Abundance and dispersal of the African black beetle, (heteronychus arator f.) (coleoptera: scarabaeidae) in Njombe region
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Date
2016
Authors
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Journal ISSN
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Publisher
Sokoine University of Agriculture
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. Abundance and dispersal of H. arator were
determined in maize fields in Njombe Region, Southern highlands of Tanzania, from
December 2013-May 2014. Soil sampling was done monthly to determine larvae
abundance of H. arator. Similarly adults 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 sampling time, high peaks recorded during
the onset of rainfall. Abundance of both larvae and adults were significantly (P < 0.001)
affected by fertilizer type. High populations were observed in farmyard manure. Dispersal
of H. arator was significantly (P < 0.001) affected by fertilizer type. A high number of
beetles moved significantly longer distances in bio slurry than farmyard and inorganic
fertilizer. The number of beetles significantly decreased with increase in rainfall (e = -
0.011, P <0.001, Exp [P] = 0.989). On the contrary, average temperature was positively
associated with number of beetles [e = 0.748, P< 0.001, Exp (P) = 2.11], Larval
abundance was significantly associated with rainfall [e = 0.0045, P < 0.03, Exp
(P) = 1.004]. To study damage and control of H. arator, a separate experiment was set up
with un treated, strip tillage, trap crop and insecticides. Results showed that damage by H.
arator progressed from seedling to milk stage of maize in all plots. H. arator significantly
(P < 0.001) affected above ground biomass, cob length, seed weight and grain yield but
not cob weight of maize. Damage however differed significantly among treatments
(P < 0.001) and across seasons (P < 0.001). Least damage was recorded in insecticide
treated plots, and highest in untreated plots. The interaction between control method and time affected damage significantly (P < 0.001).
The results provide useful input into
management of H. arator under different fertilizer practices and weather conditions.
Description
Master of Science in Crop Science
Keywords
African black beetle, Heteronychus arator f., Maize production, Fertilizer treatments