Biological Control In Landscapes

1. Biological Control In Landscapes Dr. David Shetlar The Ohio State University OARDC/OSU Extension Columbus, OH © September, 2004, D.J. Shetlar, all rights reserved

2. Integrated Pest Management (IPM) Chemical Biological Cultural

3. NOTES: While using the Integrated Pest Management (IPM) approach, ALL control options should be considered – cultural, chemical and biological. Many believe that most landscape plants can “defend” themselves from most pests if the plants are given proper care – suitable location, nutrition and food. Under these conditions, most pests have parasites, predators or pathogens that keep their populations below serious damage levels. However, urban landscapes often cause plant stress and intervention may be necessary to reduce pest attack. In these situations, most pest management specialists suggest using the least intrusive methods – plant health care and low impact pesticides. These methods help conserve biological controls.

4. ■Predators Ants & Wasps Bugs (damsel, bigeyed, stink) Beetles Mites Spiders Others ■Parasites Wasps Flies ■Pathogens Bacteria Virus Entomopathogenic Nematodes Fungi Classic Insect Biocontrols

5. NOTES: In general, BIOLOGICAL CONTROL includes the “three Ps” – Predators, Parasites and Pathogens. Predators are animals that capture and eat their prey. Parasites are animals that infest their prey, usually killing it. Insects that are parasites of other insects are called Parasitoids. Pathogens are usually microbes that are generally lethal to their insect hosts – mainly, bacteria, fungi, virus and protozoa. Some include nematodes in the pathogen category, but they are technically parasites (multicellular organisms).

6. Biocontrol or "BioBased"? ■Paenibacillus popillae – grub milky disease ■Bacillus thuringiensis - δ-endotoxin ■Saccharopolyspora spinosa - spinosyns (=Conserve™)

7. NOTES: True biological controls are either predators, parasites or pathogens. Many microbes produce chemicals that are lethal to insects if ingested or absorbed. In the previous case, the bacterium, Paenibacillus popillae, infects white grubs and it reproduces inside the grub body. Resistant spores are produced to infect future grubs. The bacterium, Bacillus thuringiensis, (BT) actually lives in soil, but it produces a protein toxin that can be lethal to insects if it is ingested. BT does NOT “infect” insects! Saccharopolyspora spinosa is another soil-dwelling microbe that produces a group of toxins that are lethal to some insects and mites. This toxin is extracted from the growing medium. BT and S. spinosa toxins are considered BIOBASED, not biological.

8. Chinese mantis, a common imported predator

9. NOTES: Is the Preying Mantis a “good bug”? Many would say “yes,” but I would then ask “why”? What do preying mantids eat? When their egg cases hatch, the nymphs prey on each other and often there is a 50% mortality rate in the first 24 hours! Mantids are generally large predators that feed on larger insects – flies, grasshoppers, honey bees, etc. In other words, they are indiscriminate predators, eating anything that is the right size, whether pest or beneficial. Do preying mantids eat aphids? Scales? Spider mites? White flies? NO! The better question to ask is, “Are preying mantids USEFUL biological controls?” (probably not!)

10. Convergent lady beetle eating aphids

11. NOTES: Is the Lady Beetle a “good bug,”? Oops, a useful predator? Lady beetles are usually called “general predators,” but each species usually specializes on certain limited groups of prey – aphids, scales, spider mites, etc. Lady beetles have multiple generations each year and they can often “react” to pest build-ups. They rarely eat each other and the adults are commonly considered “resistant” to many groups of insecticides, a good IPM trait! Therefore, lady beetles can be considered USEFUL biological controls! However, do you know its complete life cycle?

12. What is this?

13. NOTES: While many recognize the lady beetle, few recognize its larva! In order to use biological controls effectively, one must be able to recognize all the stages of a useful biological control. In fact, the larvae of lady beetles are often two to three times more efficient (eating more prey per unit time) than the adults! However, because the larvae are often considered “ugly,” they may be destroyed by unknowing persons.

14. Polistes wasp eating black cutworm

15. NOTES: Unfortunately, many biological controls are not as “cute” or aesthetically pleasing as lady beetles. As an example, many social wasps are considered to be beneficial predators by entomologists, but are not “appreciated” by the average gardener. During most of their life cycles, social wasps (including yellowjackets) prey on caterpillars, sawfly larvae and various flies. It is only during the end of the season when these wasps turn to feeding on sweets that they then become nuisance pests.

16. Keys to Successful Biocontrols • Easy to recognize • Easy to use • Public acceptance • Cost effective • Shelf life

17. NOTES: Biological controls that are “successful” usually need to fulfill several criteria. They must be recognizable, i.e., if you can’t tell what is a useful agent, then it is susceptible to being mistaken as a pest! Biological controls that are easy to use are more likely to BE used! Many do not “like” wasps, spiders, ground beetles and other “yucky” critters. These are less likely to be accepted by most people. Commercially useful biological controls must be effective AND economically feasible. If the best biological control is too expensive to use, it will not be used! Many potential biological controls can not be easily packaged and delivered to users. They have no shelf life!

18. Spiders Predatory Bugs Predatory Mites Lacewings Lady Beetles Syrphids & Other Flies Classic Landscape Biocontrols •Predators

19. NOTES: Spiders consistently end up as one of the top ten of useful landscape predators. Unfortunately, many people do not like spiders and have trouble considering them useful. To overcome this this problem, many recommend training and education about the diversity and behavior of spiders.

20. Jumping spider

21. Lynx spider

22. Wolf spider with egg mass

23. NOTES: Predatory mites are some of the best control agents that battle spider mites, thrips and other small insects. They are often misidentified as plant feeding mites, but they can be easily differentiated because most predatory mites run rapidly over the plant surface.

