IDENTIFICATION AND ANALYSIS OF WEED VEGETATION AS Ganoderma PRESENCE MARKER ON OIL PALM PLANTATION

Weeds on oil palm plantations can also be the host of Basal Stem Rot caused by Ganoderma. This study aims to identify and analyze of weed vegetation using visual estimation and squares method as Ganoderma presence marker on oil palm plantations. This research was conducted in block 17, 16, and 6 of VII afdeling, Rambutan Estate in Serdang Bedagai Regency on December 2017 to March 2018. This research used survey method with visual estimation and squares. The data used is absolute density, relative density, absolute frequency, relative frequency, important value indeks, Summed Dominance Ratio (SDR) and dry weight. Data analysis using IBM SPSS Statistics 20 software. The results showed that different weed species between oil palm was infected and uninfected by Ganoderma with visual estimation method is Cyclosorus aridus (14.78%) where as with squares method are Cyperus rotundus (10.60%), and Stenochlaena palustris (7.76%) with temperature range 28.67 to 30.80C and moisture amount 60.67 to 77.33%.


I INTRODUCTION
Growing weeds on oil palm plantations are disturbing plants that can harm palm oil growth and production.The presence is able to become a major competitor in fighting for nutrients, water, growing space, and sunlight.Weeds in oil palm plantations can also be a host for pests and diseases to grow and develop [1].Type of plant disease on oil palm plantations is basal stem rot (BSR) caused by Ganoderma boninense.The spread of Ganoderma attacks is very fast through: (1) root contact between oil palm trees, (2) Ganoderma spores spread through the wind, carried by insects, and (3) Ganoderma spores can also be spread due to harvesting and estate maintenance.In Indonesia, G. boninense was identified as the most common species that attack and causes the death of plants more than 80% from total oil palm populations and causes a decrease in palm oil products per hectare [2].Ganoderma attacks and infects every stage of oil palm plants growth.The symptoms of a disease are slow, but it can reduce production and even kill oil palm to thousands of hectares.BSR causes serious economic losses for the oil palm industry.Therefore, BSR is considered a serious threat to oil palm industry in Southeast Asian countries.Until now, there is still a need to detect and sustain control of this disease [3].BSR attacks caused by G. boninense on oil palm plantations continue to increase [4].The highest losses occurred in Indonesia and Malaysia, the lowest was reported in Africa, Papua New Guinea and Thailand [5].Usually, this disease is present in mature plants.In coastal areas of Malaysia, the average yield loss is 50% of 13year-old oil palm plantations [6].This disease has also been reported to have a loss of 30% in 13-year-old oil palm plantations in inland and peat areas [7].In Indonesia, plantations confront similar problems.In Sumatera Utara Province, when replanting (25 years) 40 to 50% died caused by this disease.When replanting, oil palm plants die more caused by Ganoderma to 25% in 7 years.The average decrease in the yield of fresh fruit bunches (FFB) from 0 to 16 ton ha -1 of each dead oil palm and 35% decrease of FFB production in growing plants [8].Some early detection of Ganoderma presence has been carried out through research from various scientific fields.However, there has never been researched that conducted early detection of Ganoderma presence based weed populations on oil palm plantations.It is necessary for identification and analysis of weed vegetation as a source of initial information to preventing of

III RESULT AND DISCUSSION
Based on identification and analysis of weed vegetation that has been carried out with visual estimation methods on oil palm was infected and uninfected by Ganoderma (Table 1).
Results showed there are 5 from 24 weeds species are dominant from oil palm was infected and uninfected by Ganoderma on visual estimation method.Based on the dominant weeds, a different species was obtained that is Cyclosorus aridus (14.78%) on oil palm was infected but not found to uninfected by Ganoderma.Presence this species is still relatively low.It is assumed the presence of these weed species has the potential as host plants for Ganoderma fungal spores.The difference in species of weeds on oil palm was infected and uninfected by Ganoderma with visual estimation methods (Figure 2).Based on field observations, only Cyclosorus aridus species (ferns group) found was infected but not found to uninfected by Ganoderma.This can be seen when observing at the field, every available weed population of ferns, there are also Ganoderma which grow and develop at the basal stem of oil palm.Observations at the field using the squares method obtained 19 weed species on oil palm was infected and uninfected by Ganoderma (Table 2).Results showed there The difference weeds species on oil palm was infected and uninfected by Ganoderma with squares method (Figure 3).Based on field observations there are Cyperus rotundus (sedges), and Stenochlaena palustris (ferns) species which contain on oil palm was infected but not found to uninfected by Ganoderma.This is caused the condition of land on moist ferns, so it can be assumed the ferns weed have nutrient content that is not balanced between Cu and Zn at leaves.This nutrient imbalance resulted the distribution of Ganoderma fungal spores developing on ferns weed leaves and spreading to basal stem of oil palm.This is consistent with literature [11] which states that high content of Cu and Zn on oil palm leaves significantly lower infected with Ganoderma.herelationship between SDR and dry weight of weed species on oil palm was infected and uninfected by Ganoderma with squares method (Figure 4).Based on 5 dominant weed species, Paspalum scrobiculatum have highest dry weight on oil palm was infected by Ganoderma amount 5.71 g.Asystasia intrusa species have highest dry weight on oil palm uninfected by Ganoderma amount 5.03 g.This relationship occurs where ganoderma spores do not harm growth and development of weeds.

Figure 1 .
Figure 1.Weeds species on oil palm plantations was (a) infected and (b) uninfected by Ganoderma

Figure 2 .
Figure 2. Differences weeds species on oil palm was infected and uninfected by Ganoderma with visual estimation method.

Figure 4 .
Figure 4.The relationship between SDR and dry weight of 5 weeds species on oil palm was infected and uninfected by Ganoderma with squares method.
, absolute frequency.relative frequency/nisbi, important value index, SDR [9] and dry weight.After weeds are identified, then cut right on the surface of soil from each plot.Then it is drying at 80ºC for 48 h [10], to obtain a constant dry weight.Analysis using with IBM SPSS Statistics 20 software.
(SDR).Parameters observed in the squares method include absolute density, relative density/nisbi

Table 1 .
Summed Dominance Ratio (SDR) of weed species on oil palm was infected and uninfected by Ganoderma with visual estimation method

Table 2 .
Summed Dominance Ratio (SDR) of weed species on oil palm was infected and uninfected by Ganoderma with squares method.

Table 3 .
The temperature and moisture factors on oil palm plantations was infected and uninfected by Ganoderma.Stenochlaena palustris which have dominated in research area.Temperatures range from 28.67 to 30.80 o C and moisture from 60.67 to 77.33%.This is the ideal condition for Ganoderma growing.This is consistent with literature [12] which states that G. boninense inhibited at sunlight area (40 to 45 o C) while optimal invitro growth is 25 to 30°C.