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Invasive organisms pose a global threat and are exceptionally difficult to eradicate after they become abundant in their new habitats. We report a successful multitactic strategy for combating the pink bollworm (Pectinophora gossypiella), one of the world’s most invasive pests. A coordinated program in the southwestern United States and northern Mexico included releases of billions of sterile pink bollworm moths from airplanes and planting of cotton engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). An analysis of computer simulations and 21 y of field data from Arizona demonstrate that the transgenic Bt cotton and sterile insect releases interacted synergistically to reduce the pest’s population size. In Arizona, the program started in 2006 and decreased the pest’s estimated statewide population size from over 2 billion in 2005 to zero in 2013. Complementary regional efforts eradicated this pest throughout the cotton-growing areas of the continental United States and northern Mexico a century after it had invaded both countries. The removal of this pest saved farmers in the United States $192 million from 2014 to 2019. It also eliminated the environmental and safety hazards associated with insecticide sprays that had previously targeted the pink bollworm and facilitated an 82% reduction in insecticides used against all cotton pests in Arizona. The economic and social benefits achieved demonstrate the advantages of using agricultural biotechnology in concert with classical pest control tactics.

Immunity deteriorates with age in animals but comparatively little is known about the temporal regulation of plant resistance to herbivores. The phytohormone jasmonate (JA) is a key regulator of plant insect defense. Here, we show that the JA response decays progressively in Arabidopsis . We show that this decay is regulated by the miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) group of proteins, which can interact with JA ZIM-domain (JAZ) proteins, including JAZ3. As SPL9 levels gradually increase, JAZ3 accumulates and the JA response is attenuated. We provide evidence that this pathway contributes to insect resistance in young plants. Interestingly however, despite the decay in JA response, older plants are still comparatively more resistant to both the lepidopteran generalist Helicoverpa armigera and the specialist Plutella xylostella , along with increased accumulation of glucosinolates. We propose a model whereby constitutive accumulation of defense compounds plays a role in compensating for age-related JA-response attenuation during plant maturation. Immunity deteriorates with age in animals but less is known about how aging affects immunity in plants. Here, Mao et al . show that responsiveness to the major insect defense hormone JA declines as plants age, but insect resistance still increases as plants accumulate secondary metabolites such as glucosinolates.

Insects have evolved effectors to conquer plant defense. Most known insect effectors are isolated from sucking insects, and examples from chewing insects are limited. Moreover, the targets of insect effectors in host plants remain unknown. Here, we address a chewing insect effector and its working mechanism. Cotton bollworm (Helicoverpa armigera) is a lepidopteran insect widely existing in nature and severely affecting crop productivity. We isolated an effector named HARP1 from H. armigera oral secretion (OS). HARP1 was released from larvae to plant leaves during feeding and entered into the plant cells through wounding sites. Expression of HARP1 in Arabidopsis mitigated the global expression of wounding and jasmonate (JA) responsive genes and rendered the plants more susceptible to insect feeding. HARP1 directly interacted with JASMONATE-ZIM-domain (JAZ) repressors to prevent the COI1-mediated JAZ degradation, thus blocking JA signaling transduction. HARP1-like proteins have conserved function as effectors in noctuidae, and these types of effectors might contribute to insect adaptation to host plants during coevolution.

The invasion of the Western Hemisphere native fall armyworm (Spodoptera frugiperda; J. E. Smith) (Lepidoptera: Noctuidae) into the Eastern Hemisphere has been notable for the rapidity and geographical breadth of new detections. In the year following the first discovery in western sub-Saharan Africa in 2016, infestations have been documented in most sub-Saharan maize growing regions and has now expanded beyond Africa with populations recently reported in India. These observations could indicate a remarkable capacity for rapid establishment and long-distance dissemination. However, while fall armyworm does exhibit extended migration in North America where it annually traverses thousands of kilometers, this behavior is known to be dependent on highly favorable wind patterns and so can't be assumed to occur in all locations. An alternative possibility is that the species has long been present in Africa, and perhaps the rest of the hemisphere, but was undetected until the enhanced monitoring that resulted after its initial discovery. Determining whether the fall armyworm in the Eastern Hemisphere is newly arrived or long pre-existing is important for assessing the risks of significant economic impacts, as the former indicates a change in pest composition while the latter does not. This study examined this issue by comparing collections from two geographically distant locations, South Africa and India. Sequence comparisons were used to quantify differences between the South Africa and India collections, assess the likelihood of their sharing a common source population, and their possible relationship with previously characterized fall armyworm from other regions of Africa. The results indicate genetic homogeneity between the South African and Indian fall armyworm populations tested and substantial similarities between these and collections from eastern Africa. The implications of these findings on fall armyworm population behavior and composition are discussed.

