IOBC/wprs Bulletin Vol. 28(2) 2005

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Diabrotica beetles are among the most important insect pests of maize production in the
United States, where 10 to 12 million hectares of maize are treated annually with soil
insecticides to protect the crop from larval damage. Crop losses and control costs attributed to
rootworms approach $1 billion annually (Krysan & Miller 1986). So far, serious yield losses
in Europe have been reported from Serbia, Hungary, Croatia, and Romania (Kiss et al.
2004a). It is therefore evident that D. v. virgifera has the potential to significantly change
European maize production practices. As many farmers, seed maize companies, customers
and environmental bodies are concerned about the spread of D. v. virgifera, sustainable
integrated control strategies are urgently needed and those options are summarised.
Material and methods
Four main options for the development of an integrated pest management of D. v. virgifera
could be considered: (1) cultural practises, (2) biological control, (3) host plant tolerance
and/or host plant resistance, and (4) selective chemical control measures. These options
were reviewed in the context of their feasibility and in terms of minimizing hazards to
environmental, crop and human health. This was based on a review of North American
studies on IPM of Diabrotica spp. (Toepfer & Kuhlmann 2004a), and on information gained
from the European research project DIABROTICA QLRT-1999-01110 (Vidal et al. 2004),
the FAO activities (Edwards et al. 1999, Kiss 2004c), the Diabrotica subgroup of the
IOBC/IWGO (Berger 2001) and the IPM guidelines of the IOBC (Boller et al. 1997).
Results and discussion
Option 1: Cultural control practises
Cultural practises such as crop rotation, tillage systems, planting and harvesting date,
modifying the soil environment or irrigation might be adopted to support the growing the
maize or to prevent/decrease the outbreaks of pest insects (Toepfer & Kuhlmann 2004a). Crop
rotation is a major non-chemical control option for preventing population increases of D. v.
virgifera (Ostlie & Noetzel 1987, Levine & Oloumi 1991, Nelson et al. 1994), and is required
by the IPM guidelines of the IOBC for maize (Boller et al. 1997). Diabrotica v. virgifera is
univoltine and its larvae require maize for their development. From experiences in the United
States (Levine & Oloumi 1991, Gray et al. 1998), it is expected that crop rotation will be the
major method to prevent larval damage in Europe (Kiss et al. 2004b). In principle, all possible
crops, fallows or vegetables can be rotated with maize for D. v. virgifera management.
However, certain crops might be less promising in long term rotation with Diabroticainfested
maize fields, such as soybean (Glycine max) or monocotyledonous crops. About 21
Poaceae are known to serve to some degree as secondary food plants for D. v. virgifera larvae
(Branson & Ortman 1967, Branson & Ortman 1970, Moeser 2003) and adults feed on nearly
every pollen source (Levine et al. 2002, Hatvani & Horvath 2002, Moeser 2003). However,
larval damage on cultivated Poacean plants other than maize has not yet been recorded.
In the common United States rotation system maize-soybean-maize, D. v. virgifera
started to develop behavioural resistance by laying eggs in soybean fields, and larval
development occurred if maize was planted in the following year (Gray et al. 1998, Levine et
al. 2002). In a four-year crop rotation trial in Hungary (Kiss et al. 2004b), the adult
emergence in maize after soybean was found to be much lower than in maize-after-soybean
fields in Indiana, USA (Barna et al. 1998). And finding few emerging adults in maize after
soybean (or other non-maize crops) does not necessarily imply an adaptation of the population
to the rotation. A part of the D. v. virgifera population naturally immigrates to non-maize crop