Herbaceous cut peony (Paeonia lactiflora Pall.) has a limited marketable period due to seasonal production. A qualitative storage period can extend the sales period. For three consecutive years, the effects of storage and subsequent vase life of the cultivars 'Sarah Bernhardt' (SB) and 'The Fawn' (TF) were monitored. Vase life after dry storage at 2 degrees C for 6 and 10 weeks under a normal atmosphere and a controlled atmosphere was compared to vase life immediately after harvest. The atmosphere was modified using a commercial pallet box (Janny MT module) which resulted in an average concentration of oxygen and carbon dioxide of approximately 3%. During storage ethylene accumulated in the pallet box, while under normal atmosphere ethylene levels remained low. Disease incidence (Botrytis cinerea) increased during storage and was higher in 2021 (a cold and wet spring) compared to 2020 (a warm and dry spring). After 10 weeks of storage, disease incidence on the flowers was significantly less under controlled atmosphere compared to normal atmosphere. A postharvest treatment before storage in 2021 with 30% pyrimethanil as fumigant significantly decreased Botrytis incidence. However, the treatment was phytotoxic. Even though the maximum efficiency of photosystem II (Fv/Fm) decreased significantly during storage and was significantly lower under controlled atmosphere, flower opening, and vase life were not equally affected. Vase life of SB was shorter after storage. However, flower opening of SB was improved after 6 weeks of storage in 2020 compared to non-stored flowers. Flower opening of TF was not different after 6 weeks and poorer after 10 weeks of storage compared to non-stored flowers. The storage atmosphere had no significant effect on flower opening and vase life in 2019 and 2020. In 2021 vase life was shorter for flowers stored under a normal atmosphere due to supplemental Botrytis infestation during vase life.

Greenhouse production is at the forefront of using IPM systems to tackle pests and diseases. The shift to IPM was a challenge for growers, but was overcome through research, extension and demonstration of the strengths of biocontrol. We provide examples from ornamental plant greenhouse horticulture with a focus on how: (1) good communication and education of growers is important for facilitating transition to IPM; (2) increased hygiene measures reduced disease pressure and control needs; (3) the success of predatory mites increased confidence in further IPM, especially when adapted to specific greenhouse circumstances; (4) management of broad mite, a difficult and elusive pest, benefited from biological control; (5) adding food to the crop will help establish a standing army of beneficials; and (6) mealy bug control still poses a major challenge, but biocontrol shows promise. We see that the increased use of dynamic spectral lighting, increased automation and multilayer growing will pose future challenges that should be addressed in ongoing research.

The ladybird Cryptolaemus montrouzieri and the green lacewing Chrysoperla carnea have shown potential for use in augmentative biological control of mealybug pests in greenhouse crops. In the context of combining these predators within an integrated pest management system, the risk of negative intraguild interactions between both predators was evaluated in a laboratory setting. Different life stages of either predator were confronted in petri dish arenas containing a Ficus benjamina leaf, and after 24 h the incidence and direction of intraguild predation (IGP) was recorded for each combination. The effect of adding Planococcus citri nymphs or Ephestia kuehniella eggs as extraguild prey on the level of IGP was also studied. IGP was frequently observed between the two predator species and was asymmetrical in favour of C. carnea in most cases. The presence of extraguild prey reduced the number of IGP events between the predators to a similar extent. The relevance of the observed intraguild interactions for the combined use of these predators in protected cultivation is discussed.

Reproductive organization and mode of propagation in social insects can vary under different environmental conditions. To test this hypothesis, colony composition of Gnamptogenys menadensis was investigated in 38 colonies from Ulu Gombak, a tropical rain forest zone in Peninsular Malaysia, and compared to earlier data from Karaenta, a tropical monsoon zone in Sulawesi. As in Karaenta, both dealate queens and gamergates (mated egg laying workers) reproduced in Ulu Gombak. Coexistence of dealate queens and gamergates was never observed. The proportion of queen colonies in Ulu Gombak was similar to that in Karaenta, indicating that the occurrence of distinctive dry season in Karaenta does not affect colony reproductive strategies. Based on colony composition and dissection data, the colony life cycle in Ulu Gombak is postulated.

BACKGROUND The temperature-size rule is a well-known example of phenotypic plasticity in ectothermic organisms. When exposed to colder temperatures, ectotherms develop more slowly, but mature at larger body sizes and vice versa at higher temperatures. We investigated whether a phytoseiid predatory mite can obtain a larger body size by rearing it at a low temperature and how the increased body size affected predatory performance on its natural prey. Therefore, we allowed the predatory mite Amblydromalus limonicus (Garman & McGregor) (Acari: Phytoseiidae) to develop at either 15 or 25 degrees C. RESULTS A. limonicus reared at 15 degrees C had a 6% larger body size than those reared at 25 degrees C. Larger predators showed higher predation rates on first instars of the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), with 9.6 instars/female/day and 8.5 instars/female/day, for larger and standard-sized females, respectively. After three generations reared at 15 degrees C, body size did not increase any further. When reared for five generations at 15 degrees C, larger A. limonicus females demonstrated a better ability to subdue second-instar F. occidentalis. CONCLUSION Low juvenile rearing temperatures may result in phytoseiid predators with a predator/prey size benefit that could improve their biological control function. (c) 2019 Society of Chemical Industry

