Pest management is being confronted with immense economic and environmental issues worldwide because of massive utilization and over-reliance on pesticides. The non-target toxicity, residual consequence, and challenging biodegradability of these synthetic pesticides have become a serious concern, which urgently requires the alternative and prompt adoption of sustainable and cost-effective pest control measures. Increasing attention in environmental safety has triggered interest in pest control approaches through eco-friendly plant-based pesticides. Botanical pesticidal constituents are effective against myriads of destructive pests and diseases. More importantly, they are widely available, inexpensive, accessible, rapidly biodegradable, and have little toxicity to beneficiary agents. The phytochemical compositions in diverse plant species are responsible for their varying mechanisms of action against pests and diseases. However, difficulties in their formulation and insufficient appropriate chemical data have led to a low level of acceptance and adoption globally. Therefore, the review seeks to highlight the status, phytochemical compositions, insecticidal mechanisms, and challenges of plant-based pesticide usage in sustainable agricultural production.

Chemical pesticides and adjuvants have caused many negative effects. Botanical compounds provide solutions for the development of environment friendly pesticides and the management of increasing pest resistance. Curcumin, a natural polyphenol, showed synergistic effects on avermectin upon the destructive agricultural pest, Spodoptera litura. However, the botanical synergist and its relevant mechanisms remain unclear. In the article, curcumin significantly enhanced the growth inhibition and midgut structural damage of avermectin on the larvae of S. litura, and the synergistic effects were confirmed with pot experiments. There were only a few influences on the gene expression of avermectin targets, while apoptotic and autophagic related genes and proteins were accumulated in the avermectin/curcumin mixed regent (0.013/0.0013 μg/mL) treated group. Moreover, the potential mechanism was explored with an in vitro model, insect Spodoptera frugiperda Sf9 cell line. Morphology observation featured the damage on cells and Hoechst33258 staining revealed the fragments of DNA after treating with the avermectin/curcumin mixed regent (10/1 μg/mL). Dansylcadaverine and LysoTracker staining, as well as the gene expressions, supposed that curcumin exhibited autophagy inducing effects and the mixed regent possessed a higher ability to induce apoptosis and autophagy. All these results suggested that the synergistic effects of curcumin on the pest management of avermectin potentially mainly derived from the enhancement of programed cell death. It provides new sights for the application of natural compounds in integrated pest management and enriches examples of synergistic mechanisms.

Summary: Meliaceae is a useful plant family owing to its high‐quality timber and its many limonoids that have pharmacological and biological activities. Although some genomes of Meliaceae species have been reported, many questions regarding their unique family features, namely wood quality and natural products, have not been answered. In this study, we provide the whole‐genome sequence of Melia azedarach comprising 237.16 Mb with a contig N50 of 8.07 Mb, and an improved genome sequence of Azadirachta indica comprising 223.66 Mb with a contig N50 of 8.91 Mb. Moreover, genome skimming data, transcriptomes and other published genomes were comprehensively analysed to determine the genes and proteins that produce superior wood and valuable limonoids. Phylogenetic analysis of chloroplast genomes, single‐copy gene families and single‐nucleotide polymorphisms revealed that Meliaceae should be classified into two subfamilies: Cedreloideae and Melioideae. Although the Meliaceae species did not undergo additional whole‐genome duplication events, the secondary wall biosynthetic genes of the woody Cedreloideae species, Toona sinensis, expanded significantly compared to those of A. indica and M. azedarach, especially in downstream transcription factors and cellulose/hemicellulose biosynthesis‐related genes. Moreover, expanded special oxidosqualene cyclase catalogues can help diversify Sapindales skeletons, and the clustered genes that regulate terpene chain elongation, cyclization and modification would support their roles in limonoid biosynthesis. The expanded clans of terpene synthase, O‐methyltransferase and cytochrome P450, which are mainly derived from tandem duplication, are responsible for the different limonoid classes among the species. These results are beneficial for further investigations of wood development and limonoid biosynthesis.

PWD (pine wilt disease) is a devastating forest disease caused by the Bursaphelenchus xylophilus, which is the major invasive species in Asian and European countries. To control this disease, fumigation, pesticide injection, and clear cutting of epidemic trees have been widely used. But these management strategies have many limitations in terms of the effectiveness and environmental impacts, especially for the overuse of chemical pesticides. Thus, PCs (phytochemicals), the various compounds extracted from plants, have drawn extensive attention owing to their special characteristics, including abundant sources, low toxicity, high efficacy, and easy degradation. This review provides an overview of the current status of using PCs as alternative approaches to manage PWD. It discusses the efficacy of various PCs, the factors influencing their nematicidal activity, and their mechanism of action against B. xylophilus. These results will reveal the application of PCs in combating these devastating diseases and the necessity for further research.

Pine wilt disease, which is induced by pine wood nematode (PWN, Bursaphelenchus xylophilus), has caused huge economic and ecological losses. To overcome the drawbacks of chemical control against PWN, twenty compounds were screened, and a synergistic botanical–chemical combination was identified. A proportion of abamectin to rotenone of 7:3 (5.73 and 1.78 mg/L, respectively) achieved the highest co-toxicity coefficient of 231.09 with a median lethal concentration of 3.18 mg/L. It revealed 0% mortality in Pinus massoniana seedlings at 60 days post-treatment when applied at 400 times the synergistic concentration (2.29 g/L abamectin + 0.71 g/L rotenone) at 7 days after PWN inoculation. Furthermore, the synergistic combination significantly affected the physiological activity and population dynamics of PWN. Female oviposition was reduced by 71.92%, the egg hatching rates declined to 13.09 ± 0.02%, and head thrashing frequency was inhibited by 99.23 ± 0.01%. The enzymatic activities of peroxidase, acetylcholinesterase, succinate dehydrogenase, and glutathione S-transferase were significantly increased, while the population size declined by 96.17%. Transcriptomic and gene expression analyses suggested a potential “Na⁺/Ca²⁺/Cl⁻ ionic storm,” since the synergistic combination significantly activated genes associated with voltage-gated calcium channels, glutamate-gated chloride channels, and amiloride-sensitive sodium channels. These findings provide an eco-friendly strategy for PWN management via chemical control.