Very high infestation levels of Thrips tabaci Lindeman were observed on onions at Ste-Clotilde (Quebec) with seasonal means of 149 and 161 thrips/plant for 1988 and 1989 respectively. No significant differences in thrips densities were detected among six yellow onion cultivars (Capable, Flame, Norstar, Progress, Rocket, Taurus) through weekly comparisons in 1988 and biweekly comparisons in 1989. / A new variable, the cumulative number of thrips-days/plant, was used to model the impact of T. tabaci on onion yields. This variable allowed for better-fitted models, especially in 1989 where greater variability of the onion yields was observed. A modified Gompertz equation gave the best fit for 1988. No yield reduction due to T. tabaci was observed up to the 1000 cumulative thrips-days/plant point, beyond which the thrips impact first increased with the feeding pressure and then gradually decreased to a minimal level corresponding to a yield loss of 43%. In 1989, thrips impact was immediate and best described by an exponential model with a maximal yield loss of 34,5%. / Economic thresholds of 964 and 251 cumulative thrips-days/plant were calculated for 1988 and 1989 respectively. Converted to thrips/leaf these correspond to 2,2 and 0,9 thrips/leaf. This conversion could facilitate their use in a field situation. / Spatial distribution of T. tabaci was analyzed in ten commercial onion fields. Within field, density was homogeneous in the majority of cases. In some fields, higher thrips densities were temporary (two consecutive weeks at most) in one or two field margins. / The Iwao method was used to calculate the acceptance boundaries of sequential sampling plans for the economic thresholds of 0,9 and 2,2 thrips/leaf and onion growth stages of 6, 7, 8, 9 and 10 green leaves. (Abstract shortened by UMI.)

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Western flower thrips (WFT), Frankliniella occidentalis (Pergande), are haplodiploids. Virgin females produce sons parthenogenetically but must be mated to produce daughters. As a result, primary and secondary (adult) sex ratios can diverge from the 1:1 ratio commonly observed in diploid systems. Field studies were conducted to examine the spatial distribution of WFT on two greenhouse crops, Bell peppers, Capsicum annuum (Linn.) and Long English cucumbers, Cucumis sativus (Linn.) to determine if there was a correlation between sex ratio and density. Leaf and flower samples were taken weekly. All adult and immature WFT were counted and sex of adults determined. Yellow sticky traps were used to monitor density and sex ratio of the dispersing adult population. Lab studies were also done to investigate if male availability affected the sex ratio and number of offspring produced by individual females. Laboratory experiments were done to assess the effects of sperm availability and maternal age on sex ratio of progeny produced. On both crops, 84 to 95 % of adult WFT in flowers were females and most larvae (> 85 %) were found on leaves. Male WFT were rare on all plant parts even when caught in high numbers on traps. Approximately 75 % of females found on plants in the greenhouse were mated. Most (70 - 90 %) WFT on traps at low densities (< 200 individuals/trap) were males. This suggests that WFT populations are initiated by virgin females that likely overwintered as pseudopupae in the greenhouse. These females initially produce only sons, and may have to wait for these to emerge before they mate and produce daughters. As WFT density within a greenhouse increases, females are probably mated soon after emergence. Sex ratio of adults on traps becomes more female biased as density increases within a greenhouse. Heavily female biased (> 65 %) sex ratios were found on traps at high population densities (> 200 individuals/trap). Sex ratio of adults on traps remained male biased in the pepper greenhouse (WL) where the population density of WFT remained low. Information regarding within-plant distribution of thrips is essential for population monitoring and control. Used together, regular examination of flowers and counts of adults on sticky traps allow quick detection of potential "hot spots" of WFT density. Sex ratio and density are highly correlated. Sex ratio of the dispersing adult population is a good predictor of outbreak potential of the extant WFT population. Two WFT predators found in greenhouses were also monitored to document their effects on WFT population density and sex ratio. Mass introductions of the predatory mite, Amblysieus cucumeris, did not successfully control WFT in most greenhouses monitored. A natural infestation of pirate bugs, Orius tristicolor occurred in the only pepper house monitored. WFT density remained low throughout the growing season. O. tristicolor shows promise for future use in integrated pest management programs designed to control F. occidentalis in commercial greenhouses. Lab studies showed that sex ratio of offspring produced by mated females was influenced by sperm supply and maternal age. Mated females produced sons and daughters which suggests that females control sex of offspring produced through selective fertilization. Once mated, two-thirds of offspring produced are females. Older females produced fewer daughters than younger females. A principle conclusion from this study is that sex ratio of the WFT population within a greenhouse can be used to predict future population dynamics. Male availability may be the most important factor affecting the number of daughters produced by individual females which in turn may determine the potential of WFT populations to increase. / Science, Faculty of / Zoology, Department of / Graduate

The objectives of this research were to evaluate management options for tobacco thrips, Frankliniella fusca (Hinds), and reniform nematode, Rotylenchulus reniformis (Linford & Oliverira), in cotton productions systems. When evaluating tillage practices for pest control, conservational tillage reduced thrips densities and damage, while the impact on nematode densities is less understood and in this study had no impact. Insecticide seed treatments remain a vital resource for controlling thrips in Mid-South cotton production systems. When incorporating an early season herbicide application for weed control, systems with an insecticide seed treatment generally tolerated herbicide injury better than those with early season stress from thrips and nematodes. When using foliar applications as an alternative option for thrips management, early season automatic applications at the cotyledon stage followed by one or two sequential applications provided similar efficacy to the insecticide seed treatment. For reniform nematode management, 1, 3-dichloropropene reduced densities lower than that of the untreated control or aldicarb; however, depending on environmental conditions this practice may not result in yield increases great enough to warrant the cost of application. These data highlight the importance of effective control of thrips whether it be via at-planting or foliar applications. 1, 3-dichloropropene reduced nematode densities and is an effective option in nematode management; however, nematodes are a stress pathogen and the ability to minimize other seasonal stresses ,such as water stress, will determine if a nematicide application may be needed. While environmental conditions may be optimal to allow for plant recoverability, effective early season pest management decreases the potential for delayed crop maturity which could lead to increased input cost or reduced yield later in the season.

