Managing Insects, Mites and Other Arthropods

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Melvin Wade
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1 Managing Insects, Mites and Other Arthropods This will be a brief look at the science behind insects and their relatives, as well as some examples of the different types of damage they can do to plants.

2 What is a pest?

3 Insects and mites are arthropods. These are some arthropods you may know.

4 There are more species of insects than any other group of organisms. Over 1 million species known. Possibly 10,000,000 species still UNIDENTIFIED.

5 Very few of the insects we currently run into are considered pests. Most of them are beneficial, or serve no apparent use other than to be part of the food chain. Less than 3% are considered pests.

6 Insects can be considered beneficial (to humans) for several major reasons. Important to be able to identify beneficial insects in all their stages, to avoid damaging them unintentionally.

7 These are the shared characteristics of arthropods. Most of these we don t need to worry about for the scope of this class. However, their growth characteristics (namely, metamorphosis) we ll spend a little time on (See accompanying animated graphic on metamorphosis in Lecture tab). Reason? Because we need to realize that both pests and beneficial insects don t look the same throughout all parts of their life; we need to be able to identify them at all stages.

8 Insect anatomy: 3 body parts: head, thorax, abdomen Wings (1 or 2 pair), 6 legs Antenna

9 Arachnids: Ex: mites, ticks, spiders 2 body parts (cephalothorax, abdomen) 8 legs, no antennae, no wings Important to know, because arachnids are NOT insects, so insecticides don t always work.

Insects with incomplete metamorphosis have an immature that resembles the adult. There is NO wormlike intermediate. Examples include a grasshopper and a squash bug.

10 Insects with incomplete metamorphosis have an immature that resembles the adult. There is NO wormlike intermediate. Examples include a grasshopper and a squash bug. One thing to note about insects with incomplete metamorphosis: both the adults and young stages can be found in same general area, feeding on same plants. Control of one stage often controls other stages as well.

Insects with complete metamorphosis have a worm-like intermediate stage that can grow. Ex: ladybug, butterfly. Another example: house fly: Adult flies lay eggs on food sources for their larva.

11 Insects with complete metamorphosis have a worm-like intermediate stage that can grow. Ex: ladybug, butterfly. Another example: house fly: Adult flies lay eggs on food sources for their larva. A larva (plural: larvae) is the worm like stage that feeds and molts until it grows into a pupa. A pupa (plural: pupae) is the transitional stage between larval and adult flies. It used to be called a resting stage, because no visible growth was occurring. However, there is a LOT of changes going on within the pupa, as the larva changes drastically into an adult.

12 In this class we have divided the symptoms of insect problems into 8 categories.

13 Scales are closely related to pests you may be more familiar with like Aphids. Unlike aphids that can walk all their life, scales are generally immobile in all but the crawler stage. Mealybugs have some characteristics of aphids, but are less mobile, like scales. Soft scales are less mobile that mealybugs. Armored scales are the least mobile.

14 Scale diagnosis: dieback. Rough looking bark, is actually thousands of scales.

15 Bumps on twigs and leaves can be caused by either scale insects or gall makers. Use the flip test to distinguish between galls and scale insects If you flip over a bump with your thumbnail and rip up plant tissue the bump is a gall. Remember galls are specialized dwellings that plants produce for gall makers out of their own plant tissue. If you flip over a bump and the plant tissue is intact, the bump is the scale insect that is sitting on the twig.

16 Scales are insects that immobile most of their lives. The adults, crawlers, and settlers of pine needle scale are typical of armored scale biology and are pictured here.

17 Euonymus scale is of Asian origin and occurs throughout the world as a pest of many woody ornamentals. In southern Indiana, this species develops 2 generations per year and overwinters as mated 2 nd and 3 rd instar females. Consequences of euonymus scale infestation include Unsightly scale coverings encrusting stems and leaves, shown here. Heavy infestations can lead to reduced photosynthetic leaf area, stunted growth, leaf abscission, and eventually, plant death.

