摘要:

Development and survival of stalk borer,Papaipema nebris(Guenée), larvae under natural conditions were investigated by intensively sampling noncrop, grassy areas and bordering corn rows. The logistic function was used to derive developmental curves based on centigrade degree-day accumulations. The curves predicted the proportion of larvae in each stadium. Comparison of developmental curves for 1984 and 1985 indicated that other factors, in addition to temperature, played a role in regulating population development. In particular, synchronization between Julian date and phenology of late instars was noted. Partial life tables were constructed to describe stage-specific mortality. Effect of parasitoids on larval populations seemed to be limited, with parasitism rates of all stages<5%. Information on larval survival has suggested the following working hypothesis on stalk borer population dynamics: weather conditions during egg hatch, as well as predation and environmental factors during larval movement to new host plants, are important factors determining stalk borer population numbers in agroecosystems.

ISSN:1754-5692    

DOI:10.1093/ee/16.1.296

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Epidemic levels of the western spruce budworm (WSB),Choristoneura occidentalisFreeman, caused average tree defoliation in west central Idaho to increase from 35% in 1984 to 83% in 1985. Associated with this increase in defoliation was a change in relative stand ranking of defoliation between the 2 yr. WSB was found to damage all types and developmental stages of reproductive structures of Douglas-fir. Differential selection of feeding sites was observed, with a significantly higher proportion of larvae found in seed-cone buds than in pollen-cone buds. Of cones examined, 76% were infested with larvae, with the average percentage of destroyed seeds per tree exponentially related to the average current defoliation of the tree. However, even in heavily defoliated trees, some potentially viable seed remained.

ISSN:1754-5692    

DOI:10.1093/ee/16.1.304

出版商:Oxford University Press    

年代:1987

数据来源: OUP