Normally, when different species of herbivorous arthropods feed on the same plant this leads to fitness-reducing competition. We found this to be different for two of Asia’s most destructive rice pests, the brown planthopper and the rice striped stem borer. Both insects directly and indirectly benefit from jointly attacking the same host plant. Double infestation improved host plant quality, particularly for the stemborer because the planthopper fully suppresses caterpillar-induced production of proteinase inhibitors. It also reduced the risk of egg parasitism, due to diminished parasitoid attraction. Females of both pests have adapted their oviposition behaviour accordingly. Their strong preference for plants infested by the other species even overrides their avoidance of plants already attacked by conspecifics. This cooperation between herbivores is telling of adaptations resulting from the evolution of plant-insect interactions, and points out mechanistic vulnerabilities that can be targeted to control these major pests. Herbivore cooperation between insect pests can result in substantially greater damage to crops but also constitutes a good target for improved pest control. Liu et al. reveal how the brown plant-hopper and the rice striped stem-borer obtain mutual benefits when feeding on the same rice plant.

Ostrinia furnacalis, is the major pest of maize causing significant yield losses. So far, many approaches have been used to increase the virulence of entomopathogenic fungal isolates. The current study is an attempt to estimate synergistic effect of Beauveria bassiana and Trichoderma asperellum in order to explore larval immune response through RNA sequencing and differentially expression analysis. In vivo synergism was examined in seven proportions (B. bassiana: T. asperellum = 1:1, 1:2, 1:3, 1:4, 4:1, 3:1, 2:1) and in the in vitro case, two inoculation methods were applied: seed coating and soil drenching. Results revealed significant decrease in plant damage and high larval mortality in fungal treatments. Fungal isolates mediated the plant defense by increasing proline, superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO) and protease activities. Seed coating method was proved to be the most effective in case of maize endophytic colonization. In total, 59 immune-related differentially expressed genes DEGs were identified including, cytochrome P450, heat shock protein, ABC transporter, cadherin, peptidoglycan recognition protein (PGRP), cuticlular protein, etc. Further, transcriptomic response was confirmed by qRT-PCR. Our results concluded that, coculture of B. bassiana and T. asperellum has the synergistic potential to suppress the immune response of O. furnacalis and can be used as sustainable approach to induce plant resistance through activation of defense-related enzymes.

Ginkgo biloba is a typical relic plant that rarely suffers from pest hazards. This study analyzed the pattern of G. biloba pest hazards in Beijing; tested the antifeedant activity of G. biloba extracts, including ginkgo flavonoids, ginkgolide, and bilobalide, against Hyphantria cunea larvae; determined the activities of glutathione transferase (GSTs), acetylcholinesterase (AChE), carboxylesterase (CarE) and mixed-functional oxidase (MFO), in larvae after feeding on these G. biloba secondary metabolites; and screened for effective botanical antifeedants in the field. In this study, no indicators of insect infestation were found for any of the examined leaves of G. biloba; all tested secondary metabolites showed significant antifeedant activity and affected the activity of the four larval detoxifying enzymes. Ginkgolide had the highest antifeedant activity and the most significant effect on the detoxifying enzymes (P<0.05). Spraying leaves with G. biloba extracts or ginkgolide both significantly repelled H. cunea larvae in the field (P<0.05), although the former is more economical and practical. This study investigated the antifeedant activity of G. biloba secondary metabolites against H. cunea larvae, and the results provide new insights into the mechanism of G. biloba pest resistance. This study also developed new applications of G. biloba secondary metabolites for effective pest control.

