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Faisal Shahzad, Changpin Chun, Arnold Schumann, and Tripti Vashisth

Since the advent of Huanglongbing [HLB (Candidatus Liberibacter asiaticus)] in Florida, several preliminary reports have emerged about the positive effects of mineral nutrition on the performance of HLB-affected citrus (Citrus sp.) trees. HLB-affected trees are known to undergo significant feeder root loss. Therefore, studies have focused on foliar nutrient application instead of soil-applied nutrients speculating that the HLB-affected trees root systems may not be competent in nutrient uptake. Some studies also suggest that HLB-affected trees benefit from micronutrients at higher than the recommended rates; however, the results are often inconclusive and inconsistent. To address this, the goal of the present study was to evaluate the nutrient uptake efficiency and the quantitative and qualitative differences in nutrient uptake of HLB-affected trees. HLB-affected and healthy sweet orange (Citrus sinensis) trees were grown in a 100% hydroponic system with Hoagland solution for 8 weeks. The trees were deprived of any fertilization for 6 months before the transfer of trees to the hydroponic solution. Altogether, the four treatments studied in the hydroponic system were healthy trees fertilized (HLY-F) and not fertilized (HLY-NF), and HLB-affected trees fertilized (HLB-F) and not fertilized (HLB-NF). HLY-F and HLY-NF trees were found to have similar levels of leaf nutrients except for N, which was found to be low in nonfertilized trees (HLY and HLB). Both HLB-F and HLB-NF trees had lower levels of Ca, Mg, and S compared with HLY trees. In addition, HLB-NF trees had significantly lower levels of micronutrients Mn, Zn, and Fe, compared with HLY-NF trees. The hydroponic solution analysis showed that HLB-F and HLY-F trees had similar uptake of all the nutrients. Considering that HLB-affected trees have a lower root-to-shoot ratio than healthy trees, nutrient uptake efficiency per kilogram of root tissue was significantly higher in HLB trees compared with HLY trees. Under nutrient-deficient conditions (day 0) only nine genes were differentially expressed in HLB roots compared with HLY roots. On the other hand, when fertilizer was supplied for ≈1 week, ≈2300 genes were differentially expressed in HLB-F roots compared with HLY-F roots. A large number of differentially expressed genes in HLB-F were related to ion transport, root growth and development, anatomic changes, cell death, and apoptosis compared with HLY-F trees. Overall, anatomic and transcriptomic analyses revealed that HLB-affected roots undergo remarkable changes on transitioning from no nutrients to a nutrient solution, possibly facilitating a high uptake of nutrients. Our results suggest the roots of HLB-affected trees are highly efficient in nutrient uptake; however, a small root mass is a major limitation in nutrient uptake. Certain micronutrients and secondary macronutrients are also metabolized (possibly involved in tree defense or oxidative stress response) at a higher rate in HLB-affected trees than healthy trees. Therefore, a constant supply of fertilizer at a slightly higher rate than what is recommended for micronutrients and secondary macronutrients would be beneficial for managing HLB-affected trees.

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Chenping Xu and Beiquan Mou

; Farouk et al., 2011 ). Soil-applied chitosan also significantly prompted seedling growth and induced early flowering of many ornamental crops ( Pichyangkura and Chadchawan, 2015 ). Similarly, the present study shows that soil-applied chitosan increased

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Timothy K. Broschat

. 2. Effects of soil-applied boron (B) on coconut palm B concentrations in leaf2, the youngest fully expanded leaf at the time of application ( A ) and the youngest fully expanded leaf at the time of sampling ( B ). Boron was applied at 0 months with

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Dennis C. Odero, Jose V. Fernandez, and Nikol Havranek

/m 2 over a 30-d growing season. In the organic soils of the EAA, negative effects of weed interference on radish are due to lack of registered effective preemergence or postemergence herbicides for broad-spectrum weed control. Many soil-applied

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Yuqing Wang, Richard J. Heerema, James L. Walworth, Barry Dungan, Dawn VanLeeuwen, and F. Omar Holguin

proposed that leaf tissue critical levels for Zn should be lower for pecan orchards managed with soil applied Zn EDTA than for those managed with foliar sprays (i.e., ≈30 mg·kg −1 for soil applied Zn EDTA vs. ≈50 mg·kg −1 for foliar applied Zn) ( Heerema

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Timothy K. Broschat

deficiencies of other antagonistic elements, complete fertilizers should be used for routine production and maintenance fertilization ( Broschat, 2005b ). Although most palms in container production and in the landscape are fertilized with soil-applied granular

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. Cushman was a dedicated scientist and will be missed as a professional colleague and friend. Systemic activity of azadirachtin and imidacloprid against japanese beetles Vitullo and Sadof (p. 316) report that two soil-applied insecticides, azadirachtin and

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that were used in nurseries for the production of tomato seedlings. The dose of compost used in the mixture depended on its initial salinity, provided that the final mix with peat did not exceed an electrical conductivity of 3.5 dS·m −1 . Soil-applied

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Bielinski M. Santos, James P. Gilreath, and Myriam N. Siham

under the VIF and metallized mulches had ≈3.7 times more MBr than the soil applied with 175 lb/acre of MBr + Pic and covered with either HDPE or LDPE mulches, and 1.8 times more fumigant than the soil applied with 350 lb/acre of MBr + Pic and covered

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Jawwad A. Qureshi, Barry C. Kostyk, and Philip A. Stansly

for control of the Asian citrus psylla, Diaphorina citri (Kuwayama) (Hemiptera: Psyllidae), in China Intl. J. Pest Mgt. 43 71 75 Rogers, M.E. Shawer, D.B. 2007 Effectiveness of several soil-applied systemic insecticides for managing the Asian citrus