Aphis craccivora (Hemiptera: Aphididae) is an important pest affecting various crops worldwide. However, only few studies have been conducted on the infection of A. craccivora by Lecanicillium and related insecticidal mechanisms. We investigated the infection process of A. craccivora by Lecanicillium araneicola HK-1 using fluorescence microscopy and scanning electron microscopy (SEM), and our results indicated that the conidia of strain HK-1 easily attached to the feet and dorsum of A. craccivora. The activities of chitinase and extracellular protease were induced in the aphid after treatment with HK-1. A bioassay on A. craccivora showed that the median lethal concentration (LC₅₀) of the fungus crude extract was 24.00 mg mL⁻¹ for 24 h of treatment. Additionally, the results showed that the crude extract disrupted the enzyme system of A. craccivora, inducing the inhibition of carboxylesterase (CarE) and the induction of glutathione S-transferase (GST) and acetylcholinesterase (AChE). Combining these results with those of a gas chromatography–mass spectrometry (GC-MS) analysis, it is suggested that p-cymene, hymecromone, 9,12-octadecadienoic acid (Z, Z) methyl ester, and 9,12-octadecadienoic acid (Z, Z) may be connected to the insecticidal effects we observed. This study provides a theoretical basis for the use of L. araneicola HK-1 as a potential biological control agent.

Predation risk posed by natural enemies can alter pest performance. In our previous study, we found Menochilus sexmaculatus provides risk cues to melon aphids, resulting in increased numbers of winged aphids. However, the effects of predation risk on multiple traits including behavior, physiology, growth rate, and reproductive capacity of pests are not clear. This study examined the effects of predation risk on host preference, the activities of two important defense enzymes (CAT and SOD), longevity, and offspring production. The Y-tube trial results showed that the risk of M. sexmaculatus significantly altered the host preference of the aphids, leading to avoidance behavior. When exposed to M. sexmaculatus for a long period (24 h), the reproductive period and offspring production were significantly decreased, and adult longevity was significantly shortened. The defense enzyme activities of SOD and CAT, as well as the MDA content (which is considered a marker of oxidative stress and cellular damage) in the aphids, significantly increased under M. sexmaculatus risk. The compounds of M. sexmaculatus extracted with n-hexane and volatile compounds collected with HS-SPME were analyzed by GC-MS, and when combined with the behavior response experiment, the results showed that the alkane compounds n-henicosane, n-docosane, n-tricosane, n-pentacosane, and n-hentriacontane may contribute to the impact of predation risk. The results will be helpful in the comprehensive evaluation of the ability of lady beetles to affect the aphid population, and provide new ideas for using these compounds in aphid control.

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae), commonly known as the Asian bean thrips, is a destructive pest of leguminous crops, causing significant damage and economic losses. In the present study, the functional responses and predation rates of two predatory mites Macrocheles mammifer Berlese (Macrochelidae) and Stratiolaelaps scimitus (Womersley) (Laelapidae) on M. usitatus pupae were evaluated. The former was discovered in a cowpea Vigna unguiculata (Linn.) Walp. field of southern China, while the latter is commonly used as a biological control agent for soil-dwelling pests. Both M. mammifer and S. scimitus females consumed more M. usitatus than protonymphs, and the predation rate of the adult stage of M. mammifer was found to be significantly higher than that of S. scimitus. Likewise, logistic regression analysis revealed that both predators exhibited a type II functional response. Females of M. mammifer and S. scimitus displayed a higher attack rate and shorter handling time (Th) compared to conspecific protonymphs when preying on pupae of M. usitatus. Female M. mammifer recorded the highest attack rate (a) of 4.028, closely followed by female S. scimitus at 3.994. The protonymph of M. mammifer had an attack rate of 2.651, while the protonymph of S. scimitus displayed the lowest rate of 1.402. Female M. mammifer exhibited the shortest handling time (0.089), indicating superior prey-handling ability. Overall, the predatory mites M. mammifer and S. scimitus demonstrated considerable promise for managing M. usitatus, with M. mammifer displaying higher efficacy than S. scimitus.

Multitrophic interactions can strongly influence the structure and functioning of ecosystems, but how plant diversity influences the direction and predictability of multitrophic interactions across agricultural and natural ecosystems remains unclear. Using 149 field studies across five continents, we found that, on average, increasing plant diversity tended to exert differential top-down and bottom-up effects in croplands versus grasslands and forests. Organic and nonorganic croplands exhibited 846 and 148% higher invertebrate natural enemy-to-herbivore abundance ratios under increased plant diversity, consistent with top-down control patterns where predator gains cause herbivore declines, enhancing crop outcomes. In grasslands and forests, increasing plant diversity was associated with bottom-up effects where enhanced productivity increased both herbivore and predator populations, with the enemy-to-herbivore ratio increasing 4.73% for grasslands and 21.2% for forests. Our findings suggest that biodiversity effects on productivity are not solely explained by direct plant-plant interactions and the resulting biodiversity-productivity relationship. Rather, they reveal patterns consistent with the framework of top-down and bottom-up effects, the relative balance of which may vary depending on ecosystem and management type. The magnitude of the effects of diversified farming on crop pests suggests that crop diversification may be an important avenue for managing crop pests preventatively and thereby enhancing agricultural sustainability.

Cnaphalocrocis patnalis (Bradley 1981) is a major pest that threatens the safety of rice production in the world. In the present study, we determined the complete mitogenome of C. patnalis. This mitogenome was 15,305 bp in length (GenBank accession No. OL449028), which contained two ribosomal RNA genes, 22 transfer RNAs, 13 protein-coding genes (PCGs) and one non-coding AT-rich region with a length of 344 bp. All the 22 tRNA genes displayed a typical clover-leaf structure, except for trnS1. Twelve PCGs were initiated by ATN codons, and COX1 started with TTG. All the PCGs used the typical stop codon ‘TAA’ and ‘TAG.’ Phylogenetic tree demonstrated that C. patnalis belongs to the family Crambidae.

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) is an important pest of leguminous crops in Asia, severely affecting cowpea quality and causing significant economic losses. The growing resistance of thrips to pesticides has reduced the efficacy of chemical control, thereby highlighting biological control as an increasingly important management strategy. Among natural enemies, predatory mites play a crucial role in suppressing M. usitatus populations. In this study, we evaluated the predatory functional response of Cosmolaelaps leeae Tseng (Laelapidae), a newly discovered indigenous predatory mite from Hainan cowpea fields, against M. usitatus. Results demonstrated that adult female C. leeae exhibited significantly higher predation rates than deutonymphs, consuming an average of 6.53 and 3.53 thrips pupae per day, respectively. Additionally, C. leeae displayed a prolonged oviposition duration (32.74 d) and high cumulative fecundity (84.05 eggs/female) when feeding on the pupae of M. usitatus. Furthermore, a cage experiment was conducted to assess the control efficiency of C. leeae on thrips populations under field conditions. Thrips population suppression increased significantly with escalating C. leeae release rates, demonstrating a density-dependent response, a characteristic of effective biological control agents. In comparative efficiency trials, C. leeae exhibited superior population suppression (1.21-fold, 1.46-fold, 1.71-fold) relative to the established commercial agent Stratiolaelaps scimitus at 3 identical release rates (5, 10, and 20 mites per pot). Overall, the predator mite C. leeae demonstrated significant suppressive effects on M. usitatus populations, suggesting its potential as a promising biological control agent.