Effect of cowpea monocultures and polycultures with sorghum and greengram on predatory arthropods

Abstract

Prior to implementing biological control, knowledge on availability of the possible enemies of pest(s) is important. Therefore, as part of a larger on-farm study whose main objective was to develop a farmerfriendly package for the management of cowpea pests, the diversity and abundance of insect predators within cowpea cropping systems (sole crops and intercrops) were monitored at three diverse locations in eastern Uganda. Coccinellids, syrphid larvae, spiders, Orius sp. and earwigs were observed at all locations. Abundance of Coccinellids and syrphid larvae were not influenced by the cowpea genotype nor cropping systems. Contrastingly, the abundance of predatory Orius sp., spiders and earwigs differed significantly among the cowpea cropping systems, being more common in the cowpea pure stands and cowpea + greengram than in the cowpea + sorghum intercrops.

Influence of intercropping with spring cereals on the occurrence of pea aphids (Acyrthosiphon pisum Harris, 1776) and their natural enemies in field pea (Pisum sativum L.)

“…This could be the reason for an earlier decline of pea aphid colonies in mixtures than in monocultures. These results are contrary to Nampala et al (2008), who compared the occurrence of several natural enemies of cowpea pests in cowpea monoculture and its mixtures with sorghum and greengram. They stated that the abundance of syrphid larvae was not influenced by the fact if the cowpea was grown in mixture or in monoculture.…”

“…In this study, the colony decline started either markedly earlier (2008, 2010PO, 2010 or was clearly sharper (2009( , 2010 in mixtures compared to monoculture. Hence, differences in the pea aphid occurrences between monoculture and mixtures became significant two or three weeks after recording the first living aphids on pea inflorescences.…”

“…Peak aphid densities were higher in monoculture than in mixtures only in two trials (2008 and2010 PO). In other two trials the peaks were recorded in T60P40 andT60S40 and/or in T60P40 (2009 and/or 2010 RA).…”

“…On June 23 a significantly higher percentage of colonies with one or more syrphid larvae was recorded in T40P60 in comparison with T100 (F 4, 70 = 5.0259; P = 0.00128) and in June 29 the Table 3. Mean percentages (%) of aphid colonies (of 10-20 individuals in size) with one or more syrphid larvae (2008( , 2009( , 2010( PO, 2010 The mean values in columns are not significantly different (Tukey's test; P < 0.05); N = 15 percentage values per treatment (5 per replication); SD = standard deviation percentages were significantly higher in all mixtures compared to T100 (F 4, 70 = 6.5435; P = 0.00016). In contrast to the data acquired in previous years the percentages of aphid colonies with syrphid larvae were markedly higher in PO trial.…”

Capability of <i>Forficula auricularia</i> linnaeus (Dermaptera : Forficulidae) to prey on<i> Aphis craccivora</i> koch (Homoptera : Aphididae) in eastern and Central Africa.

“…As previously highlighted, F. auricularia is among the abundant predators commonly associated with aphid infestations in eastern Uganda (Nampala et al, 1999) and in eastern DRC (Munyuli et al, 2007 ;Munyuli et al, 2008). However, its effectiveness as good predator is unknown in the region.…”