Influence of crop management practices on bean foliage arthropods.

Crop management practices can affect the population of phytophagous pest species and beneficial arthropods with consequences for integrated pest management. In this study, we determined the effect of no-tillage and crop residue management on the arthropod community associated with the canopy of common beans (Phaseolus vulgaris L.). Abundance and species composition of herbivorous, detritivorous, predaceous and parasitoid arthropods were recorded during the growing seasons of 2003 and 2004 in Coimbra County, Minas Gerais State, Brazil. Arthropod diversity and guild composition were similar among crop management systems, but their abundance was higher under no-tillage relative to conventional cultivation and where residues from the preceding crop were maintained in the field. Thirty-four arthropod species were recorded, and those most representative of the impact of the crop management practices were Hypogastrura springtails, Empoasca kraemeri and Circulifer leafhoppers, and Solenopsis ants. The infestation levels of major insect-pests, especially leafhoppers (Hemiptera: Cicadellidae), was on average seven-fold lower under no-tillage with retention of crop residues relative to the conventional system with removal of residues, whereas the abundance of predatory ants (Hymenoptera: Formicidae) and springtails (Collembola: Hypogastruridae) were, respectively, about seven- and 15-fold higher in that treatment. Importantly, a significant trophic interaction among crop residues, detritivores, predators and herbivores was observed. Plots managed with no-tillage and retention of crop residues had the highest bean yield, while those with conventional cultivation and removal of the crop residues yielded significantly less beans. This research shows that cropping systems that include zero tillage and crop residue retention can reduce infestation by foliar insect-pests and increase abundance of predators and detritivores, thus having direct consequences for insect pest management.

The effects of nutrients and secondary compounds of Coffea arabica on the behavior and development of Coccus viridis.

Phytochemicals may modify the food quality, reduce a plant's palatability to insects, or defend against pests. This work aimed to study 1) relationships between the nitrogen and potassium levels given to plants in nutritive solutions and the foliar phytochemical concentrations, 2) the effect of nutrients and secondary compounds of Coffea arabica on the behavior of Coccus viridis, and 3) tolerance of C. arabica to losses. Deficient, normal, and excessive nitrogen and potassium fertilization treatments were used. Each treatment had two plants (one infested and one noninfested plant). The contents of phytochemicals in the infested plants' leaves and their dry matter of roots, stems, and leaves as well as the total contents in noninfested plants, were determined. The adults and nymphs of C. viridis were counted for 60 d in all treatments. It was verified that elevated nitrogen and potassium levels in the nutritional solutions led to increased of nymphs and adults of C. viridis to the coffee plants over time. Potassium and nitrogen had both direct and indirect effects on C. viridis. The direct effect was because of the increase of the nitrogen content in the leaves. The indirect effect instead was because of reductions in the caffeine and chlorogenic acid contents in the leaves. This is the first study to show relationship nutrient levels of coffee phytochemicals in response to herbivory by scale insects. Caffeine and chlorogenic acid applied on coffee leaves stimulated the locomotory activity of the green scale, thus reducing their feeding compared with untreated leaves. The elevation of caffeine and chlorogenic acid levels in coffee leaves affect this generalist insect by stimulating the locomotion of crawlers.