An Expert System for Management of Delia coarctata (Diptera ...

An Expert System for Management of Delia coarctata (Diptera: Anthomyiidae) in the United Kingdom T. H. JONES,l J.E.B. YOUNG,' G. A. NORTON,' ANDJ. D. MUMFORD'

J. Econ.Entomol.83(5):2065-2072(1990) ABSTRACT A computer-based expert system (BULBFLY) has been developed for the management of wheat bulb fly, Delia coarctata (Fallen), in the United Kingdom. The logical structure of the decision problem is described, together with facts 'and rules necessary for the estimation of egg numbers, crop susceptibility, and control effectiveness. With this knowledge and with various levels of information supplied by the user of. BULBFLY, the expert system provides recommendations on strategic and tactical options for management of wheat bulb fly.BULBFLYgives comparative costsof the various treatments recommended, ecological and biological information on the pest, details of cultural control practices, and general advice on the safe use of insecticides. Like other knowledge-based systems in pest management, BULBFL Y offers support for practical problem solving, identification of research needs, information provision and processing, and training. KEY WORDS

Insecta, Delia coarctata, expert system, pest management

WHEAT BULBFLY, Delia coarctata (Fallen) (Diptera: Anthomyiidae), is the most serious insect pest of winter wheat in the eastern counties of the United Kingdom. In the East Anglian region alone, the crop area potentially subject to economic damage varies between 13,000 and 127,000 ha (2-17% of the total wheat area in that region) from year to year (Young 1987). Insecticides currently used against wheat bulb fly are applied as seed treatments, treatments of seedbeds, and sprays applied at egg hatch or at the first signs of plant damage. Because no single treatment gives full control, combinations of two or more treatments are normally applied, resulting in a significant cost of treatment. Weighing this treatment cost against the potential benefit of wheat bulb fly control presents the grower with a difficult decision-making problem. The decision to apply treatment is likely to become even more difficult in the future with increasing pressure to use less insecticide. One solution to the problem is to base control decisions on counts of wheat bulb fly eggs, undertaken by the Agricultural Development and Advisory Service (ADAS). However, because the egg sampling and extraction procedure is labor-intensive, an alternative means of providing advice to growers is required. With the general reduction in the public advisory sector in the United Kingdom and the requirement to charge farmers for advice, recommendations need to be specific, accurate, and

reasonably priced. The expert system, BULBFL Y, described in this paper, provides specialist advice to nonspecialist advisers; it was developed to make a significant contribution toward meeting these goals. Expert systems are computer tools for helping to solve problems and give advice. They are used in several disciplines including pest management (Jones et al. 1984, 1986; Lemmon 1986; Norton 1987; Denne 1988; Edwards-Jones et al. 1989; Heong 1990; Holt et al. 1990). These systems offer support for practical problem solving, identification of research needs, information provision and processing, and training (Mumford & Norton 1989). The three most widely used methods of structuring knowledge (knowledge representation) that can be used alone or in combination to build expert systems are rules (the most popular), semantic nets, and frames (Barr & Feigenbaum 1981, Waterman 1986). BULBFLY is a rule-based expert system. Here we describe the logical structure of the decision problem, the knowledge base (in the form of facts and rules) and the encoding of this information in computer (expert system) software. Structure of the Decision Problem

The decision points and time at which different control actions can be taken against wheat bulb fly are determined by the life cycle of the pest and the options available for control. A synopsis is presented in Fig. 1. Wheat bulb fly eggs are laid in July and August. SilwoodCentreforPestManagement, DepartmentofBiology, Oviposition occurs on the exposed soil surface of ImperialCollegeat SilwoodPark,Ascot,Berkshire SL57PY,United bare ground or under the foliage of root crops, such Kingdom. AgriculturalDevelopmentand AdvisoryService,BlockC, as sugar beet. On hatching (in January and FebGovernmentBuildings, Brooklands Avenue,CambridgeCB22DR, ruary), young larvae die unless the field has been UnitedKingdom. planted with cereals or grass. When the larvae find I

I

0022-0493/90/2065-2072$02.00/0 © 1990Entomological Societyof America

2066

JOURNAL OF ECONOMIC

Vol. 83, no. 5

ENTOMOLOGY

• as

.§

.....• M

d

:;::l ..; u

o

.....•

......

o CIl

.6 CIl

00 00