Influence of ultraviolet B rays on growth and reproduction of four pest thrips species (Thysanoptera: Thripidae) in a greenhouse and a natural enemy (Thysanoptera: Phlaeothripidae) of Them

Abstract

The effects of ultraviolet-B radiation over three hours at night on the survival and development of four agricultural pests of thrips and their predator, Haplothrips brevitubus(Karny), were investigated at 20°C under 14L10D conditions. UV-B radiation ≤ 8.7 μW/cm2 did not affect the hatchabilitiy of terebrantian eggs inserted into leaf tissue, but the four pest species of thrips showed lower percentages of adult emergence and delayed larval development at UV-B radiation ≥ 6.5 μW/cm2. No adults emerged for Thrips palmi Karny, Frankliniella occidentalis(Pergande), and Thrips tabaci Lindeman reared under UV-B radiation ≥ 6.5 μW/cm2, while 10% of Frankliniella intonsa(Trybom) reared under UV-B radiation of 8.7 μW/cm2 eclosed into the adult stage. Pest thrips emerging into adults under UV-B dose conditions exhibited curl and shortening of the forewings, and over 38% of adults had abnormal forewings even under a low dose of UV-B radiation of 1.5 μW/cm2. UV-B radiation ≤ 3.0 μW/cm2 after adult emergence did not affect the longevity and fecundity of female adult thrips in the four pest species. UV-B radiation decreased egg hatchability and the percentage of survival in the larval stages for H. brevitubus, and no thrips emerged into adults under UV-B radiation ≥4.8 μW/cm2.