R. Montandon et al., FACTORS REDUCING THE PEST STATUS OF THE RUSSIAN WHEAT APHID (HOMOPTERA, APHIDIDAE) ON WHEAT IN THE ROLLING PLAINS OF TEXAS, Journal of economic entomology, 86(3), 1993, pp. 899-905
Effects of field infestations of the Russian wheat aphid, Diuraphis no
xia (Mordvilko), on yield of winter wheat in the Texas Rolling Plains
were studied. In 1988-1989, colonies established from three different
population isolates were released into small plots in the fall and spr
ing. In 1990-1991, aphids of one colony were released at three differe
nt infestation levels on each of four release dates during the growing
season. Populations of all aphid species and number of mummified aphi
ds were monitored in 1990-1991. In 1988-1989, the aphid colonies did n
ot differ in population numbers or in their effect on yield, but fall
infestations resulted in higher Russian wheat aphid numbers and greate
r yield loss than spring infestations. In 1990-1991, an early fall rel
ease was the only release that developed high numbers and caused yield
loss. Infestations resulting from releases made in early and late win
ter and early spring did not affect yield. Initial infestation levels
of 330, 660, and 1,000 aphids per 12-m2 plot had no significant effect
on Russian wheat aphid numbers during the late part of the season or
on yield. Higher numbers of Russian wheat aphids developed in 1990-199
1 than in 1988-1989, but peaks in the populations during both years oc
curred in mid- to late April. Densities of greenbug, Schizaphis gramin
um (Rondani), and bird cherry-oat aphid, Rhopalosiphum padi (L.), and
aphid mummies were positively correlated with high Russian wheat aphid
densities. Unsuitable wind direction and lack of alternate host plant
s are discussed as possible factors that limit Russian wheat aphid inf
estations in the Texas Rolling Plains.