Adult Emergence of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) in Stored Rice Varieties and Pulses with Broken Grains

The rice weevil, Sitophilus oryzae, is a serious pest of stored paddy and rice. Much information on its development during the storage of traditional and new improved rice varieties is not found in Sri Lanka. During milling, some percentage of rice is broken, and broken rice generally enhances the development of insects. However, the ability of progeny development of S. oryzae in the presence of broken rice particles is unknown. Hence, this study was conducted to assess the progeny development of S. oryzae in different rice and pulse media with a variable percentage of broken grains. Locallyavailable rice varieties, Red Kekulu, Red Samba, Red Heeneti, Kuruluthuda, Suwandel and the pulses, cowpea, greengram and blackgram having different broken percentages were tested for progeny adult emergence at ______________________________________ Department of Plant Sciences, Faculty of Agriculture, Rajarata University of Sri Lanka, Puliyankulama, Anuradhapura, Sri Lanka. * wollylk@yahoo.com http://orcid.org/0000-0003-3748-040X This article is published under the terms of the Creative Commons Attribution 4.0 International License which permits unrestricted use, distribution and reproduction in any medium provided the original author and source are credited. 2, 4 and 6 weeks following initial infestation. The number of adults emerged varied with the grain type, broken percentage and the duration following initial infestation. Greengram (0-1.5) and blackgram (0-0.75) had very low adult emergence while Red Heeneti (0-191.75) and Red Kekulu (0.25-194.67) had the maximum adult emergence. The increase of the broken percentage initially increased the adult emergence and then decreased. The study concluded that S. oryzae adult emergence followed a trend of initial increasing and decreasing trend at the latter part in the samples with increasing percentages of broken rice. The adult emergence was higher at intermediate duration following infestation than the first and last durations. Future studies are needed to determine the reasons underlying the variation in the adult emergence across different grain types and broken percentages.

This article is published under the terms of the Creative Commons Attribution 4.0 International License which permits unrestricted use, distribution and reproduction in any medium provided the original author and source are credited.
2, 4 and 6 weeks following initial infestation. The number of adults emerged varied with the grain type, broken percentage and the duration following initial infestation. Greengram (0-1.5) and blackgram (0-0.75) had very low adult emergence while Red Heeneti (0-191.75) and Red Kekulu (0.25-194.67) had the maximum adult emergence. The increase of the broken percentage initially increased the adult emergence and then decreased. The study concluded that S. oryzae adult emergence followed a trend of initial increasing and decreasing trend at the latter part in the samples with increasing percentages of broken rice. The adult emergence was higher at intermediate duration following infestation than the first and last durations. Future studies are needed to determine the reasons underlying the variation in the adult emergence across different grain types and broken percentages.  al., 2018). Of these total post-harvest losses of grains, the damage due to insects can be quite high (Kumar and Kalita, 2017). In Sri Lanka, loss of stored paddy/rice and pulses due to insect attack is frequently reported (Kumari et al., 2020a) (Hill, 1990) and allergic reactions (Campbell et al., 2004). Insect infestations in stored grains can also lead to undesirable taste and odors, and thus make the product inedible (Arthur et al., 2012).

INTRODUCTION
The rice weevil Sitophilus oryzae (L.) (Coleoptera: Curculionidae) is a major pest of stored rice and other cereals in many tropical and subtropical countries (Hill, 1990;Arbogast, 1991;Rees, 2004;Mason and McDonough, 2012). This species has been reported from Sri Lanka in stored paddy (Kumari et al., 2020b). In Unawareness of these facts is a great

Adult Emergence of Sitophilus oryzae in Stored Rice Varieties and Pulses
impedance for the adoption of appropriate management methods.
Therefore, the objective of this research was to determine the degree of infestation by S. oryzae in whole grains and particles of different rice cultivars and pulses.

Insects
The adults of S. oryzae reared at  The current findings agree with the previous record that S. oryzae progeny emergence is higher in larger grain particles. This is believed to be a consequence of the preference of females to oviposit in larger particles (Campbell, 2002). The progeny development of another internal feeder of stored rice Rhyzopertha dominica (F.) on sorghum depends on kernel hardness (Arthur et al., 2020).

Preparation of Grains
Hardness of wheat kernels changes the progeny production in S. oryzae as well (McGaughey et al., 1990). The current study revealed that S. oryzae progeny development was greater on samples with fewer percentages of broken grains (higher percentage of intact grains). A possible explanation is that S. oryzae adults prefer larger grain particles for feeding and oviposition.
Therefore, future research needs to be designed to test the hypothesis, if there is a relationship between grain particle size, its hardness and the progeny development in S. oryzae. In contrast, progeny adult emergence in the related species Sitophilus zeamais Motschulsky was higher in fractions of maize than whole maize. Furthermore, the duration from egg laying to the inception of progeny emergence was lower in small particle sizes (Schoonhoven et al., 1974). However, in Oryzaephilus surinamensis (L.), the development was minimum in whole wheat kernels (Fleming, 1988).
Contrary to the alteration of progeny with the particle size, the survival of immature rusty grain beetles Cryptolestes ferrugineus (Stephens) is not varied among different particle sizes of cracked corn (Thorne, 1992).
The deviations from the previous studies as found in the current findings  Student-Newman-Keuls (SNK) test following ANOVA at p = 0.05.