Laboratory Bioassays

1
Field Evaluation of Three Diatomaceous Earth
Application Treatments for Controlling Stored
Wheat Insects Edmond L. Bonjour1,
Siwei Liu1, Thomas W. Phillips1, and Frank H.
Arthur2 1Oklahoma State University,
Department of Entomology and Plant Pathology, 127
Noble Research Center, Stillwater, OK 74078
2USDA-ARS Grain Marketing and
Production Research Center, 1515 College Avenue,
Manhattan, KS 66502 E-mail addresses
ELB4119_at_okstate.edu lsiwei_at_okstate.edu
tomp_at_okstate.edu arthur_at_gmprc.ksu.edu
Experimental Protocol Three DE applications
of Dryacide and an untreated control were
applied to wheat at bin filling in July 2004 (3
bins per treatment) in bins containing 170
bushels of hard red winter wheat (Fig. 1) DE
applications were as follows 1) top-layer
application to the top 50 cm of grain (500
ppm) 2) layered application top and bottom 50
cm of grain (500 ppm) in combination with an
empty bin application 3) total grain mass
application (300 ppm) All bins were challenged
with insect infestations by the addition of 100
adults each of R. dominica, T. castaneum, and C.
ferrugineus into the tops of each bin at the time
of bin filling and for the next three consecutive
weeks Field Sampling Grain samples were
collected from the bins by combining two grain
trier samples per bin at 4, 8, 12, 16, 20, and 36
weeks post-treatment and insects were sifted from
the samples and counted (Fig. 2) One probe trap
sample per bin was collected for a duration of
one week at each of the above post-treatment
periods and the insects trapped were identified
and counted (Fig. 3)
Laboratory Bioassays At the end of the 36-week
storage period, approximately 100 grams of grain
from trier samples were placed in each of 3 jars
(0.24 liter) for each bin (3 reps per treatment
per species) A total of 50 R. dominica, T.
castaneum, or S. oryzae adults that were 2-3
weeks old was added to each jar for a specific
species Bioassays for adult beetle mortality (7
day exposure) and F1 progeny production (after 7
weeks) were conducted at 28.0 C and 65
relative humidity (Fig. 4) P. interpunctella
were evaluated at 36 weeks by placing 20 eggs on
sticky black paper strips placed on 40 grams of
half-crushed wheat in 0.12 liter jars and emerged
adults were counted (Fig. 5)