Adventitious rooting, a critical process in the vegetative propagation of many ornamentals, can be affected by both light intensity and light quality. We investigated the use of spectral light quality to improve adventitious rooting of Chrysanthemum morifolium cuttings by applying different combinations of blue, red and far-red light. Additionally, unrooted cuttings were treated before planting with two auxin transport inhibitors (TIBA and NPA) to study the effect of light quality on auxin biosynthesis and/or transport. Results showed that lowering the R:FR ratio (decreasing the phytochrome photostationary state, PSS) improved rooting significantly and decreased the inhibiting effect of the auxin transport inhibitor NPA. An extra decrease of PSS by adding blue light to a red + far-red spectrum further enhanced rooting. In contrast, adding blue light to solely red light decreased rooting, an effect which was more pronounced in combination with the auxin transport inhibitors TIBA and NPA. Our results show that phytochrome plays a role in adventitious root formation through the action of auxin, but that also blue light receptors interact in this process.

The acquisition of obligate, nutritional, vertically‐transmitted bacteria has been pivotal to the evolution and diversification of many insect taxa. Sap‐feeding citrus mealybugs Planococcus citri are an interesting example of obligate nutritional symbiosis, harbouring a pair of symbionts: Tremblaya princeps and Moranella endobia . Hosts can often vary in the densities of their symbionts and symbiont cells will inevitably carry some cost to the hosts, and so it would be predicted that a higher symbiont density will have some form of benefit to the host to outweigh this cost. In the present study, we examine whether populations of citrus mealybugs, with heritably different symbiont densities, differed in their ability to exploit multiple plant species or to tolerate the stress from insecticide exposure. Plant species were found to significantly impact mealybug fitness, but higher symbiont densities did not hold any evident compensation for reduced host‐plant suitability and did not correlate with mealybug susceptibility to insecticide treatment. Planococcus citri harbour variable symbiont densities but this did not correlate with the fitness of the host. This apparently sub‐optimum symbiont density regulation in an otherwise intricate and tightly‐knit tripartite symbiosis could be an evolutionary artefact of previous conflicts of interest.

Symbiotic bacteria are highly diverse, play an important role in ecology and evolution, and are also of applied relevance because many pest insects rely on them for their success. However, the dynamics and regulation of symbiotic bacteria within hosts is complex and still poorly understood outside of a few model systems. One of the most intriguing symbiotic relationships is the obligate, tripartite nutritional mutualism in sap‐feeding, economically‐destructive mealybugs (Hemiptera: Sternorrhyncha: Pseudococcidae), which involves γ‐proteobacteria hosted within β‐proteobacteria hosted within the mealybugs. The present study examines whether there is population variation in symbiont density (i.e. infection intensity, or titre) in the citrus mealybug Planococcus citri (Risso) and how this impacts host life‐history. Symbiont density is found to differ significantly between populations when reared under controlled environmental conditions, indicating that the density of symbiont infections is influenced by host or symbiont genotype. However, symbiont density changes in populations over multiple generations, indicating that symbiont densities are dynamic. Surprisingly, given that the symbionts are essential nutritional mutualists, the density of the symbionts does not correlate significantly with either host fecundity or development. Higher levels of symbionts have no clear benefit to hosts and therefore appear to be superfluous, at least under constant, optimized environmental conditions. Excessive symbiont density may be an evolutionary artefact from a period of inefficient vertical transmission when the balance of conflict between host and symbiont was still being established.

Food supplementation is an emerging strategy to improve the establishment and resilience of generalist predators in greenhouse crops. This study was conducted to assess the pre-establishment of the generalist predatory mite Amblyseius swirskii Athias-Henriot (Phytoseiidae) on two ornamental greenhouse crops, chrysanthemum and ivy. In the first greenhouse trial, we compared two commercial products consisting of Typha angustifolia pollen and decapsulated brine shrimp cysts (Artemia spp.), respectively, with a powdered artificial diet (AD) as food supplements for the predator on chrysanthemum plants at a constant temperature regime of 25 degrees C at a 16: 8 h (L:D) photoperiod. A population of A. swirskii established well when T. angustifolia pollen or the artificial diet were applied, but did not when the Artemia product was used as a supplement. A second trial on ivy plants was conducted at two temperature regimes (a constant 25 degrees C and an alternating temperature regime of 30 degrees C/15 degrees C, both at a 16: 8 h (L: D) photoperiod), comparing T. angustifolia pollen, the artificial diet and a non-commercial strain of Artemia franciscana cysts as food supplements. At the constant temperature regime, all three food sources allowed the establishment of A. swirskii. At the alternating temperature regime, however, T. angustifolia pollen and the AD but not A. franciscana cysts allowed a population of the predator to establish. Failure of establishment on the latter food supplement was attributed to dehydration effects under low humidity conditions in the greenhouse associated with the higher daytime temperatures at the alternating temperature regime. In conclusion, this study demonstrated the potential of T. angustifolia pollen and an artificial diet as a food supplement to support a population of A. swirskii in different ornamental crops.

