Abstract
The bean flower thrips, Megalurothrips usitatus is a major pest of mung bean that causes flower dropping and significant yield loss of the crop. M. usitatus demonstrated to have variable lifespan when reared on different leguminous hosts but on mung bean, an important pulse crop in Bangladesh, is unknown. The experiment was conducted to determine the biological attributes of M. usitatus on mung bean in a climate control chamber at 26 ± 1°C, 75 ± 3% RH, and 16:8 hours L:D in the laboratory. The results revealed that the incubation period, first instar larva, second instar larva, prepupa, and pupal period of M. usitatus were 3.13 ± 0.06, 1.48 ± 0.05, 2.30 ± 0.08, 1.30 ± 0.07, and 2.26 ± 0.13 days, respectively. The combined developmental period from egg to adult was 10.54 ± 0.15 (mean ± SE) days. The larvae of M. usitatus were similar in appearance to the adults, but they lacked wings and were smaller and different in color. The first instar was pale yellow, while the second instar was darker and larger, ranging from deep yellow to orange-red. The wing pads of the prepupae were shorter than that of the pupae. The antennae of the prepupa were straight, but they were bent in the pupa. In the case of pre-adult mortality of M. usitatus, the mortality of the first instar larva was 14.41%, second instar larva 22.77%, prepupa 14.10%, and pupa 65.67%. The pre-adult mortality was 80.51% overall. Adult males had lower longevity (6.42 ± 0.44 days) than females (12.07± 1.56 days). The developmental period of M. usitatus on mung bean indicated the suitability of the leguminous crop as a potential host, as well as the need for information on the pest’s various growth stages in order to design effective management strategies.
Highlights
Thrips (Thysanoptera: Thripidae) is one of the major insect pests of mung bean (Vigna radiata) that causes severe losses of the crop (Hossain et al, 2004; Rahman et al, 2000)
The study was conducted in the laboratory of the Department of Entomology of Sher-e-Bangla Agricultural University (SAU), Sher-e-Bangla Nagar, Dhaka, Bangladesh, from May to July 2016 to observe the duration of different instars, pre-adult mortality percentage, and adult longevity of M. usitatus
According to study females of M. usitatus lay eggs within the leaf tissues, the eggs may not be apparent to the naked eyes and required two to three days for incubation (Srinivashan, 2014)
Summary
Thrips (Thysanoptera: Thripidae) is one of the major insect pests of mung bean (Vigna radiata) that causes severe losses of the crop (Hossain et al, 2004; Rahman et al, 2000). The length of the life cycle of an insect depends on the temperature and quality of the food sources, and can be as short as 10-12 days at 30oC or as long as 19 days at 20oC (Persley et al, 2007) Thrips lay their eggs in plant tissue, leaves, or flowers, and depending on the climate, they can hatch in as little as 3 days or as long as 10 days. After hatching, both larvae and adults are found inside the bean blossom, which is only open for a few days. The present study was planned to investigate the biology of M. usitatus and to determine the pre-adult mortality percentage and adult longevity on mung bean
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