Lobesia botrana & Downy Mildew Experiments

Question 1

How was innoculation performed for Lobesia botrana? (POTENTIAL EXAM QUESTION)

Answer 1

3 moth larvae at black head stage was added to a cup with a food medium

Four different treatments were sprayed into the cups:
1. No treatment (control)
2. Control (water)
3. Insecticide Mimic (conventional)
4. Insecticide Dipel ES (bt-based)

Incubation under optimal growth conditions:
-7 days
-26C/day and 20C/nigh
-70% humidity

Question 2

What methods were used to evaluate the insecticide for Lobesia botrana? (POTENTIAL EXAM QUESTION)

Answer 2

Evaluation of biological versus chemical control

-Count the living larvae
-Dead larvae are small and dry

-Use Abbott’s Formula to calculate insecticide efficiency

Question 3

How was innoculation performed for Plasmopara viticola? (POTENTIAL EXAM QUESTION)

Answer 3

V. vinifera: M-Thurgau vines were sprayed with 3 protective treatments:
-fungicide Cuprozin progress
-resistance inducer (stilbene)
-water (control)

1. Vines are inoculated with downy mildew
2. Then covered for one night (to increase humidity)
3. Incubated for 6 days uncovered
4. Covered for one night before evaluation

DM optimal conditions: warm temperatures (18-25C) and high humidity

Question 4

Collecting sporangia

Answer 4

1. Let infected leaves thaw at room temperature
2. Spray underside of leave with water (where spores are)
3. Collect water and look under microscope using a cell chamber to count population

Question 5

Infection Cycle of Plasmopara viticola (Grapevine Downy Mildew)

Answer 5

1. Primary Infection (spring)
   -Oospores (overwintering) in leaf litter/soil germinate when warm/humid
   -Zoospores (swimming) are released via rain/splash
   -Zoospored enter the stomata
2. Incubation & Symptoms
   -Fungal hyphae colonize leaf tissue
   -Oil spots
   -If high humidity: white spors on underside
3. Secondary Infection (summer)
   -Sporangia (asexual) spread by wind/rain
   -New infections on leaves, shoots, flowers, berries
   -optimal conditions: warm + humid
4. Late-Season Infection
   -As vine enters dormancy, DM produces oospores for overwintering

Question 6

What methods were used to evaluate the insecticide for Plasmopara viticola? (POTENTIAL EXAM QUESTION)

Answer 6

(I don’t know if I have this correctly)

Disease severity:
-during the epidemic
-when disease pressure is high
-evaluate as %

1. Use disease severity scheme
2. Evaluate 5 leaves from top downward
3. Analyze without statistice

Disease incidence:
-at the onset of the epidemic
-when disease pressure is low
-yes or no

4. Calculate the average using disease incidence: per plant and all plants per treatment
5. ANOVA: shows significant difference
6. Tukeys test: which are different from the rest

Question 7

Using Abbott’s Formula to calculate insecticide efficiency, why would results differ from the lab to the field?

Answer 7

1. Environmental variability (temp, humidity, light, wind, rain):
   Lab - controlled
   Field - unpredictable
2. Insect behavior:
   Lab - contained in spall cup = direct exposure to insecticide
   Field - insects move, hide, migrate
3. Insecticide degredation:
   Lab - stable
   Field - UV degredation, rain, reduce effectiveness
4. Application accuracy:
   Lab - exact/precise
   Field - sprayers uneven coverage

Question 8

What are the modes of action for insecticide Mimic (Tebufenozide)? (POTENTIAL EXAM QUESTION)

Answer 8

molting accelerator

1. premature molting in larvae
2. used primarily against caterpillar pests
3. Mimic acts preferentially as a feeding agent
4. Best effect is obtained against early larval stages
5. Acts on: apple & grape berry moth, rhombus & spring moth

Question 9

What is Bt Toxin’s mode of action? (POTENTIAL EXAM QUESTION)

Answer 9

A biopesticide produced by bacteria Bacillus thuringiensis that targets specific insects

1. Larvae ingest
2. Activation in the alkaline gut ([pH ~9.5)
3. Bind to mid-gut receptors
4. Pore formation (holes) in gut cell membranes = leaking/gut paralysis
5. Gut ruptures = death

Question 10

It Bt Toxin safe for humans or beneficial insects?

Answer 10

Yes

Humans and beneficial insects lack alkaline stomachs and Bt receptors = no effect

It is biodegradable

Used in organic farming

Question 11

What is the mode of action for Cuprozin progress fungicide? (POTENTIAL EXAM QUESTION)

Answer 11

Type: copper based fungicide

Contact fungicide = protective treatment

Max. no. treatments: 7 applications/year

BBCH: 11 – 81 (first unfolded leaf to beginning of veraison)

Reapplication Interval: 8 to 12 days

Preharvest Interval: 21 days

Question 12

What is the mode of action for the resistance inducer? (POTENTIAL EXAM QUESTION)

Answer 12

Frontiers

Chitosan-derived bio-control for DM and PM

Plant enhanced defense capability upon stimulation

Treatment before infection

It does not interfere with pathogen directly

Chitosan is the most efficient resistance inducer