Plant pathogens can profoundly affect host plant quality as perceived by their insect herbivores, with potentially far-reaching implications for the ecology and structure of insect communities. Changes in host plants may have direct effects on the life-histories of their insect herbivores, which can then influence their value as prey to their natural enemies. While there have been many studies that have explored the effects of infection when plants show symptoms of disease, little is understood about how unexpressed infection may affect interactions at higher trophic levels. We examined how systemic, asymptomatic, and seed-borne infection by the ubiquitous plant pathogen Botrytis cinerea, infecting two varieties of the lettuce Lactuca sativa, affected aphids (the green peach aphid, Myzus persicae) and two widely used biocontrol agents (the parasitoid Aphidius colemani and the ladybird predator Adalia bipunctata). Lettuce varieties differed in host plant quality. Asymptomatic infection reduced chlorophyll content and dry weight of host plants, irrespective of plant variety. Aphids reared on asymptomatic plants were smaller, had reduced off-plant survival time and were less fecund than aphids reared on uninfected plants. Parasitoids showed reduced attack rates on asymptomatically infected plants, and wasps emerging from hosts reared on such plants were smaller and showed reduced starvation resistance. When given a choice in an olfactometer, aphids preferentially chose uninfected plants of one variety (Tom Thumb) but showed no preference with the second (Little Gem) variety. Parasitoids preferentially chose aphids on uninfected plants, irrespective of host plant variety, but ladybirds did not show any such preference. These results suggest that the reduced quality of plants asymptomatically infected by Botrytis cinerea negatively affects the life history of aphids and their parasitoids, and alters the behaviors of aphids and parasitoids, but not of ladybirds. Fungal pathogens are ubiquitous in nature, and this work shows that even when host plants are yet to show symptoms, pathogens can affect interactions between insect herbivores and their natural enemies. This is likely to have important implications for the success of biological control programs.
Currently circulating influenza B viruses can be divided into two antigenically and genetically distinct lineages referred to by their respective prototype strains, B/Yamagata/16/88 and B/Victoria/2/87, based on amino acid differences in the hemagglutinin surface glycoprotein. During May and July 2005, clinical specimens from two early season influenza B outbreaks in Arizona and southeastern Nepal were subjected to antigenic (hemagglutinin inhibition) and nucleotide sequence analysis of hemagglutinin (HA1), neuraminidase (NA), and NB genes. All isolates exhibited little reactivity with the B/Shanghai/361/2002 (B/Yamagata-like) vaccine strain and significantly reduced reactivity with the previous 2003/04 B/Hong Kong/330/2001 (B/Victoria-like) vaccine strain. The majority of isolates were antigenically similar to B/Hawaii/33/2004, a B/Victoria-like reference strain. Sequence analysis indicated that 33 of 34 isolates contained B/Victoria-like HA and B/Yamagata-like NA and NB proteins. Thus, these outbreak isolates are both antigenically and genetically distinct from the current Northern Hemisphere vaccine virus strain as well as the previous 2003-04 B/Hong Kong/330/2001 (B/Victoria lineage) vaccine virus strain but are genetically similar to B/Malaysia/2506/2004, the vaccine strain proposed for the coming seasons in the Northern and Southern Hemispheres. Since these influenza B outbreaks occurred in two very distant geographical locations, these viruses may continue to circulate during the 2006 season, underscoring the importance of rapid molecular monitoring of HA, NA and NB for drift and reassortment.