Influence of weeding regime and neem seed extract on the population of insect pests and yield of cabbage in the Guinea savannah zone

Abstract

This experiment was conducted during the 2005 and 2006 cropping seasons at the research field of the Faculty of Agriculture, University for Development Studies, on Nyankpala campus near Tamale in the Guinea savannah zone of Ghana. The objectives of the study were to determine the influence of weeding regime and application of neem seed extract (NSE) on insect pest populations and yield of cabbage. The experiment was a 3 x 5 factorial laid out in randomized complete block design with three replications. The treatments consisted of: hoe weeding every 2 or 3 weeks and unweeded control combined with applications of NSE at 2% (w/v), 5% and 10%, and Karate 2.5 EC (Lambda cyhalothrin) and water-treated control. The results indicated the occurrence of broadleaves, grasses, sedges and shrubs in order of dominance as weed species. Insect species prevalent included grasshoppers (Zonocerus variegatus [L.]), crickets (Gryllus spp.), caterpillars of diamondback moth (Plutella xylostella L.), cabbage webworm (Hellula undalis F.), and flea beetles (Phyllotreta cruciferae [Goeze]). Snails (Helix pomatia L.) were the other prevalent pests recorded. Weed biomass was affected only by weeding regime and was highest on control plots followed by plots weeded every 3 weeks and every 2 weeks, respectively. Weeding regime significantly affected the populations of insect pests on cabbage. Hoeing every 2 or 3 weeks lowered pest populations with consequent stability in plant population and increased cabbage yield more than the control plots. The 10% NSE was highly effective and gave better protection to cabbage plants against pest damage than the 5% NSE, Karate, 2% NSE and watertreated control with corresponding increase in yield and cosmetic beauty of cabbage heads. Overall however, between 5% -10% NSE can be used as an alternative to the synthetic insecticide Karate to control insect pests of cabbage. Also, weeding every 3 weeks was adequate to avoid yield loss due to weed competition.

Cabbage Production in West Africa and IPM with a Focus on Plant-Based Extracts and a Complementary Worldwide Vision

“…This is more easily done in places where land tenure and available space will allow it, such as in Nigeria, the States of Ogun and Oyo, in contrast to the highly urbanised environment of Lagos [ 45 ]. Regular weeding after transplanting, every two to three weeks, eliminates the weeds in which pest insects can find shelter [ 93 ]. Watering by hand (with a watering can or hose pipe) is known to alleviate P. xylostella infestations in cabbage [ 94 ].…”

“…In total, 19 plant species representing 12 families have been reported: Anacardium occidentale L. (Anacardiaceae) [ 118 ]; three Asteraceae species ( Ageratum conyzoides L., Chromolaena odorata L. and Synedrella nodiflora (L.) Gaertn.) [ 65 , 119 , 120 ]; one Caricaceae species ( Carica papaya L.) [ 121 , 122 , 123 ]; two Euphorbiaceae ( Jatropha curcas and Ricinus communis ) [ 38 , 65 , 119 , 124 ]; three Lamiaceae species ( Crataeva religiosa , Hyptis suaveolens and Ocimum gratissimum ) [ 65 , 118 , 124 , 125 , 126 , 127 ]; one Leguminosae/Fabaceae ( Cassia sophera ) [ 65 ]; one Liliaceae ( Allium sativum ) [ 128 , 129 ]; one Meliaceae ( Azadirachta indica ) [ 25 , 52 , 62 , 71 , 93 , 120 , 121 , 122 , 123 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 ]; two Myrtaceae ( Callistemon viminalis and Melaleuca leucadendron ) [ 126 ]; one Poaceae ( Cymbopogon schoenanthus (L.) Spreng.) [ 138 ]; one Rutaceae species ( Zanthoxylum xanthoxyloides ) [ 118 ] and two Solanaceae ( Capsicum frutescens and Nicotiana ta...…”

“…one Meliaceae (Azadirachta indica) [25,52,62,71,93,[120][121][122][123][130][131][132][133][134][135][136][137]; two Myrtaceae (Callistemon viminalis and Melaleuca leucadendron) [126]; one Poaceae (Cymbopogon schoenanthus (L.) Spreng.) [138]; one Rutaceae species (Zanthoxylum xanthoxyloides) [118] and two Solanaceae (Capsicum frutescens and Nicotiana tabacum) [65,119,128,129,139,140].…”

“…Neem (A. indica) extracts are the only ones to have been evaluated or employed against most insect pests reported for cabbage in all the countries of West Africa (Table 3), whether coastal or Sahelian, e.g., Benin [130], Côte d'Ivoire [116], Gambia [71], Ghana [93,120], Nigeria [131], Senegal [25,132] and Togo [52,62,122,123,[133][134][135][136][137]. This species has been used in the form of aqueous extracts, hydroethanol extracts, methanol extracts and oils.…”

“…Species such as N. tabacum and neem A. indica, have long been known for their insecticidal properties against many crop pests [25,52,62,71,93,[120][121][122][123][135][136][137]. They were found to dominate the census of plants used on the African continent.…”