Zhengqun Zhang

Phoxim Microcapsules Prepared with Polyurea and Urea–Formaldehyde Resins Differ in Photostability and Insecticidal Activity

The application of pesticide microcapsules (MCs) in agriculture is becoming more and more popular. In this study, the effects of different wall materials on the stomach toxicity, contact toxicity, length of efficacy, and photolysis characteristics of pesticide microcapsules were investigated. The results showed that microencapsulation reduced the stomach and contact toxicities of phoxim and prolonged the efficacy of this light-sensitive chemical in the greenhouse test. Neither of the degradation curves for microencapsulated phoxim under ultraviolet light fit a first-order model, although the emulsifiable concentrate (EC) degradation curve fit it well. The phoxim-loaded polyurea microcapsules (PUA-MCs) showed significantly increased UV-resistance ability, stomach toxicity, and contact toxicity compared with the phoxim-loaded urea-formaldehyde microcapsules (UF-MCs). These experiments indicated that it is crucial to select the appropriate wall materials for pesticide microcapsules on the basis of application sites and physicochemical properties of pesticide active ingredients.

Sublethal concentration of benzothiazole adversely affect development, reproduction and longevity of Bradysia odoriphaga (Diptera: Sciaridae)

AbstractThe chive maggot, Bradysia odoriphaga (Diptera: Sciaridae), is the major pest that damages Chinese chive in China. Benzothiazole is a volatile compound derived from microorganisms secondary metabolites and has fumigant activity against B. odoriphaga. However, the sublethal effects of benzothiazole need to be evaluated before registration and application, to fully understand the potential for control of this pest. Laboratory investigations showed that sublethal concentrations (LC10 and LC30) of benzothiazole decreased the survival rate and the fecundity of B. odoriphaga compared with control. However, the developmental times of eggs, larvae and pupae, and the total preoviposition period were prolonged. Additionally, population parameters were significantly affected in the treated groups. The intrinsic rate of increase (rm) decreased to 0.1391 (LC10) and 0.1140 (LC30) day-1 compared with the control population (0.1589 day-1). The net reproductive rate (R0) in the control was 54.39 offspring/individual, whereas the R0 decreased to 41.80 and 25.08 offspring/individual in the LC10 and LC30 treatments, respectively. This study demonstrated that sublethal concentrations of benzothiazole adversely affected the developmental time, fecundity and life table parameters of B. odoriphaga. Therefore, benzothiazole has the potential to be exploited as a natural derived fumigant for the control of this pest. Graphical abstractScheme about the life table experimental setup

Effects of the microbial secondary metabolite benzothiazole on the nutritional physiology and enzyme activities of Bradysia odoriphaga (Diptera: Sciaridae).

Bradysia odoriphaga (Diptera: Sciaridae) is the major pest that damages Chinese chive production. As a volatile compound derived from microbial secondary metabolites, benzothiazole has been determined to possess fumigant activity against B. odoriphaga. However, the mechanism of action of benzothiazole is not well understood. In the present study, fourth-instar larvae of B. odoriphaga were exposed to LC10 and LC30 of benzothiazole. Sublethal concentrations (LC10 and LC30) of benzothiazole significantly reduced the food consumption of the larvae on the second day after treatment (2 DAT). However, there were no significant changes in pupal weight among the different treatments. We also measured the protein, lipid, carbohydrate, and trehalose contents and the digestive enzyme activities of the larvae, and the results suggest that benzothiazole reduced the nutrient accumulation and decreased the digestive enzyme activities of B. odoriphaga. In addition, the activity of glutathione S-transferase was significantly decreased at 6h after treatment with benzothiazole, whereas general esterase activities were significantly increased at 6 and 24h after treatment. The results of this study indicate that benzothiazole interferes in the normal food consumption and digestion process by decreasing the activities of digestive enzymes. These results provide valuable information for understanding the toxicity of benzothiazole and for exploring volatile compound for the control of this pest.

Nitenpyram seed treatment effectively controls against the mirid bug Apolygus lucorum in cotton seedlings

The mirid bug Apolygus lucorum (Meyer-Dür) has become a major pest in cotton fields and has led to significant yield losses due to the widespread use of transgenic Bt cotton in China. Eight neonicotinoid seed treatments were investigated to determine their effects on the management of A. lucorum in cotton fields. All neonicotinoid seed treatments reduced the cotton damage caused by A. lucorum, and nitenpyram at the rate of 4 g/kg seed showed the most favorable efficacy in suppressing A. lucorum populations throughout the cotton seedling stage. The neonicotinoid seed treatments had no effect on the emergence rate of cotton seeds. Although the neonicotinoid seed treatments were not significantly different from the spray treatments in the cotton yield, the seed treatments reduced the need for three pesticide applications and showed a tremendous advantage in labor costs throughout the cotton seedling stage. Overall, the neonicotinoid seed treatments, particularly the nitenpyram seed treatment, can provide effective protection and should play an important role in the management of early season A. lucorum in Bt cotton fields.

