application will become increasingly economically attractive, relative to manual weeding, as labour cost increases. This is important since urban migration in the Philippines continues to increase the scarcity of rural labour. Results also show that the onset of herbicide resistance results in substantial losses in farm profit. It is worthwhile for farmers to take management actions to prevent or delay the onset of herbicide resistance, provided that these changes are effective and not too costly. The study highlights the complexity of decision making about integrated weed management on rice farms in the Philippines.     

Responses of the alien leaf miners Liriomyza trifolii and Liriomyza huidobrensis (Diptera: Agromyzidae) to some pesticides scheduled for their control in the UK

Baseline responses to a range of pesticides scheduled for the statutory eradication of outbreaks of Liriomyza trifolii, a leaf miner alien to the UK, were established using a topical application bioassay against a susceptible laboratory population. Using the same technique the responses of outbreak populations of L. trifolii, and also the related species L. huidobrensis, have been investigated. Field populations of L. trifolii showed resistance to the pyrethroids tested but no evidence of resistance to organophosphates was found. There was some evidence of resistance to gamma-HCH. L. huidobrensis showed a response to pyrethroids similar to that of resistant L. trifolii, and levels of tolerance to organophosphates approximately eight times that of susceptible L. trifolii. The response to gamma-HCH was similar to that of susceptible L. trifolii.     

Assessing the impact of areawide pheromone trapping,pesticide applications,and eradication of infested date palms for Rhynchophorus ferrugineus (Coleoptera: Curculionidae) management in Al Ghowaybah,Saudi Arabia

The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is a highly destructive pest of date palms, Phoenix dactylifera L. (Arecales: Arecaceae), in Saudi Arabia. Data spanning a six year period (2007–2012) from Al Ghowaybah, a 1104 ha date producing region in the Al Ahsaa Directorate in Saudi Arabia, were analyzed to assess the impact enhanced management efforts that commenced in Oct. 2009 had against this pest. Within six months of initiating the areawide management program significant reductions in the mean monthly number of weevils trapped and percentage traps with R. ferrugineus were detected. Mean monthly trap captures of R. ferrugineus and the percentage of traps capturing weevils declined significantly from 2009 to 2012 by an average of 65% and 90%, respectively, indicating that trapping and dispersal pressure was significantly reduced. By 2011, average monthly trap captures and percentage of traps with R. ferrugineus were significantly lower than all pre-management capture data and this was maintained through 2012 when data collection ceased. Additionally, over the period 2010–2012, insecticide application and palm eradication rates dropped by 91% and 89%, respectively. The total number of R. ferrugineus captured in 2012 declined by 86% when compared to total captures for 2010. At the end of 2012, the estimated infestation rate of date palms in Al Ghowaybah was 0.36%, which was below the economic threshold of a 1% infestation rate set by the Directorate of Agriculture supervising the program. It is concluded that the mandatory areawide management program that commenced in Oct. 2009 against R. ferrugineus in Al Ghowaybah had a significant and rapid impact against this pest.