Chemical composition and toxicity of some Agro waste-derived insecticides against Angoumois grain moth, Sitotroga ceralella (Olivier) [Lepidoptera: Gelechiidae] infesting stored paddy grains

Background Agriculture being one of the major practices in the world has contributed to environmental pollution, especially in developing countries where there were no equipment to recycle the agricultural wastes. Considering the high level of infestation of paddy by Sitotroga cerealella and the high level of pollution caused by agricultural wastes, this research investigated the chemical composition and toxicity of agro wastes (rice husk, maize cob, groundnut and cowpea pods) as eco-friendly protectants of paddy against Sitotroga cerealella. Parameters assessed include adult mortality, oviposition, adult emergence and egg hatchability. Gas chromatography and mass spectrophotometry were used to isolate and characterize the active compounds present in the most effective crude extract. Results The results of the study revealed that all agricultural wastes showed high mortality effect on S. cerealella. Cowpea pod powder was the most toxic to adult paddy moth that caused 33.33%, 36.67%, 46.67%, 50% and 60% mortality of S. cerealella at concentrations 0.1 g, 0.2 g, 0.3 g, 0.4 g and 0.5 g/20 g of paddy grains after 24 h of exposure, respectively. The Cowpea pod, groundnut pod and maize cob extracts caused 100% mortality of S. cerealella at concentration 0.5 ml/20 g of paddy grains after 96 h of exposure, respectively. The lethal concentrations LC50 and LC90 of cowpea pod after 24 h were 0.16 and 0.64 ml which were the lowest of all agro waste extract tested. GC–MS analysis revealed that 19 chemical compounds were present in cowpea pod extract, 9, 12-Octadecadienoic acid (a methyl ester) has the highest percentage total of 39.57% and 4-Pentenal, 2-methylene (0.12%) has the least percentage total. Conclusion All the observations revealed that cowpea pod was the most effective. The findings also suggested that the selected agricultural wastes have a promising insecticidal potential and can be used as alternatives to synthetic chemical insecticides for the control of stored product insects.

Cold storage and gamma irradiation of Sitotroga cerealella Olivier eggs (Lepidoptera: Gelechiidae) in relation to the success of parasitism by Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae)

The performance of parasitism by the egg parasitoid, Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) on eggs of Angoumois grain moth, Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae) was investigated under cold storage and gamma irradiation treatments of the host eggs. Cold storage treatment could improve the parasitoid mass rearing techniques and reduced the costs of biological control programs, while gamma irradiation might be used as a supplementary support at the times of high demand. The suitability of the S. cerealella eggs, stored at – 20 °C for 0.5, 1, or 2 h. as a host for T. evanescens was evaluated. The sensitivity of S. cerealella eggs to gamma irradiation treatments and the acceptability of irradiated eggs for parasitism by T. evanescens females for the parental P and F1 generations were examined. The results revealed that parasitism was drastically reduced more than adult’s emergence and sex-ratio (% of females) after cold storage periods of S. cerealella eggs. Moreover, the parasitism percentages were relatively reduced to (97.1, 96.1, 93.03, and 92.7 %) after irradiating the S. cerealella eggs at 40, 60, 80, and 100 Gy, respectively than the control (97.3% emergence). The percentages of emergence and females’ percent were slightly decreased by gamma irradiation doses, while, equal preferred by the F1 generation of parasitoid that produced from irradiated S. cerealella eggs.

INSECTICIDE ACTIVITY OF PLANT EXTRACTS OF THE NORTHEASTERN BRAZILIAN FLORA FOR THE CONTROL OF Sitophilus zeamais [Mots, 1885] AND Sitotroga cerealela [Olivier, 1819

One of the typical crops of the semiarid tropic is the maize Zea mays L., a rustic plant cultivated in the Brazilian northeastern semiarid region mainly by small farmers. It is one of the sources of protein and carbohydrates and an economic alternative for job creation, especially for rural populations. Among the factors limiting its cultivation are pests, among which weevil and Angoumois grain moth. This work aims to evaluate the insecticide activity of plant extracts obtained from medicinal plants of the Brazilian northeastern flora for the control of Angoumois grain moth and weevil under laboratory conditions. The methodology consisted in the production of plant powders, which were mixed with 99.8% alcohol, and then macerated and filtered. Using a rotary evaporator and applying a water bath, it was possible to separate the alcohol from the filtered solution, resulting in a creamy paste, which is the extract itself, later used in tests with insects. Preliminary tests were applied at the concentrations of 0% [control] to 100% ml of extracts. Extracts with a mortality rate ³50% were analyzed by bioassays and four replicates, each consisting of a lot of five insects. The experimental design was completely randomized.

Residual Efficacy of a Deltamethrin Emulsifiable Concentrate Formulation against Rhyzopertha dominica (F.) and Sitotroga cerealella (Oliver) after Partial Treatment of Brown Rice

Rhyzopertha dominica (Fab.), the lesser grain borer, and Sitotroga cerealella (Olivier), the Angoumois grain moth, are internally feeding stored product insects that can infest raw grains. In this test, brown rice was treated with 0.5 and 1.0 ppm of a new emulsifiable concentrate (EC) formulation of the pyrethroid deltamethrin and stored for 12 months. One day after treatment, and every 3 months for 12 months, treated rice was mixed with untreated brown rice in the following ratios: 0:100 (untreated controls), 10:90, 25:75, 50:50, 75:25, and 100:0 (all treated). Bioassays were conducted by exposing 10 parental adults of each species on the rice mixtures and assessing progeny production, feeding damage, and weight loss. The progeny of S. cerealella ranged from 105.6 F1 adults on untreated brown rice to 69.4 F1 adults on 100% treated rice, but there was little feeding damage or weight loss. The progeny production of R. dominica declined from 177.4 F1 adults on untreated rice to 9.8 F1 adults on 100% treated rice. Weight loss and feeding damage were correlated with progeny production. The results show that the new deltamethrin formulation could be used for protection of brown rice, but S. cerealella may be less susceptible to deltamethrin compared to R. dominica.