| dc.description.abstract | Climate-change leads to extreme droughts, but it is difficult to predict how crop pests are
affected. Drought may alter behavior of crop pests such as aphids that facilitate
transmission of pathogens like Fusarium graminearum, causing Fusarium foot and root
rot in barley crops by feeding close to the susceptible base of plants. Ground dwelling
generalist predators like Carabid beetles, and wolf spiders are important aphid enemies
during the aphid colonization phase in barley crops in Sweden. This study sought to
determine the influence of drought on interactions among aphids, aphid predators, and
Fusarium infections on spring sown barley (Hordeum vulgare L.) in Sweden. To
evaluate the influence of drought on predation of aphids by Carabid beetles and Wolf
spiders, the experimental design used was factorial with two factors, i) drought and no
drought, ii) predators present and predators absent. Similarly, the experimental design
used to assess the influence of drought on interactions between aphids and Fusarium
infections on barley sown during spring was factorial with three factors, i) drought and
no drought, ii) aphids and with no aphids, iii) Fusarium and with no Fusarium. To
evaluate the influence of drought on predation of aphids by Carabid beetles and Wolf
spiders, the total number of aphids per cage and the proportion of aphids present on
different parts of each barley plant sampled (below ground, 0-1 cm above ground, >1cm
above ground on stem, and on the leaves) was recorded. Data was subjected to normality
test to determine its distribution and analyzed using generalized linear mixed effects
models with the lme function in the nlme package in R 3.4.2. To assess the influence of
drought on interactions between aphids and Fusarium infections, the total number of
aphids present at 0-1 cm above ground, >1cm above ground on stem, and on the leaves
per plant in each pot was recorded. The data was subjected to normality test and
analyzed using generalized linear mixed effects models with the lme function in the
nlme package in R 3.4.2. Disease scores on the barley inoculated with Fusarium were
recorded and the data analyzed using one-way ANOVA test. There was a significant
effect of Fusarium inoculation on barley plants. In addition, Fusarium significantly
reduced the number of aphids on the whole plant and 0 to 1 cm above the ground. The
study concluded that drought increased proportion of aphids (Rhopalosiphum padi L.)
below ground. In addition, a strong effect of predation by Carabid beetles and Wolf
spiders reduced the number and proportions of these aphids below ground only in dry
conditions. This study recommends the need for further studies to establish how drought
intensity is likely to affect interactions among pest populations, their natural enemies and plant pathogens. | en_US |
