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Bemisia tabacitransmits begomoviruses that cause the most devastating disease of Capsicum chinensein tropical regions. Here we first evaluated the incidence and severity of Begomovirussymptoms on habanero pepper landraces H-224 and H-241 and commercial cultivar Jaguar that were naturally infested with B. tabaciin the field. Then we treated H-241 in the greenhouse with different botanical insecticides and assessed the Begomovirussymptoms. In the field, the mean area under the disease progress curve for incidence and severity did not differ significantly (P> 0.05) among the peppers tested; however, the final incidence of symptoms was significantly lower on Jaguar pepper than on the two landraces. Jaguar and H-241 had higher fruit yield than H-224. In the greenhouse experiment, the botanical insecticides protected H-241 against viral symptoms similarly to the treatment with only chemical insecticides. The fruit yield did not differ significantly between plants treated with the botanical insecticide combinations (2.1–2.5 kg plant−1) and those treated with only chemical insecticides (2.3 kg plant−1). The use of botanical insecticides holds promise as an environmental-friendly option to manage B. tabaci-transmitted begomoviruses in habanero pepper.

The whitefly Bemisia tabaci(Gennadius, 1889) (Hemiptera: Aleyrodidae) is a globally important insect pest, causing extensive damage and losses in horticultural production systems. New natural options are needed to control the whitefly. Ethanol extracts (92) of different organs from 40 plant species of the Yucatan Peninsula were evaluated against B. tabaciin a greenhouse, and an adult repellency index (RI) was determined for leaves and an oviposition deterrence index (ODI) for the extracts. Ethanol extracts at 1% (w/v) after 48 h suppressed the population density of B. tabaci. Leaves of Malpighia glabraL. had the highest repellent activity, causing a decrease in the population density of adults (RI 0.05) and eggs (ODI − 85). Three fractions differing in polarity were obtained by partitioning the ethanol extract of M. glabra, and the hexane fraction had an intermediate RI, but the ODI was not active. LC–UV–HRMS analysis of the fractions showed the presence of syringaresinol, 10-hydroxy-pheophorbide a, pheophorbide a, and lupenone, the first report of these four for this species. Eleven unknown compounds were also detected. This bioprospecting research on botanical extracts from native species of the Yucatan Peninsula enriches our knowledge of potential sources of products for pest management. M. glabrais a promising candidate for further formulation and application studies to control B. tabaci.

The objective of this experiment was to assess the impact of different planting patterns on light availability for cowpea within the intercrop canopy, as well as to evaluate the corresponding effects on cowpea's physiological characteristics and grain yield in maize/cowpea intercropping systems. The experiment utilized a randomized complete block design with four replicates and included six treatments: sole cowpea with 40 kg N ha−1(T1) and 80 kg N ha−1(T2), simultaneous sowing of maize and cowpea with 40 kg N ha−1(T3) and 80 kg N ha−1(T4) and cowpea sown 3 weeks after maize with 40 kg N ha−1(T5) and 80 kg N ha−1(T6). Results showed that sole cowpea had higher light interception and leaf area index than intercropped maize/cowpea, regardless of sowing date and nitrogen supply. The highest photosynthetic rates of cowpea were observed in the intercropping maize/cowpea sown simultaneously with 40 kg N ha−1and sole cowpea with 80 kg N ha−1. The water use efficiency of cowpea was found to be higher when intercropped with simultaneously sown maize, regardless of nitrogen supply, with values of 3.23 μmol CO2/mmol H2O and 3.3 μmol CO2/mmol H2O for treatments T3 and T4, respectively. Moreover, the highest cowpea grain yield was observed when maize and cowpea were sown simultaneously with the application of 80 kg N ha−1(0.99 t ha−1), while the lowest yield was obtained when cowpea was sown 3 weeks after maize (0.37 t ha−1), irrespective of nitrogen supply. Overall, our findings suggest that maize/cowpea intercropping with simultaneous sowing of maize can enhance the grain yield of cowpea in the Yucatan Peninsula.

In the last decade, attention has been drawn to a defense priming mechanism between plants of the same species through volatile organic compounds so that neighboring plants can prepare for the potential arrival of herbivorous insects. The induction of plant response priming by Tetranychus urticaeKoch (Tetranychidae) in Phaseolus vulgaris(Fabaceae) seedlings was evaluated through different communication pathways, focusing on resistance mechanisms (physical and chemical defenses: thickness, hardness, and foliar phenols) and plant tolerance (stem length, diameter, leaf area, and number of leaves). Five treatments were established: (1) Emitting seedling (with T. urticae); (2) direct communication (sender and recipient seedlings separated at 40 cm with free transfer of mites); (3) aerial communication (sender and recipient seedlings communicated aerially at 40 cm, but physically excluded from T. urticae); (4) positive control (seedling isolated but with T. urticae); and (5) negative control (seedling isolated and without T. urticae). Plant defense priming responses were recorded, interestingly, by different means of communication: aerial for tolerance and direct for resistance. When responses were induced by air rather than directly, trade-offs between plant resistance versus tolerance to herbivory were found. Notably, the principal component analysis showed a clear grouping of the variables of tolerance toward air communication and resistance toward direct communication. This strongly suggests the existence of different activation pathways for plant communication depending on tolerance and resistance mechanisms, a potential result of energy production costs.

