Diversity and distribution of stored grain insect pests of pulses and their natural enemies

Biodiversity of stored grain insects is often neglected as many of the workers think that it has limited or no diversity as consumer tolerance towards insect pests in stored grains is zero. Survey was conducted in six districts of Hyderabad-Karnataka region to find out the diversity and insects infesting major stored pulses during 2014-15. Callasobruchus analis L., C. maculates F., C. chinensis L. and T. castaneum H. were insect pests observed in collected pulse samples. Dinarmus basalis R., D. vagabundus T.,Dinarmus sp. and Uscana sp. were the hymenopteran parasitoids on pulse beetle collected from the samples. Rank abundance showed that C. analis was dominant species found on stored pulses.

Effect of adult feeding on progeny production and sex ratio of Dinarmus basalis (Rond.) (Hymenoptera: Pteromalidae)

Context: Dinarmus basalis (Rond.) is a larval-pupal ectoparasitoid of the pulse beetles, Callosobruchus (Coleoptera: Bruchidae). This parasitoid could be used in suppressing the pulse beetle populations in stored conditions. Objective: To observe the influence of different food supplements on the progeny production and sex ratio of D. basalis when exposed to the pulse beetles separately. Materials and Methods: Mated females of D. basalis were introduced into separate Petri dishes (9.5 cm diam) containing 50 mature mung seeds infested with C. chinensis and C. maculatus. The parasitoids were provided with host and honey, host and sugarcane, host and egg yolk, host and yeast and host and agar, and host without food individually. After 24 h, the parasitized larvae with seeds were changed and the female parasitoids were provided with foods daily until adults died. After emergence total number of hosts and parasitoids were counted. The sex ratio of D. basalis were also calculated and their chi-squared tests were made. Results: The mean number of progeny production of D. basalis on C. maculatus-infested blackgram was significantly greater than those reared on C. chinensis-infested mug in all food regimes (Table 1). The progeny production on two host beetles differed significantly in relation to different foods (F= 4.85, P<0.01. C. chinensis; F= 38.34, P<0.01, C. maculatus). The most effective food supplement was honey, which enhanced offspring production of D. basalis on both the hosts, and egg yolk was the least effective. The percentage of progeny was more or less female-biased in all the treatments except the control. Conclusion: Food supplementation of D. basalis will significantly increase the efficiency of the parasitoid against storage pests including the pulse beetles. DOI: http://dx.doi.org/10.3329/jbs.v19i0.13004 J. bio-sci. 19 77-80, 2011

Competition in the Parasitization of Callosobruchus maculatus between Dinarmus basalis and Choetospila elegans on Vigna unguiculata (Walp.) Seeds

<p>Laboratory study was carried out to investigate the efficacy of hymenopteran parasitoids, (<em>Dinarmus basalis</em> and <em>Choetospila elegans)</em> parasitization of <em>Callosobruchus maculatus</em> on cowpea (<em>Vigna unguiculata</em>) seeds in the Department of Crop Science, University of Calabar, Nigeria. Treatments were the inoculation of <em>D. basalis</em> (sole), <em>C. elegans</em> (sole), a mixture of <em>D. basalis</em> and <em>C. elegans</em> into infested cowpea seeds and the control which received no parasitoids. The introduction of parasitoids was repeated at 3 d interval, and all treatments were replicated 3 times. Result indicated that early introduction of the parasitoids caused significantly (P ? 0.05) higher mortality of <em>C.maculatus</em> than late introduction. Mix culture of both parasitoids was significantly more efficacious than sole culture. The emergence of each parasitoid and the mortality of <em>C. maculatus</em> in sole culture showed a highly significant (P ? 0.01) positive relationship (r = 0.487) between <em>C. maculatus</em> and <em>D. basalis</em> but non-significant (P ? 0.05) though positive association (r = 0.289) with <em>C. elegans</em>. A multiple regression analysis between <em>C. maculatus </em>mortality and the emergence of the two parasitoids in mix culture also indicated a highly positive significant (P ? 0.01) relationship (R = 0.751, R² = 0.564). Pearson Correlation analysis also showed a significant (P ? 0.05) positive association (r = 0.464, and 0.401) between <em>C. maculatus</em> mortality and emergence of <em>C. elegans</em> and <em>D. basalis</em> in mix culture, respectively. However, a non significant (P ? 0.05) negative relationship (r = -0.336) was observed between the two parasitoids in their emergence in mix culture, but <em>D. basalis</em> contributed more to the mortality of <em>C. maculatus</em> than <em>C. elegans</em>. Data from this study showed that <em>D. basalis</em> and <em>C. elegans</em> have potentials to be deployed as biological control entities in the management of <em>C. maculatus</em> as a part of the integrated pest management strategies of storage pests in the tropics.</p>