Suitability of selected drought tolerant grass species as trap plants for chilo partellus (swinhoe) in Kisumu County, Kenya

The stem borer, Chilo partellus Swinhoe (Lepidoptera: Pyralidae) is a pest that attacks plants in the poacea family in tropical lowland areas of Africa. Yield losses in maize are caused by the borer feeding on plant stems, leaves, grains and tussles. It is difficult to control C. partellus since larvae hide in stems. Spraying with insecticides only kills eggs and adults. Other methods used to control C. partellus include biological, physical, geneticaland cultural methods. Trap plants are used to control C. partellus and they fall under cultural practices. Trap plants are crops grown to attract pests to feed or oviposit on them hence protect target crops from pest attack. Trap plants are eco-friendly and locally available. The purpose of this study was to seek for an alternative control measure by use of trap plants to manage C. partellus. The grasses that were selected from 42 grass species at Kenya Agriculture Livestock Research Organization– Kisii for this study included Pennisetum sphacelatum, P. mezianum, Hypperhania tamba, Hyparrhenia cymbaria, Panicum maximum, Sporobolus pyramidalis, S. consimilis, Chloris gayana, Bracharia brizantha and Bracharia mulato II. These grasses were selected because they can withstand drought. The field experiments were conducted at Nyakach Sub-County in Western Kenya. The grasses were planted in plots measuring 2 m x 2 m with spacing of 30cm by 70cm in a randomized complete block design and there were three replicates. Greenhouse experiments were conducted at KALRO – Kisii. Each grass was transplanted into ten plastic pots measuring 30cm diameter and 60cm depth. The pots were arranged in rows with three replicates. Sorghum sudanensis was used as a control trap plant for C. partellus. Ten C. partellus larvae were introduced onto potted plants two weeks after transplanting. Data on the number of larvae, entry and exit holes, “leaf window”, eggs and tunnel lengths were collected from five grass stems from field and greenhouse experiments one month after planting and transplanting respectvely. The grasses were selected using simple random sampling method. Subsequent data collection was done after every two weeks for 4 months. The data obtained was subjected to ANOVA and analysed using Statistical Analysis System 2010. The means that were significant were separated using the Student-NewmanKeuls test at a significance level of p = 0.05. The results of this study showed that there were significant differences in the mean number of egg batches and eggs in both field and greenhouse experiments. In the field experiments, Sorghum sudanensis and Pennisetum sphacelatum had the highest mean number of egg batches which significantly differed from those of Sporobolus pyramidalis, Hyparrhenia tamba, Bracharia brizantha, Bracharia mulato II, Chloris gayana, Pennisetum mezianum, Hyparrhenia cymbaria and Panicum maximum. Sorghum sudanensis and Pennisetum sphacelatum had the highest mean number of entry holes. Chloris gayana had lower mean number of entry holes but this did not significantly differ from those of Sporobolus pyramidalis, Bracharia mulato II, Hyparrhenia tamba, Panicum maximum and Bracharia brizantha. Sporobolus consimilis, Hyparrhenia cymbaria and Pennisetum mezianum least attracted C. partellus for feeding in both experiments.