Navigation Menu+

Pest Management in Fruit Production

Integrated Pest Management
I. History.
Fruit growers became slightly dependent on chemicals in 1800′s when Bordeaux
mixture and lime sulfur came into widespread use.
In 1940′s, synthetic organic pesticides became available, and evolved into a multibillion dollar industry. Yields and quality improved greatly; growers became
dependent on pesticides.
Today, chemicals de-emphasized, have shorter half-lives and non-target effects;
BUT, still pose environmental and health hazards, kill beneficial organisms, and
cause development of resistance in target organisms.
Chemicals are still the major means of pest control in fruit production.
II. Definition.
IPM A pest management system that, in the context of the associated environment and
the population dynamics of the pest species, utilizes all suitable techniques and
methods in as compatible a manner as possible and maintains pest populations
at levels below those causing economic injury.
* Definition does not exclude the use of chemicals.
* Objective: optimization of control in terms of the overall economic, environmental,
and social needs of mankind.
* Requires higher level of management; better education, more supportive
research.
* On average, reductions of .25% are realized with IPM vs. calendar or spray
schedule approach, but in some years, pesticide applications in IPM programs are
equal or may slightly exceed that dictated in spray schedules.
III. Control Tactics.
1. Resistance – Breeding or selection of crop species or cultivars that are genetically
resistant to one or more pests.
A plant is truly resistant if the pest organism cannot complete its life cycle within
the plant and manifest the signs or symptoms of the disease.
A plant is tolerant of a disease if the signs and symptoms are present but growth,
production and survival are not affected at economic levels.
2. Cultural Control – Manipulating pest populations or those of predators or parasites by
cultural practices other than spraying.a. Sanitation.
- Removal of “mummified fruit” from trees which harbor fungal spores (brown rot
of stone fruits)
- Removal of leaf litter, detritus, infected or dead branches in trees, to minimize
level of inoculum
- Cleaning tools after use on disease-affected trees
van der Planck’s law: X = Xo
e
rt
X= amount of disease at any point in time
Xo= amount of initial inoculum
r= rate of disease spread (depends on environment, pathogen, host)
t= time over which disease increases
b. Alternate hosts. Remove plants from around the orchard which harbor disease
organisms/pests.
Cedar-apple rust (remove cedars from orchard borders)
White pine blister rust (some currants and gooseberries are alternate hosts.
Wild plums – carry plum leaf scald and peach phony mycoplasmas; harbor
plum curculio, fruit moths.
c. Pruning/training.
- better light (UV) penetration in canopy
- leaves to dry faster (light, air circulation)
- better spray penetration, chemical measures more effective.
* Over-pruning stimulates vigorous, succulent growth which may be more prone to
attack by insects or fungi.
d. Fertilization.
- Excess N induces vigor, draws aphids often.
- Nutrient stress weakens plants, natural defenses less active.
e. Irrigation.
- Overhead irrigation keeps foliage wet longer, and may help disseminate
organisms that are naturally disseminated by raindrop impact (citrus canker
bacterium, fire blight).
- Intermittent irrigation may be helpful in arid areas by washing off dust which
harbors mites (used on guard rows).
- Saturated soil around drip emitters – root or foot rot problems?f. Orchard floor management.
- Mulch or high weeds next to trunk = mice, vole damage.
- Cultivation damages trunks, roots;may spread soil-borne diseases or nematodes
- Mowing when foliage feeding insects are present on sod cover can force insects
up into trees to find food (Grasshoppers).
- broad-leaved weeds may attract insects to orchard; mowing beneficial.
- Certain species may be unattractive; may slow movement; e.g, ‘Stella’ wheat,
Nimblewill in peach orchards for nematodes.
- Some natural weed species may provide nectar and pollen for beneficial
insects.
3. Biological control – The regulation of pest populations by their natural enemies
(predators, parasites, or pathogens).
a. Beneficial arthropods.
Creature Feeds on
Ladybird beetles aphids
Lacewings aphids
Syrphid flies aphids
Chalcid wasps parasitize insect larvae
Trichogramma wasps parasitize larvae and pupae of lepidoptera
predaceous thrips mites and scale
predator mites other mites
preying mantis soft-bodied insects
Beneficial nematodes can actually be applied thru irrigation! 90-96% control of black
vine weevil in cranberry, but at 10x the cost of chemical control ($300/acre) !!
Beneficials – take time to build-up; have special requirements, very sensitive to insecticide
sprays.
Two important aspects = Food sources and alternate host insects.
1. Food sources
Parasitic wasps – need pollen and nectar to live. Obtain these from plants like
(Umbelliferae) carrot, yarrow, dill, anise; mustards; some composites like Blackeyed Susan, daisies, goldenrod. Some gather nectar from foliar nectaries of peach
and cherry.
Example: codling moth control.
71% larvae parasitism and 9.2% pupal parasitism in an unsprayed, weedy
orchard.Only 7.5% larvae and 0% pupae parasitism in nearby sprayed, cleancultivated orchard.
In sprayed but weedy orchard, 17% larvae and 18% pupae parasitism.
2. Alternate hosts
Sometimes necessary for overwintering, completion of life cycle.
Examples:
Ragweed borers – can support parasites of oriental fruit moth; ragweed left
in or around orchard may be beneficial.