Calonectria pseudonaviculata, the causal agent of the disease of Buxus spp. known as ‘box blight’, was first detected in the mid‐1990s in the UK and New Zealand. Since then, the geographic range of box blight has rapidly expanded to at least 21 countries throughout temperate regions of the world, causing significant losses in nurseries, gardens and wild boxwood populations. This study determined the genetic diversity in a collection of 234 Calonectria isolates from diseased Buxus plants, originating from 15 countries and four continents. Two genetic clades, G1 and G2, were identified within this sample using multilocus phylogenetic analysis. The application of genealogical concordance phylogenetic species recognition criteria using four independent nuclear loci determined that the Calonectria isolates in these two clades are separate phylogenetic species. The isolates in the G1 clade were upheld as C. pseudonaviculata sensu stricto. Based on phylogenetic distinctiveness and the lack of mating, a new species is proposed, Calonectria henricotiae sp. nov., for the Calonectria isolates in the G2 clade. A PCR‐RFLP assay and real‐time PCR assays were developed to easily and reproducibly differentiate these species. To assess the practical implications of the identification of the two species, their physiology, fungicide susceptibility and pathogenicity were compared. No differences in pathogenicity were observed. However, C. henricotiae isolates exhibited greater thermotolerance and reduced sensitivity to specific triazole as well as strobilurin fungicides. The identification of a second phylogenetic species causing box blight may have a substantial impact on the epidemiology and control of this destructive disease.

Efficient adventitious rooting is a key process in the vegetative propagation of horticultural and woody species. A well-rooted cutting is essential for optimal growth and high quality plants. The use of spectral light quality to influence adventitious rooting has been studied for many years, but got a lot more attention since LEDs came on the market for horticultural practices. Contrasting results of the effect of light quality on adventitious rooting are reviewed in this Paper. Even though more fundamental research is needed to easily determine which light quality can be used for a specific species, the use of LEDs for adventitiuus rooting is promising. For in vitro plantlets implementation can he done easily, for in vivo cuttings, the use of LEDs seems also promising in a multi-layered system. The controlled environment will lead to a year-round high quality rooted cutting Production.

Reliance on carbohydrates during flower forcing was investigated in one early and one late flowering cultivar of azalea (Rhododendron simsii hybrids). Carbohydrate accumulation, invertase activity, and expression of a purported sucrose synthase gene (RsSUS) was monitored during flower forcing under suboptimal (natural) and optimal (supplemental light) light conditions, after a cold treatment (7°C + dark) to break flower bud dormancy. Post-production sucrose metabolism and flowering quality was also assessed. Glucose and fructose concentrations and invertase activity increased in petals during flowering, while sucrose decreased. In suboptimal light conditions RsSUS expression in leaves increased as compared to optimal light conditions, indicating that plants in suboptimal light conditions have a strong demand for carbohydrates. However, carbohydrates in leaves were markedly lower in suboptimal light conditions compared to optimal light conditions. This resulted in poor flowering of plants in suboptimal light conditions. Post-production flowering relied on the stored leaf carbon, which could be accumulated under optimal light conditions in the greenhouse. These results show that flower opening in azalea relies on carbohydrates imported from leaves and is source-limiting under suboptimal light conditions.

Abstract Beneficial eukaryotic–bacterial partnerships are integral to animal and plant evolution. Understanding the density regulation mechanisms behind bacterial symbiosis is essential to elucidating the functional balance between hosts and symbionts. Citrus mealybugs, Planococcus citri (Risso), present an excellent model system for investigating the mechanisms of symbiont density regulation. They contain two obligate nutritional symbionts, Moranella endobia, which resides inside Tremblaya princeps, which has been maternally transmitted for 100–200 million years. We investigate whether host genotype may influence symbiont density by crossing mealybugs from two inbred laboratory‐reared populations that differ substantially in their symbiont density to create hybrids. The density of the M. endobia symbiont in the hybrid hosts matched that of the maternal parent population, in keeping with density being determined either by the symbiont or the maternal genotype. However, the density of the T. princeps symbiont was influenced by the paternal host genotype. The greater dependency of T. princeps on its host may be due to its highly reduced genome. The decoupling of T. princeps and M. endobia densities, in spite of their intimate association, suggests that distinct regulatory mechanisms can be at work in symbiotic partnerships, even when they are obligate and mutualistic.