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Chemical Identification
Common Name
Milbemectin
中文通用名
密灭汀
IUPAC
A mixture of: (10E,14E,16E,22Z)-(1R,4S,5'S,6R,6'R,8R,13R,20R,21R,24S)-21,24-dihydroxy-5',6',11,13,22-pentamethyl-3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene-6-spiro-2'-tetrahydropyran-2-one and (10E,14E,16E,22Z)-(1R,4S,5'S,6R,6'R,8R,13R,20R,21R,24S)-6'-ethyl-21,24-dihydroxy-5',11,13,22-tetramethyl-3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene-6-spiro-2'-tetrahydropyran-2-one in the ratio 3 to 7
CAS
A3: (6R,25R)-5-O-demethyl-28-deoxy-6,28-epoxy-25-methylmilbemycin B; A4: (6R,25R)-5-O-demethyl-28-deoxy-6,28-epoxy-25-ethylmilbemycin B
CAS No.
51596-10-2 (milbemycin A3) + 51596-11-3 (milbemycin A4)
Molecular Formula
A3: C31H44O7; A4: C32H46O7
Molecular Structure
Category
Activity
Acaricide, insecticide.Milbemectin is primarily an acaricide although it also has activity against some homopteran and lepidopteran pests. It is both a contact and a stomach poison and is active against all developmental stages of mites; it is most active against immature motile stages with slightly lower activity to eggs and adults. Once absorbed, the product exhibits translaminar movement similar to avermectin. The product is rapidly degraded on the surfaces of leaves. Sankyo reports that sub-lethal doses are sufficient to lower the reproduction rate of adults and that the persistence of the product can be extended in this way.

Milbemectin has shown no cross-resistance to conventional acaricides. Cross-resistance to avermectin is possible, but bioassays conducted by the company demonstrated that there was no reduced susceptibility of avermectin-resistant mites to milbemectin. As it is also safe to beneficials and exhibits excellent crop safety, it can be used in integrated pest management and resistance management programmes.

In field trials carried out in the Pacific Northwest (USA) on apple and pear, the product was found to provide excellent control of mites at 1.8 - 2.6 L/ha, which was comparable to Agri-Mek at 0.9 - 1.2 L/ha. Residual control lasted on average 30 - 40 days, and efficiency was improved with the addition of oil. For control of pear rust mite, the product was equal to Agri-Mek. It also provided equivalent control of western tentiform leafminer but at rates of 2.9 L/ha or greater. Pear pyslla is suppressed for 14 - 21 days at rates of 2.9 - 4.4 L/ha.

Milbemectin was found to control 1st instar larvae of the sweet potato whitefly (Bemisia tabaci) in controlled environments, but was much less effective on older larvae (Phytoparasitica, 1999). Milbemectin is rapidly photodegraded and exposure of treated cotton seedlings to 3 hours of sunlight rendered it ineffective in controlling adult whiteflies. However, adding a mineral oil adjuvant restored activity. In the field, milbemectin was more effective than cypermethrin in controlling whitefly on cotton even without an oil adjuvant.
CropUse
CropUses:
cotton, grapefruit, ornamentals, pome fruit, stone fruit, soft fruit, tea, vegetables

5-70 g ai/ha

Premix

Type

AI concn

Emulsifiable concentrate (EC)

1% (w/w)

Wettable powder (WP)

2% (w/w)

Physical Properties
Molecular weight:A3: 528.7; A4: 542.7; Physical form:White, crystalline powder. Density:A3: 1.1270; A4: 1.1265 (both 25 °C); Composition:A mixture of the homologues milbemycin A3 (methyl) and milbemycin A4 (ethyl) in the ratio 3 to 7. Melting point:A3: 212-215 °C; A4: 212-215 °C; Vapour pressure:A3: <1.3 ×10-5; A4: <1.3 × 10-5 (both in , 20 °C); Henry constant:<9.93 × 10-4 Pa m3 mol-1 ; Partition coefficient(n-octanol and water):A3: logP = 5.3; A4: logP = 5.9; Solubility:A3: In water 0.88 (20 °C). In methanol 64.8, ethanol 41.9, acetone 66.1, n-hexane 1.4, benzene 143.1, ethyl acetate 69.5 (all in g/l, 20 °C). A4: In water 7.2 (20 °C). In methanol 45; Stability:Unstable to alkali.;
Toxicology
Oral:Acute oral??LD50 for male mice 324, female mice 313, male rats 762, female rats 456 /. Percutaneous:Acute percutaneous??LD50 for male and female rats >5
Environmental Profile
Ecotoxicology:?
Algae: (72 h) >7.3 /l.Bees:LD50(oral) 0.46 mg/bee; (contact) 0.025 mg/bee.Birds:LD50for male chickens 660, female chickens 650, male Japanese quail 1005, female Japanese quail 968 /.Daphnia:LD50 (3 h) for D. pulex >100 .Fish:LD50(96 h) for rainbow trout 4.5, carp 17 mg/l.Worms:LD50 (14 d) for Eisenia foetida 61 .?

Environmental fate:
?Soil:Soil 50 16-33 d.WATER SOLUBILITY: At 20°C: A3: 0.88 ppm; A4: 7.2 ppm
Transport Information
Signal Word:WARNING; Hazard Class:II(Moderately hazardous)

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