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]

Thomisidae: Oxytate sp.

Spiders in Agro-Ecosystems

Spiders in cotton orchards

Spiders in macadamia orchards

Spiders in citrus orchards

Spiders in pistachio orchards

Spiders in strawberry fields

Spiders on grapes

Spiders as predators of termites

Spiders as predators of mites

Tetragnathidae: Tetragnatha sp