Performance of Chaetosiphon fragaefolii (Hemiptera: Aphididae) in Different Strawberry Cultivars

The green aphid Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae) is one of the most important pests of strawberry production systems worldwide. One of the fundamental points for developing management strategies for this aphid is the understanding of its population growth since this allows predictions about future population peaks and which are the most appropriate hosts for its survival and reproduction. Thus, the goal of this study was to evaluate the biological and population growth parameters of C. fragaefolii in four strawberry cultivars (Albion, Aromas, Camarosa, and San Andreas). The highest survival of the nymph stage was observed in 'San Andreas' (87%) and the lowest in 'Camarosa' (43%). 'Albion' had the highest net reproductive rate (R₀ = 6.39) and the mean time for the population to double in number (TD = 5.61), thus presenting the best reproductive parameters for C. fragaefolii. 'Camarosa' and 'Aromas' had the lowest R₀ values (2.65 and 2.70, respectively) and the highest TD values (10.89 and 10.34, respectively). We conclude that antibiosis mechanisms are involved in the resistance process of 'Camarosa' to C. fragaefolii. The characterization and the use of resistant cultivars can be an essential strategy to assist aphid management.

Influence of Trichomes in Strawberry Cultivars on the Feeding Behavior of Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae)

Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae) is the predominant aphid in strawberry (Fragaria × ananassa Duchesne) production systems in Brazil. This pest species directly damages the plants and is also responsible for spreading viruses. Further, C. fragaefolii often renders strawberry cultivation unviable, because of its high reproductive rate, as well as the large number of individuals generated through parthenogenesis. The present study aimed to (1) evaluate the feeding behavior of C. fragaefolii in four strawberry cultivars (Albion, Aromas, Camarosa, and San Andreas) and (2) identify the resistance factors associated with the number and type of trichomes in the cultivars, and also its effect on the feeding behavior of C. fragaefolii, using the electrical penetration graph (EPG) technique. The results revealed an intrinsic relationship between the number of trichomes on the cultivar and feeding behavior of C. fragaefolii. A higher number of trichomes, both tector and glandular, was observed in Albion compared to that of other cultivars, resulting in a longer no probing (Np) period per insect, and a longer Np phase. A relatively short phloem phase and ingestion time of the phloem sieve elements were also observed in Albion. These results suggest that the trichomes act as a physical barrier creating difficulties for C. fragaefolii to feed, thereby altering its feeding behavior in the four cultivars studied.

Biological parameters and fertility life table of Aphis forbesi Weed, 1889 (Hemiptera: Aphididae) on strawberry

This study provides the first contribution of the biology and life table of Aphis forbesi Weed, 1889 (Hemiptera: Aphididae), an important strawberry pest throughout the world. This species lives in the crown and leaf petioles of the plant. It is difficulty to rear this species in laboratory due to protocooperation with ants observed only in the field. We studied the life cycle of A. forbesi on the leaves of the Albion strawberry cultivar at 25 ± 2 °C, 60 ± 10% relative humidity, and a 12-h photophase. The experiment was randomised with 100 replicates. The parameters of the fertility life table were calculated using TabVida. In the population studied, 25% and 46% had four and three instars, respectively. A mean of 1.43 nymphs per female per day was generated. The mean reproductive period was seven days and the mean longevity was 10 days. In every 11 days there is a generation of A. forbesi, where each female has the potential to generate between 6 to 9 individuals daily, increasing its population by 1.2 times. The average life cycle was 16.8 days. High viability observed in all instars and the resulting values of R0, rm and λ suggest that A. forbesi has the capacity to increase their numbers in a short period of time, while generating high populations in strawberry crops, requiring differential management.

