Eat your seeds
Invertebrate seed predators, like beetles or crickets, are an important component of agroecosystems that can help regulate weed populations. The invertebrates consume weed seeds as a high-protein food source, just like humans eat seeds and nuts. Previous research has shown that different types of invertebrate seed predators have preferences for different types of weed seeds. Although numerous studies have quantified weed seed losses from invertebrate seed predators, limited research has been conducted on the potential for invertebrate seed predators to consume cover crop seeds. Because the germination of cover crop seeds is essential to a good cover crop stand, there could be a potential impact from invertebrate seed predators that hasn’t yet been studied.
Cover crop seed predation
Cover crops are commonly broadcast seeded, and because seeds are left on the soil surface they are susceptible to invertebrate seed predators. In our work, we hypothesized that 1) invertebrate seed predators will consume cover crop seeds as much as weed seeds, 2) seed preference will vary by plant and invertebrate seed predator species, and 3) seed consumption will be driven by seed morphology and nutritional characteristics.
We conducted seed preference trials with four common invertebrate seed predators (Pennsylvania dingy ground beetle, Common black ground beetle, Allard’s ground cricket, Fall field cricket) in laboratory ‘No Choice’ and ‘Choice’ feeding experiments to compare seed predation of ten cover crop species (barely, annual ryegrass, pearl millet, forage radish, cereal rye, white mustard, crimson clover, red clover, triticale, hairy vetch) and three weed species (velvetleaf, common ragweed, giant foxtail). In the ‘No Choice’ feeding experiments the crickets and beetles had only a single type of seed to choose from, and we counted how many seeds were left after the feeding period. In the ‘Choice’ feeding experiments the crickets and beetles were given all the seed varieties at once and at the end of the trial we assessed which seeds were most preferentially eaten.
What seeds were preferred?
We found that all four invertebrate seed predators readily consumed cover crop seeds. Cover crops with hard seed coats and seed hulls, such as hairy vetch and barley, were generally not preferred, likely because the hard seed coat or hull was a barrier to the invertebrate. Of the four species of invertebrates, the fall field cricket ate the most seeds when in ‘No Choice’ trials (averaging 100% of seeds offered). Our results suggest that farmers should select cover crop species that are avoided by invertebrate seed predators—like cover crop seeds with hulls or seed coats—if they plan on broadcasting the seed.