Exploration of entomopathogenic fungi as potential biocontrol of corn earworm (Helicoverpa armigera (Hübner)

In Indonesia, H. armigera caused loss in corn production until 40% and almost attack all region. Therefore, this pest is a concern especially in corn plantations in Indonesia. In the development of H. armigera pest control, the use of entomopathogenic fungi increases after the potential risks of using chemical pesticides in various aspects. Biological control using entomopathogen agents is an alternative control method that has been studied widely and considerably more effective and environmentally friendly. This study aims explore entomopathogen that attack H. armigera which will later be formulated and projected as candidates for biopesticides controlling H. armigera. This research sited in East Java, South Sulawesi, and North Sulawesi in 2011. This research was divided into several stages within a year which were carried out including surveys and samples collection, isolation, characterization, morphological identification and molecular identification (genotyping phylogenetic tree). The research found several pathogens from several location such as Rhizopus sp., Beauveria bassiana, Fusarium sp., Aspergilus flavus, and Gliocladium sp. The character of each Entomopathogenic fungus showed that every isolate has different color and shapes. Based on the results of DNA amplification from eleven fungal isolates using BOX primers, various fragments were produced with sizes ranging from 225 to 1250 bp. The results also showed that all the isolates tested had polymorphic bands with a polymorphic information Content (PIC) value of 0.84. This indicates that these isolates have a low level of polymorphism.

Hemp Pest Spectrum and Potential Relationship between Helicoverpa zea Infestation and Hemp Production in the United States in the Face of Climate Change

There has been a resurgence in the cultivation of industrial hemp, Cannabis sativa L., in the United States since its recent legalization. This may facilitate increased populations of arthropods associated with the plant. Hemp pests target highly marketable parts of the plant, such as flowers, stalks, and leaves, which ultimately results in a decline in the quality. Industrial hemp can be used for several purposes including production of fiber, grain, and cannabidiol. Thus, proper management of pests is essential to achieve a substantial yield of hemp in the face of climate change. In this review, we provide updates on various arthropods associated with industrial hemp in the United States and examine the potential impact of climate change on corn earworm (CEW) Helicoverpa zea Boddie, a major hemp pest. For example, temperature and photoperiod affect the development and diapause process in CEW. Additionally, drought can lead to a reduction in hemp growth. Host plant diversity of CEW may prevent populations of the pest from reaching outbreak levels. It is suggested that hemp varieties resistant to drought, high soil salinity, cold, heat, humidity, and common pests and diseases should be selected. Ongoing research on effective management of CEW in hemp is critical.

Neonicotinoids can cause arrested pupal ecdysis in Lepidoptera

Recently, we reported a novel mode of action in monarch butterfly (Danaus plexippus) larvae exposed to neonicotinoid insecticides: arrest in pupal ecdysis following successful larval ecdysis. In this paper, we explore arrested pupal ecdysis in greater detail and propose adverse outcome pathways to explain how neonicotinoids cause this effect. Using imidacloprid as a model compound, we determined that final-instar monarchs, corn earworms (Helicoverpa zea), and wax moths (Galleria mellonella) showed high susceptibility to arrested pupal ecdysis while painted ladies (Vanessa cardui) and red admirals (Vanessa atalanta) showed low susceptibility. Fall armyworms (Spodoptera frugiperda) and European corn borers (Ostrinia nubilalis) were recalcitrant. All larvae with arrested ecdysis developed pupal cuticle, but with incomplete shedding of larval cuticle and unexpanded pupal appendages; corn earworm larvae successfully developed into adults with unexpanded appendages. Delayed initiation of pupal ecdysis was also observed with treated larvae. Imidacloprid exposure was required at least 26 h prior to pupal ecdysis to disrupt the molt. These observations suggest neonicotinoids may disrupt the function of crustacean cardioactive peptide (CCAP) neurons, either by directly acting on their nicotinic acetylcholine receptors or by acting on receptors of inhibitory neurons that regulate CCAP activity.

Maize-Crotalaria spectabilis intercropping in organic system and relations with the insect community

The objective of this study was to evaluate the canopy insect community associated with maize intercropped with different arrangements of Crotalaria spectabilis and the effects on the damage caused to maize by Spodoptera frugiperda and Helicoverpa zea. The treatments were intercropping systems of maize with Crotalaria spectabilis: CR - Crotalaria spectabilis sown on the same rows as maize; CBR - Crotalaria spectabilis sown between the rows of maize; CRBR - Crotalaria spectabilis sown on the rows and between the rows of maize, and M - maize monocrop. The experimental plot consisted of five rows of maize, five meters long, spaced 0.8 m apart. Assessments were made of the following parameters: insect community present in the maize canopy, leaf damage caused by the fall armyworm (S. frugiperda) and the corn earworm (H. zea), maize grain yield and shoot dry weight of maize and crotalaria. The CRBR intercropping system was characterized by the presence of predators and parasitoids, especially from the families Forficulidae and Braconidae: 79% and 82%, respectively. The maize monocrop, in turn, was mainly characterized by the presence of chewing and sucking phytophagous insects and predators. There was no influence of plant arrangements on the damage to maize caused by S. frugiperda (mean variation between 0.47 and 0.64 of damage) and H. zea (ranging between 6.42 and 7.49 of damage), neither on the grain yield of the crop (variation between 4129.57 kg ha-1 and 5653.77 kg ha-1). Our results suggest that C. spectablis sown in the rows and between the rows of maize has the potential to optimize conservative biological control, without, however, affecting the grain yield of the cereal

