Key factors for modelling secondary spread of barley yellow dwarf virus

Abstract

Data for constructing and testing a simulation model of movement by aphids during the late autumn, winter and early spring period were obtained from an outdoor experiment. Adult wingless grain aphids (Sitobion avenae (Fabricius)) and bird cherry aphids (Rhopalosiphum padi (Linnaeus)) were released on trays of barley seedlings, planted at field density, placed under three levels of sheltering: protection from wind and rain, protection from wind alone, and unprotected. After one week all plants were destructively sampled and the positions of all aphids on the tray were noted. The experiment was repeated monthly from November to March.

More aphids were retrieved from fully protected plots than from those protected only from wind, or unprotected, suggesting that rain may increase levels of mortality. Consistently more S. avenae were retrieved than R. padi, supporting previous suggestions that S. avenae are more winter hardy. Fewer aphids moved away from the plants on which they were released when protected from wind and rain, than when protected only from wind, or unprotected. Rain had a greater impact on whether or not aphids moved away from a plant than did wind, and more R. padi moved than S. avenae. The distance moved by both species was less when protected from rain than when protected from only wind or unprotected, and for all months except December the mean distance travelled by R. padi was greater than by S. avenae.

There is a need for thorough validation of the model using viruliferous aphids.

Key findings

1. Rain increased both the amount of aphid movement and the distance travelled more than did wind. However, rain also increased mortality, which may offset the effect of increased aphid dispersal on virus spread.

2. R. padi were more mobile and moved further than did S. avenae, but consistently more S. avenae were retrieved than R. padi suggesting their greater survival.