Missing temporal effects of soil insecticides and entomopathogenic nematodes in reducing the maize pest Diabrotica virgifera virgifera

Abstract

Control methods for the larvae of the maize pest Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) are known to produce inconsistent results under field conditions. To better understand the effects of plant protection products on the rootfeeding larvae, we looked for changes in efficacy of the granular soil insecticides chlorpyrifos, cypermethrin, and tefluthrin during a cropping season, as well as a fluid-applied entomopathogenic nematode Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae). Twelve field-scale experiments carried out in Hungary between 2010 and 2018 revealed that treatments, whether chemical or biological, are able to reduce D. v. virgifera. However, results were variable with failures in about a quarter of the experiments. Unexpectedly, our findings indicated only limited effect of time on treatments, meaning all products appeared capable of continuously reducing larvae during their time in the soil. Only chlorpyrifos seemed to slightly lose and tefluthrin to slightly increase efficacy over time. Nevertheless, there is no major evidence that failure of treatments is due to temporal effects. Other factors may play a larger role and merit investigation under field conditions.

A knowledge-based approach to designing control strategies for agricultural pests

“…When separating the field trials into those that demonstrated the efficacy of a product (i.e., the difference between control and treatment NIS damage values was greater than the uncertainty of the field trials) and those that did not meet this criterion, then the model was able to predict 86% of the 81 field observations proving efficacy and 95% of the 38 field observations that did not show efficacy. Variability in product performance across a limited number of field trials ( Toth et al, 2020 ) can be a major constraint on product development. A field study may fail to demonstrate efficacy for an otherwise efficacious product because of low pest pressure ( Furlan et al, 2006 ), a redistribution of the pesticide within the soil profile that occurs too quickly or too slowly depending on rainfall ( Sutter et al, 1989 ; Sutter et al, 1991 ), the use of an application strategy that limits efficacy ( Tinsley et al, 2016 ), or because too much time elapses between pesticide application and the appearance of the pest ( Sutter et al, 1989 ).…”

Phytotechnology with Biomass Production

“…The Western corn rootworm Diabrotica virgifera virgifera Le Conte is a native to North America, where it is considered as the main pest of corn (Yu et al, 2019). The pest is present in many European countries, spreading constantly year by year (Toth et al, 2020). Corn is the only crop in which high population densities can develop.…”

Biology and Management of Pest Diabrotica Species in South America

“…Rhabditid nematodes (Steinernematidae and Heterorhabditidae) have been studied to control corn rootworms for decades, often with promising results. In the field, Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) was as effective as tefluthrin in controlling Diabrotica virgifera virgifera in corn crop [119] and with a long residual action in the soil [120,121]. Seventeen native and exotic entomopathogenic nematode isolates (Steinernematidae and Heterorhabditidae) were tested against D. speciosa under laboratory and greenhouse conditions in Brazil on eggs, third (last) instars, and pupae.…”

“…High mortality rates were obtained with Heterorhabditis sp. RSC01 and JPM04, Steinernema glaseri, and Heterorhabditis amazonensis on larvae and pupae, while eggs were unaffected [121]. These nematodes are considered to have great potential to control D. speciosa in irrigated maize and potatoes [122] (Table 1).…”