Cereal yield losses caused by lepidopterous stemborers at different nitrogen fertilizer rates in Ethiopia

Abstract

Field trials were carried out at three locations in the cool-wet western and one location in the semiarid eastern ecozones of the Amhara State of Ethiopia to determine the effects of nitrogen fertilizer on pest infestation and yield losses caused by lepidopterous stemborers in maize and sorghum. Three N fertilizer levels, i.e. 60, 120 and 180 kg/ ha for maize, and 41, 64, and 87 kg/ha for sorghum, were compared with a zero N treatment. The dominant pest species were the noctuid Busseola fusca (Fuller) and the invasive crambid Chilo partellus (Swinhoe). Leaf N content was positively related to N fertilizer dosage. In general, pest density, parasitism, plant growth and borer damage variables increased with crop growth stage. On sorghum, in the cool-wet western Amhara, increasing levels of N fertilizer also tended to increase pest density, plant growth and damage variables. In the semiarid ecozone, parasitism by the exotic parasitoid Cotesia flavipes Cameron tended to increase with N level. In the cool-wet ecozone, sorghum yields increased by up to 74% because of fertilization; losses caused by stemborers decreased linearly with N dosage from 49% to 36%. In maize, because of low borer densities, there were no discernable trends for pest infestation and yield losses. In the cool-wet ecozone, sorghum yields were positively related to insecticide application and plant height, and negatively to damage variables such as tunnelling and peduncle damage. In semiarid eastern Amhara, the effects of fertilizer on pest, damage and yield were low on both crops because of the higher soil fertility. The results indicate that the profitability of nitrogen fertilizer as an integrated pest management tactic in the control of cereal stemborers depends, among others, on the severity of borer damage and the soil fertility status prevailing in an area. It is concluded that N fertilizer helps minimize the impact of borers on grain yields, especially on sorghum and in the cool-wet ecozone.

The profitability of maize–haricot bean intercropping techniques to control maize stem borers under low pest densities in Ethiopia

“…Despite the importance of these crops in the country, yields are very low due to both biotic and abiotic stresses. Among the major biotic constraints are lepidopteran stem borers such as the noctuid Busseola fusca Fuller and the crambid Chilo partellus (Swinhoe), which in outbreak areas cause between 25% and 100% yield loss (Getu et al 2001;Emana and Tsedeke 1990;Gashawbeza and Melaku 1995;Wale et al 2006). In the past, national and international agricultural research institutions have placed major research emphasis on host plant resistance (Ajala et al 2001;Bosque-Pérez et al 1997), biological control Schulthness et al 1997;Zhou et al 2001) and habitat management techniques based on management of soil nutrients (Sétamou et al 1993), trap plants (Ndemah et al 2002) and mixed cropping (Chabi-Olaye et al 2005a;Schultness et al 2004).…”

Egg parasitoids of noctuid stemborers on maize in Kenya

“…Among the most important biotic constraints to maize production are lepidopteran stemborers such as the noctuid Busseola fusca (Fuller) and the invasive crambid Chilo partellus (Swinhoe) (Polaszek and Khan 1998;Seshu Reddy 1998). Various stemborer control techniques, such as chemical control, botanicals, host plant resistance and cultural control, have been researched and tested Bruce et al 2004;Ali et al 2006;Matama-Kauma et al 2006;Wale et al 2006a;Songa et al 2007). Since the 1990s, both the International Institute of Tropical Agriculture (IITA) in West Africa, and the International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya, have given increased emphasis on biological control.…”

Effect of fertilizer and crop variety on the survival of Busseola fusca (Lepidoptera: Noctuidae) in cereals in Ethiopia

“…Improving soil fertility complements pest control measures (Saroja et al, 1987). Various authors Chabi-Olaye, 2005;Mgoo et al, 2006;Wale et al, 2006a) have shown that nitrogen is associated with the survival of young stemborer larvae and the resulting pest infestation as well as the plants' tolerance to subsequent attacks. Furthermore, reports from western Africa show that the nutritional status of maize affects noctuid borer densities and the ability of the plants to compensate for pest damage.…”

“…Until very recently (Wale et al, 2006a), there was no information on the influence of soil nutrients, and especially nitrogen on various trophic levels of the cereal system in Ethiopia. Chemical fertilizers, especially nitrogen, are commonly used in northwestern Ethiopia, but previously it was not known how fertilizers affect stemborer densities in relation to the yields of cereals in these regions.…”