Side effects of selected insecticides on the <Emphasis Type="Italic">Tuta absoluta</Emphasis> (Lepidoptera: Gelechiidae) predators <Emphasis Type="Italic">Macrolophus pygmaeus</Emphasis> and <Emphasis Type="Italic">Nesidiocoris tenuis</Emphasis> (Hemiptera: Miridae)

Tuta absoluta is a pest native to South America that produces significant damage to tomato crops and was first detected in Europe in late 2006. Data obtained during 2008 from commercial tomato crops in which IPM was applied suggested that good pest control was possible through the combined action of the predatory mirid bugs Macrolophus pygmaeus and Nesidiocoris tenuis and the use of selective insecticides. The aim of our study was to evaluate the lethal and sublethal side effects of three of the insecticides most widely used to control T. absoluta on these predators: azadirachtin, spinosad and indoxacarb. Seven days after applying the treatment at the maximum recommended field rates, the mortality produced by indoxacarb ranged from 28% for nymphs of M. pygmaeus to 77% for females of N. tenuis and were significantly higher than those produced by azadirachtin, spinosad and the control (<13%). However, indoxacarb did not affect the number of descendants of females exposed to residues during the last days of their preimaginal development. In contrast, spinosad significantly reduced the offspring of M. pygmaeus and azadirachtin significantly reduced the offspring of N. tenuis females. The sublethal effects of azadirachtin and spinosad on predator reproduction should therefore not be ignored. This information could be useful when selecting the most appropriate insecticide to control T. absoluta in greenhouses and field crops in which M. pygmaeus and N. tenuis are used as biological control agents.     

Few indirect effects of baculovirus on parasitoids demonstrate high compatibility of biocontrol methods against Tuta absoluta

BACKGROUND

Combining different biocontrol agents, particularly micro- and macroorganisms, can contribute to new and sustainable pest control approaches. Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive pests of solanaceous crops. An emerging management strategy consists of biological control using microbial insecticides such as baculoviruses, but with limited efficacy. Thanks to their high target specificity, baculoviruses can be used simultaneously with natural enemies such as parasitoids for improved control of T. absoluta. However, potential indirect nontarget effects of baculoviruses on parasitoids can result from overlapping resource requirements. We assessed whether ovipositing parasitoid females discriminated against virus-treated hosts and examined the outcome of within-host competition between the hymenopteran parasitoids Necremnus tutae (Reuter) (Eulophidae) and Dolichogenidea gelechiidivoris Marsch (Braconidae), and the Phthorimaea operculella granulovirus (PhopGV, Baculoviridae) that infects T. absoluta larvae.

RESULTS

Female D. gelechiidivoris discriminated against virus-treated hosts, whereas N. tutae did not. We found few indirect virus-related effects depending on the species, the sex, and the time of virus treatment. Effects were ambivalent for D. gelechiidivoris offspring and ranged from increased male longevity when infection occurred before parasitization to reduced emergence and male longevity when infection occurred after parasitization. N. tutae offspring showed a longer development time and shorter male longevity when they developed in virus-treated hosts.

CONCLUSION

The virus had a low impact on parasitoid offspring. In rare cases, adverse effects were detected; however, the low magnitude of these effects is unlikely to reduce the fitness of parasitoid offspring, therefore both parasitoids seem compatible with the baculovirus for control of T. absoluta. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Stratified sampling in fruit orchards using cluster-based ancillary information maps: a comparative analysis to improve yield and quality estimates

Precision Agriculture - Estimation of yield or other fruit quality parameter is of great interest to farmers to decide on management actions just before harvesting and, in any case, to anticipate...     

Mobile terrestrial laser scanner applications in precision fruticulture/horticulture and tools to extract information from canopy point clouds

LiDAR sensors are widely used in many areas and, in recent years, that includes agricultural tasks. In this work, a self-developed mobile terrestrial laser scanner based on a 2D light detection and ranging (LiDAR) sensor was used to scan an intensive olive orchard, and different algorithms were developed to estimate canopy volume. Canopy volume estimations derived from LiDAR sensor readings were compared to conventional estimations used in fruticulture/horticulture research and the results prove that they are equivalent with coefficients of correlation ranging from r = 0.56 to r = 0.82 depending on the algorithms used. Additionally, tools related to analysis of point cloud data from the LiDAR-based system are proposed to extract further geometrical and structural information from tree row crop canopies to be offered to farmers and technical advisors as digital raster maps. Having high spatial resolution information on canopy geometry (i.e., height, width and volume) and on canopy structure (i.e., light penetrability, leafiness and porosity) may result in better orchard management decisions. Easily obtainable, reliable information on canopy geometry and structure may favour the development of decision support systems either for irrigation, fertilization or canopy management, as well as for variable rate application of agricultural inputs in the framework of precision fruticulture/horticulture.     