Cyclic outbreaks of defoliating insects devastate forests, but their causes are poorly understood. Outbreak cycles are often assumed to be driven by density-dependent mortality due to natural enemies, because pathogens and predators cause high mortality and because natural-enemy models reproduce fluctuations in defoliation data. The role of induced defenses is in contrast often dismissed, because toxic effects of defenses are often weak and because induced-defense models explain defoliation data no better than natural-enemy models. Natural-enemy models, however, fail to explain gypsy moth outbreaks in North America, in which outbreaks in forests with a higher percentage of oaks have alternated between severe and mild, whereas outbreaks in forests with a lower percentage of oaks have been uniformly moderate. Here we show that this pattern can be explained by an interaction between induced defenses and a natural enemy. We experimentally induced hydrolyzable-tannin defenses in red oak, to show that induction reduces variability in a gypsy moth’s risk of baculovirus infection. Because this effect can modulate outbreak severity and because oaks are the only genus of gypsy moth host tree that can be induced, we extended a natural-enemy model to allow for spatial variability in inducibility. Our model shows alternating outbreaks in forests with a high frequency of oaks, and uniform outbreaks in forests with a low frequency of oaks, matching the data. The complexity of this effect suggests that detecting effects of induced defenses on defoliator cycles requires a combination of experiments and models.

Bacillus thuringiensis (Bt) constitutes the active ingredient of many successful bioinsecticides used in agriculture. In the present study, the genetic diversity and toxicity of Bt isolates was investigated by characterization of native isolates originating from soil, fig leaves and fruits from a Turkish collection. Among a total of 80 Bt isolates, 18 of them were found carrying a vip3 gene (in 23% of total), which were further selected. Insecticidal activity of spore/crystal mixtures and their supernatants showed that some of the Bt isolates had significantly more toxicity against some lepidopteran species than the HD1 reference strain. Five isolates were analyzed by LC-MS/MS to determine the Cry protein composition of their crystals. The results identified the Cry1Ac protein and a Cry2A-type protein in all isolates, Cry1Ea in 3 of them and Cry1Aa in one. The sequence analysis of the new vip3 genes showed that they had a high similarity to either vip3Aa, vip3Af or vip3Ag (94-100%). The vip3Aa gene of the 6A Bt isolate was cloned and sequenced. The protein was named Vip3Aa65 by the Bacillus thuringiensis Nomenclature Committee. The expressed and purified Vip3Aa65 protein was tested against five lepidopteran species and its toxicity compared to that of a reference protein (Vip3Aa16). Both proteins had similar toxicity against Grapholita molesta and Helicoverpa armigera, whereas Vip3Aa65 was less active than Vip3Aa16 against three species from the Spodoptera genus. A tetrameric structure of the Vip3Aa65 protein was detected by gel filtration chromatography. The study revealed some isolates with high insecticidal activity which can be considered promising candidates to be used in pest control.

Glucosinolates are plant secondary metabolites used in plant defense. For insects specialized on Brassicaceae, such as the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), glucosinolates act as \"fingerprints\" that are essential in host plant recognition. Some plants in the genus Barbarea (Brassicaceae) contain, besides glucosinolates, saponins that act as feeding deterrents for P. xylostella larvae, preventing their survival on the plant. Two-choice oviposition tests were conducted to study the preference of P. xylostella among Barbarea leaves of different size within the same plant. P. xylostella laid more eggs per leaf area on younger leaves compared to older ones. Higher concentrations of glucosinolates and saponins were found in younger leaves than in older ones. In 4-week-old plants, saponins were present in true leaves, while cotyledons contained little or no saponins. When analyzing the whole foliage of the plant, the content of glucosinolates and saponins also varied significantly in comparisons among plants that were 4, 8, and 12 weeks old. In Barbarea plants and leaves of different ages, there was a positive correlation between glucosinolate and saponin levels. This research shows that, in Barbarea plants, ontogenetical changes in glucosinolate and saponin content affect both attraction and resistance to P. xylostella. Co-occurrence of a high content of glucosinolates and saponins in the Barbarea leaves that are most valuable for the plant, but are also the most attractive to P. xylostella, provides protection against this specialist herbivore, which oviposition behavior on Barbarea seems to be an evolutionary mistake.