Abstract
The invasive African black beetle Heteronychus arator F. is a serious pest of crops in Tropical and sub Tropical regions, including East Africa. Literature on ecology of this pest in Sub Saharan Africa is scarce. Dispersal and abundance of H. arator were determined in maize fields in Njombe Region, in the Southern highlands of Tanzania, from December 2013 to May 2014. Adults of H. arator were collected monthly by hand picking and pitfall traps. Results showed that larvae were present throughout the growing season, with low population at planting and peak period coinciding with optimum soil moisture. The abundance of adults varied with time, with high peaks recorded in January. Abundance of both larvae and adults were significantly affected by fertilizer type, with high populations in farmyard manure. The type of fertilizer significantly affected dispersal of H. arator. A high number of beetles moved significantly longer distances in farmyard and inorganic fertilizer compared to bioslurry a day after release. Abundance of of beetles was negatively correlated with rainfall but positively correlated with average temperature, while abundance of larvae was positively correlated with rainfall. The results provide useful input into management of H. arator under different fertilizer practices and weather conditions.
Highlights
The African black beetle Heteronychus arator F. is a polyphagous insect attacking a wide range of cultivated crops, with a high preference for pastures (King et al 1981; Matthiessen et al 1997)
We studied dispersal spatial and temporal abundance of the beetle in patchy maize fields in Southern highlands of Tanzania in relation to fertilizer application
Two way analysis of variance (ANOVA) results showed that larval abundance was not significantly affected by fertilizer type (F(2, 54) = 2.93, p < 0.06) or month F(5, 54) = 2.29, p < 0.058)
Summary
The African black beetle Heteronychus arator F. is a polyphagous insect attacking a wide range of cultivated crops, with a high preference for pastures (King et al 1981; Matthiessen et al 1997). Heteronychus arator originated from South Africa (Venter and Louw 1978), and invaded South America and the Oceania. Heteronychus arator attacks various crops during various stages of growth, from seedling to maturity (Ahad and Bhagat 2012). Losses of up to 20–30 % of sown maize (Drinkwater 1987) and up to 70 % of potato (Venter and Louw 1978; Matthiessen and Learmonth 1995) have been reported. Each adult H. arator can attack 2–5 tubers of potato (Matthiessen and Learmonth 1995). It is a pest of phytosanitary significance and it has caused great losses where it has been introduced
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