Effect of drying and storage of corn seeds (Zea mays L.) on postharvest insect pest control in laboratory scales

Corn is one of the word’s most essential carbohydrate-producing food crops. In addition to being used as a staple food for most of the world’s population, corn seeds are also an essential component of animal feed. The purpose of this study was to determine the effect of drying and storage time on the presence of warehouse pest populations. The research method was carried out by drying corn seeds under sun exposure for 6 hours/day. The experiment consisted of four treatments, namely drying time repeated three times. Observations consisted of weight loss of corn seeds, the population of warehouse pests, and damage intensity. The results of the observations were then analyzed by statistical tests followed by a real difference test. The results showed that the weight of corn seeds decreased with the length of the drying process. Drying for 18 hours was effective in suppressing the presence of warehouse pests such as S. zeamais (197.67 adults) and T. castaneum (1.67 adults). Drying time in addition to affecting the presence of warehouse pests, also significantly affects the intensity of the attack. Drying for 24 hours has a lower damage rate (13.05%) when compared to other drying times.


Introduction
Corn seed is the most important staple food for people in the world.At present, corn seeds are also the main component of animal feed.Damage to corn seeds is caused by several factors, starting from the harvesting process to storage.Damage to the storage area is the most critical stage because it can cause the biggest yield loss.The main cause of damage to storage areas is warehouse pest attacks.Inventory of warehouse insect pests on corn seeds can occur in the field before the post-harvest process.At the storage stage, corn seeds will be damaged by various types of warehouse pests.The pests that often damage corn seeds are Sitophilus oryzae, S. zeamais, Tribolium castaneum, Sitotroga cerealella, Corcyra cephalonica, Ephestia cautella, and Rattus dominica [1,2,3,4,5].
Warehouse pests that are dominant in damaging maize seeds in the tropics include S. zeamais (flour beetle) [6,1,3].This pest is polyphagous which can damage various types of grains such as rice/grain, corn, wheat, and sorghum [7,8].Yield losses by warehouse pests in storage are estimated to be around 30% (Suleiman, Rosentrater, and Bern 2015, ) [8].Storage for 6 months can cause seed damage up to 70-90 % in the tropics [9] .The research results of Prastowo and Susanti [10] showed that maize weight loss reached 17% when stored for six months with about 85% seed damage.The length of storage of corn seeds has an effect on the level of damage by warehouse pests [11].The stability of corn seeds in storage is also influenced by the postharvest management process.The postharvest management of corn seeds can be achieved by maintaining its freshness so that it can be available all 1230 (2023) 012086 IOP Publishing doi:10.1088/1755-1315/1230/1/012086 2 the time [12].One of the activities that can extend the shelf life of corn seeds is drying.Drying is an attempt to reduce the water content to a certain extent so that biological reactions stop and microorganisms and insects cannot live in it [12,14].
The quality of corn seeds is determined by its water content, the higher the corn's moisture content, the lower the quality.The high moisture content of corn can result in damage to corn seeds by postharvest pest attacks.In this regard, research on the effect of drying time and storage of corn seeds on the level of postharvest damage by pests needs to be carried out.This study aims to determine the effect of drying and storage time on the presence of warehouse pest populations.

Time and place of research
The research carried out for four months, from August to December 2022.Newly harvested Bisi 2 variety corn was obtained in Satui Sub-District, Kotabaru District, Banjarbaru City, South Kalimantan.Inventory and identification of warehouse pests were carried out at the Entomology Laboratory, Faculty of Agriculture, Universitas Lambung Mangkurat, Indonesia.

Research methods
Drying Corn Seeds of the Bisi-2 Varieties; Prior to the drying process in direct sunlight, the corn is shelled and cleaned of dirt adhering to the corn seeds.The total weight of the corn seeds used as the research sample was 45 kg.Corn seeds that have been selected as samples, were then weighed with a digital scale with a weight of 3 kg for each replicate.The drying process of corn seeds takes place according to each drying treatment, namely 0, 6, 12, 18, and 24 h.The process of drying corn seeds takes place from 09.00 a.m -15.00 p.m.Each treatment was repeated three times, resulting in 15 combinations of repetitions.The results of drying in each repetition in each treatment were then weighed again to obtain the dry weight of corn seeds.Furthermore, the corn seeds are put into sacks of rice and stored for four months.

Parameter observation 2.3.1. Measurement of moisture content of corn seeds
Measurement of the moisture content of corn kernel samples was carried out before and after drying using a moisture meter.Measurements were made on five treatments which were repeated three times.The data from the measurement of water content was then analyzed.

Inventory of pests on corn seeds with storage for 4 months
Calculation of pest populations on corn seeds during 4 months of storage, is done by calculating the number of pest species populations that attack in each replicate for each treatment.The results of pest population data are then followed by data analysis.

The final weight of corn seeds after drying
Corn kernel samples in each repetition for each treatment, then the final weight was calculated in the following way: Weight = initial weight weight after drying.

