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This study investigated the effect of photoperiod and temperature on the bionomics of the three Thrips tabaci lineages (L1 and L2 – leek-associated, and T – tobacco-associated). The experiment was performed in the laboratory under the following conditions: 23 °C 16L/8D and 8L/16D, and 15 °C under 8L/16D. Reproductive diapause was detected in the T lineage at 23 °C and 8L/16D, but not in the L1 and L2 lineages, while all three lineages diapaused at 15 °C and 8L/16D. Adult longevity of L1, L2, and T lineages were 29.51, 25.69, and 29.76, respectively, at 23 °C under 16L/8D; 30.9, 28.52, and 38.06, respectively, at 23 °C under 8L/16D; and 48.9, 34.22, and 76.89 days, respectively, at 15 °C. Mean fecundity of L1, L2, and T lineages were 89.30, 80.31, 86.76, respectively, at 23 °C under 16L/8D; 40.14, 46.94, and 39.34, respectively, at 23 °C under 8L/16D; and 7.0, 13.85, and 17.87, respectively, at 15 °C. The difference in responses to photoperiod and temperature could be a factor to cause a sympatric population variation of the different T. tabaci lineages under the same environmental condition.

The present study aimed to investigate whether adult males could fertilize immature female pupae in the leek (L1) and tobacco-associated (T) Thrips tabaci lineages and to investigate the potential effects of mother to son inbreeding on the appearance of deuterotokous females in the T lineage. To confirm the pupal insemination, a single female pupa was exposed to a single adult male for 24 hours. The removal of a male from the tube that contained the female pupa was made before the female pupa emerged to adulthood. Emerged female adults were isolated and reared individually and the sex of their progeny was determined in the larval stages. To examine a mother and son inbreeding, a single female adult was exposed to her son for 48 hours, and for two consecutive generations, the mode of reproduction was determined by identifying the sex of the progeny. This result showed that pupal insemination was not successful; thus, all the tested females produced only male progeny. Virgin inbred females produced both male and female progeny that refers to deuterotokous reproduction mode. Three virgin females produced a total of 20 females and 75 males in two consecutive generations. A study concluded that deuterotokous mode of reproduction is not a persistent mode of reproduction in the T lineage but is a result of irregularity in the mode of reproduction, and it might be changed because of brother and sister inbreeding and need further studies.

Thrips tabaci Lindeman is a cosmopolitan and polyphagous insect pest. It is known worldwide and recorded on more than 300 plant species. T. tabaci is a key pest of onion and several other crops, and its control is vital to the production and profitability of crops. If onion thrips population is not controlled, damage can reduce yield volume and quality. In addition to direct damage to the host plants, T. tabaci has been characterized as an asymptomatic vector of three devastating tospovirus species, such as Tomato spotted wilt virus, Iris yellow spot virus, and Tomato yellow ring virus. For this reason, several synthetic insecticides were used for control. However, these insecticides bring unwanted effects, like pesticide resistance, elimination of nontarget species, environmental pollution, and threats to human health. To solve the negative consequences of insecticides, biopesticides, such as plant secondary metabolites, entomopathogenic viruses, bacteria, fungi, and nematodes, have been recognized as effective alternatives. The use of plant-based insecticides and entomopathogenic control methods gained more attention in integrated pest management. Their strong side is lack of residues, saving beneficial insects and minimizing air and water pollution. Plant-derived compounds and entomopathogenic biological control agents offered a variety of biological modes of actions against onion thrips, such as repellency, feeding deterrence, anti-oviposition, fecundity deterrence, metamorphosis inhibition, and parasiting the host’s body.

Some thrips species are considered as model insect organisms to study reproductive biology since some closely related (sub) species were mainly reproducing by arrhenotoky, thelytoky and in some rare cases as deuterotoky. As other insect species, thrips are associated with endosymbiotic bacteria and this bacteria has led to manipulating their reproductive biology. The main goal of this paper is to review the reproductive modes, potential reproductive manipulators and their strategies to change the reproductive biology of thrips species. Thrips species are reproducing through, arrhenotoky, thelytoky and deuterotoky. Wolbachia, Cardinium, Rickettsia and Spiroplasma have been detected in the reproductive organs of some thrips species and the most common insect reproductive manipulators by causing cytoplasmic incompatibility, thelytokous parthenogenesis, male killing and feminization. [ABSTRACT FROM AUTHOR]

Temperature strongly affects insect biological response. Effects of temperature on the sex ratio, preoviposition, fecundity, egg hatchability rate, and adult longevity of the L1 and T Thrips tabaci lineages were studied under laboratory conditions at three constant temperature levels (15, 23, and 30°C) on cabbage and tobacco leaf discs, respectively. Results showed that temperature affects all the tested life table parameters of L1 and T lineages. The proportion of female's log‐linearly increased as temperature increased. Preoviposition period, fecundity, adult longevity, and egg hatchability rate were reduced significantly with increasing temperature. In both lineages, the lowest egg hatchability rates were recorded at 30°C and the highest rates were recorded at 15°C. Mean fecundity of the L1 and T lineages were 107.63 and 84.83 at 23°C, respectively, and mean fecundity of the L1 and T lineages were 19.88 and 70.82 at 15°C, respectively. The lowest mean fecundity was recorded at 15°C and 30°C for the L1 and T lineages, respectively. Mean longevity were 34.22 and 81.82 days at 15°C for L1 and T lineages, respectively. Whereas, the shortest mean longevity (13.63 and 13.91 days) was observed at 30°C for the L1 and T lineages, respectively. Our results demonstrated that 23°C was the optimum temperature for fecundity among the studied temperature levels for the studied population of the L1 and T T. tabaci lineages. [ABSTRACT FROM AUTHOR]