Manipulating Fertility of Potted Chrysanthemum Influences Cotton Aphid (Aphis gossypii) Populations

by Fred T. Davies, Jr., Amanda Chau, Kevin M. Heinz, Chuanjiu He, and Andrew D. Cartmill

This study tested the hypothesis that increased nitrogen will enhance insect pest populations of cotton aphid (Aphis gossypii Glover). Slow-released, pre-incorporated fertilizer was supplied to rooted cuttings of chrysanthemum (Dendranthema grandiflora var. 'Charm') potted in 6-in (15.2 cm) containers. Plants were grown for eleven weeks in growth chambers under three fertility levels of Nutricote 18N-6P2O5-8K2O - 0.5x rate: 3 lb yd-3 (1.8 kg m-3 (7.2 kg m-3). After 5 weeks, plants were inoculated at five aphids per pot. Each pot contained four rooted cuttings, which is the industry standard.

Ornamental crops in Texas rank first economically among agricultural commodities. During the 1990's there was a 10.3% increase per annum in Texas ornamental crop production. However, horticultural and pest management inputs to ornamentals are 10-fold greater than with other commodity crops. Consequently, fertilizers, pesticides and growth regulators are carried off in effluents. Texas Surface Water Quality Standards (proposed in July 2000) protect, maintain, and restore Texas water resources to guarantee the health of Texas citizens. These Standards mandate monitoring by regulatory agents for pollutants and that nurseries submit environmental management plans. The challenge to the $1.3 billion (per anum) Texas ornamental industry - resulting from this policy - will be to optimize inputs, refuce effluents, and maintain quality yields. The utilization of best management practices (BMP) such as recycling irrigation water, increased slow release fertilizer usage, and biological pest control are some of the practices that the nursery industry has implemented (Yaeger et al. 1997).

To better maintain the economic health of this vital industry, while addressing environmental concerns, our research is focusing on how precision fertilization crop yield and quality. In thihs preliminary study, the effect of nitogen fertilization on the abundance of cotton aphid, Aphis gossypii was studies on chrysanthemum, Dendranthema grandiflora var. "Charm". We tested three fertilization treatments that consisted of 0.5x, 1x, and 2x (the recommended nitrogen level). Thirty-five days after four rooted cuttings per pot were established, plants pinched, treated with B-9 at 3500 ppm, and placed under short-day conditions - five apterous aphids were transferred to each pot. Aphids were counted weekly over a seven-week period. The experiment was harvested after 78 days and all treatments evaluated for plant growth and leaf tissue elemental analysis.

SNA Research Conference. 48: 168-172. 2003.