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Insect Defoliation and Population Dynamics in Blends of Resistant and Susceptible Soybean Cultivars
Author(s) -
Sij John W.,
Bowers Glenn R.,
Way M. O.,
Boykin D. L.
Publication year - 1999
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1999.00021962009100010013x
Subject(s) - cultivar , biology , insect , population , agronomy , yield (engineering) , horticulture , botany , demography , materials science , sociology , metallurgy
Phytophagous insects can cause significant economic yield loss in soybean [ Glycine max (L.) Merr.] production areas of the southern United States. Although breeding efforts have resulted in developing insect‐resistant cultivars, the yield potential of these cultivars is generally lower than conventional cultivars under conditions of light insect pressure. The objective of this study was to determine if a blend of insect resistant and insect susceptible cultivars affords some degree of insect control while maintaining high yields under high insect pressure environments. Experiments were conducted on a Labelle soil (Oxyaquic Vertic Argiaquolls) near Beaumont, TX, in 1990 to 1992. The 3‐yr field study included five population ratios of Maturity Group VIII cultivars Dowling (insect susceptible, S) and Crockett (insect resistant, R): 100 S:0 R, 75 S:25 R, 50 S:50 R, 25 S:75 R, and 0 S:100 R. Plots were sampled weekly for insects and percent leaf defoliation when insect populations began to increase in late summer. Data were analyzed with blend treated as a linear trend. Insect counts of six major pests showed that, of 18 possible year‐insect combinations, in only three cases were there significant population differences due to blend. In late season, the percent defoliation of Crockett increased in all 3 yr as the percentage of Crockett in the blend increased. By contrast, as the percentage of Dowling in the blend increased, the percent defoliation of Dowling decreased in 2 of the 3 yr. Therefore, blending Crockett and Dowling did not offer insect defoliation protection for Dowling and may have had an opposite effect. Maximum percent defoliation for Crockett was generally 40 to 50% less than that for Dowling. In 1990 and 1991, blending had no effect on yield or seed quality. In 1992, there was a significant, negative effect on yield ( b = −4.46) and seed quality ( b = 0.01) as the percentage of Crockett increased in the blend. Blends of these cultivars did not improve yield of Dowling under conditions of insect pressure compared with a pure stand of Dowling. A blend of insect resistant and susceptible cultivars did not appear to be a suitable insect control management strategy in soybean.