1 Introduction

Cowpea (Vigna unguiculata L.) is an important leguminous crop in semiarid regions across Africa and Asia, particularly Egypt and Saudi Arabia. It belongs to the Fabaceae family, which includes the most important crops, such as faba bean, soybean, and cowpea. Many efforts have been made to improve the yield of faba bean (El-Flaah et al. 2021; El Nahhas et al. 2021; Mohamed, Mazrou, et al. 2022), soybean (Abdelaal et al. 2021; Khaffagy et al. 2022), common bean (Alharbi et al. 2025), and cowpea (Bondok et al. 2024; Souza et al. 2024) under normal and stress conditions. The protection of seeds and grains is an important process during plantation and storage. Seeds and grains can be considered the main sources of protein and carbohydrates in poor and developing countries. Chemical pesticides are a common method for pest control (Abo Arab et al. 2022; Mohamed, Keratum, et al. 2022; Taha et al. 2020; El-Tokhy et al. 2020); however, they have many harmful effects on natural enemies and the environment. As a result of the harmful effect of uncontrolled use of synthetic pesticides that was necessary to find alternative methods can protect stored products without side effects on environment (Abdelaal 2020; Essawy et al. 2020; Ismail et al. 2023).

The alternative methods include physical, biological, and natural methods. One of the most important and friendly natural methods is essential oils and plant extracts (El-Talpanty et al. 2024; Omar et al. 2024). High temperature is one of the most important physical methods that can be used as pesticide alternatives in storage. In addition, it is easy to apply and has no residual effects on seeds or grains. Using high temperatures may decrease the cost of production and require a few workers for application. Storage is a very important and complex logistics process for moving grains from producer to processor and grain products from processor to consumer (Anderson 1973). Its purpose is to equilibrate fluctuations between two major factors: supply and demand. Improper management of harvested grain causes significant quantitative and qualitative postharvest food losses are estimated to range from 9% in the United States Pimentel (1991) up to 50% in some parts of the developing nations. Some insects (e.g., Sitopillus oryzae, Tribolium castaneum, Rhyzopertha dominica, and Tribolium granarium Everts) have also been directly associated with seed damage, Aspergillus flavus growth, and production of the mycotoxin aflatoxin (Sinha 1990). The weevil S. oryzae is an effective vector in the United States (Barry et al. 1985). Many major pests of stored wheat are R. dominica (Fabricius) and S. oryzae (L.). The two species cause the most grain damage because the immature stage develops inside the grain kernels (Hagstrum and Subramanyam 2006). Legume seeds are considered the main source of protein for human and animal nutrition (Smart 1985). Callosobruchus maculatus causes substantial losses to pulses in storage worldwide (Righi-Assia et al. 2010). It is known to cause up to 100% loss of stored cowpeas (Jackai and Daoust 1986). Heavy reliance on chemical control has led to widespread insecticide resistance, control failures, and reduced interspecific completion in many countries. Continuous research is required to replace conventional pesticides with inexpensive and eco-friendly natural plant products with active safe components, including the use of powdered plant parts, oils, and extracts that result from secondary metabolism in plants (Lale 2002). C. maculatus and R. dominica are two major stored product insects and that cause about 100% weight losses (Abouelatta et al. 2016, 2020; Abu Arab et al. 2022; Arab et al. 2022; Abo Arab et al. 2022). Therefore, the present study was conducted to evaluate the effect of high temperatures on both insects (adults and immature stages) as well as the effect of temperature on seed germination.

2 Materials and Methods

3 Statistical Analysis

The data were transformed, and analysis of variance (one-way ANOVA) was used to test for differences between treatments using SPSS version IS software (SPSS Inc. 1955).

4 Results

5 Discussion

The present study included one of the most important natural bioassay methods (the effect of high temperature) for controlling stored-product insects. This method has no side effects on humans or on the environment. In the current study, the range used for high temperature (45°C–80°C) influenced the criteria (mortality% of adults and immature stages, hatchability%, and reduction%), as well as the effect on weight loss% and germination%. These results are in accordance with those of Zewar (1993), who reported that complete mortality of R. dominica occurred at 60°C or 65°C for 15 and 10 min, respectively. All treatments significantly decreased the weight loss of cowpea seeds with increasing temperatures and exposure periods. In addition, our results agree with those of Mahroof et al. (2003), who studied the use of elevated temperatures (≥ 40°C–60°C) or heat treatments for managing insects in food-processing facilities as an alternative to space fumigation with methyl bromide. To determine the time-mortality relationship for eggs, young (neonate) larvae, old larvae, pupae, and adults of T. castaneum, these stages were exposed to temperatures of 42°C, 46°C, 50°C, 54°C, 58°C, and 60°C. Generally, the mortality at each stage increases with an increase in temperature and exposure time. Dosland et al. (2006) found that heat treatment involves raising the ambient temperature of a food processing facility to 50°C–60°C for 24 h or less to kill all life stages of stored insects. Brijwani et al. (2010) found that high-temperatures treatment (50°C–60°C) of flour mills can control all life stages of T. castaneum in 24 h. Golic et al. (2011) reported that short-term exposure of weevils from the Sitophilus genus at a temperature of 50°C had adversely affects their survival and progeny production and that there is a potential for its successful use as a physical measure in the control of insect pests. Loganathan et al. (2011) investigated high temperatures for the control of C. maulatus in chickpeas. They found that 40°C for varying durations dramatically affected all tested stages: eggs, larvae, pupae, and adults. The lethal times to reduce survival by 50% (LT50) at 42°C for eggs, larvae, pupae, and adults were 18, 57, 78, and 71 h, respectively. Except for malathion and temperature in the present study, the oils, powders, and inert dusts had negative effects on germination compared with the untreated treatment. Patil et al. (1994) and Zayed and Manal (2012) found that malathion had no adverse effects on the germination of cowpea seeds. Mbata and Phillips (2001) reported that high temperatures can be used instead of fumigation and chemical pesticides to protect stored products from pests.

6 Conclusion

It can be concluded from our results that, the treatment at 55°C/40 min, 60°C/30 min, 65°C/20 min, 70°C/20 min, 75°C/15 min, and 80°C/5 min caused complete mortality 100% of C. maculatus. However, the complete mortality 100% of R. dominica was obtained with the treatment 55°C/30 min, 60°C/25 min, 65°C/20 min, 70°C/15 min, 75°C/10 min, and 80°C/5 min. Furthermore, temperature at 45°C/30 min, 55°C/20 min, 60°C and 65°C/15 min, 70°C and 75°C/10 min, and 80°C/5 min did not have any harmful effects on wheat grain and cowpea seed germination.

Conflicts of Interest

The authors declare no conflicts of interest.