Paecilomyces niveus Stolk & Samson, 1971 (Ascomycota: Thermoascaceae) as a pathogen of Nasonovia ribisnigri (Mosley, 1841) (Hemiptera, Aphididae) in Brazil

Nasonovia ribisnigri is a key pest of lettuce (Lactuca sativa L.) in Brazil that requires alternative control methods to synthetic pesticides. We report, for the first time, the occurrence of Paecilomyces niveus as an entomopathogen of the aphid Nasonovia ribisnigri in Pinhais, Paraná, Brazil. Samples of mummified aphids were collected from lettuce crops. The fungus P. niveus (PaePR) was isolated from the insect bodies and identified by macro and micromorphology. The species was confirmed by sequencing Internal Transcribed Spacer (ITS) rDNA. We obtained a sequence of 528 bp (accession number HQ441751), which aligned with Byssochlamys nivea strains (100% identities). In a bioassay, 120 h after inoculation of N. ribisnigri with pathogenic P. niveus had an average mortality of 74%. The presence of P. niveus as a natural pathogen of N. ribisnigri in Brazil suggests that it may be possible to employ P. niveus to minimize the use of chemical insecticides.

Aphid Species and Population Dynamics Associated with Strawberry

Aphids are among the major pests associated with strawberries in Southern Brasil. In this study, we identified the main species that occur in strawberry fields in the states of Paraná and Rio Grande do Sul, Brasil. We also compared the effectiveness of different sampling methods and studied the population dynamics of aphid species during two strawberry crop cycles in the municipality of Pinhais, state of Paraná, Brasil. Chaetosiphon fragaefolii (Cockerell) and Aphis forbesi Weed were the main species associated with strawberry. The method of hit plant and the Möericke trap showed equal effectiveness to capture wingless and winged insects. The peak population of aphids in the state of Paraná occurred from September to November. This information can help producers to implement strategies to monitor and control the major aphid species that occur in strawberry culture.

Natural enemies associated to aphids in peach orchards in Araucária, Paraná, Brazil

Natural enemies of the Class Insecta are important agents in the balance of aphid populations and an alternative to using insecticides to control these insects. The aim of this study was to identify the species of natural enemies associated with aphids present in peach orchards and observe the efficiency of capturing different sampling methods. The experiment was conducted from July, 2005 to September, 2006 in six peach orchards 'Chimarrita', in Araucária, PR, Brazil. The samples were taken by visual analysis in peach plants and weeds, yellow pan traps, sticky traps and funnels. Predator species were identified: Cryptolaemus montrouzieri, Cycloneda pulchella, Cycloneda sanguinea, Eriopis connexa, Harmonia axyridis, Hippodamia convergens and Scymnus sp. (Coleoptera, Coccinellidae), Allograpta sp., Palpada sp. and Toxomerus sp. (Diptera, Syrphidae) and Chrysoperla sp. (Neuroptera, Chrysopidae) and the parasitoids: Diaretiella rapae, Opius sp. and Praon sp (Braconidae). Examples of Encyrtidae and Eulophidae await identification. Chrysoperla sp. was a less abundant species. There were no statistically significant differences between the different sampling methods tested.

First record of Spintherophyta semiaurata (Klug) (Coleoptera: Chrysomelidae) damaging strawberry flowers

Spintherophyta semiaurata (Klug) is reported for the first time damaging flowers of strawberry (Fragaria x ananassa) in the municipality of São José dos Pinhais, State of Parana, Brazil.

Population fluctuation and faunal indices of aphids (Hemiptera, Aphididae) in peach orchards in Araucária, PR

Aphids are sap-sucking insects that mainly attack shoots and young leaves of peach trees and many other plant species; however, knowledge of the Brazilian aphid fauna is scant. The objective of this study was to identify aphid species collected in peach orchards (Prunus persica Batsch) and to determine their faunal indices for occurrence and dominance. The experiment was conducted from July 2005 to September 2006 in six Chimarrita peach orchards in the municipality of Araucária, PR, Brazil. The survey of aphid species was conducted by visual samplings on peach trees and using Möericke-type yellow traps containing water. A faunal analysis was made using aphid occurrence and dominance indices. Brachycaudus persicae (Passerini, 1860) was the only aphid species that was found colonizing peach in Araucária/PR. Although most aphids collected were classified as rare, some can be considered potential peach colonizers, such as Myzus persicae (Sulzer, 1776) which was given the status of common or intermediate in some of the orchards studied. The population fluctuation of aphids showed a negative correlation with rainfall and positive correlation with temperature and relative humidity.