Zeamais Mots Research Articles

Assessment of the toxicity of Carica papaya plant powders against Sitophilus zeamais (Mots) (Coleoptera: Curculionidae) on maize seeds during storage

The toxicity of Carica papaya plant parts powder (leaf, stem bark, root and flower) at different dosages (0.5, 1.0, 1.5, 2.0 and 2.5 g) against Sitophilus zeamais infesting stored maize grains were assessed at the Biology Laboratory of the Federal College of Agriculture, Ibadan. Treatments were admixed with 30 g of maize grains, infested with 10 teneral adults of S. zeamais and stored in 3.0 mm petri dishes. The experiment was laid out in completely randomized design (CRD) and replicated four times each. Data were collected on adult mortality, oviposition and percentage weight loss of the grain in each of the replicate. Data collected were analyzed using analysis of variance, while sample means were separated with the aid of least significant difference (LSD) at 5%. There were significant differences in adult mortality of S. zeamais treated with different dosages of the plant parts powder. The flower powder of the plant recorded the highest mean adult mortality (10) compared to the lowest adult mortality of 0.1 obtained at the control experiment. The flower part powder also revealed the lowest mean eggs laid (oviposition) (7.1) and the lowest grain damage loss (1.4%) when compared with the values of 18.7 and 40.0 obtained for mean eggs laid and percentage weight loss obtained with stem bark and control treatments respectively. This clearly showed that the powder of the flower of C. papaya showed good potential as bio-insecticide for protecting stored maize grains.

A New Light on the Evolution and Propagation of Prehistoric Grain Pests: The World's Oldest Maize Weevils Found in Jomon Potteries, Japan

Three Sitophilus species (S. granarius L., S. oryzae L., and S. zeamais Mots.) are closely related based on DNA analysis of their endosymbionts. All are seed parasites of cereal crops and important economic pest species in stored grain. The Sitophilus species that currently exist, including these three species, are generally believed to be endemic to Asia's forested areas, suggesting that the first infestations of stored grain must have taken place near the forested mountains of southwestern Asia. Previous archaeological data and historical records suggest that the three species may have been diffused by the spread of Neolithic agriculture, but this hypothesis has only been established for granary weevils in European and southwestern Asian archaeological records. There was little archeological evidence for grain pests in East Asia before the discovery of maize weevil impressions in Jomon pottery in 2004 using the “impression replica” method. Our research on Jomon agriculture based on seed and insect impressions in pottery continued to seek additional evidence. In 2010, we discovered older weevil impressions in Jomon pottery dating to ca. 10 500 BP. These specimens are the oldest harmful insects in the world discovered at archaeological sites. Our results provide evidence of harmful insects living in the villages from the Earliest Jomon, when no cereals were cultivated. This suggests we must reconsider previous scenarios for the evolution and propagation of grain pest weevils, especially in eastern Asia. Although details of their biology or the foods they infested remain unclear, we hope future interdisciplinary collaborations among geneticists, entomologists, and archaeologists will provide the missing details.

The effect of Sitophilus zeamais (Mots) (Coleoptera: Curculionidae) on the quality and viability of stored maize in Nigeria

The effect of 10, 20, 30, 40, and 50 adult Sitophilus zeamais on the quality of 1 kg lots of white maize maintained at 25-30°C and 65-85% r.h. was observed. Per cent moisture, oil, Free Fatty Acid (FFA) content and germination were determined at 2-week intervals for 10 weeks. Moisture content of infested maize ranged from 11.51 to 12.92%, There was a significant correlation between moisture content and degree of infestation (r =0.88; P < 0,05; Y = 11.908 + 0.006 x). The range of oil content of infested maize was 4.83-5.75%. There was a significant correlation between oil content and degree of infestation (r = -0.097; P < 0,05; Y = 5.08 -0.0076 x). The free fatty acid (FFA) of infested maize was 5.82-6.86%. The heterogeneity at various infestation levels was significant (F = 81.38; d.f. — 5; P < 0.001). There was an increase in FFA, with increasing infestations, although the correlation was not significant. The germination of maize, 10 days after planting, at various infestation levels was 43.0-97.5%. There was a decrease in germination, as level of infestation increased. The heterogeneity in germination at various infestation levels was significant (F = 19.21; d.f. — 5; P < 0.001). Possible reasons for the results obtained, are presented.

Comparison of sarcosine and methionine sulfoxide levels in symbiotic and aposymbiotic larvae of two sibling species, Sitophilus oryzae L. and S. zeamais mots. (Coleoptera: Curculionidae)

Sarcosine and methionine sulfoxide were investigated in several wild or laboratory-reared symbiotic and aposymbiotic strains of Sitophilus oryzae and S. zeamais. The amino acid composition of fourth-instar larvae indicated that a high level in sarcosine found together with a low level of methionine sulfoxide were biochemical characteristics of the aposymbiotic state in this genus. Nutritional experiments demonstrated that the synthesis of these two amino acids depended on dietary precursors. Since sarcosine and methionine sulfoxide are both methionine derivatives, it is therefore suggested that methionine metabolism in Sitophilus larvae might differ according to the presence or the absence of the symbiotic bacteria.

Some factors affecting the infestation of wheat and maize by Sitophilus oryzae (L.) and Sitophilus zeamais Mots. (Coleoptera: Curculionidae)

Cultures of various stocks of S. oryzae (L.) and S. zeamais Mots. were maintained for several generations at 25°C and 70% r.h. on both wheat and maize, on only one of these foods, or on rice. In every generation a subsample of adults was placed in a mixture of wheat and maize (equal weights of each) for 5 days, after which the two cereals were separated and incubated and the number of progeny counted. A substantial majority of S. oryzae and much less substantial majority of S. zeamais emerged from wheat. In both species the majority was a little less when the laying adults had passed their developmental stages upon maize or rice. In alternate generations the foods were presented to another subsample in separate piles 40 cm apart. The progeny distribution was very similar to that found with intermingled foods. In intervening generations the foods were presented to S. zeamais in suspended bags which could only be reached by flight. When this occurred, more emergences, in many cases over 90%, were found from maize than wheat. When the adults associated with the suspended bags were counted at the end of the 4-day experiment the numbers were as one would expect from the emergences. When similar counts were made daily, however, approximately equal numbers were found associated with each food and observations suggested that directional flight by females did not take place.