Sunflower
results in cross pollination. Some sunflower varieties will not produce highest yields
unless pollinators are present. All varieties will produce some sterile seed (without
meats), but varieties differ in their degree of dependence on insect pollinators.
Autogamous sunflower hybrids do not require bees for maximum yield and will yield the
same when covered by bags as uncovered. In non-autogamous sunflower varieties,
pericarp (bull) development is normal but no ovules or meat develop. Wind is relatively
unimportant in cross-pollination of sunflower. Some of the older open-pollinated
varieties such as Peredovick set only 15 to 20% of seed without pollinators, whereas
many hybrids set 85 to 100% seeds without pollinators.
Insect pests have become major potential yield-reducing factors in sunflower production
in the northern Midwest (Table 4). Insects specific to sunflower that feed on the heads
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