Feeding Inhibition of the Brown Planthopper, Nilaparvata lugens (Homoptera: Delphacidae) on a Resistant Rice Variety

Brown planthopper, Nilaparvata lugens, nymphs grown on a resistant rice variety, Cheongcheong-byeo, died within 3 days with low survival rate below 5%, whereas those on a susceptible rice variety, Tae-baegbyeo, maintained ca. 70% survival rate. However, the insects transferred to the susceptible variety after one or two days showed higher survival rates than those kept on the resistant variety. In a choice test, the insects preferred the susceptible variety to the resistant variety at 24 h after releasing into a rearing cage. Glucose, fructose and sucrose were determined from the honey-dew excreted by those insects fed on each variety. The amount of each sugar from the honey dew of the insects fed on the resistant variety was less than those on the susceptible variety. Similar pattern of the difference was observed from the comparison of the total amino acids contents between the honeydews derived from N. lugens grown on two rice varieties. However, the amounts of sugars were not significantly different between varieties in the phloem exudates extracted from the cut stem of both varieties by EDTA solution or distilled water. These results indicate that N. lugens might have some difficulties to uptake the phloem sieve elements of resistant variety, although the resistant variety has equal or more amounts of sugars compared to the susceptible variety.