Plant Problems and Pests

Horticulture 2

C. Vick

What is a pest? A pest is anything that causes injury to or

loss of a plant (host plant) Categories:

Insects Nematodes Weeds Diseases Rodents

Insects: Bio review:

Anatomy: 3 segments

Head, thorax, abdomen Exoskeleton 3 pairs of legs

Feeding: Determined by the

structure of its mouth Mandibles=chewing Elongated beaks=

piercing and sucking Reproduction:

Sexual in most; asexual in some like aphids

Life Cycle: Metamorhosis

Incomp: Egg-nymph-adult

Complete: Larvae-pupae-adult

Facts: Over 800,000 species of

insects Approx 100,000 of those

are found in the US Less than 1,000 are

considered pests of plants and people

Insect-related pests: Spiders and mites

4 pairs of legs 2 body sections

Centipedes 2 pair of legs per body segment

Sowbugs and pillbugs seven pairs of legs

Snails, crayfish and slugs (snail with no shell)

Damage by pests: Dependent of the life stage

Example with Japanese beetle: Larval stage (grub) may feed on grass roots Adult stage may feed on ornamental crops

Usually caused by feeding on plants Can be caused by their presence alone

(burrowing, nesting, mound-building)

Insect control program: ID the insect and population/monitor Determine the potential for damage Assess the potential environmental issues Decide on control measures Use control measures Evaluate the results Assess resulting environmental issues

Nematodes: Also known as roundworms Approx 500,000 species in

the world Approx 2,200 that are plant

parasitic (sizes range from 1/75 to 1/10 inches long)

Female uses stylet mouth to piece host and to feed (Injecting enzymes to prepare cellular contents for ingestion)

Nematode Diagnosis: Be careful to not diagnose on symptoms alone as

they can mimic other conditions: Low or unbalanced fertility Sun scald or frost damage Poor drainage Drought damage Insect or mite injury Wilt or root-rot fungi Herbicide damage

Accurate diagnosis requires laboratory testing

Nematode Prevention: Note: some nematodes may be beneficial in plant

growth Preventing harmful nematodes:

Categories: Ecto-parasitic (attached outside host) Endo-parasitic (feed externally on host and internally within

the roots) Semi-endo-parasitic (partially embedded)

Preventative measures: Use disease-free planting materials Proper site preparation Follow cultural practices to ensure steady and vigorous plant

growth

Nematode Treatment: How to determine if treatment is warranted:

Look at population numbers per 100 cc of soil Nematode action threshold varies by type of worm and host:

Sting nematodes=10 Lance nematodes=60 Ring nematodes=500 EXCEPT in centipedegrass which then =150 Stubby-root nematodes=100 Root-knot nematodes=80

Monitor the above in spring and summer when populations are at their peak

Correct other problems before resulting to chemical means: pH Fertility Insect damage Population combinations and numbers

Root-knot nematode damage to a tomato plant:

Root-knot root damage:

Banana crop damaged by nematode worms