Effects of trans ‐2‐hexenal on reproduction, growth and behaviour and efficacy against the pinewood nematode, Bursaphelenchus xylophilus

BACKGROUND Bursaphelenchus xylophilus is a serious quarantined pest that causes severe damage and major economic losses to pine forests. Because of the adverse effects of some traditional nematicides on humans and the environment, the search for new plant toxicants against these nematodes has intensified. Nematicidal activity of trans-2-hexenal, which is a six-carbon aldehyde present in many plants, was tested against the nematode. RESULTS trans-2-Hexenal showed significant efficacy against B. xylophilus in a dose range of 349.5-699 g m-3 by fumigation of pinewood logs. Additionally, it had significant nematicidal activity against different life stages of B. xylophilus in an in vitro test, with second-stage larvae (L2s) being the most sensitive, with an LC50 value of 9.87 µg mL-1 at 48 h. Egg hatch was also significantly inhibited. Further studies revealed that trans-2-hexenal inhibited the reproductive activity of B. xylophilus, with negative effects on reproduction rate and egg numbers. Moreover, trans-2-hexenal reduced the body length of B. xylophilus. Respiratory rate and thrashing behaviour of B. xylophilus also decreased following treatment with this compound. CONCLUSION trans-2-Hexenal had significant nematicidal activity against B. xylophilus, providing a basis for elucidation of the mode of action of trans-2-hexenal against plant-parasitic nematodes in future studies.

Baseline Sensitivity of Botrytis cinerea to the Succinate Dehydrogenase Inhibitor Isopyrazam and Efficacy of this Fungicide

Isopyrazam is a new broad-spectrum, foliar-absorbed and -translocated succinate dehydrogenase inhibitor fungicide. In this study, 159 Botrytis cinerea isolates collected from different geographical regions of Shandong Province of China were characterized for baseline sensitivity to isopyrazam. Furthermore, the protective and curative activity of isopyrazam on strawberry fruit and the control efficacy in the field were also determined. In contrast to its mycelial growth, the spore germination of B. cinerea was inhibited completely by lower concentrations of isopyrazam, about 1 μg ml-1 on yeast-peptone-acetate medium. Frequency distributions of isopyrazam 50% effective concentration (EC50) values were unimodal curves, with mean EC50 values of 0.07 ± 0.04 (standard deviation) and 0.68 ± 0.36 μg ml-1 for the inhibition of spore germination and mycelial growth, respectively. In addition, there was no positive multiple resistance between isopyrazam and other classes of botryticides such as diethofencarb, iprodione, pyrimethanil, or SYP-Z048. In field trials conducted during 2014 and 2015, isopyrazam used at a concentration of active ingredient at 150 and 200 g ha-1 provided a control efficacy ranging from 76.7 to 87.8% on leaves and from 81.5 to 90.7% on fruit. These results suggest that isopyrazam has the potential to play an important role in the management of gray mold.

Effects of Sublethal Concentrations of Cyantraniliprole on the Development, Fecundity and Nutritional Physiology of the Black Cutworm Agrotis ipsilon (Lepidoptera: Noctuidae)

To better understand the sublethal effects of cyantraniliprole on the black cutworm Agrotis ipsilon (Lepidoptera: Noctuidae), several studies were carried out to investigate sublethal effects on development stages, population parameters, feeding indices and nutrient content of A. ipsilon. The result of a bioassay showed that cyantraniliprole had high toxicity against A. ipsilon fourth-instar larvae with an LC50 of 0.354 μg.g−1 using an artificial diet. Compared with controls, sublethal doses of cyantraniliprole at LC5, LC20 and LC40 levels prolonged larval and pupal duration and extended mean generation time and total preovipositional period. In addition, survival rate, reproductive value, intrinsic and finite rates of increase and net reproduction rate declined significantly. Meanwhile, cyantraniliprole had markedly antifeedant effects; decreased the relative growth rate (RGR), the relative consumption rate (RCR), the efficiency of conversion of ingested food (ECI), the efficiency of conversion of digested food (ECD); and increased the approximate digestibility (AD) significantly. This phenomenon contributed to the decrease of nutrient contents, including lipids, protein and carbohydrates, to the point that insufficient energy was available for normal growth. Therefore, sublethal concentrations of cyantraniliprole decreased growth speed and reduced population reproduction of A. ipsilon. This result provides information useful in integrated pest management (IPM) programs for A. ipsilon.

