Micronutrient Fertilization of Greenhouse Cucumbers Mitigates Pirimicarb Resistance in Aphis gossypii (Hemiptera: Aphididae)

Salicylic acid functionalized zein for improving plant stress resistance and as a nanopesticide carrier with enhanced anti-photolysis ability

BACKGROUND

There is a serious global problem of salinization of arable land, causing large reduction in world food production. Use of plant hormones is an effective way to reduce damage caused to crops and salt stress.

RESULTS

In this study, PEI-EDA was modified with AM-zein and grafted with plant hormone SA (AM-zein-SA) and used as a nano-pesticide carrier to load emamectin benzoate (EB). The use of AM-zein-SA as a nano-pesticide carrier could reduce the damage caused by salt stress to crops. The structure of AM-zein-SA was characterized by FTIR, UV, fluorescence, Raman, and ¹H NMR spectroscopic techniques. AM-zein-SA could effectively improve the resistance of EB to ultraviolet radiations, resistance of cucumber to salt stress, and the absorption of EB by plants. The experimental results showed that AM-zein-SA could effectively improve the anti-UV property of EB by 0.88 fold. When treated with 120 mmol NaCl, the germination rate of cucumber seeds under salt stress increased by 0.93 fold in presence of 6.25 mg/L carrier concentration. The POD and SOD activities increased by 0.50 and 1.21 fold, whereas the content of MDA decreased by 0.23 fold. In conclusion, AM-zein-SA nano-pesticide carrier could be used to improve the salt resistance of crops and the adhesion of pesticides to leaves.

CONCLUSION

AM-zein-SA, without undergoing any changes in its insecticidal activity, could simultaneously improve the salt stress resistance and salt stress germination rate of cucumber, reduce growth inhibition due to stress under high-concentration salt, and had a good effect on crops. In addition, EB@AM-zein-SA obviously improved the upward transmission rate of EB, as compared with EB. In this study, SA was grafted onto zein-based nano-pesticide carrier, which provided a green strategy to control plant diseases, insects, and pests while reducing salt stress on crops in saline-alkali soil.

Soil Fertilization With Medicinal Plant Processing Wastes Suppresses Tuta absoluta (Lepidoptera: Gelechiidae) and Aphis gossypii (Hemiptera: Aphididae) Populations

Organic soil amendments can influence insect pest populations and the damage to plants they cause. In this study, the effects of medicinal plant processing wastes (MPPWs) applied as organic fertilizers on the host preference and performance of Tuta absoluta and Aphis gossypii were investigated on tomato and cucumber plants, respectively. Processing wastes of cumin, rosemary, thyme, artichoke, chamomile, fenugreek, and nettle were applied in four levels of 0, 20, 40, and 80 g dry matter/1kg culture media in pot experiments. Results showed the application of MPPWs, especially 80 g of nettle, reduced the number of T. absoluta eggs (from 0.8 to 0.4 egg/leaf) and their hatching percentage (from 90 to 76%). The highest and lowest number of aphids were observed in control (36 aphids/plant) and treated cucumbers with 80 g of cumin (18 aphids/plant). Also, the lowest intrinsic rate of increase (0.08 d-1) and net reproductive rate (20 offspring) of T. absoluta were observed in tomatoes fertilized with nettle. The highest and lowest net reproductive rate of A. gossypii were obtained on control and treated plants with 80 g of nettle, respectively. Results of damage assessment showed that the percentage of dry weight loss in the aphid-infested plants was reduced by the use of MPPWs, so that lowest weight loss was observed in the treatment with 80 g of nettle. In conclusion, soil amendment using MPPWs could result in lower pest populations and may improve plant tolerance to insect pest stress, thus these by-products could be considered a valuable tool in pest management.

Physiological Differences Between Seasonal Dimorphs of Agonoscena pistaciae (Hemiptera: Aphalaridae) Elicit Distinct Host Plant Responses, Informing Novel Pest Management Insights

We examined differences in the physiology and life history between dimorphs of the common pistachio psyllid, Agonoscena pistaciae (Burckhardt and Lauterer) (Hemiptera: Aphalaridae), and how they differ in elicitating host plant production of key metabolites and volatile compounds involved in the recruitment of herbivores and natural enemies. Summer morphs had higher activities of glutathione S-transferase, carboxylesterase, acetylcholinesterase, and cytochrome P450 monooxygenase, superoxide dismutase, catalase, peroxidase, phenoloxidase, and a higher total protein content compared to winter morphs, whereas the latter had higher amounts of lipid, carbohydrate, and glycogen. Winter morphs were heavier, with a higher chitin content and longer preoviposition period, but greater fecundity and longevity than summer morphs. A lower LC50 to thiamethoxam for winter morphs resulted in higher mortality following exposure to the recommended rate of this insecticide in a greenhouse trial. Feeding by winter morphs elicited more strongly the release of volatile compounds known to be attractive to other herbivores, whereas feeding by summer morphs elicited more strongly the release of volatiles implicated in the attraction of natural enemies. Feeding by psyllids increased the concentrations of nitrogenous compounds, carbohydrates, vitamins, and amino acids in plants, the winter morph eliciting larger changes and more improved host plant quality. We conclude that winter morphs are more vulnerable targets for chemical control in early spring, whereas management of summer morphs could rely more on conservation biological control.