Entomophagous Insects – The Insect-Consuming Insects. Predators and Parasitoids. What is “Natural Control” ?. Natural Control is the everyday occurrence of predation of one insect upon another. In so doing, populations of predators effect populations of prey and vice versa. .
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Entomophagous Insects – The Insect-Consuming Insects Predators and Parasitoids
What is “Natural Control” ? Natural Control is the everyday occurrence of predation of one insect upon another. In so doing, populations of predators effect populations of prey and vice versa. This is analogous to the classic relationship between the arctic hare and fox populations.
In the Natural World Predators Are Abundant and Are Always Searching For a Meal A Ground Beetle Attacking a Land Snail
Ground Beetle Attacking Caterpillar Forest Tent Caterpillar As you can see, ground beetles are not very choosy. They will eat about anything that they can overpower.
Wasp Feeding on Birch Leafminer Larva Wasp Birch Leaf Miner
What is Biological Control? • Biological Control is natural control that involves manipulation of predator populations to control pest populations in agro-ecosytems. • “Biocontrol” has been an active area of applied population ecology for about 50 years. • Today it is highly commercialized and is a viable addition to the arsenal used to combat pests. • It is part of a larger approach called “Integrated Pest Management” or I.P.M.
“Beneficials” • May be predators, parasitoids or pathogens • May serve singly or in combination as “natural enemies” but populations often have to be manipulated. • Reduce pest populations to economically tolerable levels rather than eliminating the pest. • Environmentally compatible. • Costs are comparable to pesticides.
Predators • Commonly used predators include lady-bird beetles, green lacewings, mantids and predatory mites. • Commercially available from insectaries.
Qualities of Good Predators • Considerably larger in size than the prey. Why? • Feed in juvenile stage as well as in the adult. • Focused feeding habits - specific predators are better than general ones usually. • Ability to switch to an alternative food source when prey populations are reduced. • Must be able to adapt to local environmental conditions.
The Mealybug Destroyer – An Australian Import A member of the ladybird beetle family.
Green Lacewing Eggs Eggs Are Laid on Stalks to Lessen Cannibalism
Predator Uses Sickle-Like Mandibles That are Hollow to Suck Out Contents of Bollworm
Other Well-Known Predators – Most Available Commercially • Preying Mantids • Some stink bugs (Hemiptera) • Minute pirate bug ( “ ) • Some nabid bugs • Some mites are predatory
Why Aren’t All Insect Predators Effective As Good Biological Control Agents? • ?
Parasitoids • Generally a non-social wasp (braconids and ichneumonids are commonly used) or a tachinid fly • Egg(s) are laid on/into host by female using a modified stinger (ovipositor) • Larvae hatch and consume tissues of prey. • Move to surface of prey, pupate and emerge as adults
Typical Posture of Ichneumonid Wasp Female Preparing to Oviposit After ovipositing, the wasps deposits a pheromone on surface that deters oviposition by a 2nd. female. Why is this behavior very adaptive?
TrichogrammaWasp Ovipositing Into Abdomen of Aphid (Note egg at lower left)
Tachinid Fly Adult Note numerous bristles on abdomen
Tachinid Eggs on Caterpillar Female Fly Attaches Eggs to Exterior of Body. They Hatch and Bore In.
Tachinid Larva Emerging Pupation Outside of Host
Host Caterpillar Containing Half Dozen Tachinid Pupae In this example, pupation is occurring inside the host.
Parasitoids Attack All Developmental Stages of Insects • Egg • Larva • Pupa • Adult
The following 5 slides illustrate a sequence from one generation to the next.