The effect of three rates of cyantraniliprole on the transmission of tomato spotted wilt virus by Frankliniella occidentalis and Frankliniella fusca (Thysanoptera: Thripidae) to Capsicum annuum

Tomato spotted wilt virus (TSWV) is a thrips-transmitted virus that causes major losses in many crops worldwide. Management of TSWV is complex, requiring multiple preventive measures. Currently, there are few chemical options that control thrips populations before they feed upon and transmit TSWV to crop plants. Cyantraniliprole (Cyazypyr™) is an anthranilic diamide insecticide currently under development that exhibits anti-feedant properties. Transmission of TSWV by Frankliniella fusca (Hinds) to Capsicum annuum L. seedlings was reduced in plants treated with Cyazypyr™ applied to the soil at the rates of 1.45, 2.90 and 4.41 mg ai/plant. Mortality of F. fusca at 3 days post treatment did not differ significantly on excised foliage of Cyazypyr™ treated and control plants, but feeding injury was significantly less on treated foliage. Transmission of TSWV by Frankliniella occidentalis (Pergande) was not reduced in plants treated with 4.41 mg ai/plant.     

An Evaluation of Frankliniella occidentalis (Thysanoptera: Thripidae) and Frankliniella intonsa (Thysanoptera: Thripidae) Performance on Different Plant Leaves Based on Life History Characteristics

To compare the performance of Frankliniella occidentalis (Pergande) and native Frankliniella intonsa (Trybom) on cucumber and tomato leaves in laboratory, life history characters were investigated, and life tables were constructed using the method of age-stage, two-sex table life. Compared with tomato leaf, there were shorter total preoviposition period (TPOP), higher fecundity, longer female longevity, and higher intrinsic rate of increase (r) of both F. occidentalis and F. intonsa on cucumber leaf. Meanwhile, on cucumber leaf, the shorter TPOP, higher fecundity, longer female longevity, and higher value of r were found on population of F. intonsa but on tomato leaf which were found on population of F. occidentalis. From above, cucumber leaf was the preference to population development of both F. occidentalis and F. intonsa compared with tomato leaf. Nevertheless, on cucumber leaf, population of F. intonsa would grow faster than that of F. occidentalis, which was the opposite on tomato leaf. As to the population development in fields, much more factors would be taken into account, such as pollen, insecticide resistance, and effects of natural enemies etc.     

Development,Survival, and Reproduction of Orius insidiosus (Hemiptera: Anthocoridae) Reared on Frankliniella invasor (Thysanoptera: Thripidae)

The minute pirate bug Orius insidiosus (Say) is an important predator in mango agroecosystems. It attacks several species of thrips, particularly Frankliniella invasor Sakimura, which is considered a species of economic importance in mango. We investigated the effect of six diets on the development, survival, and reproduction of O. insidiosus: 1) first instars of F. invasor, 2) second instars, 3) adults, 4) pollen, 5) pollen plus thrips larvae, and 6) water. Individuals fed on thrips larvae, with or without pollen, completed their immature development significantly faster. Nymphs of O. insidiosus were able to complete their development feeding on pollen only, while individuals that received water as a diet were unable to reach the adult stage. The highest intrinsic growth rate was obtained when O. insidiosus were fed on pollen plus thrips larvae, and the lowest when individuals were fed on thrips adults. Our studies show that a diet of pollen plus F. invasor larvae is optimal for O. insidiosus development and population growth.     

El Niño-Southern Oscillation (ENSO): Impact on tomato spotted wilt intensity in peanut and the implication on yield

The impact of El Niño – Southern Oscillation (ENSO) on weather patterns could have cascading effects on several diseases of important crops in the southeastern United States. One such disease is spotted wilt of peanut caused by the Tomato spotted wilt virus (TSWV). Significant economic losses have been recorded by peanut growers in the southeastern United States since the disease was first reported in 1986. The virus is transmitted by western flower thrips Frankliniella occidentalis and tobacco thrips, Frankliniella fusca. The objective of this study was to examine the influence of El Niño – Southern Oscillation on spotted wilt intensity and peanut yield. Our analysis was based on field trials conducted between 1994 and 2005 at field locations in Georgia and Florida in the United States. The spotted wilt intensity (%) in two peanut genotypes and the corresponding yield were recorded and evaluated. Each season was categorized by ENSO (El Niño, Neutral or La Niña) based on the NOAA Climate Prediction Center classification scheme. Results showed that the interaction between ENSO and peanut genotypes significantly affected spotted wilt intensity. Spotted wilt intensity was significantly lower during La Niña when compared to El Niño or Neutral years. The results also showed a significant correlation between spotted wilt intensity and peanut yield. Incorporating findings from this study into the existing TWSV risk index could aid peanut producers in making management decisions for reducing spotted wilt.     

