COMBINING EFFECTS OF CULTURAL PRACTICES AND RESISTANT CULTIVARS ON REDUCING THE INCIDENCE OF Meloidogyne spp. AND Thrips palmy Karny ON POTATO

48 Indonesian Journal of Agricultural Science 11(2), 2010: 48-56 Wiwin Setiawati et al. COMBINING EFFECTS OF CULTURAL PRACTICES AND RESISTANT CULTIVARS ON REDUCING THE INCIDENCE OF Meloidogyne spp. AND Thrips palmy Karny ON POTATO Wiwin Setiawati, Asih Kartasih Karjadi, and Thomas Agoes Soetiarso Indonesian Vegetables Research Institute Jalan Tangkuban Perahu No. 517 Lembang, PO Box 8413, Bandung 40391, Indonesia Phone +62 22 2786245, Facs. +62 22 2786416, Email: ; Submitted 16 April 2010; Accepted 10 June 2010 ABSTRACT Root-knot nematode (Meloidogyne spp.) and melon thrips (Thrips palmy Karny) are two serious pests on potato. These pests are conventionally controlled with synthetic pesticides. Cultural practices based on integrated pest management (IPM) are alternative methods to control these pests. The study aimed to determine the effectiveness of combined applications of cultural practices and potato cultivars in reducing the incidences of nematode and thrips. Treatments evaluated were methods of nematode and thrips control by implementing IPM and conventional practices. A split-plot randomized complete block design with four replications was used. The main plots were IPM or cultural practices (subsoiling, soil solarization and use of trap crop of marigold Tagetes erecta) and conventional practices using synthetic pesticides. The subplots were five potato cultivars, i.e. No. 095 (Herta x FLS–17), 720050/Kikondo, 676068/ I.1085, Granola, and Atlantic. The results showed that applications of cultural practices in combination with potato cultivars reduced Meloidogyne spp. population and potato tuber damage by 53.70% and 61.36%, respectively, as well as a significantly decreased thrips population. In the cultural control plots, thrips populations were below the action threshold (10.0 nymphs per leaf), therefore no single application of pesticide was used. This was in contrast to the conventional control treatments where insecticide was spayed 10 times until harvest. The subsoiling and solarization cut off the life cycle of the thrips and any survive thrips were trapped by marigold plant. Population of T. palmi on the five potato cultivars differed significantly; the lowest population was found on the cultivars No. 095 (Herta x FLS-17) and 676068/I.1085. The cultural control practices combined with potato cultivar No. 095 (Herta x FLS–17) were the best treatment for controlling Meloidogyne spp. and T. palmi on potato and also produced the highest yield (31.01 t ha -1). The study suggests that cultural control practices in combination with resistant cultivars are recommended as a suitable IPM to control nematode and thrips on potato crops. [Keywords: Potato, Meloidogyne spp., Thrips palmy, Tagetes erecta, integrated pest management] INTRODUCTION Potato (Solanum tuberosum L.) is one of the most important food crops in the world after wheat, rice, and maize. In Indonesia, potato areas are 64,151 ha, producing 1,071,543 t of tubers, but the average yield is still low (16.7 t ha -1 ) (Statistics Indonesia 2009). Apart from other factors, the main cause for poor yield is a number of pests and diseases, including root-knot nematode (Meloidogyne spp.) and melon thrips (Thrips palmy Karny). These pests cause serious losses on potato, especially during the dry season. Root-knot nematodes are small microscopic roundworm organisms grouped as a major pathogen of vegetable crops including potato throughout the world. The symptoms of haulm are similar to those caused by root damage. These nematodes reduce plant growth and cause fewer, small, pale green leaves which then tend to wilt in warm condition. Infected roots show variable-sized “knots” or galls. Infected tubers are deformed and have internal symptoms of nematode feeding. Severely infested plants may die prematurely and affect the quantity and quality of marketable vegetable yields (Kingland 2001). They infest plant roots by producing galls through their feeding habits (Nesmith 2000). Damaged population densities and potato yield losses due to Meloidogyne spp. in Indonesia were estimated to be around 15%. Yield losses of 50-80% in vegetable crops from this nematode have been common (Siddiqi 2000). Thrips palmy is other major pest of potato and has been spread widely and rapidly in tropical or subtropical regions. In Indonesia, T. palmi was first described on tobacco in 1925 from Medan, North Sumatra (Sakimura et al. 1986; Nakahara 1994). Both nymphs and adults suck the cell contents from leaves, stems, flowers and fruits. Initial damage symptoms on potato are silvery feeding scars on the lower leaf surface, usually alongside the midrib and veins. Heavily infested plants show a silvered or bronzed appearance, deformed and stunted leaves and might be died. As described by Sastrosiswojo and Basuki (2002), infestation of T. palmy in Indonesia caused considerable damage by 40-50% and yield losses of Combining effects of cultural practices and resistant cultivar ... 49 35-55% (Dibiyantoro 1996). Furthermore, T. palmi is difficult to manage due to a number of factors including high female reproductive capacity, rapid life cycle (egg to adult), residence in habitats such as unopened terminal buds that protect them from exposure to contact insecticide and resistance to various insecticides. Indonesian potato farmers used very heavy pesticides (16-20 applications during one season) and most of farmers (63%) sprayed the crops twice a week (Rauf et al. 2000). Continuous application of pesticides might cause pest resurgence, secondary pest outbreaks, development of pest resistance, and also destroy natural enemies. Work by the Entomology Department of the Indonesian Vegetables Research Institute (IVEGRI) over the last three years has shown that T. palmi populations increased possibly as the result of uncontrolled broad spectrum insecticide use on potato crops. The pest becomes resistant to insecticides and reduced natural enemies of the thrips (Seal 1994; Tobing 2007). Soil fumigation with methyl bromide (MB) was frequently used to control root-knot nematode. Fortunately, MB has been banned in Indonesia since January 2008, and in many countries MB has been restricted its use due to its hazardous effect on stratospheric ozone. Cost-effective and safe strategies to control rootknot nematode and thrips are essential to maintain production efficiency and quality. There are good opportunities to reduce chemical inputs using integrated pest management (IPM). As in any IPM strategy, the primary strategies are using biological and cultural controls, supported by selective pesticides, only when necessary. Cultural controls are equally as important as the biological controls and include soil preparation, soil solarization to control nematodes and soil-borne diseases (Stevens 1990; Katan and DeVay 1991), intercrop with marigolds (Tagetes spp.) for nematode and insect pest management (Khan et al. 1971; Ploeg 1999), seed source and varietal s (...truncated)