Strawberry leafroller – hosts parasitic wasps that attack oriental fruit moth.
Unsprayed strawberries nearby may help.
Blackberries and prunes – support non-damaging leafhoppers which
provide eggs for overwintering of grape leafhopper parasites. Plantings of
grapes next to blackberries or prunes have lower infestations of leafhoppers.
Lady bugs – reproduce more slowly than aphids, outbreaks can occur
despite presence.
Legume cover crops provide a substrate for pea aphids, which
support lady bugs.
In USSR: Codling Moth control.
- One spray of broad-spectrum insecticide in early spring
- 3 releases of Trichogramma wasps
- 2 sprays of Bacillus thuringiensis
* This program gives adequate control – 3.5% infestation vs. 1.5% infestation for a
strict chemical program; Unsprayed control = 54% infestation.
b. Pathogens, parasites.
1.Bacillus thuringiensis (“B.t.”) – Rod-shaped, gram positive, crystalliferous, sporeforming bacterium. Useful only against caterpillars. e.g., Oriental fruit moth,
codling moth
- Annual sales of B.t. = 35-45 million $, not quite 1% of 5 billion/yr insecticide
market (1988 data).* Biotech – gene for Bt endotoxin constructed, put into soybeans and other crops -
“natural” pest control?
2. Baculoviruses – Most promising of viruses of insect pests.
- Controls 39 insect pests in forestry (16) and agriculture (23).
- Like B.t., these do not affect vertebrates or plants, only arthropods; so safe for
environment and man.
- Slow kill; at best 4 days, worst = 2-3 weeks; feeding slows as death approaches.
Too slow???
- Most effective on small larvae.
3. Fungi.
Hirsutella fungus kills citrus rust mite; greasy spot oil sprays in mid-summer
reduce populations, allow rust mites to build.
4. Autocidal Control – Manipulation of pests so that they contribute to their own
destruction.
Radiate males, causes sterility. Release sterile males into an area with normal
males and females – most matings bear no eggs.
5. Chemical Control – The use of chemical agents to reduce pest populations; ideally,
chemicals are selective for the target pest and do not harm beneficial organisms such as
pollinators, or predators, parasites and pathogens of the pest species.
6. Attractants, Repellents, and Hormones – Nontoxic chemicals which alter the behavior
or physiology of the pest and prevent completion of the life cycle. Also used to monitor
pest populations.
a. Mating disruption: Pheromones are chemical “trails” which lead males to
females. If area saturated with pheromone, males and females cannot find each
other.
1. Codling moth: “Isomate-M” – pheromone impregnated into a twist-tie.
- one tie/tree, works for 90 days
- may require 1 “knock down” spray if populations are high.
* Doesn’t work in small or long and narrow orchards, or those with
irregular borders.2. Grape berry moth: Ties also available soon.
- Primary insect pest of grapes; often only pest that requires sprays to
control.
* Ties can double as ties to hold canes to wires.
- requires about 200 ties/acre.
b. Juvenile hormones: “Juvenoids” – hormones that interrupt dormancy process,
disrupt life cycle.
Pear psylla – small, cicada-like insect that feeds on foliage, also a vector of pear
decline.
Juvenoids interrupt diapause (dormancy process), exposing susceptible
forms of the insect to winter weather. Eggs laid by sprayed individuals do
not survive winter; spray in fall.
7. Quarantine and Eradication – The confinement of a pest to a given area (quarantine)
or the elimination of the pest from a given area (eradication)
Citrus canker in Florida:
Eradicated in 1920′s, back again. Eradicated by burning affected trees and
neighboring trees.
8. Mechanical – Physically killing or removing pests.
e.g., vacuuming leafhoppers fromgrapevines.An air-blast sprayerrun in reverse
creates a vacuum, goes down the rows and sucks insects into bags. Can use dead
bugs in bags as fertilizer!!
Claim is 50-90% control, but still unproven.
“If it flies, we can get it; if it crawls, forget it”
IV. Supportive Tactics.
A. Population sampling, monitoring – “Scouting”. = regular inspection of the orchard to
assess population levels of pests. The basis for IPM.
Growers currently avoid because: (New York survey data)
1. Cost of hiring additional personnel to scout.
2. Lack of trained personnel available for hire.
3. Complexity of sampling procedures.
4. Lack of effectiveness of sampling at an acceptable cost.Cost of scouts ??? < $100/acre for large operations. At least this much can usually
be recovered by avoiding unnecessary sprays.
Benefit ??? – as much as 3-fold reduction in pesticides, if environment is
“cooperative”.
* Former student of HORT 4020 made $22/hr alfalfa scouting !!
Example scouting procedure: Spotted tentiform leaf miner – apple pest.
- Sample at “pink” stage (prior to bloom).
- Sample 4 flower clusters from each quadrant of 5 trees (random).
- Count # eggs on undersides of 2nd, 3rd, and 4th leaves of each spur (leaf #1 =
basal)
- If average >1 egg/leaf, or total >60 on all leaves, then spray at pink or petal fall
stages. If below this threshold, wait until 2nd generation (July) to sample again.
B. Establishment of economic thresholds. Systematic research of pest population size
vs. economic injury.
* Difficult, time consuming work; thresholds may vary with intended market,
season, cultivar, etc.