Sex- and Tissue-Specific Expression Profiles of Odorant Binding Protein and Chemosensory Protein Genes in Bradysia odoriphaga (Diptera: Sciaridae)

Bradysia odoriphaga is an agricultural pest insect affecting the production of Chinese chive and other liliaceous vegetables in China, and it is significantly attracted by sex pheromones and the volatiles derived from host plants. Despite verification of this chemosensory behavior, however, it is still unknown how B. odoriphaga recognizes these volatile compounds on the molecular level. Many of odorant binding proteins (OBPs) and chemosensory proteins (CSPs) play crucial roles in olfactory perception. Here, we identified 49 OBP and 5 CSP genes from the antennae and body transcriptomes of female and male adults of B. odoriphaga, respectively. Sequence alignment and phylogenetic analysis among Dipteran OBPs and CSPs were analyzed. The sex- and tissue-specific expression profiles of 54 putative chemosensory genes among different tissues were investigated by quantitative real-time PCR (qRT-PCR). qRT-PCR analysis results suggested that 22 OBP and 3 CSP genes were enriched in the antennae, indicating they might be essential for detection of general odorants and pheromones. Among these antennae-enriched genes, nine OBPs (BodoOBP2/4/6/8/12/13/20/28/33) were enriched in the male antennae and may play crucial roles in the detection of sex pheromones. Moreover, some OBP and CSP genes were enriched in non-antennae tissues, such as in the legs (BodoOBP3/9/19/21/34/35/38/39/45 and BodoCSP1), wings (BodoOBP17/30/32/37/44), abdomens and thoraxes (BodoOBP29/36), and heads (BodoOBP14/23/31 and BodoCSP2), suggesting that these genes might be involved in olfactory, gustatory, or other physiological processes. Our findings provide a starting point to facilitate functional research of these chemosensory genes in B. odoriphaga at the molecular level.

Concentrations of imidacloprid and thiamethoxam in pollen, nectar and leaves from seed-dressed cotton crops and their potential risk to honeybees (Apis mellifera L.)

Neonicotinoid insecticides (NIs) have recently been recognized as co-factors in the decline of honeybee colonies because most neonicotinoids are systemic and can transfer into the pollen and nectar of many pollinated crops. In this study, we collected pollen, nectar and leaves from a cotton crop treated with imidacloprid and thiamethoxam to measure the residue levels of these two NIs at different application doses during the flowering period. Then, the residual data were used to assess the risk posed by the systemic insecticides to honeybees following mandated methods published by the European Food Safety Authority (EFSA), and a highly toxic risk to honeybees was highlighted. Imidacloprid was found in both pollen and nectar samples, whereas thiamethoxam was found in 90% of pollen samples and over 60% of nectar samples. Analysis of the pollen and nectar revealed residual amounts of imidacloprid ranging from 1.61 to 64.58 ng g-1 in the pollen and from not detected (ND) to 1.769 ng g-1 in the nectar. By comparison, the thiamethoxam concentrations in pollen and nectar ranged from ND to 14.521 ng g-1 and from ND to 4.285 ng g-1, respectively. The results of this study provide information on the transfer of two NIs from seed treatment to areas of the plant and provides an understanding of the potential exposure of the bee and other pollinators to systemic insecticides.

Chlorfenapyr, a Potent Alternative Insecticide of Phoxim To Control Bradysia odoriphaga (Diptera: Sciaridae)

Bradysia odoriphaga is the major pest affecting Chinese chive production, and in China, it has developed widespread resistance to organophosphorus insecticides. Chlorfenapyr is a promising pyrrole insecticide with a unique mechanism of action that does not confer cross-resistance to neurotoxic insecticides. However, the effect of chlorfenapyr on organophosphate-resistant B. odoriphaga is not well understood. The present study evaluated the potential of chlorfenapyr for the control of phoxim-resistant B. odoriphaga. The results showed that chlorfenapyr had significant insecticidal activity to B. odoriphaga in multiple developmental stages, and there were no significant differences in susceptibility between the field (phoxim-resistant) and laboratory (phoxim-susceptible) populations. The pot experiment and field trials confirmed the results of our laboratory bioassays. In the field trial, chlorfenapyr applied at 3.0, 6.0, or 12.0 kg of active ingredient (a.i.)/ha significantly decreased the number of B. odoriphaga and improved the yield compared to phoxim at 6.0 kg of a.i./ha and the control conditions. Moreover, the final residues of chlorfenapyr on plants were below the maximum residue limits (MRLs) as a result of its non-systemic activity. These results demonstrate that chlorfenapyr has potential as a potent alternative to phoxim for controlling B. odoriphaga.