Sorghum is a plant that mainly requires chemical nitrogen fertilization. There are organic fertilizers that can provide nutrients to plants with great benefits to the soil, such as chicken manure. To determine the influence of organic fertilization on nitrate reductase (NR), glutamine synthetase (GS), and the amount of chlorophyll, sorghum plants were grown using the following four treatments: soil (T1), soil + chicken manure 100 kg ha⁻¹ of nitrogen (N) (T2), soil + chicken manure 200 kg ha⁻¹ N (T3), and soil + ammonium sulfate 100 kg ha⁻¹ N (T4). Leaves were sampled in the vegetative stage (VS), the reproductive stage (RS), and the maturation stage (MS). The highest NR activity occurred in plants with T2 and T3 in the VS. The highest GS activity was in T3 and T4 in the RS. The amount of chlorophyll a was the same in all phenological stages. However, the amount of chlorophyll b was influenced by the type of fertilization at different phenological stages. Organic fertilizers (OF) produced the highest NR activity. On the other hand, GS activity was higher with chemical fertilization (T4), which was equal to the second dose of organic fertilization (T3). Finally, chlorophyll a and b were influenced by both types of fertilization, and was different from T1.

Background. In arid environments plants face aridity and herbivory, therefore it has been proposed that both are convergent selective forces. However the drivers of insect herbivory in these ecosystems remain poorly understood. Question. Does insect herbivory vary in two plant associations subject to different levels of aridity? To what extent differences in herbivory are determined either by foliar traits, or predation by birds? Study species. Citharexylum tetramerum, Viguiera pinnatilobata, and Solanum tridynamum. Study site. We compared two-plant associations: the mezquital with a closed canopy and wettest conditions and the tetechera a dry place with an open canopy at the Zapotitlán Valley, México. Methods. We evaluated leaf traits (N, C, water content, leaf strength and trichomes), herbivore insects abundance and the effects on herbivory when some predators are excluded. Results. Herbivory was higher in the drier site (tetechera) than in the more humid one (mezquital) in one year but not in the second one. In both plant associations herbivory increased when predators of herbivores were excluded. Plants in mezquital had more water and nitrogen content than plants in tetechera. The later had higher carbon concentration and carbon:nitrogen ratio, leaf strength and density of trichomes. Abundance of herbivore insects and insect predation were higher in the most arid site. Conclusions. Our results show that insect herbivory increases in the most arid site and that predation by birds plays a role as a driver of herbivory, while resistance to aridity seems to be the main driver of leaf structural characteristics.

Plant products or substances mediate interactions among organisms from different trophic levels, including phytophagous insects. These interactions have been cited in a chemical-ecology context for species of Coleoptera Melolonthidae. However, there are no previous reports of these interactions among melolonthid beetles species distributed in Mexico and host plants. For the above, the interaction between adults of ‘rose chafer’ Macrodactylus nigripes Bates (Coleoptera:Melolonthidae) and ‘seep willow’ shrub Baccharis salicifolia (Ruíz and Pav.) Pers. (Asteraceae) was recorded and the leaves volatiles of seep willow that might be involved in the attraction of these insects were extracted and identified. The sequence of behavior patterns that conforms this interaction was described. Females of M. nigripes emerge from the soil and flight to the leaves of seep willow shrubs. Each female settled on leaf and they place their mandibles on the leaf margin and start moving them from right to left to obtain small leaf fragments to ingest. In addition, females exhibit a similar ‘calling’ behavior as well as the others species. Following the females, males emerge from the soil and repeat the females’ behavior, approaching them for mating. A list of the leaves volatiles of seep willow was generated by solid phase microextraction (SPME) and coupled gas chromatography – mass spectrometry (GC-MS), where the most abundant chemicals were α-pinene, trimethylindan and cyclohexylbenzene. These compounds have been previously reported in other plant species, including some species considered as host plants for Melolonthidae.

El “frailecillo” Macrodactylus nigripes Bates es considerado una de las plagas que afecta a varios cultivos en México, entre ellos el durazno (Prunus persica (L.) Batsch). El objetivo de este trabajo fue extraer e identificar los compuestos volátiles de P. persica con Headspace estático (HE) y Headspace dinámico (HD). De los compuestos identificados se evaluó a través de bioensayos con electroantenografía (EAG) y con olfatómetro la actividad biológica que éstos tienen en la comunicación química de M. nigripes. Se extrajeron e identificaron compuestos de P. persica con Headspace dinámico (HD) y Headspace estático (HE), a través de cromatografía de gases acoplada a espectrometría de masas (CG-EM). Se llevaron a cabo pruebas de electroantenografía (EAG) y olfatómetro con R-(+)-limoneno y (Z)-3-hexenil acetato, que provocan actividad biológica en melolóntidos. En pruebas con EAG se obtuvieron respuestas antenales significativas a R-(+)-limoneno y (Z)-3hexenil acetato en ambos sexos. En el olfatómetro se observó que R-(+)-limoneno no produjo una respuesta significativa, mientras que (Z)-3-hexenil acetato generó respuestas significativas a las concentraciones 200 y 250 µl/ml.

Melanaphis sacchari is a cosmopolitan pest that causes losses in sorghum crops, so new management methods are needed. In addition, the type of fertilization used influences plant compositions and pest infestation, and allelochemicals are a promising method for the possible management of M. sacchari. In this work, we measured the preference of M. sacchari through chemical stimuli towards sorghum plants grown under greenhouse conditions without fertilization (F0), conventional fertilization (CF), and organic fertilization (OF). Leaves were collected from sorghum plants fertilized with 200 kg N ha⁻¹ using ammonium sulfate and poultry manure. Extracts were obtained using Soxhlet extraction, and the compounds were identified using a gas chromatograph coupled with mass spectrometry (GC-MS). Sorghum extracts were individually tested through bioassays to determine M. sacchari preference. The abundance and number of compounds in sorghum differed depending on the type of fertilization used. M. sacchari showed a preference for the extract from CF sorghum plants (76.66%) over the extract from OF plants (23.34%). Therefore, the type of fertilization can be used as a tactic to prevent higher infestations of M. sacchari. The biological activity of the compounds identified here with M. sacchari should be determined for future pest management strategies using allelochemicals, given that the sugarcane aphid uses chemical signals to locate its host plant.

The type of fertilization used influences plant compounds and pest infestation. We measured, through chemical stimuli, the preference of Melanaphis sacchari for sorghum plants fertilized by means of conventional fertilization (CF) or organic fertilization (OF). Leaves were collected from sorghum plants fertilized with 200 kg N ha-1 using ammonium sulfate and poultry manure. Extracts were obtained using Soxhlet extraction, and the compounds were identified using a gas chromatograph coupled with mass spectrometry (GC/MS). Sorghum extracts were individually tested through bioassays to determine M. sacchari preference. The abundance and number of compounds in sorghum differed depending on the type of fertilization used. M. sacchari showed a preference for the extract from CF sorghum plants (76.66%) over the extract from OF plants (23.34%). Therefore, the type of fertilization can be used as a tactic to prevent higher infestations of M. sacchari. The biological activity of the compounds identified here with M. sacchari should be determined for future pest management strategies using allelochemicals, given that the sugarcane aphid uses chemical signals to locate its host plant.