version: 20/4/2007

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Monitoring for Plant Diseases and Insects

In field crops, rational pesticide use appropriate and timely judgements are made about pest incidence.  There is an extensive literature on monitoring techniques and decision making, that has been reviewed by Mumford and Knight[1].  When appropriate decisions are combined with the most suitable (even relatively simple) RPU techniques, yield increases can be spectacular, and perhaps the greatest potential gains will be achieved by combining improved monitoring systems with better application and pesticide selection.

In crops such as cotton, over use of chemical insecticides has resulted severe resurgence of certain pests which has hampered cotton growing[2].  On the other hand, the introduction of appropriately applied insecticides to cotton in central southern Africa during the 1960s, typically more than doubled yield and improved lint quality[3].  In many countries there is considerable scope for more judicious selection of products and reducing the numbers of sprays (combined with appropriate agronomic practices).  The crucial factor is crop scouting; in Africa, simple aids such as the “peg-board”[4] have been used effectively over a long period, especially when backed up by an infrastructure for pest scouting. 

Original and improved (below, left picture) pegboards: developed as a cotton scouting aid in Zimbabwe. The system works best when scouts are trained to recognise bollworm eggs (right)

Besides simple observation, a number of well known techniques are available for monitoring pest attacks.  The Biopesticide Manual currently lists 45 pheromones and other attractants, some of which are used as pesticides in their own right, to disrupt mating of leipdopteran and coleopteran pests, or to attract insects towards treated areas or baits.  Probably the most frequent use of pheromones is as a monitoring tool to time insecticidal applications.  Simple aids such as incandescent light traps, combined with as thorough knowledge of pest biology also can be most effective.

CPB pheromone in a 'delta' trap.
This is an especially promising line of research for improved management of the cocoa pod borer in Indonesia.

The development of monitoring techniques for spores of fungal diseases is crucial for many plants, ranging from N. European field crops to cocoa.  Developments in imuno-assay techniques provide exiting methods for improved plant disease monitoring – but the spores must be sampled first. 

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Here we provide some useful links (not on this server) …

Plant Pathogens

General: Research into sampling methods etc.
Plant disease monitoring products:



Yellow sticky boards

Information on using pheromones

Pheromone traps – available product ranges
(Sprayable pheromones for mating disruption etc: http://www.certisusa.com/products/index.html )

[1] Mumford, J.D. and Knight, J.D. (1997)  Injury, damage and threshold concepts. In: Methods in Ecological and Agricultural Entomology, Eds: D.R. Dent & M.P. Walton,  CAB International, Wallingford. Ch.8, 203-220.

[2] van den Bosch (1980) The Pesticide Conspiracy.  Prism Press, Dorchester, UK, 226 pp (originally published in 1978 by Doubleday & Co., USA)

[3] Tunstall, J., and Matthews, G.A. (1966). Large scale spraying trials for the control of cotton insect pests in Central Africa.  Empire Cotton Growing Review, 43 121-139.

[4] Beeden, P. (1972)  The pegboard - an aid to cotton pest scouting. PANS 18, 43-45.