Observation of the number of intact corn seeds after 4 months of storage.
Calculation of the number of intact corn seeds is done by separating the infected corn seeds from the corn seeds that have become powder from the intact corn seeds.Observational data on the number of whole corn seeds were then tabulated and further tests were carried out on all significantly different treatments.

Analysis of observation results
Data were analyzed with variance-based Completely Randomized Design (CRD).The results of the study were tested statistically with analysis of variance and continued with the LSD (Least Significance Different) test level of 0.05.

Moisture content of corn seeds
Content of corn seeds Moisture content is one of the important factors determining the quality of the best corn seeds.Therefore, the drying stage is a process always in the post-harvest stage of food, especially in postharvest corn crops.The drying process for the purpose of reducing the water content is related to the quality level of the beans at the shelling and storage stages.In the shelling process, the moisture content will affect the level of seed damage, while in storage the moisture content will affect the shelf life of corn seeds.The moisture content of corn seeds after treatment is shown in Table 1.The process of drying corn seeds is carried out in direct sunlight with temperatures ranging from 32-33 °C.The moisture content of shelled corn seeds without drying in the sun ranges from 20.51 %.The condition of the water content is relatively high when compared with other long-drying treatments.The data on changes in water content were indicating that drying time had a very significant effect on changes in the moisture content of corn seeds.
Based on SNI shelled corn No: 01-3920-1995 it explains that the moisture content of shelled corn seeds for maximum consumption is 14% for quality 1 and 2, for quality 3 the maximum moisture content is 15 %, and for quality 4 the maximum moisture content of corn seeds is 17 % [13].Corn that is shelled without drying until drying for 12 hours does not meet the requirements for consumption water content based on SNI, as shown in Table 1.Meanwhile, corn seeds with drying for 18 and 24 hours have corn seeds moisture content that already meets consumption requirements based on SNI, so corn seeds from shelling do not need to be dried anymore.Moisture content is the main factor determining the storability of rice which is influenced by temperature, oxygen, seed conditions, storage time, and biological factors (fungi and insects) [11,16,18].

The average weight of corn seeds after drying treatment
Parameters of the final weight of corn seeds after drying treatment are presented in Table 2.The results showed that there was a decrease in grain weight before and after drying.The initial weight of corn seeds before drying was 3 kg/replication.In this study, the final weight of corn seeds after drying showed that drying time had a significant effect on the total weight of corn seeds.The rate of decrease in the average weight of corn seeds during drying is shown in Figure 1.The results of the analysis in Figure 1 show that at an initial weight of 3 kg the average shrinkage at 6 hours of drying time becomes 2.91 kg or the equivalent of a shrinkage weight of 0.08 kg.The drying process for 24 hours was able to reduce the average weight to 2.76 kg or a shrinkage of 0.23 kg from the initial average weight.The average final weight of corn seeds after drying treatment shows that drying for 6 hours and 12 hours does not show a significant difference, but it is different.with drying for 12 hours showed a very significant difference to drying for 18 and 24 hours.The treatment without drying had a weight of 3 kg of corn seeds showing a statistically significant difference with other long drying treatments.This indicates that doing a minimum of drying for 18-24 hours can reduce the moisture content of the corn seeds which will affect the final drying weight and quality of the corn seeds in storage.
The effect of temperature and drying time has a significant effect on the quality of corn seeds in storage.The results of this study are supported by Moreno et al. [17] which stated that the drying temperature had a significant effect on the microwave drying process and the germination rate of corn seeds.Drying naturally produces high quality products, if supported by maximum weather conditions during the drying process [13].

Characteristics of corn seed pests in storage
During the observation, it was found that two types of pests actively damaged corn seeds in storage.The pests that actively attacked the storage of corn seeds were S. zeamais and T. castaneum (Figures 2a and 2b).

. Sitophilus zeamais
Pests this pest is called zeamais which has an elongated head forming a snout (Figure 2.a).The S. zeamais insect is a small beetle with a size of 3-4.5 mm, similar to S. oryzae, but its genetics are larger [20,21,22].The male S. zeamais has an aedeagus with a central ridge, whereas, in the female, it has Y-shaped prongs pointed at the end and wider apart [3,18,19].
The beetle is dark brown, with a slim body shape and slightly flattened.On the pronotum there are six pairs of serrations that resemble sawtooth.The shape of the head resembles a triangle.On the forewings, there are clear longitudinal stripes.There are four spots of slightly reddish yellow on the front, two spots on the left wing, and two spots on the right wing [20,21].

Tribolium castaneum.
The beetle is flat, reddish brown to dark brown in color, and have a body length of 3-4 mm (Figure 2b).The eggs are cloudy white, 1.5 mm long, and oval in shape.The larvae are yellowish-white, 5-6 mm long, and at the end of the abdomen there is a small, dark fork protrusion, the pupa is yellowishwhite, 3.5 mm long, free-type.This beetle has a characteristic that distinguishes it from other beetles, namely, it has a capitate angle or three antennae which suddenly enlarge at the end, has a narrow eye that is not closed, and consists of 3-4 eyes [18].

