South Africa is the world’s fourth-largest producer of avocado
(Persea americana Mill.) The frequent build-up of pest populations and
their control are a major factor in the effective and economic production of
avocados. Spiders as one of the predators commonly found in orchards and could
play a role in the natural control of pest species. Research indicated an
increasing interest in, and recognition of spiders as control agents of insects
and mites. A single spider species may not be able to control a single pest
species but spider assemblages can be effective in stabilizing pest populations.
However, a buffering effect of spiders can be achieved through the combined
activities of a variety of species in a given habitat. Studies indicated that
spiders play an important role in the suppression of pests in a variety of
orchards. Little is known about spider assemblages on avocados both
locally and elsewhere. The only other study of spiders inhabiting avocado
orchards was done in Israel to determine their role as natural enemies of the
giant looper Boarmia (Ascotis) selenaria Schiff. In South Africa at
least 30 species of mites and insects attack avocado. To determine the presence
and diversity of predator species a comprehensive survey of arboreal spiders
made over a period of a year from two cultivars of avocado from two farms in the
Mpumalanga Province of South Africa. It forms part of the South African National
Survey of Arachnida (SANSA) of agroecosystems . The spiders were sampled fortnightly from ten trees per orchard
using dichlorvos as a knock-down spray. A total of 3715 spiders represented by
26 families, 68 genera and 90 species were recorded. The Salticidae was the most
abundant family and represented 31% of all spiders collected followed by the
Thomisidae with 24% and the Tetragnathidae with 12%. The thomisid Oxytate
argenteooculata (Simon, 1886) was the most abundant species representing
22% overall followed by Thyene coccineovittata Peckham & Peckham
with 12%, T. natali Peckham & Peckham with 11% and Tetragnatha
subsquamata Okuma 1985 with 9%. The families richest in species numbers
were the Araneidae with 20 species, followed by the Salticidae (14) and the
Thomisidae (12). The wandering spider dominated the fauna, representing 77% of
all individuals collected while 23% were web builders. Further reading: Dippenaar-Schoeman, A.S., Van den Berg, A.M., Van den
Berg, M.A. & Foord, S.H. 2005. Spiders in avocado orchards in the
Mpumalanga Lowveld of South Africa: species diversity and abundance (Arachnida:
Araneae). African Plant Protection 11:8-16. [ Spiders in avocado orchards.pdf] | 
