Diversity and Pest Management
by Jonathan Lundgren, Ph.D
Humans have been battling against bugs for millennia and history has shown that insects have killed more humans than bullets or bombs through disease transmission. But not all insects are pests — for every harmful insect there are 1700 beneficial or neutral insects and many of these are incredibly important to the productivity of our agricultural systems.
Insects contribute hundreds of billions of dollars to the US economy every year through a myriad of services. Insects are incredibly efficient at the conversion of feed to protein, which makes them invaluable as the basis for many food webs. Insects provide pollination services to most fruits and vegetables that we consume, but we are now learning that pollination is also beneficial to major crops such as soybeans. Pollinators and Beneficial Insects pollinate approximately 75% of the crop plants grown worldwide for food, fiber, beverages, condiments, spices, and medicines. If your farm is growing any crops that require insect pollination to produce maximum yield, it is vital to provide food and shelter for these beneficial species.
Beneficial insects are also a major frontline defense against crop harming pests such as aphids. Giving beneficial insects a sanctuary free of pesticides and tillage and providing plant material for nesting fulfills the majority of the needed requirements to develop a healthy population. Many of our beneficial predatory insects also rely on alternative food sources, such as nectar, at some point of their life cycle. If you have been battling a pest species in your crops, it may be that you have created an environment in which that pest can thrive and not be challenged. Attracting beneficial and predatory insects will lead to a more balanced system and pest problems naturally become less of a concern. It is highly desirable to have a healthy population of lady beetles, lacewings, syrphid flies, crab spiders, wolf spiders, mantids, and other predators living in or near crop fields. Building an army of beneficial insects that can be ready to pounce on destructive pests is a great benefit, but for this to happen the proper environment needs to be created. Building populations of beneficial predators can be accomplished with cover crops, insectary strips, and companion crops.
Cover crops can attract predators and build their populations in preparation for protecting the next cash crop. Healthy predator populations can be encouraged and maintained by having a diverse mixture of both cash crops and cover crops. This creates a sequence of pollen and prey insects throughout the year, ensuring a constant and consistent food source through the entire growing season. Many species of predators can also utilize pollen as an alternate food source in the absence of insect prey. Since pollen does not run or fight back, it is an excellent food for newly hatched predators. The larvae of lady beetles, lace wings, and syrphid flies (all good aphid predators) can exist largely on pollen if there is insufficient prey. Cover crops that flower and produce abundant pollen and nectar include buckwheat, mustards, phacelia, and many clover species.
Pollinators and Beneficial Insects
Insects and animals pollinate approximately 75% of the crop plants grown worldwide for food, fiber, beverages, condiments, spices, and medicines. If your farm is growing any crops that require insect pollination to produce maximum yield, it is vital to provide food and shelter for these beneficial species.
There are nearly 4,000 wild bee species in North America, all of which are dependent upon a consistent pollen/nectar source through the entire growing season. Green Cover Seed carries more than 35 plant species that are highly attractive and supportive to pollinator species. We can help you custom design mixtures that will flower and attract beneficial insects prior to the time your cash crop will need their services.
Giving beneficial insects a sanctuary free of pesticides and tillage and providing plant material for nesting fulfills the majority of the needed requirements to develop a healthy population. Many of our beneficial predatory insects also rely on alternative food sources, such as nectar, at some point of their life cycle. If you have been battling a pest species in your crops, it may be that you have created an environment in which that pest can thrive and not be challenged. Attracting beneficial and predatory insects will lead to a more balanced system and pest problems naturally become less of a concern.
Predatory Insects and Spiders
According to our favorite bug guy, Dr. Jonathan Lundgren, for every yield robbing insect there are 1,700 beneficial or neutral insects. We like those odds and we believe that it is highly desirable to have a healthy population of lady beetles, lacewings, syrphid flies, crab spiders, wolf spiders, mantids, and other predators living in or near crop fields. Building an army of beneficial insects that can be ready to pounce on destructive pests is a great benefit, but for this to happen the proper environment needs to be created. Building populations of beneficial predators can be accomplished with cover crops, insectary strips, and companion crops.
Every plant is attacked by insects and cover crops are no exception. In most cases, cover crops are attacked by insects that do not harm the following cash crop. For example, pea aphids that feed on a cover crop of winter peas will not bother grain sorghum plants the next year, but the predatory insects feeding on those pea aphids can also feed on sorghum aphids. Cover crops can attract predators and build their populations in preparation for protecting the next cash crop. Healthy predator populations can be encouraged and maintained by having a diverse mixture of both cash crops and cover crops. This creates a sequence of pollen and prey insects throughout the year, ensuring a constant and consistent food source through the entire growing season.
Many species of predators can also utilize pollen as an alternate food source in the absence of insect prey. Since pollen does not run or fight back, it is an excellent food for newly hatched predators. The larvae of lady beetles, lace wings, and syprhid flies (all good aphid predators) can exist largely on pollen if there is insufficient prey. Cover crops that flower and produce abundant pollen include buckwheat, mustards, phacelia, and many clover species.
The typical method of using cover crops is to grow them prior to the cash crop, terminate them, and plant the cash crop into the residue. This usually does not allow the cover crop to bloom and produce pollen and predators will often leave the dead cover crop, because the prey insects leave or die off. One method to keep the predators in the field is to leave strips of live cover crop every 2 or 3 sprayer boom passes throughout the field during termination. Predators can move and survive longer in these strips and the strips can be terminated and planted later after the emergence of the cash crop on the rest of the field.
A twist on this idea is the use of insectary strips. These are permanent strips of flowering plants that produce abundant pollen. This is an excellent way to use field access road, field borders, pivot roads, headlands, waterways, and turn rows. It is also a good way to eliminate point rows. Many flowering plants can also make excellent hay in combination with perennial grasses. In addition to their use in attracting predatory insects, they can also be of great benefit to pollinator species like honeybees and bumblebees.
An additional innovation is the use of companion crops to attract beneficial insects during the growth of a cash crop. One example is the use of companion crops in double-crop sunflowers after wheat. Interplanting flowering plants like buckwheat, clovers, flax, and mustards can attract pollinators, which cross pollinate sunflowers (cross pollinated sunflowers produce 25% better yield than self-pollinated sunflowers). Interplanting can also attract beneficial insects to control pests. The presence of strongly scented flowering plants is thought to prevent head moths from finding sunflower fields.
Sugar Cane Aphid Case Study
A great example of using companion crops and insectary strips for pest control is the use of companions to control sugar cane aphids in sorghum. Jimmy Emmons, an Oklahoman farmer, has found success with this approach. Last summer, he planted grain sorghum at 4 lbs per acre mixed with 1 lb of flax, 3 lbs of buckwheat, and 5 lbs of mungbeans to attract aphid predators. Jimmy also planted a 13 foot wide strip of a flowering cover crop mix around his field, as well as one strip through the middle of his field to help attract predators. He was the only sorghum farmer in his area without problems from sugar cane aphids. One of his neighbors spent $40,000 dollars spraying for sugar cane aphid and still did not completely control the aphids. According to Jimmy, the companions may have cost a little yield due to competition, but not nearly as much as the sugarcane aphid would. He selected covers that would be shorter than the sorghum and therefore less competitive and would have feed value if they somehow ended up in the grain tank. “I am not saying that if you do what I did, that you won’t have aphids,” said Jimmy. “All I can say is this is what I did last year and that I did not have aphids and I plan to continue doing it.”
