Adjuvants to improve aerial control of the citrus mealybug Planococcus citri (Hemiptera: Pseudococcidae) using entomopathogenic nematodes
Date
2013-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Cambridge University Press - CUP
Abstract
The citrus mealybug, Planococcus citri, is a highly destructive pest of citrus,
occurring only in the aerial parts of plants. Humidity will be one of the key
factors to consider when using entomopathogenic nematodes (EPN) as
biological control agents. Different adjuvants can be added to suspensions of
EPNs, to improve control as a foliar application. An aqueous suspension
containing Heterorhabditis zealandica and 0.3% Zeba® significantly increased
P. citri mortality by 22% at 80% relative humidity (RH) with a temperature cycle
starting at 22°C for 14 h and 11°C for 11 h. The same polymer formulation was
tested for Steinernema yirgalemense and mortality of P. citri increased by 21% at 60% RH and by 27% at 80% RH. The addition of Nu-Film-Pw and Zebaw to
H. zealandica suspensions did not significantly retard application run-off on
citrus leaves. The combination of Nu-Film-P® and Zeba®, however, was able to
significantly retard sedimentation, increasing the average number of nematodes deposited on 2-cm² leaf discs by 10 nematodes. In an aqueous suspension, nematodes settle rapidly to the bottom, resulting in an uneven distribution of nematodes. Xanthan gum, at a concentration of 0.2%, was highly effective at retarding sedimentation, with 72% of the initial nematode number still in suspension after 1 h. Zeba®, at a concentration of 0.3%, despite not being as effective as Xanthan gum, nevertheless still retarded sedimentation significantly. This is the first report of the potential of Nu-Film-P® and Zeba® to improve EPN performance against P. citri when used above ground in citrus orchards.
Description
Keywords
Citrus mealybug -- Biological control -- South Africa, Citrus -- Diseases and pests-- Biological control -- South Africa, Nematodes as pest control agents -- South Africa, Insect nematodes -- South Africa
Citation
Van Niekerk, S. & Malan, A.P. 2013. Adjuvants to improve aerial control of the citrus mealybug Planococcus citri (Hemiptera: Pseudococcidae) using entomopathogenic nematodes. Journal of Helminthology, FirstViewArticle, doi:10.1017/S0022149X13000771.