Flower strips as a bridge habitat facilitate the movement of predatory beetles from wheat to maize crops

Biological Control and Habitat Management for the Control of Onion Thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), in Onion Production in Quebec, Canada

Onion thrips (Thrips tabaci) can pose a significant threat to onion crops, causing leaf damage, reduced bulb size and quality, and yield loss during severe infestations. Conventional insecticide use has been the primary method for managing this pest species, but the efficacy of this approach is inconsistent. Furthermore, emerging pest resistance is a growing concern in some regions. This two-year field study aimed to assess the effectiveness of several pest management strategies in controlling onion thrips populations and limiting their impact on onion yields. The strategies tested consisted of habitat manipulations (including flower strips and straw mulch), biological control agents (Stratiolaelaps scimitus, Neoseiulus cucumeris, Amblyseius swirskii, and Beauveria bassiana), as well as physical barrier control methods (exclusion nets, kaolin, and mineral oil). Habitat manipulation techniques, particularly the use of flower strips, reduced thrips populations by up to 50% and increased onion yields by 25%. In contrast, exclusion nets had a detrimental effect on onion yields, and the other alternative control methods produced results comparable to those obtained for untreated controls. When used alone, biological control agents were not effective at maintaining thrips populations below economically damaging levels. This study offers valuable insights into effective and sustainable pest management practices for the onion industry.

Cnidium monnieri (L.) Cusson Flower as a Supplementary Food Promoting the Development and Reproduction of Ladybeetles Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

Predaceous ladybeetles are highly polyphagous predators that ingest supplementary food from flowering plants. Flowering plants widely grown in agroecosystems can sustain multiple natural enemies of agricultural pests, and the pollen and nectar resources from flowering plants may have a positive role in natural enemies. Cnidium monnieri (L.) Cusson, an annual herb with many flowers, blooms from May to July. C. monnieri can support several predatory natural enemies, and the addition of C. monnieri strips increases the density of Harmonia axyridis (Pallas) and improves the biological control of apple aphids in an apple orchard. H. axyridis is also the most important natural enemy in wheat aphid biocontrol and is attracted to healthy and aphid-infested C. monnieri plants. In addition, adult Propylaea japonica Thunberg survives significantly longer on C. monnieri flowers than on a water-only diet. In this study, a laboratory experiment was conducted to assess (i) the effect of nutritional supplements derived from C. monnieri flowers on the development and reproduction of H. axyridis under a wheat aphids-only diet; (ii) the effect of C. monnieri flowers on H. axyridis adult reproduction performance. We compared the larval durations, survival, weight, adult longevity, and reproduction of H. axyridis reared on wheat aphids-only and aphids plus C. monnieri flower diets. The results showed that H. axyridis larvae reared on aphids plus flowers had significantly greater weights and survival rates, shorter larval durations, and produced 1.62 times more eggs than those reared on wheat aphids-only diets. H. axyridis adults ingesting a C. monnieri flowers plus an aphid diet increased egg production 1.44 times compared to the aphids-only diet. Our study demonstrates that C. monnieri flowers as a supplementary food positively affect the survival, development, and reproduction performance of H. axyridis.

Licorice strips enhance predator-mediated biological control in China's cotton crop

BACKGROUND

Habitat management such as field- or farm-level diversification can conserve arthropod natural enemies, enhance biological pest control and lower (or suspend) insecticide use in agricultural crops. These approaches however have been underexploited to manage the aphid Aphis gossypii in cotton cropping systems of Xinjiang, China. In this study, we investigated whether the presence of licorice (Glycyrrhiza uralensis) at the field edge benefits generalist predator abundance and aphid biological control in local cotton crops.

RESULTS

Field trials during 2020 and 2021 showed that licorice strips enhanced the in-field abundance of generalist predators (primarily ladybeetles) 2.2-4.3 fold during early season, i.e. initial growth before A. gossypii peak infestation pressure. During peak outbreak conditions in July, treatment fields with licorice strips experienced a respective 17.5-61.2% lowered aphid density and 12.3-14.6-fold higher predator-to-aphid abundance ratio (PAR) than control fields. In late season (aphid decline phase) of either year, cotton fields with licorice strips also attained a respective 4.7-9.9 fold higher PAR. Exclusion cage assays quantitatively assessed predator-mediated A. gossypii biological control and the relative contribution of licorice strips. The biocontrol services index (BSI) was 2.8 times (2020) and 1.4 times (2021) higher at 5 m distances from the licorice strip as compared to control fields.

CONCLUSION

Licorice strips in the immediate vicinity of cotton fields benefit generalist arthropod predators and improve aphid biological control throughout the cotton cropping season. These findings help to integrate habitat management within integrated pest management (IPM) frameworks in the biggest cotton production region of China. © 2022 Society of Chemical Industry.