The resistance of maize weevil(Sitophilus zeamais), an important agricultural pest of stored grain, on aluminium phosphide fumigant(PH3) has been reported recently in Korea. Many researchers reported that ethyl formate(EF), a potential methyl bromide alternative fumigant, showed good efficacy on several grain pests. In this trial, based on CTP (concentration × time products), we evaluated efficacy of EF on phosphine resistant and susceptible maize weevil. Each of insect strains were collected in grain storehouses and examined the PH3 resistance according to FAO method (Busvine, 1980). L(Ct)90 of PH3 resistant and susceptible strain was 48.3 and 0.3 g h m-3, respectively. When treated with EF, L(Ct)90 of PH3 resistant and susceptible strain was 90.0 and 110.9 g h m-3, respectively. In the case of EF, there was no difference between resistant and sucsecptible strain compare with PH3. These results indicates that EF is a potential alternative for aluminium phosphide resistance management in grain storehouses.

Maize weevil is one of the most common and critical storage pest in the world. In this study, the insecticidal activity of the methanol extracts derived from Caesalpinia sappan was evaluated against adults of maize weevil, using by direct contact and fumigant methods. Based on the two methods, ethyl acetate fraction of the C. sappan extracts had 100% mortality against Maize weevil adults at 10 mg. The biological constituent of C. sappan extract was isolated by various chromatographic techniques and identified as juglone. On the basis of 72 h LD50 values, in the direct contact bioassay, the insecticidal activity of juglone (0.010 mg/cm2) was the most effective, followed by 1,4-NQ (0.018 mg/cm2) and menadione (0.087 mg/cm2). In a fumigant bioassay, the insecticidal activity of juglone (0.014 mg/cm2) was the most effective, followed by 1,4-NQ (0.015 mg/cm2) against maize weevil adults. On the other hand, menadione, lawsone, and 2-methoxy-1,4-NQ observed no insecticidal activity or weak. These results suggested that active compound of C. sappan materials could be used as biological control agent against maize weevil. Therefore, further research should be performed to the structure activity relationship of juglone and compared with its derivatives.

Maize weevil (Sittophilus zeamais) and Indian meal moth (Plodia interpunctella) are the dominant species among the stored grain insect pests of the rice grain and bran. This experiment was conducted to investigate developmental characteristic and damages of S. zeamais and P. interpunctella on the rice. Under five constant temperatures, 15, 20, 25, 30 and 35℃, developmental periods from egg to adult of Sittophilus zeamais were 43.0, 36.4, 29.2, 20.8 and 16.3 days, respectively. With egg periods being 9.6, 7.3, 5.2, 3.2 and 2.6 days, and larval periods being 25.2, 22.6, 19.8, 14.5 and 11.3 days, and adult periods being 129.3, 116.1, 108.6, 89.2 and 73.3 days, respectively. Damages of S. zeamais adult at 15, 20, 25 and 30℃ were 67.2, 96.2, 134.0 and 174.5 for 24hr on the rice. Damages of P. interpunctella larval 15, 20, 25 and 30℃ were 56.2, 78.3, 109.4 and 138.7 for 24hr on the rice. The duration of maximum occurrence were June to August for S. zeamais, late May to early August for P. interpunctella.

This study was performed to evaluate the contact toxicity and residual toxicity of the 26 commercially registered insecticides against cigarette beetle, Lasioderma serricorne and maize weevil, Sitophilus zeamais adult. Among 26 insecticides, seven insecticides (chlorpyrifos, chlorpyrifos-methyl, fenitrothion, fenthion, phenthoate, cypermethrin, α-cyhalothrin) against L. serricorne adult and five insecticides (chlorpyrifos, chlorpyrifos-methyl, fenitrothion, fenthion, phenthoate) against S. zeamais adult showed perfect mortality. LC50 (ppm) values of those selected insecticides were appeared lowest value on α-cyhalothrin (1.46 ppm) against L. serricorne adult and chlorpyrifos-methyl (0.64 ppm) against S. zeamais adult, respectively. However, chlorpyrifos-methyl still remain high toxicity until 90th days after treatment against both L. serricorne and S. zeamais adults. From above results, it will be useful information to select insecticides effective against L. serricorne and S. zeamais adults.

We have gathered rice grain and bran from conventional mills and RPC(Rice Processing Complex) for the survey of stored grain insect pests. Maize weevil(Sittophilus zeamais) is the dominant species among the stored grain insect pests of the rice grain and bran. Under three constant temperatures, 15, 20 and 25℃, developmental periods from egg to adult were 43.0, 37.5 and 29.2 days, respectively. With egg periods being 9.6, 7.3 and 5.2days, and larval periods being 25.2, 21.8 and 19.8days, and adult periods being 126.1, 110.3 and 108.6days, respectively. The adults of Maize weevil feed basically on the same the foods as the larvae but not as restricted in their diets because the larvae need to develop inside whole grains. Feeding of S. zeamais adult usually began 3∼4 days after emergence at 25℃. Then adult feeding ca. one rice a day, reaching a peak of 20∼40days after emergence.

This paper presents sequential sampling plans for evaluating the pest density based on complete counts from probe in a rice storage warehouse. Both maize weevil and Indian meal moth population showed negative binomial dispersion patterns in brown rice storage. For cost-effective monitoring and action decision making system, sequential sampling plans by using the sequential probability ratio test (SPRT) were developed for the maize weevil and Indian meal moth in warehouses with 0.8 M/T storage bags. The action threshold for the two insect pests was estimated to 5 insects per ㎏, which was projected by a matrix model. The results show that, using SPRT methods, managers can make decisions using only 20 probe with a minimum risk of incorrect assessment.