Cover Crops Enhance Natural Enemies While Help Suppressing Pests in a Tea Plantation

Abstract

Tea is an economically important crop, consumed by billions of people. Despite the increasing market for pesticide-free products, the use of pesticide in tea is still high. In order to investigate whether intercropping promotes biological control organisms, Chamaecrista rotundifolia (Pers.) Greene, Indigofera hendecaphylla Jacq., Trifolium repens L., and Vigna sinensis (L.) were separately intercropped with free weeding as control in a tea plantation at Yangli, China. Arthropods were collected by taking sweep-net samples, and treatment effects on assemblages were investigated. The combined species richness of all arthropods and that of parasitoids was significantly increased in intercropped treatments while the species richness of herbivores and predators was only greater in C. rotundifolia and I. hendecaphylla intercropped treatments. Compared with control, the combined abundance of all arthropods, and that of herbivores was lower, while the abundance of parasitoids and its taxa was greater in all intercropped treatments. The abundance of predators and its taxa was greater only in tea plantations intercropped with C. rotundifolia or I. hendecaphylla. Of the herbivores, the abundance of Empoasca onukii Matsuda, Sternorrhyncha, Aleyrodidae, and Pentatomidae was greater in the areas intercropped with C. rotundifolia in comparison with the control, but the abundance of Thysanoptera and Geometridae caterpillars was lower. The recorded increase in the abundance of beneficial arthropods may explain the lower abundance of Thysanoptera or Geometridae caterpillars detected in the intercropped tea plantations. Our results indicate that intercropping has the potential to enhance arthropod biodiversity, and to provide an option for sustainable pest control in tea plantations.

Effects of cover crops on beetle assemblages in tea plantations

“…Nevertheless, weeded, bare ground rows (Bar) also showed significantly higher species richness than in the control. The underlying mechanisms of the two significant differences, however, are probably different; C. rotundifolia likely attracts beneficial insects by providing shelter or other resources (Chen et al , 2019a, b), whereas bare soil surfaces open up opportunities for ambush predators to easily find prey (Schmidt & Rypstra, 2010). Since these normally generalist species that are specifically adapted to disturbed habitats are more likely to stay in the adjacent field margins, their long-term value in tea canopies as biological control agents may be limited.…”

“…Existing evidence on efficacy of cover crops in enhancing beneficial species in tea plantations is mixed (Chen et al , 2019a, b). Song et al (2006) found that predatory Coleoptera abundance was significantly higher in tea interplanted with white clover ( Trifolium repens L., 1753) compared to tea monocultures, and this change led to better suppression of hemipteran pests.…”

Predation Pressure in Tea (Camellia sinensis) Plantations in Southeastern China Measured by the Sentinel Prey Method

“…However, in our study site, carabids were not a dominant group (G. Pozsgai, FAFU, Fuzhou, personal communication), and they are mostly night-active [38]; thus, one would not expect such a reciprocal relationship if carabids were responsible for most of the attacks on our caterpillars. It is plausible to assume that most of the arthropod attacks were made by day-active predators, such as ants and spiders, that are common in these habitats [11], and these would be directly threatened by invertivorous birds looking for food. It was also clear that at least some bird species were more active on the tea plantation than in the forest fragment (T. Imboma, personal observation).…”

“…Several major pests of tea are arthropods [10]; therefore, biocontrol agents in tea ecosystems could be important. Planting various flowering plants in-between rows of tea in Fujian can increase the abundance of various natural enemies [11], and increase their potential to control pests in tea.…”

“…When it comes to predation, the sentinel prey approach is a simple, easy and reliable quantitative method [19]. Given that in Fujian Province, southern China, insects are the most important pests in tea [11], the artificial caterpillar method [20] is suitable for both identifying the main predators active, as well as for a quantitative comparison of the impact of different landscapes on this specific ES [19].…”