Jr. Brazzle et al., MULTIVARIATE APPROACH TO IDENTIFYING PATTERNS OF BEMISIA-ARGENTIFOLII(HOMOPTERA, ALEYRODIDAE) INFESTING COTTON, Environmental entomology, 26(5), 1997, pp. 995-1003
The influence of agronomic factors on the abundance and distribution o
f Bemisia argentifolii Bellows & Perring infesting cotton was describe
d using principal component and multiple regression analyses. Densitie
s of immature whitefly from leaf samples and 10 measures of cultural a
nd management practices, which included insecticide use, cropping patt
erns, planting date, field size, and natural enemy abundance, were qua
ntified for 56 and 30 cotton fields located throughout the Imperial Va
lley, California, in the summers of 1993 and 1994, respectively. White
fly densities declined with increasing insecticide use and field size.
Large (>32 ha), frequently sprayed fields exhibited lower whitefly de
nsities than small fields receiving <5 insecticide applications. White
fly densities were significantly and negatively related to the proximi
ty and acreage of spring melons to the 56 cotton field sampled in 1993
, suggesting spring melon fields as a source of whitefly infesting cot
ton. A similar relationship was also observed early in the 1994 season
. In addition, densities of adult natural enemy numbers were positivel
y correlated with immature B. argentifolii, suggesting that the existi
ng natural enemy complex did not regulate whitefly populations in the
cotton fields sampled in 1994. Consistent positive relationships among
planting dates and whitefly densities on all sample dates and for bot
h years suggest that cotton fields planted earlier in the season will
be host to fewer whiteflies relative to those fields planted later in
the season. Within the constraints presented by cotton production with
the Imperial Valley, results from this study suggest that cotton shou
ld be planted early in the season and far from melons to reduce whitef
ly pressure within cotton.