18 Wintering stage: Eggs Generations per year: 2 with crawlers in May and July Host: Lilac, birch, dogwood, ash, elm, poplar, soft maple, privet, willow, walnut, hemlock, rosaceous plants (Apples and Roses)

19 Pine needle scale.

20 Soft scale insects produce honeydew. Example: tulip poplar scale.

21 Pine bark adelgid. Related to scale, aphids. Fluffy white, can cover limbs of pines and cause serious stress and decline.

22 Galls are bumps of plant tissue that rip when removed Left- Cooley s spruce gall (top) and gall making adelgids (bottom) Right- Hackberry nipple galls (top) and gall making psyllids (bottom)

23 Horned oak gall, on tree

24 Oak trees commonly have lumpy, woody growths on them. This is usually from horned oak galls. Caused by tiny wasps. Life cycle complicated, control is very difficult. Can weaken tree over the years.

25 Sucking insects remove chlorophyll and leave white stippled marks. Both spider mites and lacebugs can cause these white stipples. In the next few slides you will see how lacebug injury can be separated from spider mite injury.

26 The stippling on these leaves is caused by the lacebug. One of the most common insect pests of azaleas. Different host plants all have different species of lacebug attacking them. The oval eggs found on leaf undersides are typical of lacebugs.

27 In this picture, we see adult lacebugs (right, and one on left) and cast off skins of molting larvae (left). Also notice the shiny black dots: this is their fecal material (bug poop). All of this will be found on the undersides of the leaves.

28 Spider mites, while not true insects, also cause piercing/sucking damage. This stippling pattern is very common on broadleaf plants.

29 Spider mites can do tremendous damage to evergreens, but the symptoms are not very clear. Usually, portions of the plant get pale green, then move into yellow and brown before defoliating.

30 Under heavy infestations, will often see webbing running along the stems and petioles of the leaves.

31 With a really good hand lens, you might be able to see the adult spider mites and their eggs. Very tiny, very hard to see.

32 To check for mites, we usually perform the white paper test in the landscape. Hold a sheet of white paper under a potentially infested branch. Best to choose a branch with light to moderate symptoms; there won t be any mites on completely dead limbs. Give the branch a couple of sharp smacks with your gloved hand or a stick. If there are mites, they will fall to the paper. They will be smaller than pepper flakes. Unlike dirt and debris, after a moment, the mites will begin to slowly crawl across the paper. Main reason to identify mite damage versus any other pest? Mites are not true insects, they are arachnids. Many insecticides, such as carbaryl (Sevin) won t work against them. Proper identification is needed for proper control.

33 Chewing insects produce characteristic kinds of defoliation. Some young caterpillars, Japanese beetles can skeletonize leaves. Skeletonization means that the soft green tissue of the leaves has been eaten, but the veins have been left behind. Some older caterpillars, sawfly larvae, and some beetles completely defoliate leaves.

34 Flea beetles eat tiny holes into leaf; we call this a shothole pattern. Hard to see insect, usually all we have to go on is the type of damage they do.

35 Slugs are not arthropods, but they can cause damage in the landscape. They tend to eat elongated holes... And leave slime trails. Usually not visible during the day, look for them in the evening and on cool, overcast days.

36 Black vine weevil leaves a characteristic irregular notch in the leaves the adult stage. This is very minor damage; however, in the larval stage, they feed on roots of ornamentals, causing stunting, decline and death. Leaf cutter bees (a beneficial pollinator) use leaves when making nests. They cut vary uniform circular holes in the edges of the leaves. They favor roses.

37 Japanese beetles: about half-inch long, shiny metallic, with white tufts around abdomen. Feed on over 350 species of plants, prefer lindens, grapes, cherry/plums, smartweed. Will also feed on soybeans and corn silks. Feeding injury described as skeletonization, because they feed on green tissue and leave veins alone.

