The effect of apple cultivar on the distribution of Amblyseius andersoni was studied in an experimental orchard where tetranychids were virtually absent and eriophyids reached low to moderate populations. Seven apple scab-resistant cultivars, showing some differences in their leaf morphology, were compared. Each cultivar was grafted onto three different rootstocks inducing increasing vigor. The intraplant distribution of A. andersoni was also studied by monitoring predator densities on basal and apical leaves. In the first year, the colonization of different cultivars by A. andersoni showed definite patterns, sometimes associated with the abundance of the eriophyid Aculus schlechtendali. In the second experimental season, eriophyids reached negligible levels and the effect of cultivar on A. andersoni abundance was less clear. Florina and N.Y. 18 491 cultivars were colonized in both years by relatively high phytoseiid numbers, while TSR 29T219 and Priscilla showed low populations in at least one season. The results observed on the remaining cultivars were intermediate or indefinite. The role of leaf pubescence on phytoseiid colonization is discussed.

The effect of apple cultivar on the distribution of the predatory mite Typhlodromus pyri was studied in an experimental orchard where spider mites occurred at negligible densities. Seven apple scab-resistant cultivars, showing some differences in their leaf morphology, were considered. In particular, their leaf blade was classified according to four levels of pubescence. The distribution of T. pyri along the shoots was also studied. In the first experimental year the colonization of different cultivars by T. pyri showed definite patterns, sometimes influenced by the occurrence of eriophyids. One year later, T. pyri abundance again showed some differences among cultivars in conditions of prey scarcity. In both years large phytoseiid populations were recorded on the cultivar N.Y. 18491, despite the low eriophyid occurrence, probably because of its highly pubescent leaf undersurfaces. In contrast, Prima and TSR 29T219, characterized by slightly pubescent leaf undersurfaces, supported low phytoseiid densities independently of prey availability.

Plant-insect interaction governs the dynamics of insect populations with respect to their interrelation with the environment. The objective of the present study was to identify the influence of antecedent crops, species and diameters of wild plants on the quiescent population of phytophagous stink bugs. The experiment was conducted in the months of June and July in Parada Link, municipality of Santa Maria, Rio Grande do Sul state, Brazil in two fields under crops of rice and soybean. In the off season, alternative host wild plants such as Andropogon bicornis, Andropogon lateralis, and Erianthus angustifolius with 10, 20, 30 and 40 cm in diameter were selected. Six wild plants were sampled for each crop, species, and diameter, totaling 144 experimental units. The stink bug species were identified and quantified. Soybean and rice previous cultivation, as well as the species and diameter of the wild plant, influence the quiescent population of Dichelops furcatus, Edessa meditabunda, E. rufomarginata, Euchistus heros, Piezodorus guildinii, and Tibraca limbativentris phytophagous stink bugs. The host plants A. bicornis, A. lateralis, and E. angustifolius were utilized for the maintenance of the populations of phytophagous stink bugs in the off-season periods. Soybean cultivation in floodplain areas has a negative impact on the quiescent population of T. limbativentris. RESUMO: A interação inseto-planta é o que rege a dinâmica de populações de insetos em interrelação com o ambiente. O trabalho teve por objetivo identificar a influência

Contribuição dos autores: Eduardo Engel realizou o experimento, a análise de dados, a revisão bibliográfica, a escrita científica e a apresentação dos resultados; Maurício Paulo Batistella Pasini contribuiu com a escrita científica, a análise de dados, a apresentação dos resultados e a revisão gramatical; Daniele Caroline Hörz Engel realizou o experimento, a revisão bibliográfica, a revisão ortográfica e a apresentação dos resultados. Fontes de financiamento: Não houve fonte de financiamento. Conflito de interesse: Os autores declaram não haver conflito de interesse.

In different parts of the world, aphid populations and their natural enemies are influenced by landscapes and climate. In the Neotropical region, few long-term studies have been conducted, maintaining a gap for comprehension of the effect of meteorological variables on aphid population patterns and their parasitoids in field conditions. This study describes the general patterns of oscillation in cereal winged aphids and their parasitoids, selecting meteorological variables and evaluating their effects on these insects. Aphids exhibit two annual peaks, one in summer–fall transition and the other in winter-spring transition. For parasitoids, the highest annual peak takes place during winter and a second peak occurs in winter–spring transition. Temperature was the principal meteorological regulator of population fluctuation in winged aphids and parasitoids during the year. The favorable temperature range is not the same for aphids and parasitoids. For aphids, temperature increase resulted in population growth, with maximum positive effect at 25°C. Temperature also positively influenced parasitoid populations, but the growth was asymptotic around 20°C. Although rainfall showed no regulatory function on aphid seasonality, it influenced the final number of insects over the year. The response of aphids and parasitoids to temperature has implications for trophic compatibility and regulation of their populations. Such functions should be taken into account in predictive models.