Use of fluorescence to determine reduction in Bemisia tabaci (Hemiptera: Aleyrodidae) nymph feeding when exposed to cyantraniliprole and imidacloprid through systemic applications

The Bemisia tabaci whitefly is an important pest of many agricultural crops. Direct feeding by this pest can cause physiological plant symptoms including irregular ripening in tomatoes and silverleaf disorder in squash. In addition, B. tabaci can transmit more than 100 plant viruses that cause severe diseases that affect crop yield and quality. Insecticides are often applied to control this pest and they may be applied to the foliage and/or to the soil. Insecticides that kill quickly or cause feeding cessation reduce the damage caused by B. tabaci on the host plant most effectively. In this study fluorescence was used to assess B. tabaci feeding and to determine the effect of systemically applied insecticides on feeding by the pest. Cyantraniliprole (Verimark™) and imidacloprid (AdmirePro^®) produced a rapid reduction in B. tabaci feeding. At 24 h after a systemic application, the percentage of whitefly nymphs still feeding in plants treated with cyantraniliprole (anthranilic diamide) and imidacloprid (neonicotinoid) were 19% and 33%, respectively. Both products showed a good reduction in insect feeding and since they have different modes of action they should be considered as rotational partners for B. tabaci control in areas where there is no resistance to neonicotinoid insecticides. While the fluorescein sodium salt cannot be used to trace the uptake of insecticides, it has been shown to reliably demonstrate feeding cessation of whitefly nymphs after foliar and systemic applications of insecticides.     

Effect of cowpea/maize mixed cropping on the incident light at the cowpea canopy and flower thrips (Thysanoptera: Thripidae) population density

The effect of mixed cropping of cowpeas with maize on light intensity in the cowpea canopy and on population density of Megalurothrips sjostedti (Trybom) was investigated in the field and in cages. Significantly less (P< 0 · 05) light was intercepted by the cowpea canopy in the cowpea/maize mixed crop than in the cowpea crop alone. The population density and activity of M. sjostedti were significantly less in the mixed crop than in the single crop. There were significant correlations between light interception and differences in the population density of nymphs (r=0 · 79), adults (r=0 · 84) and the overall activity (r=0 · 93) of M. sjostedti. In a screenhouse choice test, M. sjostedti preferred unshaded cowpea plants to shaded ones. The results suggested that reduced light intensity in the cowpea/maize mixture contributes to the relative scarcity of M. sjostedti in the mixture.     

温度、光、pH值对茶尺蠖病毒活性的影响

试验结果表明,茶尺蠖核型多角体病毒的多角体悬液经80℃(水浴)、干多角体经120℃(烘箱)恒温处理15分钟时,多角体失去活性。夏季,干多角体薄层经阳光直射24hr后几乎失去活性。病毒悬液的pH值在4～8之间对病毒活性无影响。     

Effect of Tetranychus urticae (Acari: Tetranychidae) on yield,quality, and economics of tomato production

The twospotted spider mite, Tetranychus urticae Koch, is an important and consistent pest of vegetables in central and western North Carolina, particularly on tomatoes, Solanum lycopersicum L. Small plot experiments were conducted in 2007, 2008 and 2009 in which acaricides were applied to early and late-planted staked tomatoes based on threshold levels ranging from 0 to 50 mites per leaflet, with a non-treated control included. Vine ripe fruit were harvested at weekly intervals from all plots, and fruit were weighed and graded for size and quality. A partial budget analysis was conducted to compare net profitability among treatments. Results from 2007 to 2008 showed that total and marketable yield was higher in plots with low versus high densities of T. urticae, and that yield differences were mostly due to number of fruit harvested rather than size of fruit. In 2009 there were no differences in yields among treatments. Gold fleck caused by T. urticae feeding directly on the fruit was another factor that influenced marketability, with more fruit affected and a higher percentage of surface area affected in higher densities versus lower densities of T. urticae. Net profitability varied considerably among planting dates and years, but an action threshold level to avoid yield losses by T. urticae injury on staked tomatoes appeared to be about eight mites per leaflet on a second or third recently expanded leaf.     

水稻矮缩病毒对介体昆虫黑尾叶蝉生物学参数及种群增长的影响

【目的】 水稻矮缩病毒(RDV)是水稻普通矮缩病的病原。该病害主要依赖于黑尾叶蝉经卵以持久增殖方式传播,危害水稻。本研究旨在明确RDV对黑尾叶蝉存活、发育、繁殖和种群增长的影响,分析病毒对介体昆虫的间接影响。【方法】 采用室内实验比较了黑尾叶蝉在健康水稻及感病水稻上的发育繁殖情况,组建了实验种群生命表,并调查了RDV对种群增长的影响。【结果】 与健康水稻相比,感病水稻上叶蝉若虫期存活率更高,雌若虫发育历期显著缩短,雄成虫寿命显著延长,产卵量显著增加,其他生物学参数无显著差异。五个生命表参数仅净生殖率(R₀)存在显著差异,感病水稻上叶蝉R₀显著高于健康水稻。饲喂感病水稻的养虫笼内叶蝉种群增长更快,总成虫数量更多,在接虫后的第4、5和6月显著高于健康水稻上的数量。【结论】 水稻矮缩病毒可以提高黑尾叶蝉的存活率和产卵量,并促进种群的增长。