Compatibility of Insecticides with Rice Resistance to Planthoppers as Influenced by the Timing and Frequency of Applications

Abstract

The brown planthopper, Nilaparvata lugens (Stål)(BPH) is a pest of rice in Asia. We examined the effects of seven insecticides combined with host resistance against BPH. In a screenhouse environment, we treated BPH-infested and non-infested resistant (IR62) and susceptible (IR64) rice with buprofezin, carbofuran, cartap hydrochloride, cypermethrin, deltamethrin, fipronil, or thiamethoxam + chlorantraniliprole. In one experiment, plants received one, two or three applications. In a second experiment, plants received one early or late insecticide application. Carbofuran and fipronil reduced planthopper biomass densities but resistance did not contribute to these effects (i.e., resistance was redundant). Single applications of cartap hydrochloride (at 20 or 50 days after sowing (DAS)), cypermethrin (20 DAS), or buprofezin (50 DAS) reduced BPH biomass densities on IR62 (i.e., synergies); other insecticides and application times, and multiple applications of all insecticides did not reduce BPH biomass densities on IR62 more than on IR64 (i.e., either resistance or insecticides were redundant). Deltamethrin (three applications) was antagonistic to resistance, but host resistance tended to buffer against the negative effects of single deltamethrin applications. Yields of infested IR62 were not statistically improved by insecticide applications. Late applications reduced yields of non-infested rice. We discuss how prophylactic insecticide applications could destabilize BPH populations and reduce the productivity and profitability of resistant rice.

Interactions between Rice Resistance to Planthoppers and Honeydew-Related Egg Parasitism under Varying Levels of Nitrogenous Fertilizer

“…Seed of both varieties was acquired through the germplasm bank at IRRI. Recent greenhouse studies have verified that, compared to IR64, the resistant variety IR62 reduces planthopper population or biomass build-up over successive generations after initial infestation [ 53 ]. Furthermore, research using field cages indicates that IR62 prevents ‘hopperburn’ (i.e., planthopper-induced death of rice plants) [ 54 ].…”

Diversified Rice Farms with Vegetable Plots and Flower Strips Are Associated with Fewer Pesticide Applications in the Philippines

“…Each of these chemicals has been associated with severe environmental or health effects. For example, cypermethrin was shown to induce outbreaks of planthoppers in rice, partly by reducing the rice plant's defenses against these herbivores [16,18,20], and chlorpyrifos and paraquat were associated with acute and chronic effects on human health [40][41][42]. Since many of the farmers reported the trade names and not the active ingredients, we noted that a large proportion (ca.…”

“…Because of the low financial returns from research into developing homemade botanical extracts for pest management, these technologies remain understudied [51,52]. However, their use reduces profitability losses associated with prophylactic chemical pesticide applications and the resulting environmental contamination [18]. Nevertheless, botanical extracts can still be damaging to human and livestock health (causing burns and irritation), can be phytotoxic to rice plants and other crops, and can interfere with rice ecosystem services-including regulatory ecosystem services [63,64].…”

“…However, natural enemies are often highly vulnerable to insecticides and other pesticides [16]. Indeed, outbreaks of key rice pests such as planthoppers, stemborers, and leaffolders have been linked to excessive pesticide use throughout Asia [16][17][18]. These outbreaks were associated with a declining abundance of natural enemies, particularly during early rice crop stages [14,16].…”

Beneficial interaction between rice stunt virus and its insect vector Nilaparvata lugens Stal based on life table

“…BPH has spread over Bali Province with the most damage found in Badung Regency as hopperburn symptoms (Listihani et al 2022a). BPH causes severe damage called hoppernburn (Nguyen et al 2019;Quais et al 2020;Horgan and Penalver-Cruz 2022). In addition to being a pest, it is also a virus vector, so its presence around plantations poses a risk of even larger loss.…”