Predictive theory on how plant diversity promotes herbivore suppression through movement patterns, host associations, and predation promises a potential alternative to pesticide-intensive monoculture crop production. We used meta-analysis on 552 experiments in 45 articles published over the last 10 years to test if plant diversification schemes reduce herbivores and/or increase the natural enemies of herbivores as predicted by associational resistance hypotheses, the enemies hypothesis, and attraction and repellency model applications in agriculture. We found extensive support for these models with intercropping schemes, inclusion of flowering plants, and use of plants that repel herbivores or attract them away from the crop. Overall, herbivore suppression, enemy enhancement, and crop damage suppression effects were significantly stronger on diversified crops than on crops with none or fewer associated plant species. However, a relatively small, but significantly negative, mean effect size for crop yield indicated that pest-suppressive diversification schemes interfered with production, in part because of reducing densities of the main crop by replacing it with intercrops or non-crop plants. This first use of meta-analysis to evaluate the effects of diversification schemes, a potentially more powerful tool than tallies of significant positive and negative outcomes (vote-counting), revealed stronger overall effects on all parameters measured compared to previous reviews. Our analysis of the same articles used in a recent review facilitates comparisons of vote-counting and meta-analysis, and shows that pronounced results of the meta-analysis are not well explained by a reduction in articles that met its stricter criteria. Rather, compared to outcome counts, effect sizes were rarely neutral (equal to zero), and a mean effect size value for mixed outcomes could be calculated. Problematic statistical properties of vote-counting were avoided with meta-analysis, thus providing a more precise test of the hypotheses. The unambiguous and encouraging results from this meta-analysis of previous research should motivate ecologists to conduct more mechanistic experiments to improve the odds of designing effective crop diversification schemes for improved pest regulation and enhanced crop yield.

Wood density (WD) is often used as a proxy for hydraulic traits such as vulnerability to drought-induced xylem cavitation and maximum water transport capacity, with dense wooded species generally being more resistant to drought-induced xylem cavitation, having-lower rates of maximum water transport, and lower sapwood capacitance than light-wooded species. However, relationships between WD and the hydraulic traits that they aim to predict have not been well established in tropical forests, where modeling is necessary to predict drought responses for a high diversity of unmeasured species. We evaluated WD and relationships with stem xylem vulnerability by measuring cavitation curves, sapwood water release curves, and minimum seasonal water potential (Ψmin) on upper canopy branches of six tree species and three liana species from a single wet tropical forest site in Panama. The objective was to better understand coordination and trade-offs among hydraulic traits and the potential utility of these relationships for modeling purposes. We found that parameters from sapwood water release curves such as capacitance, saturated water content, and sapwood turgor loss point (Ψtlp,x) were related to WD, whereas stem vulnerability curve parameters were not. However, the water potential corresponding to 50% loss of hydraulic conductivity (P50) was related to Ψtlp,x and sapwood osmotic potential at full turgor (πo,x). Furthermore, species with lower Ψmin showed lower P50, Ψtlp,x and πo,x suggesting greater drought resistance. Our results indicate that WD is a good easy-to-measure proxy for some traits related to drought resistance, but not others. The ability of hydraulic traits such as P50 and Ψtlp,x to predict mortality must be carefully examined if WD values are to be used to predict drought responses in species without detailed physiological measurements.

Hops (Humulus lupulus L.) are an essential ingredient in brewing, adding bitterness and flavor to beer. Driven by the recent craft beer movement, hop production is expanding into nontraditional hop-producing states. In Florida, while commercial hop production is almost nonexistent, the number of craft breweries in Florida increased from 45 in 2011 to 285 in 2018, and the economic impact of Florida?s craft beer industry exceeds $3 billion. This new 7-page article, written by Shinsuke Agehara, Aleyda Acosta-Rangel, Zhanao Deng, Jack Rechcigl, and Simon Bollin and published by the UF/IFAS Horticultural Sciences Department, provides guidelines and considerations for building a hop yard in Florida, using the UF/IFAS Gulf Coast Research and Education Center’s research hop yard as a model.https://edis.ifas.ufl.edu/hs1354

No abstract

The booming craft beer industry, rising prices of hops, and demand for locally-produced ingredients have recently increased interest in local hop production among growers and brewers. This article describes crop management practices and labor inputs required for small-scale hop production in Florida, with the aim of assisting growers with investment and farm management decisions. It is part of a larger series that will review the challenges of hop production in Florida, based on research experience at the UF/IFAS Gulf Coast Research and Education Center in Balm, FL. This new 6-page publication of the UF/IFAS Horticultural Sciences Department was written by Shinsuke Agehara, Mariel Gallardo, Aleyda Acosta-Rangel, Zhanao Deng, Jack Rechcigl, Tianyuan Luo, and Qi Qiu.https://edis.ifas.ufl.edu/hs1409