Damage Caused by Spodoptera frugiperda J.E Smith on Corn in Climate Zones in South Sulawesi, Indonesia

Corn, as one of the main commodities in South Sulawesi, cannot be separated from pests such as Spodoptera frugiperda. J.E Smith. S. frugiperda is a new invasive pest in Indonesia and has been reported to spread throughout the provinces, including South Sulawesi. However, information on S. frugiperda damage in South Sulawesi was still limited. The purpose of this research is to determine how S. frugiperda affects corn plants in South Sulawesi’s potential agricultural climate zones, specifically the west, east, and transitional sectors. Surveys from October to December 2022 were carried out in three regencies representing each climate zone in South Sulawesi. The scouting method was used to conduct field observations on 50 plant samples at each location. Use a visual rating scale of 1 (no damage) to 5 (severe plant stunting and funnel damage) to determine the severity. The intensity of attack during the observation recorded the highest rate of attack in the transitional sector The highest attack rate was in the transitional sector (Luwu), with a total damage category and attack intensity of 48.7%, while the lowest was in the eastern sector (Wajo), with an attack intensity of 32.80%. The highest larval density was in the transitional sector (Luwu), with an average range of 0.04-0.52 larva/plant, while the lowest was in the western sector (Takalar), with an average range of 0.04-0.06 larva/plant. The infested corn plants in the all-climate zone in South Sulawesi showed various typical damages caused by S. frugiperda.


Introduction
South Sulawesi plays a role in Indonesia's corn production.The climate potential in South Sulawesi for agricultural development, such as corn, is very supportive, and the development areas are grouped into three sections based on the relative similarity of the climatic zones, namely the West, East, and Transitional Sectors.The western area is impacted by westerly breezes, and the eastern area is affected by easterly breezes, which are firmly connected with the blustery and dry seasons [1].
The food crops belonging to the Graminae family, including corn, rice, wheat, sorghum, and sugarcane, serve as its main hosts.S. frugiperda is polyphagous [11].Imago is a long-range flier with a high cruising range; therefore, S. frugiperda can migrate to other growing regions where primary hosts are available [12].S. frugiperda also damaged the corn plant throughout its life cycle, from the vegetative to the generative phases.Mild larvae attacks can damage the surface of the leaf skin so that it appears transparent, whereas in heavy attacks there is frost around the corn [13].
The S. frugiperda population's existence and growth must be monitored because they can result in significant yield losses.Several studies have shown that S. frugiperda attacks in Indonesia are very high, where the intensity of damage has reached 26.50% to 70% in Lampung [14], 58,31% to 78,75% in East Java [15], 85% to 100% in East Nusa Tenggara [13], and 47.84% in Bali [9].However, the information on S. frugiperda damage in corn production centers in South Sulawesi was still limited.The purpose of this research is to determine how S. frugiperda affects corn plants in South Sulawesi's potential agricultural climate zones, specifically the west, east, and transitional sectors.

Study Area
This observation was carried out in three regencies, which represent each climate zone in South Sulawesi, and the sub-districts within each of those regencies were chosen based on where the main corn-producing centers are, namely Takalar (4015'10.27"S 1200 0'47.10"E) from the west sector, Wajo (4015'10.27"S 1200 0'47.10"E) from the east sector, and Luwu (3016'10.21"S 1200 16 '23.38"E)from the transitional sector (Figure 1) from October to December 2022.

Damage due to S. frugiperda
The scouting method involves direct observation of plants to identify them.Because the survey area is large enough to cover all of the land, this scouting method was used.The corn fields were scouted using a ''W" pattern approach, and the total sample observed was 50 plants (10 consecutive plants at five different spots along the ''W" transect) [16].The collected data was carried out every week for each observable location until the corn was six weeks old.Using a rating scale for grading damage severity on whorl-stage plants, the percentage of severity was determined by the severity of pinholes, shot-holes, lesions, tattering, and dead hearts.[14].Attack intensity and level of leaf damage were determined by examining damage or attack symptoms caused by S. frugiperda in the same maize plant sample evaluated by [17] based on the leaf damage scale in Table 1.

Data Analysil s
Thel avel ragel pel rcel ntagel of pel st il nfel statil on il s dil splayel d graphil cally.Data on larval populatil on del nsil ty wel rel also prel sel ntel d graphil cally.

Rel sult and dil scussil on
3  Thel lowel st larval del nsil ty was il n thel wel stel rn sel ctor (Takalar), wil th an avel ragel rangel of 0.04-0.06larvael pel r 50 plants.Thel obsel rvablel arel a was a largel dry land arel a abovel thel hil lls, and thel farmel rs il n thel arel a dil d not do sil multanel ous plantil ng, whil ch causel d thel agel s of thel corn plants to dil ffel r.Thel numbel r of S. frugil pel rda larvael that attack corn plants has rel portel dly del crel asel d il n rel cel nt sel asons, accordil ng to local farmel rs.Il t has bel el n supportel d by data from thel Cel ntel r for Food Crops and Hortil culturel Protel ctil on of South Sulawel sil , whil ch prel sel nts il nformatil on for thel gel nel ral til mel pel ril od of 2022 (January-Octobel r).Thel arel a of corn affel ctel d by S. frugil pel rda il n Takalar il s 3.95 ha.Control el fforts havel bel el n succel ssful so that thel rel il s a vel ry sil gnil fil cant del crel asel il n thel arel a of thel corn affel ctel d at thel bel gil nnil ng of el mel rgel ncel from thil s pel st attack, whil ch il s an arel a of 170.55 ha (2019).
Anothel r factor that causel s dil ffel rel ncel s il n attack il ntel nsil ty and thel populatil on il s thel clil matel , whil ch il ncludel s tel mpel raturel , rail nfall, and humil dil ty.Accordil ng to thel study, Takalar had an avel ragel tel mpel raturel of 29.41°C and a humil dil ty of 78.39%, Wajo had an avel ragel tel mpel raturel of 30.69°C and a humil dil ty of 82.46%, and Luwu had an avel ragel tel mpel raturel of 27.06°C and a humil dil ty of 86.82%.Thel hil gh larval populatil on and il ntel nsel attack actil vil ty il n Luwu arel il mpactel d by thel local tel mpel raturel , whil ch il s il del al for thel del vel lopmel nt of S. frugil pel rda larvael .Thil s rel sel arch [18] supports thel fil ndil ng that thel optil mum tel mpel raturel for thel del vel lopmel nt of Spodoptel ra frugil pel rda larvael il s 28°C (del vel lopmel nt can occur at a tel mpel raturel bel twel el n 11°C and 30°C for a pel ril od of til mel ).Thel il del al condil til ons for thel growth of S. frugil pel rda, accordil ng to [23] arel bel twel el n 24°C and 33°C wil th 60% to 90% humil dil ty.

Conclusil on
The survey results in South Sulawesi found that S. frugiperda affected maize plants in the climate zone, especially in the western, eastern, and transitional sectors, with various typical damages caused by S. frugiperda.The highest attack rate was in the transitional sector (Luwu), with a total damage category and attack intensity of 48.7%, while the lowest was in the eastern sector (Wajo), with an attack intensity of 32.80%.The highest larval density was in the transitional sector (Luwu), with an average range of 0.04-0.52larva/plant, while the lowest was in the western sector (Takalar), with an average range of 0.04-0.06larva/plant.

Acknowlel dmel nt
Thel authors would lil kel to thank thel Il ndonel sil a El ducatil on El ndowmel nt Fund -LPDP for fundil ng thil s rel sel arch.

Figure 1 .
Figure 1.Map of the observation location