In Mexico, outbreaks of phytophagous papaya mites (Oligonychussp.) can threaten papaya production by damaging young leaves, causing a reduction in plant vigour and fruit yield. In the present study, we evaluated the effect of conventional acaricides on the papaya mite and on predatory mites Neoseiulus californicusand Phytoseiulus persimilis. In the laboratory, residual toxicity was tested by exposing Oligonychussp. to acaricide-immersed leaves and the predatory mites to acaricide-coated glass vials. In the greenhouse and small field plots, mite-infested papaya leaves were sprayed with different acaricides to evaluate their control of Oligonychussp. In the laboratory, abamectin, spirodiclofen, and fenpyroximate caused the highest mortality (95–100%) of Oligonychussp. adults and nymphs on day 1 after application. These acaricides also caused 100% adult mortality of both predatory mites. Spirodiclofen and etoxazole killed all eggs of Oligonychussp. In the greenhouse and small field plots, abamectin, spirodiclofen, and fenpyroximate were effective at controlling the population of adults, nymphs, and eggs of Oligonychussp.

ABSTRACTSolubilization of inorganic P-sources and production of siderophores and indole-3-acetic acid (IAA) by Beauveria brongniartiiwere quantified and then, the effects of biofertilization using B. brongniartiion the plant growth, fruit yield and quality of Capsicum chinensewere evaluated. Beauveria brongniartiisolubilized more P from Ca3(PO4)2(158.95 mg L−1) than FePO4(31.7 mg L−1) and produced siderophores (59.8% of Fe3+-Chrome azurol-S degradation) and IAA (31.2 mg L−1). Plants fertilised at 100% of the recommended dosage (120N-150P-150K) had the tallest height at 30 (37.56 cm, P= 0.0494), 45 (57.56 cm, P= 0.0510) and 60 (67.87 cm, P= 0.0461) days after transplanting (dat) compared to plants inoculated and fertilised at 75% (90N-112.5P-112.5K) during the same period (30 dat = 30.68 cm, 45 dat = 45.81 and 60 dat = 55.75 cm). Inoculated plants with B. brongniartiihad a higher foliar N content (3.53%, P= 0.0532) than non-inoculated plants (3.31%). The fruit weight (FW = 6.767 g, P= 0.00001), longitudinal fruit diameter (LFD = 37.82 mm, P= 0.0001) and equatorial fruit diameter (EFD = 25.59 mm, P= 0.0003) were also higher in inoculated versus non-inoculated plants (FW = 5.632 g, LFD = 33.98 mm and EFD = 24.10 mm). The P-solubilizing ability and siderophore and IAA production of B. brongniartiiplayed an important role in the plant growth, foliar nutrient content and fruit quality of C. chinenseplants.

The fall armyworm Spodoptera frugiperdaJ. E. Smith (Lepidoptera: Noctuidae) is one of the most damaging pests of maize production in tropical areas. Leaf damage caused by its feeding depends greatly on chemical and physical leaf traits. In the present study, the degree of leaf damage by S. frugiperdain three maize landraces (Chimbo, Elotillo and San Pableño) and three commercial cultivars (Vs-536, Dekalb 390 and Impacto) was evaluated in a naturally infested field experiment. Morphological leaf traits were measured and associated with the degree of leaf damage at three sample dates 15, 30 and 45 days after emergence when developmental stages of plants were V5, V8 and V12, respectively. Overall, maize landraces showed lower leaf damage than commercial cultivars. Particularly, the landraces Chimbo and Elotillo had the lowest leaf damage, calculated by the area under the severity progress curve. Morphological leaf traits varied significantly (p< 0.05) among maize genotypes, but their patterns were not consistent in all sample dates. Pearson correlation analysis showed that leaf damage was negatively correlated with leaf toughness (rs= − 0.45, p< 0.001) at the developmental stage V12 and positively correlated with trichome density (rs= 0.44, p< 0.001) at developmental stage V8.

