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Contact and Gustatory Effects of Spinosad on the Survivability of Sitophilus Oryzael. (coleoptera: Curculionidae) in Wheat

Umme Habiba
Institute of Biological Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh

W Islam
Institute of Biological Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh

Selina Parween
Institute of Biological Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh

Abstract/ Executive Summary:

The present study was planned to evaluate the effect of spinosad on the survivability and development of Sitophilusoryzae on four wheat varieties viz., BARI-26, BARI-28, Shatabdi-21 and Prodip-24. Three doses in three replications for spinosad were applied to four wheat varieties. Spinosad concentrations significantly increased the total developmental period compared to the control in a dose-dependent manner on four wheat varieties. The highest developmental period took 41.67±0.33 days to become adult was recorded in S-21 at 0.0003μl/g of spinosad in F1. All adults of F1did not reach in F2 because surprisingly all adults died after emergence. So, no developmental period was found in S-21 (0.00±0.00) and B-28 (0.00±0.00) days at 0.0003μl/g spinosad in F2. On the other hand, five mated females were released on the treated wheat with different concentrations of spinosad for 10-15 days; then they were removed. Treated wheat was checked for up to 30 to 60 days and observed the progeny for two successive generations (1st and 2nd). Each combination of insect species, insecticide rate, and exposure duration were replicated three times. Among four wheat varieties, the lowest adult emergence was recorded as 08.00±0.58 in F1 and totally controlled in F2 generation in S-21 variety at 0.0003μl/g. Spinosad concentrations significantly increased the total developmental period compared to the control in a dose-dependent manner on four wheat varieties.

Keywords: Contact and gustatory effects, Spinosad, Developmental period, Sitophilus oryzae

Location: Entomology and Insect Biotechnology Laboratory, Institute of Biological Sciences, University of Rajshahi, Bangladesh

Start Date:

End Date:

Program Area: Pest Management

Commodity: Wheat

Objectives:

The present investigation characterizes the effectiveness of spinosad against S. oryzae adult mortality and the survivability of adult’s emergence and its developmental time in economically important stored-product grain insect, S. oryzaein two successive generations on four wheat varieties.

Methodology:

In the present bioassay method spinosad were investigated against adults of Sitophilusoryzae by dietary exposure termed Treated Food Method (TEM) (Talukder and Howse 1994). S. oryzae was obtained from the stock culture without any exposure to insecticides, maintained in the control temperature room, at Entomology and Insect Biotechnology Laboratory, Institute of Biological Sciences, University of Rajshahi, Bangladesh. Untreated and infestation free of wheat varieties viz., BARI-26, BARI-28, Prodip-24 and Shatabdi-21 were used. Mass cultures were maintained in plastic containers (2.5 litre). The whole culture procedure was maintained in a control temperature room at 30±1^oC and 70±5% RH. About 250 adults of S. oryzae were placed in the plastic container with 250g of whole wheat grain for 10-15 days, then they were removed and placed on fresh grains to get a new progeny and avoid generation overlapping. The whole process was repeated several times to ensure 100% adult collection from the old culture medium to obtain homogenous generations throughout the experiment. Mouth of the container was covered with muslin cloth using a rubber band, to prevent the possible contamination and escape of insects (Mondal and Parween 1997). Preparation of food medium for mass-culture:Whole wheat grains were used as the food for the weevils. Wheat grains were collected from the local market, Shaheb Bazar, Rajshahi. After washing in water, the wheat was sun-dried and finally sterilized in an oven at 60ºC for 6hrs. Sterilized wheat grains kept for 15 days to allow its moisture content (13.5%) to equilibrate with that of the environments. Sterilized wheat was used as food for mass-culture. Preparation of food medium for experiments: Four kinds of wheat grains (B-26, B-28, P-24 and S-21) were collected from the Wheat Research Institute, Shampur, Rajshahi, Bangladesh. These grains were washed and cleaned by sieving through 500 micrometer aperture sieve and sterilized in an oven at 60ºC for 6hrs. Then grains were kept in plastic containers (3 liters) that were cleaned before and use throughout the experimental period for S. oryzae.Collection of weevils: After tremble the container some of the grain was taken on the working table with the help of a medium sized spoon. The adults were collected using a camel hair brush and placed in treatment. Source of spinosad: Spinosad is light grey to white in colour with slight odour stale water. About 500ml of spinosad (PRN-MAPP-12054, cafno 20012-019, Lot No-3068404) was obtained from Dow Agro Sciences, UK. Concentration of spinosad was 120g spinosad/litre.Spinosad 0.0018μl was obtained in a glass vial by the help of micropipette and added 6ml distilled water properly by using 2ml syringe and 0.0003, 0.00015 and 0.000075μl/g were prepared by serial dilution. Bioassays: Wheat grains 1gof each variety of wheat was soaked in different concentrations of spinosad separately and then dried at room temperature for 24hrs in a 6 cm glass Petri dish.From mass culture five mated females were released on the treated wheat with different concentrations of spinosad for 10-15 days; then they were removed. The Petri dish was covered and the medium containing eggs and larvae were placed in the control room temperature until adult emergence. Treated wheat was checked for up to 30-60 days and observed the progeny for two successive generations (1st and 2nd). After every 10 days, newly treated fresh wheat was added with it. A similar set of experiment was carried out on wheat soaked with distilled water only, as a control batch. The room temperature was maintained at 30±1ºC with 75% RH in the control temperature throughout the study period. As, S. oryzaeis an internal feeder so, only adults production for this species was recorded for F1and F2. Adults unable to move when prodded gently with a hair brush were considered dead. The number of progeny for S. oryzae was based on all visible live adults found in wheat. Each combination of insect species, insecticide rate, and exposure duration was replicated three times, and each replicate was treated separately. Adult emergence and adult survivability of S. oryzae was determined to untreated and treated wheat with spinosad concentration for two successive generations.Data collection and statistical analysis:Data were subjected to analysis of variance using SPSS-20 version. Means comparisons were performed by Turkey’s tests (p<0.05). The percent reduction of adult emergence in treatments compared to control (PRC) was calculated by using the formula provided by Mian and Mulla.

Source of Information: Bangladesh J. Zool. 47(1): 253-262, 2019 ISSN: 0304-9027 (print) 2408-8455 (online)

Article Link (Online Journal): DOI: https://doi.org/10.3329/bjz.v47i2.44336

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results of the present study indicate that there was a significant impact of spinosad on the adult emergence and total developmental period of S. oryzaein wheat varieties. From a practical point of view, 0.000075 and 0.00015μl/g of spinosad gave decreasing adult emergence levels. Consequently, spinosad at 0.0003μl/g was higher concentration and can satisfactorily control of adult emergence of S. oryzaein successive two generations.

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