Vol 11, No 2 (1999)

Buletin Hama dan Penyakit Tanaman

Table of Contents

Articles

The research was conducted in sub-district of Ciledug (Cirebon) with the objectives to study the infexiation and larvaal population development id onion armyworm. Spodoptera exigua (Habner) (Lepidoptera: Noctuidae), on shallots grown in lowland. Monitoring of egg masses and leaf damage were made at 3-4 days internal while of larvae at 1 week internal. Outbreak took place during the dry season of August-October 1995 when population density reached 0.8 egg mass and 23 larvae per hill, and subsequently all hills were heavily damaged. Throughout the rainy season of December 1995-February 1996, egg masses and larvae were difficult to find. Result of hand-picking showed that larval population during dry season was 78 times higher than those of rainy season. Larvae exhibited body color vartations. During the epidemics 80 percent of the larvae were dark whereas,during the endemics only 10 percent, the rest were light green. Level of egg parasitization was 0,9 percent coused by Tricogramma xp. (Hymenoptera; Trichogrammatidae) and telenomus sp. (hy menoptera; sceltonidae ), and larval parasitization 5.7 percent coused by Microplitis sp. (Hymenoptera; Braconidae), Euplectrus sp. and stenomesius sp (Hymeno[tera; Eulophidae), and Peribaea sp. (Diptera; Tachinidae). Low level of parasitization together with the abundance of food supply and dry season were believed to be the main foctors contributing to the population outbreaks. Hand-picking of egg masses and larvae conducted regularly, as practiced by the farmer group in the village of Dukuh wringin (Brebes(, should be adopted as a key activity for mitigating S. exigua infestation during dry season; and therefore, this practice should disseminated to farmers in other areas.

Aunu Rauf
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Asniwita Asniwita, Rusmilah Suseno, Sri Hendrastuti Hidayat, Budi Tjahjono
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Hasriadi Mat Akin, Sudarsono Sudarsono, Rusmilah Suseno
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Rina Sriwati, Meity S. Sinaga, Abdul Muin Adnan' Ika Mustika
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Critical Period of Tomato toAlternariasokuri (Ell. & G. Martin) Sor. infection and its determinant. Determination of critical period (susceptible period) of plant is one of the strategies in Integrated Pest Management (LPM), because it can reduce or minimize pesticide use. Study about the critical penendo of tomato was cam'ed out in the field of Bangbayang village, in the Cicwug district of Sukubumi. Tomato plant cultivar Zntan at dzremnt age (50, 60, 70 and 80 &ys after sowing [DAS] were inoculated with 15 ml of Id s p o ~ l suspension of Alternaria solani per plant, that have been added with Agristick 2% and llveen 80 2%. Observation that was conducted include disease severity, the height of plant, dry weight of plant biomass and total Jiuit production. Leaves of diferent age (50, 60, 70, 80 DAS) at d@rent part of plant (lower, middle and upper canopy) were analyzedfor totalprotein by Auto Analyzer ZZMethod, totalphenol by Follin- Denis Method and total sugar content by L u ~ h o o rMl ethod. The result showed that the older plant have the higher disease severity. The same trend can be seenjkm the age of leaves i.e. leaves fLom the lower part ofplants (olakr) am more susceptible than the middle and upper leaves. The critical period of the plant is at the age of 50 - 60 DAS. TotalJiuit production is not determined by disease severity, instead it is more determined by the age of plant infected. l%em is a tendency that the interaction among total protein and phenol content efect the susceptibility of the plant to the pathogen as can be seen the following regression equation: Y = 167 - 3.1 9 X2 - 22.58 X3 (R= 0.76).
Sientje Mandang Sumaraw
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