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Using Bees to Disseminate Trichoderma to Strawberries for the Control of Botrytis Fruit Rot

by Joe Kovach

INTRODUCTION

Over the past few years several studies have shown that bees can disseminate beneficial fungi, bacteria, and viruses to strawberries, pome fruits, and clover. Botrytis cinerea causes the familiar gray molds that are evident on a variety of fruits, including grapes, strawberries, and raspberries. Infection by B. cinerea on strawberry occurs in the flower and remains quiescent until the fruits mature. It then develops abundantly, causing fruit rot. Current IPM recommendations call for one to two fungicide applications (usually Ronilan) at bloom, depending on variety, bloom length, and weather conditions, for control of this pest.

Trichoderma harzianum 1295-22 is a commercially produced biocontrol agent that controls several plant pathogenic fungi including Botrytis. Mode of action can be

  • mechanical

  • chemical

Honey bee at apple blossom.
click to see larger image
Trichoderma harzianum strangling Pythium.
 click to see larger image
Electron micrograph of Pythium cell wall pitting caused by Trichoderma harzianum.
click to see larger image
Bumble bee visiting a strawberry flower.
click to see larger image
Beehive inserts at hive exit containing Trichoderma harzianum.
click to see larger image
Strawberry flowers inoculated with Trichoderma harzianum.
click to see larger image

OBJECTIVE

To determine whether bumble bees and honey bees can successfully disseminate the spores of T. harzianum to strawberry flowers for Botrytis fruit rot control.

METHODS

  • "Allstar" strawberries located at the NYSAES were used, 1 row by 5 m plots, 6 reps of each treatment.

  • Bees were excluded from plots using cages and rowcovers.

  • A granular formulation of Trichoderma was placed into bee hive inserts.

  • Trichoderma was evaluated at bloom

  • Fruit was evaluated at harvest and 4 days later to determine latent Botrytis infections.

RESULTS

Strawberry Flowers

 

TRT

% flowers w/ T.h. (5/23)

Check

46 a

Ronilan

37 a

Honey bee

100 b

T.h. spray

100 b

Bumble bee

100 b

Strawberry Harvest

TRT

% Botrytis

Ronilan (1 spray@bloom)

4 a

Honey bees close to hive

5 a

Honey bees far from hive

6 ab

Bumble bees

7 ab

Trichoderma (1 spray)

12 b

Check

23 c

means followed by the same letter are not significantly different (LSD, P<0.05)

 

Bees & Trichoderma Strawberries

 

TRT

 

wt/berry

 

seeds/berry

 

Trich. spray

4.8

282

Ronilan

5.7

313

Check

6.1

296

Honey bee far

7.1

406

Bumble bee

7.4

376

Honey bee close

8.4

377

 

Bees & Trichoderma Strawberries

 

TRT

 

wght/berry

 

seeds/berry

 

Bees

5.6 a

366 a

No Bees

4.3 b

298 b

25 - 30% increase in weight & seed #'s

 

SUMMARY

Plant protection benefits were achieved by using bees as disseminators of Trichoderma. In addition, strawberry yields were increased by the presence of these pollinators.

Research conducted by Joe Kovach, IPM Fruit Coordinator, IPM Program, Cornell University.

 

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