ABSTRACT:The synthesis of chitosan methylcarbamate (ChMC) and ethylcarbamate (ChEC) is described by using a new methodology. Polymers with substitution degrees up to 63% for ChEC and 68.5% for ChMC were obtained. Derivatives with lower substitutions were acid soluble but those with higher ones were completely insoluble. This could be due to the loss in hydrophilic sites when the substitution degree increases. The reaction conditions and degree of substitution obtained for both derivatives were also described. A complete chemical characterization was carried out by spectroscopic techniques. The thermal degradation of chitosan and derivatives were studied in the range 25-500°C and both derivatives were shown to be thermally less stable than chitosan.
Obscure mealybug, Pseudococcus viburni (Signoret), is a cosmopolitan pest that causes damage by suction of vascular juices and the production of honeydew, as well as for being a quarantine insect. Within control options, entomopathogenic fungi are a good alternative, nevertheless, more research is needed. In this research, the Metarhizium anisopliae var. anisopliae (Metschnikoff) isolate Qu-M984 was evaluated on P. viburni under laboratory conditions. Virulence was evaluated by lethal dose 50 (LD 50 ) and lethal time 50 (LT 50 ), for each of the four life stages of the female. The doses tested were 10 5 , 10 6 , 10 7 and 10 8 conidia mL -1 . Also fecundity, egg size, fertility, and longevity of adult females were evaluated at doses of 10 5 and 10 6 conidia mL -1 , the evaluations were made every 2 d throughout the insect life time. The LD 50 and LT 50 obtained were variable for each life stage, although without statistical differences among life stages (P > 0.05), ranging from LD 50 = 7.3 × 10 5 to 4.9 × 10 9 conidia mL -1 and LT 50 = 7.74 to 9.97 d at 10 8 conidia mL -1 . Significant differences (P ≤ 0.05) were observed on longevity at 10 6 conidia mL -1 . Longevity was 29% less compared to the control. This result on longevity at relatively low dose is relevant due to the fact that decrease possibilities to find live quarantine insects at the moment of harvest. Fertility, fecundity and egg size showed no differences (P > 0.05).
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