Sampling insect pests and damage

Insects were sampled in each treatment at the maximum tillering stage of rice. A sweep net (40-cm diameter) was used to sample insect pests and natural enemies in all plots. Twenty complete sweeps were made randomly at the canopy level of the plants. The collected insects were kept in labeled bags and transported to the laboratory for sorting, identification and quantification.

Yellow sticky traps (20 × 25 cm; Zhangzhou Enjoy Agriculture Technology Co., Ltd., Fujian, China) were also used to record insect pests and their natural enemies in the experimental plots. Individual traps were fixed to bamboo canes and placed in rice plots such that sticky boards were positioned just above the plant canopy. After 48 h, all sticky traps were removed, taken to the laboratory and stored at 4 °C until all insects were counted and identified. This sticky trap was used only in one site due to lack of sufficient number of traps.

Percent parasitism of key pests was monitored using sentinels eggs of the brown planthopper (BPH), white-backed planthopper (WBPH), rice hispa and yellow stem borer (YSB). To create sentinel egg baits, potted 45-day-old rice plants were exposed to the respective pests in the lab. For the BPH and WBPH, five gravid females were caged on each pot with six plants for 48 h after which adult planthoppers were removed and the plants placed in the experimental plots. Three pots with six plants/pot each were placed in random positions centrally in each plot. For YSB, moths were captured from the field and caged on greenhouse-grown potted rice plants. After 24 h, for oviposition, YSBs were removed and plants were placed in the field in a similar manner to that used for planthopper eggs. Rice hispa egg bait traps were similarly prepared and placed in the field. After 48 h of exposure to parasitoids in the field, the plants were returned to the laboratory and kept in a greenhouse at room temperature for 4 days to allow parasitoid emergence. After this time, the plants were microscopically observed to determine the number of parasitized and nonparasitized eggs.

The hill counting method⁵⁷ was also used to record insect pests, their damage symptoms and the number of natural enemies per hill. During the reproductive stage of rice crops, damage symptoms, termed white head, caused by YSBs were recorded and expressed as % white head. The % white head was calculated using the formula below.

The goal of this study was to evaluate the effect of flowering plants on rice bunds on pest and their natural enemies in rice fields. Treatment effects on the abundance of predators, parasitoids, insect pests, parasitism and rice yields were analyzed by one-way ANOVA, and a post hoc Tukey’s honest significance test (Tukey’s HSD). To improve homogeneity, where needed the data were log or arc sine transformed before analysis. In addition, when the value of the data was 0, then transformation was conducted by ln(n + 1). All data were analyzed using SPSS software version 16.0.