The present work was carried out to gain insight into the chemical defense of maize against phytophagous insects. Leaves of sixteen landrace populations were extracted with ethanol. Deterrent activity of extracts was evaluated on Spodoptera littoralisand Rhopalosiphum padiunder laboratory conditions. Most of the ethanolic extracts negatively affected settling of R. padi, but only the extract Xn-69 affected feeding of S. littoralis. Active extracts were combined based on their TLC pattern. Bioassay-guided fractionation using biomass gain (ΔB) and food consumption (ΔI) of S. littoralisshowed that the active fraction contained three phytosterols: sitosterol, stigmasterol and campesterol as the major constituents. These compounds might be responsible for the negative effects of extracts on biomass gain through the inhibition of food consumption of S. littoralislarvae. These phytosterols might provide in maize nonpreference resistance mechanism against insect pests.

Fungal metabolites are promising alternatives for the development of biorational pesticides. In this sense, microfungi from tropical regions are valuable sources of natural compounds for pest management. With the aim of broadening the search for new eco-friendly products to manage plant pests, this study was carried out to evaluate the biological activity of 23 tropical fungal extracts on three species of phytophagous insects and a plant parasitic nematode. In addition, the active principles of the most effective extract were identified. The insect deterrent activity of fungal extracts was evaluated on the settling of aphids Myzus persicaeand Rhopalosiphum padi, and on the feeding of lepidoptera larva Spodoptera littoralis; the nematostatic activity was evaluated on the mobility of Meloidogyne javanica. Active metabolites from Gliomastix masseeiwere identified by GC–MS techniques and by comparison with commercial standards. Results showed seven extracts with strong effect on the settling of M. persicaeand R. padi(settling inhibition >80%). The calculated median of effective concentration (EC50) values ranged from 8 to 38μg/cm2for the extracts of Clonostachys roseaand G. masseei, respectively. Bioassay-guided separation of the ethyl acetate extract of G. masseeirevealed the presence of fatty acids and their derivatives, where methyl 9-octadecenoate was the most active compound with EC50values of 16μg and 35μg/cm2for M. persicaeand R. padi, respectively. Extracts of C. roseaand G. masseeicould be a promising option in the control of pest aphids in agriculture.

Background: The two-spotted spider mite, Tetranychus urticaeKoch (Trombidiformes: Tetranychidae), is one of the most damaging mites in agriculture. Due to the concern for the intensive use of synthetic acaricides, entomopathogenic fungi represents a feasible alternative to T. urticaemanagement. In the present study, 7 isolates of Metarhiziumwere characterized physiological and molecularly (based on the ITS1-5.8s-ITS2 rDNA) and evaluated for their acaricidal activity [mortality, mean and 90 lethal concentration (LC50: LC90) and mean and 90 lethal time (LT50: LT90)] against T. urticaeunder laboratory conditions. Results: Sequencing of the ITS1-5.8s-ITS2 rDNA region indicated that the 7 isolates belong to M. anisopliae. The isolates Ma114 (3.7 ± 0.006 mm day−1), Ma109 (3.5 ± 0.009 mm day−1) and Ma106 (3.5 ± 0.006 mm day−1) had the highest radial growth rate and Ma114 (92.2 ± 0.86%) and Ma108 (94.4 ± 1.07%) had the highest germination percentage. All isolates were pathogenic to T. urticae, causing mortality that ranged from 45.3 to 85.3%. The LC50and LC90were 1.2 and 2.8, 1.1 and 2.5, and 1.2 and 2.8 × 108conidia mL−1for isolates Ma110, Ma109 and Ma106, respectively, while the LT50and LT90were 7.7 and 16.5, and 7.2 and 16.1 days for isolates M110 and Ma109, respectively. Conclusion: The isolates Ma110 and Ma109 of M. anisopliaewere moderately pathogenic and virulent against T. urticae.

Stingless bees are potential pollinators of commercial tropical crops and their use may increase in the short term. However, studies comparing the toxicity of pesticides to different individuals and species are lacking, making it difficult to evaluate their short- and long-term effects on colonies and populations of these insects. In this work, we tested the lethality of compounds from the main pesticide groups on stingless bees of the species Melipona beecheii Bennett, Trigona nigra Provancher, and Nannotrigona perilampoides Cresson. The LD50 (in micrograms per bee) for each pesticide was calculated for callow workers and foragers of the three species as well as for gynes and drones of M. beecheii. The results showed that all species were highly susceptible to the evaluated compounds. Nicotinoid pesticides were the most toxic, followed in descending order by permethrin, diazinon, and methomyl. We found evidence of a relationship between the body weight of the species and their LD50 for permethrin and methomyl (r = 0.91 and 0.90, respectively) but not for diazinon (r = −0.089). An analysis of contingency tables showed that within each species, callow workers had higher mortalities than foragers (P < 0.01). In M. beecheii at similar pesticide dose more males died compared with females [χ2 (0.01),1 = 10.16]. However, gynes were less resistant than workers [χ2 (0.01),1 = 8.11]. The potential negative consequences of pesticides to native stingless bees are discussed considering the reproductive biology of these insects. It is important to take actions to prevent damage to these key species for the ecology and agriculture of México and Latin America.