Introduction. Plum cv. SantaRosa shows climacteric behaviour and grows profitably under sub-temperateconditions in India. After ripening, it has a very limited shelflife (3–4 days) in ambient conditions [(38 ± 2) °C and at (68 ± 4)%RH]. Hence, there is an urgent need to extend its marketabilityusing recent techniques. Materials and methods. Plumswere harvested at the pre-climacteric and climacteric stages ofmaturity and packed with newspaper shreds (control), KMnO4-impregnatedchalks, KMnO4-impregnated newspaper shreds or ethylene-absorbent sachets;then they were transported by road to New Delhi. The biochemicaland physiological analyses were carried out at 3-day intervals onplums stored in supermarket conditions [(20 ± 1) °C and at (90 ± 2)%RH] for 15 days. Results and discussion. Untreatedfruits had less firmness than those which were packed with ethyleneabsorbents. The activities of fruit-softening enzymes such as lipoxygenase(LOX), polygalacturonase (PG) and pectin methylesterase (PME) increasedrapidly in the control treatment in comparison with plums packed withvarious ethylene absorbents, the least being either with ethylene-absorbentsachets or with KMnO4-impregnated newspaper shreds. Plums of pre-climacteric andclimacteric maturity attained respiration and ethylene evolutionpeaks on the 9th day and 6th day, respectively. Conclusions. Theplums of pre-climacteric and climacteric stages of maturity packed withethylene-absorbent sachets showed the best results in supermarketconditions in maintaining the firmness, quality and shelf life ofplum up to the 12th day and 9th day of storage, respectively.

Oryzaephilus mercator and O. surinamensis are stored grains and processed food pests, the latter being responsible for major economical losses. Polyacrylamide gel electrophoresis was used to analyse esterase patterns during insect development. Seven esterases, three cholinesterases, two carboxylesterases and two acetylesterases, were identified in O. mercator, one of which was proper to adults. Five esterases, of which four were cholinesterases, occurred in O. surinamensis. Strains of O. mercator and O. surinamensis were also exposed to malathion and chlorpyrifos-methyl. According to the LC50 estimates, OmLC-M and OmLA strains of O. mercator and OsLB strain of O. surinamensis were the most resistant to both insecticides. However, higher sensitivity to malathion and chlorpyrifos-methyl has also been verified in some of its esterases. Cholinesterases OmEST-1 and OsEST-5 seem to be involved in this resistance. These results suggest that organophosphate tolerance may be related to genetic variability in esterase isoenzymes.

Populations of the whitefly, Bemisia tabaci collected from the Americas and the Caribbean Basin were examined for non-specific esterases and for the ability to induce characteristic phytotoxic disorders in key assay species as a means of investigating biogeographic diversity. Esterase markers were used to detect polymorphisms among regional B. tabaci populations and to establish the present distribution of B. tabaci biotypes in the region. The A biotype occurred only in contiguous locales in northern Mexico and the southwestern US, while the B biotype was present throughout much of the Caribbean Basin and the US, and in Brazil. Distinct C and D type esterase markers were observed for Costa Rican and Nicaraguan B. tabaci populations, respectively. The 0 or null type population was collected only from Jatropha gossypifolia (L.) in Puerto Rico. Laboratory colonies of the A and the B biotypes were almost equally sensitive to an organophosphate, profenofos. The B biotype was more resistant to a pyrethroid, permethrin, suggesting the existence of a biotype of fi. tabaci, with a history of exposure to pesticides with a pyrethroid-based chemistry. In mating studies involving reciprocal crosses between the A and the B biotypes, very few F, female progeny were produced, indicating either minimal or non-existent reproductive compatibility between these haplo-diploid B. tabaci populations, presently considered to be the same species. Evidence is presented for the recent and widespread introduction, and subsequent spread of the B biotype throughout the US, the Caribbean Basin, and other proximal locations.

The development of phase phenism in L. erysimi involved function related changes in the activity of hydrolytic enzymes. The esterase activity decreased from first to third instar and then increased in the fourth instar and adults. The decrease in the third and the increase from fourth instar up to adults was more in alatae than apterae. The acid phosphatase activity was maximum in second instar. It decreased in the third and then increased again in the fourth instar and adults. The increase was more in alatae than in apterae. The alkaline phosphatase showed a similar trend but was in contrast to acid phosphatase and showed low activity in alatae as compared to apterae.