Thrips (Thysanoptera) associated with onion (Allium cepa L.) and Welsh onion (Allium fistulosum L.)

Abstract

We determined the abundance, species composition, sex ratio and seasonal dynamics of thrips on one cultivar of Welsh onion (Allium fistulosum) and eight cultivars of onion (Allium cepa) in South Poland within three vegetation seasons (2014–2016). Nine species of Thysanoptera were identified on A. cepa and A. fistulosum. Irrespective of the onion cultivar, Thrips tabaci was the dominant species (64.4% of all collected thrips specimens), while Frankliniella intonsa also occurred in high numbers (28.3%). Conversely, Welsh onion was most often inhabited by F. intonsa (62.7%), although T. tabaci was also numerous (28.3%). The predatory Aeolothrips intermedius accounted for 4.5% on A. cepa and 2.9% on A. fistulosum. In the most numerous species, T. tabaci, F. intonsa and A. intermedius populations were formed mainly by females. The cultivar most colonised by thrips was Kroll of A. fistulosum. The tested cultivars of A. cepa demonstrated varying degrees of attractiveness to thrips in the subsequent years. The relationship between populations of T. tabaci, F. intonsa and A. intermedius changed in the subsequent months of the growing season. In June, mainly T. tabaci and F. intonsa occurred on onion plants, while from July, the percentage shares of F. intonsa and the predatory A. intermedius in the thrips population on many onion cultivars increased. The level of attractiveness of A. cepa related to onion thrips, which is reported as a main pest of onion, varies depending on the year and cultivar.

Genetic diversity of thrips populations on Allium species around the world

“…We found that the main species of thrips that affects onion and its related species is Thrips tabaci , which is in agreement with previous studies [ 5 , 29 , 41 , 42 ]. Other thrips species such as Thrips palmi , Scirtothrips dorsalis , Frankliniella tenuicornis , Frankliniella intonsa , and Frankliniella occidentalis , were present at specific locations.…”

“…intonsa at Sansai might be associated with the presence of Allium fistulosum in the Allium spp field since it has been reported as the common host plant for F . intonsa [ 29 ]. Apart from that, the Allium field in Sansai was surrounded by several (crop) species, including banana, bamboo, and herbs such as marigold and weeds, from which thrips may have moved into the field.…”

“…However, the number of incidents with T. tabaci in onions in Georgia is increasing [28], which might be explained by the fact that T. tabaci outcompetes F. fusca on onion [44]. The occurrence of F. intonsa in A. cepa and A. fistulosum has also been reported in Poland [29]. Thrips palmi and S. dorsalis are commonly reported in melon and pepper, respectively [45] and both thrips species occur occasionally in Allium spp.…”

“…tabaci is the most important pest in onion [ 5 ], other thrips species have been found on onion as well [ 28 ]. It is important to know which thrips species affect onion, their genetic diversity and distribution around the world, as well as the seasonal dynamics in the populations and the reproductive mode to develop improved control strategies to be implemented in future Integrated Pest Management programs [ 29 ]. This research aimed to 1) identify thrips species in fields with onions or onion-related species at 14 locations around the world; 2) determine genetic variation and mode of reproduction within T .…”

“…Although T. tabaci is the most important pest in onion [5], other thrips species have been found on onion as well [28]. It is important to know which thrips species affect onion, their genetic diversity and distribution around the world, as well as the seasonal dynamics in the populations and the reproductive mode to develop improved control strategies to be implemented in future Integrated Pest Management programs [29]. This research aimed to 1) identify thrips species in fields with onions or onion-related species at 14 locations around the world; 2) determine genetic variation and mode of reproduction within T. tabaci, and relate these with the haplotypes reported in the NCBI sequence database; 3) compare the genetic variation within and between sampled thrips per location; 4) analyze the geographical distribution of the T. tabaci haplotypes as well as the correlation between the genetic and geographic distances of populations; and 5) analyze the seasonal variation in the composition of thrips populations at three locations.…”