THE IMPACT OF THE SWEET POTATO WEEVIL (CYLAS FORMICARIUS) INFESTATION ON SWEET POTATO PRODUCTIONNina J. Lapinangga, Yosefus F. da Lopez, Jacqualine A. Bunga and Jemrift H.H. Sonbai
Sweet potato is the seventh-ranked carbohydrate-producing plant in the world besides wheat, rice, potatoes,corn, barley, and cassava. In Indonesia, the plant becomes an important food crop besides rice and corn but its productivity tends to decrease, one of the influencing factors is Cylas formicarius disorders. The study was to determine the impact of C. formicarius infestation on the production of four sweet potato varieties.The study was arranged in a factorial randomized block design (RBD), consisting of two treatments, i.e.sweet potato varieties and plant spacing. Parameters measured were the population of the pest (per kg of tubers), the percentage of infested tubers (%), the severity of infested tubers, the weight of tubers (kg/6m2),and the productivity of sweet potato (ton/ha). The data obtained were analyzed using analysis of variance(ANOVA), Duncan Multiple Range Test (DMRT), and Pearsonâs Correlation. ANOVA was to determine whether there is a significant effect between the treatments tested. If a significant effect between treatments existed, a posthoc test using DMRT at the confidence level of 95% is used to decide if there are significant differences in mean values between the treatments compared. Pearsonâs correlation was to find out the correlations between the severity of infested tubers and the population of larval and imago on infested tubers. The results presented that the population of C. formicarius in the tubers of sweet potato varieties ranged from 0.2813.31 per kg of tubers with an average of 5.95 per kg of tubers. The population of C. formicarius in the tubers of sweet potato var. Daya was 0.28 per kg of tubers and lower than those in var.Local (2.23 per kg of tubers), var. RIS 03065-03 (7.95 per kg of tubers), and var. Jago (13.31 per kg of tubers).The infested tubers ranged from 3.11 to 42.06% with an average of 17.90%. The lowest infested tubers were found in the sweet potato var. Daya, i.e. 3.11%, followed by 6.50% in var. Local, 19.94% in var. RIS 030605-03, and 42.06% in var. Jago, respectively. The lowest severity of infested tubers was found in the sweetpotato var. Daya (17.78%), followed by var. Local (23.33%), var. RIS 03065-03 (36.67%), and var. Jago (41.67%),respectively. A strong correlation between the population of C. formicarius and the severity of infested tubers(r = 0.98) was found, indicating that the higher the population of C. formicarius, the higher the severity of infested tubers. The infestation of C. formicariusmay damage and decrease the yield of the sweet potatoes.The highest decrease in yield occurred in sweet potatovar. Jago (60.7267.26%), followed by var. Local (64.60%),var. RIS 03065-03 (36.47%), and var. Daya varieties (10, 01%), successively. The results of this study suggested that sweet potato var. Daya is more resistant to C. formicarius and cultivating the sweet potato may increase the productivity of sweet potato in Indonesia.
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