Environ Sci Pollut Res DOI 10.1007/s11356-016-7692-z RESEARCH ARTICLE Risk assessment of maize damage by wireworms (Coleoptera: Elateridae) as the first step in implementing IPM and in reducing the environmental impact of soil insecticides L. Furlan1 & B. Contiero 2 & F. Chiarini1 & M. Colauzzi1 & E. Sartori1 & I. Benvegnù1 & F. Fracasso 1 & P. Giandon3 Received: 27 April 2016 /Accepted: 12 September 2016 # The Author(s) 2016. This article is published with open access at Springerlink.com Abstract A survey of maize fields was conducted in north- double crops, A. sordidus as prevalent damaging species, east Italy from 1986 to 2014, resulting in a dataset of 1296 and surrounding landscape mainly meadows, uncultivated records including information on wireworm damage to maize, grass and double crops. The multifactorial model also showed plant-attacking species, agronomic characteristics, landscape how the simultaneous occurrence of two or more of the afore- and climate. Three wireworm species, Agriotes brevis mentioned risk factors can conspicuously increase the risk of Candeze, A. sordidus Illiger and A. ustulatus Schäller, were wireworm damage to maize crops, while the probability of identified as the dominant pest species in maize fields. Over damage to a field with no-risk factors is always low (<1 %). the 29-year period surveyed, no yield reduction was observed These results make it possible to draw risk maps to identify when wireworm plant damage was below 15 % of the stand. A low-risk and high-risk areas, a first step in implementing be- preliminary univariate analysis of risk assessment was applied spoke IPM procedures in an attempt to reduce the impact of to identify the main factors influencing the occurrence of dam- soil insecticides significantly. age. A multifactorial model was then applied by using the significant factors identified. This model allowed the research Keywords Agriotes brevis . Agriotes sordidus . Agriotes to highlight the strongest factors and to analyse how the main ustulatus . Wireworms . Maize . Damage risk factors . factors together influenced damage risk. The strongest factors Multifactorial model . Mutual-fund were: A. brevis as prevalent damaging species, soil organic matter content >5 %, rotation including meadows and/or Introduction Responsible editor: Philippe Garrigues The implementation of integrated pest management (IPM) * L. Furlan strategies against wireworms has been extremely difficult [email protected] due to the lack of available information on the key aspects of the species concerned (Furlan 2005). IPM strategies have B. Contiero [email protected] not played a significant role in maize and other arable crops to date (Furlan and Kreutzweiser 2015) despite the strong nega- P. Giandon [email protected] tive impact of using soil insecticides (i.e., neonicotinoids) to control wireworms (van der Sluijs et al. 2015). EU Directive 1 Veneto Agricoltura, Viale dell’Università, 14, 35020 Legnaro, PD, 2009/128/EC on the sustainable use of pesticides made it Italy compulsory to implement IPM for all annual crops in 2 Dipartimento di Medicina Animale, Produzioni e Salute—Università Europe from January 2014. Therefore, accurate information degli Studi di Padova, Viale dell’Università, 16, 35020 Legnaro, PD, about IPM strategies for annual crops is urgently needed, but Italy this information must take into account that arable farming has 3 ARPAV Servizio Osservatorio Suolo e Bonifiche, Via S. Barbara, few resources in terms of income, labour and technology. In 5/a, 31100 Treviso, TV, Italy order to implement IPM at low cost, it is important to establish Environ Sci Pollut Res the risk factors that cause an increase in wireworm population Damage assessment levels and the consequent damage. This research aimed to: When random untreated maize strips/plots (3 or 4.5 m wide) – find out the main entomological, agronomical and climat- had been sown alternately with treated strips/plots, the most ic factors that significantly increase the risk of wireworm effective insecticides available were used (Table 2). damage; One litre of the fungicide Celest® XL (metalaxil-m + – assess the most probable maize damage level in the pres- fludioxonil) per ton of seed was mainly used to treat all ence of one or more risk factors; and the maize seeds planted. At the 2–3 and 6–8 leaf stages, – establish the most effective procedure to implement IPM two sub-plots of 20 m × 4 rows of maize per portion of of wireworms in maize, considering the major risk factors untreated field (0.1–0.2 ha) or untreated strip (3– that increase wireworm populations. 