The Impact of Insect Herbivory in the Level of Cannabinoids in CBD Hemp Varieties

Background In the United States, industrial hemp is defined as a Cannabis sativa L. plant not containing more than 0.3% delta-9-tetrahydrocannabinol (D9THC) by dry weight. Plants respond to insect herbivore damage by changing their chemistry to counter the effects of herbivore attack. Here, we hypothesized that the corn earworm (Helicoverpa zea) infestation might impact the level of cannabinoids (Cannabidiol (CBD) and D9THC). Results In a laboratory trial, the CBD hemp, Cherry Blossom, and The Wife varieties were subjected to herbivore damage (HD), Mechanical damage (MD), and Control. After 24hrs of the treatments, we found a significant increase in CBD and D9THC in HD plants compared with MD and Control plants. Similar experiments were conducted in the field condition. A substantial increase in CBD and D9THC observed in herbivore damaged hemp plants compared to the control plants. However, in the field trial, the levels of cannabinoids were not significantly higher in The wife variety. Interestingly, the Corn earworm larvae fed with CBD and D9THC spiked diet showed a significant reduction in body mass, as compared to the larvae fed with the control diets.ConclusionsThe level of cannabinoids seems not genetically fixed somewhat; it is affected by insect herbivory. Our results suggest that CBD hemp plants are exposed to insect herbivory spikes in cannabinoid production and surpass the 0.3 % legal limit of D9THC. The growth and development of Corn earworm, the number one hemp pest in North America affected by cannabinoids. The increased concentration of CBD and D9THC observed in herbivore damaged hemp plants might be associated with the direct deterrence of the corn earworm larvae. Further research underway using different hemp varieties to assess if herbivory and other biotic stressors impact the level of cannabinoids.

Populations of Helicoverpa zea (Boddie) in the Southeastern United States are Commonly Resistant to Cry1Ab, but Still Susceptible to Vip3Aa20 Expressed in MIR 162 Corn

The corn earworm, Helicoverpa zea (Boddie), is a major pest targeted by pyramided Bacillus thuringiensis (Bt) corn and cotton in the U.S. Cry1Ab is one of the first insecticidal toxins used in Bt crops, while Vip3A is a relatively new toxin that has recently been incorporated into Cry corn with event MIR 162 and Cry cotton varieties to generate pyramided Bt traits targeting lepidopteran pests including H. zea. The objectives of this study were to determine the current status and distribution of the Cry1Ab resistance, and evaluate the susceptibility to Vip3Aa20 expressed in MIR 162 corn in H. zea in the southeastern U.S. During 2018 and 2019, 32 H. zea populations were collected from non-Bt corn (19 populations), Cry corn (12), and Cry/Vip3A cotton (1) across major corn areas in seven southeastern states of the U.S. Susceptibility of these populations to Cry1Ab and Vip3Aa20 was determined using diet-overlay bioassays. Compared to a known susceptible insect strain, 80% of the field populations were 13- to >150-fold resistant to Cry1Ab, while their response to Vip3Aa20 ranged from >11-fold more susceptible to 9-fold more tolerant. Mean susceptibility to each Bt toxin was not significantly different between the two groups of the populations collected from non-Bt and Bt crops, as well as between the two groups of the populations collected during 2018 and 2019. The results show that resistance to Cry1Ab in H. zea is widely distributed across the region. However, the Cry1Ab-resistant populations are not cross-resistant to Vip3Aa20, and H. zea in the region is still susceptible to the Vip3Aa20 toxin. Vip3Aa20 concentrations between 5 and 10 µg/cm2 may be used as diagnostic concentrations for susceptibility monitoring in future. Additional studies are necessary to elucidate the impact of the selection with Bt corn on resistance evolution in H. zea to Vip3A cotton in the U.S.

Spatial and temporal distribution of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) and Euxesta spp. (Diptera: Otitidae) in the corn crop

The aim of this study was to verify the pattern and the spatial and temporal behavior of the corn earworm and corn-silk fly in the corn crop. Hybrid corn was planted without chemical insect control in one hectare, this area was divided into 100 plots of 100 m². For the occurrence of Euxesta spp. all parts of the plants were visually analyzed, whereas for Helicoverpa zea (Boddie) 10 ears were removed at random from each plot, totaling 1,000 ears per sample. Population fluctuation was related to the phenological stages of corn. For spatial behavior, the dispersion indices, frequency distribution models and geostatistics (Krigagem) were analyzed. The corn earworm (small and large) and corn-silk fly showed aggregate pattern and spatial behavior. The reach of caterpillars <1 cm had an area of influence greater than caterpillars > 1 cm, with spatial dependence being considered moderate. The corn-silk fly had a maximum area of influence of 1.33 ha with moderate and weak spatial dependence. The maps demonstrated that these insects occur dispersed throughout the corn area, but with aggregations influenced by the adjacent areas and edges of the crop. The largest occurrence of corn earworms was at the R3 stage. It was also found that the corn-silk fly followed the occurrence of the corn earworm. It is concluded that the studied pests have an aggregate spatial tendency in the corn crop and with the influence of adjacent areas, in addition to presenting related population peaks in the reproductive period of the corn crop.