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The influence of modern wheat production practices on Sunn pest impacts in Romania

To develop an understanding of the biology and damage (frequency, extent and impact) to wheat production from Sunn pest, Robert Loughman visited Dr Constantin Popov, Head of Crop Protection, National Agricultural Research and Development Institute Fundulea, Romania.

The pentatomid Sunn Pest causes loss of both grain yield and grain quality. Sunn pest’s feeding activity on developing wheat grain changes grain protein quality, due to enzymes in bug saliva. Among 14 Eurygaster spp. three are considered dangerous but only E. integriceps is regarded as very dangerous in Romania.

First recognised in 1924 in Romania, the worst recognised infestation occurred in 1969 when 65% of grain production was damaged. Sunn pest remains problematic with a high frequency of remnant natural woodland interspersed throughout wheat production areas as these sites offer a winter refuge habitat for Sunn pest.

Intense feeding as adults on developing cereal grains results in 40% body fat accumulation which is regarded as contributing to high rates of survival through a long hard winter diapause, among floor debris of these remnant forest areas. Local data show that pest attack is higher under dry and warm drought conditions compared with cold and wet weather. On top of the direct impact on productivity, occurrence of bug damaged grain above 2-3% affects baking performance and bug damaged grain is unacceptable to manufacturers.

Developments in agriculture were examined with Mr Christophe Huiban, a progressive farmer from south Romania. Romanian agriculture has undergone considerable development since the fall of the communist regime in 1989 but remains complex. In broad terms, agriculture exists in two forms:

  1. Former state communes that were frequently privatised through the breakup and subsequent allocation/purchase of very small land parcels to individual families for subsistence farming, many of which remain today. Small landholding subsistence agriculture remains problematic for consistent Sunn pest control.
  2. Consolidated farms areas typically around 1000-2000ha (occasionally up to 50,000ha) under current modern agricultural practice include intensive productions systems achieving 6-8t/ha. A significant influence has been “large area” farmers from western Europe (e.g. Denmark, France) that have introduced intensive production systems with crop monitoring and up to two synthetic pyrethroid sprays per season which results in effective Sunn pest control.

At present there is no conservation tillage practiced in Romania and as such no experience with this system change in terms of influencing occurrence or damage from Sunn pest. Beyond the modernisation and consolidation trends identified, system developments in wheat production to this point do not appear to have significantly influenced occurrence or practice for Sunn pest control.

To understand current crop protection strategies in Romania and how they relate to Sunn pest management Robert visited Mr Sorin Staicu, Bayer CropScience, Bucharest, the largest of the agrichemical suppliers in Romania with a market share estimated at 37%. The only recognised control is with synthetic pyrethroids ($2-6 Euro/ha depending on product) which have now replaced organophosphates.

Probably the biggest influences on Sunn pest control has been the availability of generic and proprietary synthetic pyrethroids with high efficacy. Spray thresholds have been established by Fundulea entomologists at 7 adults/m2 around late April early May (i.e. adults surviving from last season) or 5 larvae/m2 between mid May and late June (i.e. new season population). The purpose of these thresholds is to keep Sunn pest damaged below maximum allowable grain receival standards for milling grade wheat.

The recognised Romanian expertise in E. integriceps exists with Dr Constantin Popov at the National Agricultural Research and Development Institute of Romania, Fundulea. Dr Popov has records over the period 1963-2009 for the location, forest adult infestation severity, crop larval density and treated (affected) area.

This may represent a suitable resource for modelling seasonal climatic influences and infestation prediction if the data can be referenced to relevant regional temperature information. The addition of end of season pheromone trapping and adult weights could be explored for added precision.

A modelling approach to seasonal pest and disease risk prediction could give Australian researchers pertinent insights into this pest in terms of the importance of environmental conditions on out-of-season survival relative to in-season population development that may improve understanding of the potential for this pest to continue to spread and impact in wheat production areas outside its current range.