Abstract
Tri-trophic interactions between fertilizer applications, cotton aphid (Aphis gossypii Golver) and associated beneficial insects were studied to investigate direct and indirect effects of fertilizers (types and ratios) on potato plants under field and greenhouse conditions, A. gossypii and associated beneficial insects. Fertilizers regimes showed direct impacts on the potato plant phenology and indirect effects on both A. gossypii population and the associated beneficial insects. Our data indicated that potato plants had been influenced by fertilizer elements used within tri-trophic system comprising potato plants, cotton aphid, and certain associated beneficial insects. This demonstrates that a bottom-up interaction is robust and has a particular value in the attraction of beneficial insects towards the potato plant signals due to used fertilizers which can also have a function when plants are attacked by A. gossypii. Yet, flexibility in the use of fertilizers (as chemical cues) is conserved, and that may help beneficial insects to specifically focus on the odor of plants that carry potential plant hosts and avoid plants that are only attacked by non-hosts. These results support the still controversial notion that fertilizer elements, at least in part, help plants to serve as functional signals to attract the enemies of the harmful insects. These observations declare the benefits of the tri-trophic interactions as an ecological phenomenon in particular and the food chain in general. Additionally, this study may be useful to be used as a predictable model with the associated beneficial insects which may have key roles in overall aphid suppression or regulating its population. Impact of fertilizers on potato phenology characteristics and the cotton aphid population density seems to be variable based on types and ratios of the fertilizers. Interfacing the impact of natural enemies (plant-pest-natural enemies) through tri-trophic relationship within the food chain verified to be straightforward way of predicting on the impact of beneficial insects-guild on the cotton aphid population density.
Highlights
Herbivores insects and associated natural enemies are considered one of the important basic components in the food chain and food web within any agricultural system
This demonstrates that a bottom-up interaction is robust and has a particular value in the attraction of beneficial insects towards the potato plant signals due to used fertilizers which can have a function when plants are attacked by A. gossypii
Our results showed that the correlation coefficient relationships between potato nutrition, potato characters, the cotton aphid and the beneficial insects in tri-trophic interaction of the food chain had very clear relationships [22]
Summary
Herbivores insects and associated natural enemies are considered one of the important basic components in the food chain and food web within any agricultural system. Few studies have addressed the tri-trophic levels within a food web, such as, host plant, herbivore insects and their natural enemies in certain agro-ecosystems [2]. The tri-trophic interactions between plants, harmful insects and the associated natural enemies can afford an essential basis for planning an effective biological control method [3]. These findings could help to improve the effectiveness of the biological control agents when applied to suppress the herbivore populations. Study of trophic interactions among organisms has developed from simple plant- herbivore or prey-predator interactions to a more complex approach involving three or more trophic levels
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