6m×100–300 m) were chosen at random and the plants observed. During plot trials, in the two central rows of each untreated plot, all plants were counted and divided into Bhealthy^ and Bdamaged^; the plots covered an area of 15–18 m × 1.5 m. The location and the number of sub- Materials and methods plots were the same in both the untreated/treated strips and completely untreated fields. In order to assess wireworm An extensive survey of maize fields was conducted in damage on emerged plants, typical symptoms (e.g., wilting northeast Italy (area covered: 45.64 °N, 12.96 °E and of central leaves, broken central leaf due to holes in the 45.05 °N, 11.88 °E) from 1986 to 2014 (29 consecutive collar, wilting of whole small plants) were assessed and years), resulting in a dataset of 1296 records. Each record the soil around the unhealthy plants was dug up to a depth includes all the information in Table 1. The fields sur- of 5–6 cm; any larvae found near the collar were collected veyed represent a balanced sample of agronomic condi- and identified. Wherever maize plants were missing from tions in northeast Italy. All the entomological (collection the rows, the soil was dug up in order to assess possible of larvae, species determination) and agronomic (crop wireworm damage to seeds and/or emerging seedlings. stand and damage, cultivation practises, yield) informa- Total plant damage was calculated as the sum of damaged tion was directly collected with at least six inspections emerged plants and seeds. In order to establish the effect of per field each year. Just 6 % of the rotation and landscape wireworm damage on yield, the same observations were data was from farmer interviews (i.e., previous year data made on the treated strips/plots, when used. Finally, the regarding fields reported for the first time and new to the strips and the plots were harvested and the maize grain authors). Data for the other parameters were collected weighed. Maize grain samples were collected and their hu- from official regional databanks (see Soil properties). midity measured with a Pfeuffer-Granomat (the same ma- The majority of the fields surveyed were untreated (no chine was used for all samples each year). The four fields soil insecticide or insecticide-coated seeds), except for in which maize stands were irregular and damaged due to those seeded alternately, with untreated and treated maize factors other than wireworm activity (e.g., bird damage, low in strips/plots (particularly where higher wireworm densi- emergence due to low soil moisture, flooding) were not ties were recorded with bait trapping method [Furlan considered. In order to isolate the Bwireworm damage 2014]), and those inspected after severe damage was re- effect^, analysis excluded the five fields under considerable ported and found to be treated with soil insecticides. Land pressure from factors other than wireworms (e.g., other par- treated with soil insecticides (including insecticide-coated asites such as viruses or rootworms, Diabrotica virgifera seeds) accounted for 3.96 % of the total land surveyed. virgifera LeConte). Fields in which the general conditions Every year, any field suffering from newly reported wire- were good, but the soil insecticide had not worked properly worm damage was added to a database of farms being and the stand of treated maize plots was not optimal were continuously surveyed (about 100 ha a year with few ex- not used to evaluate the effect on yield (two cases only). ceptions) in order to increase the records for severe dam- Only damage assessments from untreated strips were regis- age. These additional fields accounted for 8.15 % of the tered in the database (the mean of the sub-plot assessments entire dataset. A total surface area of 4646 ha was studied for each considered field). When farmers reported wireworm over 29 years; the mean was 160 ha per year with a SD of outbreaks, we included any fields that could be inspected 121.3 ha. A minimum of 15 ha was studied in 1991 and a within the sixth leaf stage whenever damage could be reli- maximum of 489 ha in 2014. Therefore, the survey com- ably assessed and the species identified (95 % of reported prised a random sample of maize fields in the investigated cases were included). Larvae collected from damaged plants area with a moderately higher incidence of cases of con- were used to attribute the damaging species to each record; siderable wireworm damage. fields were included in the database when a minimum of Environ Sci Pollut Res Table 1 List of the variables included in the database Risk factors Variable Type Classification Maize cultivated land (%) (ha) Site identification Year Qualitative 1986–2014 Farm Qualitative Municipality Qualitative Province Qualitative BL, PD, RO, TV,VE, VI, GO, PN, UD Region Qualitative Veneto, Friuli Venezia Giulia 4509.69, 136.7 Plot Qualitative Field Qualitative GPS coordinate