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Environmental factors exert a great effect on the occurrence of aphids and thrips, their abundance and damage done in cereal crops, as well as the time of appearance of these pests in the crops, timing of their control and means used. Species diversity of aphids and thrips in winter rye, triticale, wheat, and spring barley was identified. Variation of the abundance of the main species of aphids and thrips in the mentioned crops was determined in relation to crop growth stages and environmental factors. For the first time in Lithuania we estimated migration activity of R. padi and S. avenae using a suction trap and compared with the abundance of these aphid species in cereal crops. The experimental data obtained in this study enables assessment of damage done by aphids and thrips in winter rye, triticale and wheat crops and estimation of expedience of the application of aphids and thrips control measures. Thrips threshold of harmfulness at which it is expedient to apply control measures was identified in winter rye.

Made available in DSpace on 2014-06-11T19:35:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-12-07Bitstream added on 2014-06-13T20:45:43Z : No. of bitstreams: 1 albuquerque_fa_dr_botfca.pdf: 1798197 bytes, checksum: 60366c6885a9cad436dbac48035038c5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Com o objetivo de identificar as possíveis espécies de tripes associadas à cultura do milho, a espécie predominante, a proporção de adultos e ninfas, a época de ocor-rência, o período crítico de ataque e a influência do sistema de plantio e das condições climáti-cas sobre a população de tripes e métodos de amostragem, foram conduzidos ensaios na Fa-zenda Experimental de Iguatemi, localizada no Município de Maringá, PR, no período de ou-tubro de 2001 a fevereiro de 2004. As avaliações foram realizadas por meio da coleta de tri-pes com armadilhas adesivas azuis e coletando-se plantas de milho, cortadas rente ao solo, colocadas em sacos plásticos e levadas ao laboratório, onde foram lavadas em álcool 70%, para extração dos tripes. A determinação dos danos provocados pelo tripes foi estudada em cinco experimentos inteiramente casualizados, correlacionando diferentes níveis populacionais de tripes e produtividade. Foi empregado o inseticida thiamethoxan, em tratamento de semen-tes, e pulverizações com metamidofós, em diferentes estágios de desenvolvimento das plantas, para obter parcelas com diferentes níveis de incidência de tripes em períodos pré-determinados. Foram identificadas oito espécies de tripes associadas à cultura do milho, na região, sendo Frankliniella williamsi Hood, 1915, a mais freqüente (99,43%). Verificou-se que a incidência de tripes na cultura de milho em solo coberto com aveia dessecada foi menor do que em solo nu, ou coberto por aveia tombada ou incorporada, sendo que imediatamente após a emergência das plantas a população de tripes era composta quase que exclusivamente por adultos imigrantes. A população de formas jovens começou a aumentar a partir dos 14 dias após a emergência das plantas, indicando a capacidade reprodutiva do tripes na cultura do milho. Foi verificada correlação negativa entre... . / Aiming to identify the possible species of thrips associated to the corn crop, the predominant species, the adult/nymph rate, occurrence time, critical period of attack, influence of the sowing system and climatic conditions on the population of thrips and sampling methods, essays were carried out at the Experimental Farm of Iguatemi, in Maringá, Paraná State, Brazil, from October 2001 to February 2004. The evaluations consisted in collecting thrips with blue adhesive traps and collecting corn plants cuted at soil level, placed into plastic bags and took to the laboratory, where they were washed in alcohol 70%, for the extraction of thrips. The determination of the damages caused by thrips was studied in five experiments, totally randomized, correlating different population levels of thrips and productivity. The insecticide thiamethoxan was applied in seed treatment and methamidophos, in sprayings in different stages of plant development to obtain areas with different levels of incidence of thrips in periods previously established. Eight species of thrips associated to corn crop were identified in the area, being Frankliniella williamsi Hood, 1915, the most frequent (99.43%). It was verified that the incidence of corn thrips in soil covered with dried oats was smaller than in nude soil or in soils covered by cuted or incorporated oat, considering that, immediately after the plants emergence, the population of thrips was composed almost exclusively by emigrant adults. The young population began to increase from 14 days after plant emergence, on indicating thrips reproductivity capacity in corn crops. Negative correlation was verified between the rainfall index and the number of thrips collected in blue traps, but it was not observed any correlation among the number of thrips by corn plant and the number of thrips collected in those traps. It was verified that more than 30 thrips... (Complete abstract, click electronic address below).

Experiments were conducted to evaluate the management of thrips (Thysanoptera: Thripidae) in peanut and cotton and the interaction between thrips and tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), in cotton. Although management of thrips with foliar insecticides historically has not been recommended in peanut, the current study observed significant yield benefits from the management of thrips with foliar insecticides. This was especially evident when peanut plants were stressed from herbicide injury. In another experiment, significant differences were observed among cotton varieties in terms of their susceptibility to thrips injury. Finally, an interaction between thrips injury and tarnished plant bug injury in cotton was not observed in these studies. However, both thrips and tarnished plant bug caused significant yield losses in cotton. Results from these experiments will be important for improving current integrated pest management programs in both cotton and peanut.