38 Eastern tent caterpillar on left, seen very early in spring. Webbing in crotch of branches. Fall webworm comes on in early to mid summer. Forms webbing at end of branches. Control: physical removal (pruning, scooping); spray with B.t. (Bacillus thuringiensis, Dipel).

39 Bagworms: caterpillars enclosed in bag. Very common on evergreens, like juniper and arbor vitae, but can be on almost any plant. Overwinter as egg inside bag.

40 Bagworms hatch in early June in southern Indiana. Very easy to control at this point with B.T. By July, need to switch to Sevin, malathion, etc.

41 Tree borers usually blamed for killing off tree. Borers are attracted to trees under stress. First sign is decline and dieback.

42 On trunk, may see exit holes and loose bark (left). Sometimes see frass (sawdust, wastes) coming from holes, or piling up beneath tree (right).

43 If pull bark away, will see different designs of feeding galleries, depending on species. Left: engraver beetles; right, Emerald Ash Borer

44 If you see holes in a straight line, it s caused by a sapsucker, not insects. Borer exit holes have no pattern, and are usually not as numerous.

45 General borer life cycle: 1. Adult lays eggs on susceptible host trees, usually in cracks and crevices of bark. 2. Eggs hatch within 2 or 3 weeks. 3. Young larvae begin chewing through bark to reach cambium (sapwood). 4. Feeding of larvae accounts for longest part of this insect s life cycle. Depending on species, can remain under bark for a couple of months, to nearly a full year, to more than 2 or 3 years. 5. As winter approaches, many species will bore deeper into trunk for protection from cold. 6. Larvae pupates. 7. Adults chew an exit hole in trunk and emerge. They fly and mate and start the life cycle over again.

46 Several common insect borers, their principal hosts, and time to control (basically, 3 weeks after adults fly).

47 Emerald ash borer is one of the most devastating pests to come to the US in many decades. Will talk about it in more detail during tree pest talk.

48 Leaf miners: larvae lives inside leaf, feeding on soft tissues between upper and lower epidermis. Usually larvae of a fly.

49 When sucking insects kills plant tissue they deform plant growth when new tissue grows around dead tissue.

50 Thrips are very tiny insects that cause distortion and tissue discoloration and death by sucking the sap out. They are so small that they can live within the opening blossoms and not be seen. Very hard to control.

51 Spittlebugs are another sucking insect. The nymphs release a bubbly mass of liquid, usually at the base of leaf petioles and stems, in which they hide. Usually not very damaging, but unsightly.

52 Root feeders: insects spend part (most) of life underground. Usually in larval stage.

Root feeder life cycle (in this case, Japanese beetles): Eggs are laid underground by adult female beetles in early summer. The eggs usually hatch within 3 weeks.

53 Root feeder life cycle (in this case, Japanese beetles): Eggs are laid underground by adult female beetles in early summer. The eggs usually hatch within 3 weeks. The larva is a typical C-shaped grubworm, which spends most of the next 10 months underground, feeding on the roots of turfgrass. As winter approaches, the grubs migrate downward to keep from freezing. In the spring, they migrate back up toward the surface as the soil warms. They ll feed a little more, and then pupate for a month. They then emerge as adult beetles starting in June; the adults feed on many ornamental and garden plants, until they mate and start the life cycle all over again. Controlling the grub stage does not necessarily protect your ornamentals from beetle damage, since the adults can fly long distances.

54 Cicada egg laying injury. The damage is caused by the female cutting a slit into the twig to lay her egg; she will lay up to a dozen or more per twig. Very rare to see this, except in years when the periodical (17 year) cicada emerges.

Tree and Shrub Insects

Tree and Shrub Insects Aphids Aphids are small soft-bodied insects that suck plant juices. High aphid populations can cause leaves to yellow, curl, or drop early. The most bothersome aspect of aphids is the honeydew they produce.