1. The Effects of Nitrogen on the Population Dynamics of the Chilli Thrips, Scirtothrips dorsalis (Thysanoptera: Thripidae), on Hydroponically Grown Jalapeño pepper (Capiscum annuum).
Daniel C. Diaz and Dr. Dakshina R. Seal University of Florida – Tropical Research and Education Center, Homestead, FL
Introduction
Chilli Thrips Biology
Feed on all above ground parts of the host plants.
Have a wide host range of over 200 plant species.
Is a major pest of ornamental and landscape plants but also fruit and vegetable crops such as peppers, citrus, strawberry, grape, onion, tomato, and cotton.
Potential economic impact of $3-6 billion dollars in the USA from crop losses annually.
Why Hydroponics?
Hydroponic crop production offers many advantages over traditional soil production.
Hydroponics allows for the use of vertical growth systems, which increase crop population per square foot.
Hydroponic plants grow faster than traditionally grown field plants which means a shorter time between planting and harvest and an increase in yield.
Water efficiency can be at least doubled in a hydroponic system since water is only introduced when it is lost to the plant (Burrage). Much less water is lost to evaporation.
Many soil-borne pathogens and pests are avoided as well since there is no soil.
Materials and Methods
With nitrogen being the independent variable, I have used five separate hydroponic systems with varying nitrogen concentrations as treatments in the hydroponic nutrient solution.
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Hydroponic Drip System
Conclusions
The 4% nitrogen treatment was found to have the highest mean number of leaves per plant with a value of The other treatments were around the same level in the low 200’s. The 8.5% and the 4% both produced the most flowers per plant with an average of and 8.25 flowers, respectively. Non of the 2.5% nitrogen treated plants ever produced any flowers.
There were more thrips found on the lower third of the pepper plants on each nitrogen concentration. The middle section was more favorable for chilli thrips in the 4, 5.5, and 7% treatments while the top section was slightly more favorable for the thrips in the 2 and 8.5% treatments. This means that when a grower is field scouting for chilli thrips, the lower third section of the pepper plant should be the first place to look. This also has implications when deciding on where a chemical pesticide should be applied. Although whole plant coverage should strived for, special emphasis should put on the lower third section of the pepper plant while spraying.
The 7% and 4% nitrogen treatments also had the largest mean plant area of and cc’s respectively. The 2.5% nitrogen was the smallest average volume of cc’s. The 2.5% treatment bore no fruit while the 4% and 8.5% nitrogen treatments produced at least 8 fruit per plant on average. It seems there is little benefit in using twice the recommended amount of fertilizer to obtain a net increase on only two fruit per plant on average.
Acknowledgments
I would like to thank the Seal Lab at the Tropical Research and Education Center in Homestead, FL: Dr. Dak Seal, Cathie Sabines, Charles Carter, Jesus Teyes, and Dr. Cliff Martin. I could not have done this work without their guidance and help.