Characterization of biotype T ofBemisia tabaci associated withEuphorbia characias in Sicily

The T biotype ofBemisia tabaci (Gennadius, 1889), a population found colonizingEuphorbia characias L. plants on the Nebrodi-Peloritani mountains in Sicily, was biologically characterized. The minimum development time was 29.7 days at 28°C. Based on the regression of 1/dayvs T, the rate of development was calculated as 0.00206, the theoretical lower temperature threshold for development as 9.3°C, and the sum of effective temperatures as 485.1. At 25° C, egg-to-adult development was significantly shorter onDatura stramonium (30.1 days) than on eitherEuphorbia pulcherrima orEuphorbia characias (35.6 and 35.4 days, respectively). The fourth instar nymphs grown onD. stramonium had the typical oval outline and seven pairs of dorsal setae located on cone-like processes, often barely visible. The fourth instar nymphs and their pupal cases grown onE. characias had the outline deformed by the presence of hairs on the lower surface of the leaf. The pupae onD. stramonium were significantly larger (both longer and wider) than those reared onE. characias; on both host plants, female pupae were significantly larger than male ones. Analysis of variance showed that width of females onD. stramonium was significantly larger than the width of those reared onE. characias. Attempts at courtship between T- and Q-biotypes were observed, but adults from different biotypes were never seen mating. Only males were obtained from the seven heterologous crossing attempts, either way, whereas homologous, control breeding produced males and females. The T biotype was able to transmitTomato yellow leaf curl Sardinia begomovirus (TYLCSV) fromD. stramonium toD. stramonium, from tomato to tomato and from tomato toD. stramonium. Attempts to transmit TYLCSV fromD. stramonium to tomato were unsuccessful. The transmission efficiency was significantly lower when tomato was the test plant. The diverse biology and ecology of the T biotype confirm that it is genetically different from most Mediterranean biotypes. This paper is dedicated to the dear memory of our colleague Dr Claudio Arnò, who died on March 12, 2004, while this paper was being written.     

Growth and blood chemistry of Atlantic halibut (<Emphasis Type="Italic">Hippoglossus hippoglossus</Emphasis> L.) in relation to salinity and continuous light

In order to study the possible interactive effects of salinity and photoperiod on growth, feed conversion, and blood chemistry in juvenile halibut, 2,604 (initial mean weight 26.8 g ± 0.2 SEM) juvenile halibut were exposed to six different combinations of salinities (13, 21, or 27‰) and photoperiods [continuous light, C and simulated natural photoperiod (65°N), SNP] for 129 days. Improved (10–20%) growth and 10–24% higher feed conversion efficiency were observed at low and intermediate salinities compared to the high salinity groups. Improved feed conversion efficiency (20%) and temporary growth enhancing effects (10%) of continuous light were observed, but effects faded out as day length in the simulated natural photoperiod group increased. No interactive effects of photoperiod and salinity on growth feed conversion or measured blood chemistry variables (blood sodium, pH level, haematocrit, bicarbonate content, and total carbon dioxide). It is suggested that juvenile Atlantic halibut should be reared at low and intermediate salinities and at continuous light, as this will improve growth and increase feed conversion efficiency.     

Comparison of Neospora caninum distribution, parasite loads and lesions between epidemic and endemic bovine abortion cases

It has been suggested that the abortion herd pattern could influence bovine foetal neosporosis. Here, a comparison of (i) Neospora caninum DNA-detectability by PCR, (ii) N. caninum-associated lesions and (iii) parasite loads in target organs was made between epidemic and endemic abortion cases. We observed that N. caninum DNA was predominantly detected in more than one organ in the foetuses from herds with epizootic rather than endemic abortion cases (P<0.05, Fisher F-test). The highest parasite burdens were found in the heart in foetuses from outbreaks of epidemic abortion and in the brain in endemic cases (P<0.05, Kruskal-Wallis H-test). Moreover, foetuses from epidemic outbreaks had significantly higher parasite burdens in heart (P<0.05, Mann-Whitney U-test) than endemic abortion cases. Epidemic abortion cases showed higher lesion frequencies in liver (P<0.05, Fisher F-test). This report confirms that the abortion herd pattern is an important factor that influences pathogenesis in natural N. caninum infections.