The population of maize weevil (Sitophilus zeamais)
The average population of S. zeamais pests can be seen in Table 3, where at drying 0 hours and 6 hours, it significantly affected the population of maize weevils with treatment drying 12, 18, and 24 h.This is because drying greatly affects water content, while water content above 14% is very susceptible to postharvest pest attacks.In addition, the storage time is also very long, namely 4 (four) months so it has a significant effect on the population of maize weevils (S. zeamais.).This is in accordance with the research of [20] who said that postharvest product storage for 60 days was able to increase the number of maize weevil populations in some local Central Kalimantan rice varieties.Besides that, it is also strengthened by the research of [21] who stated that postharvest product storage for 8 (eight) weeks could spur new S. zeamais imago to increase along with the length of postharvest grain product storage.The treatment without drying showed a population of 2,196 maize powder pests.This shows that the pest population is the highest when compared to other drying treatments.Drying for 18 hours showed the lowest number of flour beetle populations, around 197.67 adults, but not significantly different from the drying treatment for 24 hours, namely 285 adults.Data on the total population of S. zeamais on corn seeds were indicating that drying time had a very significant effect on the total population of S. oryzae pests on corn seeds.

The population of pests (Tribolium castaneum)
On storage showed that the higher the water content the higher the population of the warehouse pest of flour beetle T. castaneum (Table 4).Corn seeds that went through no drying process had a population of 27.67 adults, but statistically, there was no significant difference with other drying treatments.The mean value followed by the same letter for the same variable is not significantly different Pest populations of T. castaneum in the 18 and 24 h drying process had a lower population level when compared to those without drying and drying for 6 hours.Drying time for 18 hours with 4 months of storage resulted in 1.67 adults.Another study conducted by Dal Bello and Fabrizio [22] stated that the T. castaneum pest population increased with the length of time corn seeds were stored.The length of storage will increase the humidity.The more humid an environmental condition will increase the moisture content of corn seeds so that it will increase the population of flour beetle.The higher the population of maize weevils, the lower the quality of corn seeds.These quality changes include corn seeds that break easily, contain flour, and have a yellowish color.

Whole grain (seeds)
The effect of drying time (hours) on damage to corn seeds is presented in Table 5.The average corn seeds without drying treatment had 6,004.67intact seeds but showed no significant difference with the drying treatment for 6 hours.2436.934 The mean value followed by the same letter for the same variable is not significantly different based on the LSD test at 5% level The drying process for 24 hours showed the highest intact corn seeds, namely 9, 670 (seeds), and showed a very significant difference to the treatment without drying and drying for 6 hours.However, drying for 18 hours with a value of 9,631.61intact corn seeds did not show a significant value for the 24-hour drying treatment.This indicates that drying for 18 hours and/or 24 hours will produce the maximum intact corn seeds when compared to other drying times.
The more population of maize weevils will cause increased damage to corn seeds.This is reinforced by Syahrullah's research [23,24] which states that the higher the number of S. oryzae imago, the higher the damage to corn seeds by these pests.

Conclusions
Based on observations about the effect of drying time on moisture content and the level of damage to corn seeds, the following conclusions can be drawn; Drying time for 24 hours can reduce the moisture content of corn seeds according to the SNI standard for shelled corn No: 01-3920-1995 which is suitable for consumption, which is around 14%.Low moisture content can reduce the population of warehouse pests on corn seeds during storage.Storage of corn seeds for four months was invaded by two types of warehouse pests namely Sitophilus zeamais and Tribolium castaneum.

4 Figure 1 .
Figure 1.Effect of drying time on shrinkage of corn seeds (kg)

Figure 2 .
Figure 2. Corn Seed Pests: 2a) S. zeamais and 2b) T. castaneum 3.3.1.1.Sitophilus zeamaisPests this pest is called zeamais which has an elongated head forming a snout (Figure2.a).The S. zeamais insect is a small beetle with a size of 3-4.5 mm, similar to S. oryzae, but its genetics are larger[20,21,22].The male S. zeamais has an aedeagus with a central ridge, whereas, in the female, it has Y-shaped prongs pointed at the end and wider apart[3,18,19].The beetle is dark brown, with a slim body shape and slightly flattened.On the pronotum there are six pairs of serrations that resemble sawtooth.The shape of the head resembles a triangle.On the forewings, there are clear longitudinal stripes.There are four spots of slightly reddish yellow on the front, two spots on the left wing, and two spots on the right wing[20,21].

Table 1 .
The moisture content of corn seeds after treatment The mean value followed by the same letter for the same variable is not significantly different based on the LSD test at 5% level

Table 2 .
The effect of drying time (hours) on the average dry weight of corn seeds (kg) The mean value followed by the same letter for the same variable is not significantly different based on the LSD test at 5% level

Table 3 .
The effect of drying time (hours) on the total population of S. zeamais (tails)

Table 4 .
The effect of drying time (hours) on the total population of Tribolium castaneum

Table 5 .
The effect of drying time (hours) on damage to corn seeds