24. Predatory mite

25. NOTES: Lady beetles are some of the most popular, acceptable and useful biological controls found in urban landscapes. However, the group is a large and diverse one, and some of the adults are often not recognized since they are not the typical red-orange beetles with black spots. One group is generally black with red spots. These are often called twice-stabbed lady beetles (several species) and most are scale predators. Many small lady beetles are simply tiny black beetles with or without spots. These are often scale or mite predators. Each lady beetle has a characteristic larva that is often not recognized as being a “baby” lady beetle!

26. Transverse lady beetle adult.

27. Coleomegilla maculata, often called simply “C-mac” lady beetle.

28. A twicestabbed lady beetle adult feeding on pine needle scales.

29. Convergent lady beeltle larva, a typical form.

30. Beetle larvae Scales Twicestabbed lady beetle larvae eating magnolia scales. They look like mealybugs, the classic “wolf in sheep’s clothing”!

31. Tiny Stethorus lady beetle larva, a mite predator.

32. Multicolored Asian lady beetle, eggs, larva, pupa and adult forms.

33. NOTES: There are many “bugs” (insects in the Order Hemiptera) that are predators of other insects and mites. While less recognized than Lady beetles, many of these are extremely important in keeping a variety of ornamental and turf pests in check. The group is a large and diverse one, with adults ranging from the large wheel bug (about 1.25-inches long) to the tiny minute pirate bugs (less than 0.1-inch long). Unfortunately, some of the beneficial bugs belong to families that also contain pest species, e.g., stink bugs and plant bugs. In such cases, an expert may be needed to help identify the good bugs from the bad bugs!

34. Bigeyed bugs are common predators of turf infesting pests, like chinch bugs. They also occasionally climb up ornamental plants in search of prey. They run and fly rapidly. They are identified by having the head width as wide or wider than the body width. Damsel bugs are common on perennials and flowers where they are generalist predators.

35. These lace bugs are running away from a minute pirate bug. These tiny bugs normally feed on eggs and mites, but they will take on larger prey. This predaceous stink bug is feeding on a pine sawfly larva. These stink bugs specialize in feeding on caterpillars and sawflies.

36. A predatory bug feeding on a gypsy moth larva. Many predatory bugs use toxic saliva that rapidly kills large prey. Bites from such bugs can be very painful.

37. NOTES: Lacewings (Order Neuroptera) include several families insects that have predatory larvae though some adults also feed on other insects. The green lacewings and brown lacewings are the most commonly seen landscape neuropterans. Both groups have lizard-shaped larvae that are armed with a pair of sucking mandibles. The mandibles of the green lacewing larvae are curved and the brown lacewing larvae have straight mandibles. A little known group of lacewings, the dustywings, are small insects that feed primarily on mites. The adults have white powder on their wings and may be mistaken for a whitefly or bark louse adult. The larvae look like overweight, miniature brown lacewing larvae.

38. Green lacewings lay stalked eggs so that the cannibalistic larvae don’t kill each other. Green lacewings are very common in urban landscapes. They should not be confused with the plant pests – lace bugs.

39. Green lacewing larvae have curved mandibles. Green lacewings pupate within small barrel-shaped cocoons.

40. Brown lacewing adult (left) and larva feeding on aphid (right). Dustywing adult near spruce spider mites, a favorite prey.

41. NOTES: There are many predatory flies, both as adult flies and larvae (maggots). One of the most common groups is the hover flies or syrphids. These brightly colored flies are commonly mistaken for sweat bees or other bees since they commonly hover around nectar-producing flowers. The adults are harmless, but the larvae have a pair of sharp hooks with which they latch onto aphids, their favorite food. Many other flies feed on other insects while in the adults stage and many more flies have larvae that are parasitic, not predatory.

42. Typical adult syrphid on a flower. Most of these flies are excellent bee mimics. Syrphid larva feeding on an oak aphid. Syrphid eggs next to birch leaf aphids.

43. Some syrphid maggots are elaborately colored and have fleshy extensions along the body side. This tiny maggot is the larva of the predatory aphid midge. These flies feed on aphids and spider mites.

44. An anthomyiid fly feeding on a leafhopper nymph.

45. NOTES: There are many groups of beetles, other than lady beetles, that are also general predators, both as adults and/or larvae. Ground beetles and rove beetles are often in the top 10 of common landscape predators. Unfortunately, many people do not like these large, rapidly running predators. Such people are likely to kill these beetles rather than let them help control other insects.

46. Ground beetles range from brown and black to iridescent blues and greens. Most are predators, but a few feed on plants. Ground beetle larvae are often better at seeking out and preying on other insects than the adult stage.

47. Spiders Predatory Bugs Predatory Mites Lacewings Lady Beetles Syrphids & Other Flies Classic Landscape Biocontrols •Predators •Parasites Wasps Flies

48. NOTES: While one of the largest and most important groups of biological controls, parasitic insects are often disliked because of peoples’ general fear of wasps and flies. Insects that are parasites of other insects are commonly called parasitoids because they eventually kill their host. Unlike their social bee and wasp cousins, parasitic wasps generally do not posses a sting. However, a few do have stings, but they will not use them unless severely provoked. Many parasitic flies have larvae that enter their hosts’ bodies. The maggots eat most of the body contents before the host dies. These larvae may emerge to pupate while some remain in the host body to pupate. Talk about the model for the movie “Aliens”!

49. Aphid wasps are small black wasps that lay eggs in the bodies of aphids. Upon completing development, the wasp larva causes the aphid body to swell into an aphid “mummy.”

50. This hornworm was parasitized by a parasitic wasp with larvae that fed inside the body but they have pupated on the surface. This cutworm has parasitic wasp larvae that are feeding externally.