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Phylloid Strawberries and Glyphosate

During the 2003-04 strawberry season, an increase in samples of phylloid berries were brought in to the Gulf Coast Research and Education Center - Dover.  Phylloid strawberries are nicknamed “brocco-berries” or “tassel berries” since the seeds (achenes) become masses of frilly, green, vegetative tissue (Fig. 1).  Normally, this is associated with infection of the plant by leaf-hopper vectored diseases caused by phytoplasmas.  Phytoplasmas are single-celled organisms that lack a rigid cell wall and live in phloem (food conductivity) tissue.  Phytoplasmas are distributed worldwide and affect many crops, causing over 300 diseases.  Phylloid berries are one of the symptoms of infection by aster yellows or strawberry green petal phytoplasmas.  To determine the causal agent of the phylloid problem that was seen last season, especially with the cultivar Strawberry Festival, Dr. Natalia Peres, plant pathologist, undertook a project to develop a rapid diagnostic test for detection of phytoplasmas by PCR. Surprisingly, all the phylloid berries tested negative. 

At the 2004 International Strawberry Symposium in Australia, a paper was presented on the effect of the herbicide glyphosate on strawberry phyllody.  Since glyphosate is the number one herbicide used by strawberry growers in Florida, she and Dr. John Duval designed a trial this season to look at glyphosate effects on the incidence of phylloid in strawberry. Three concentrations (0.001, 0.01, and 0.1 of the labeled rate) of the herbicide were applied one day or 4 weeks after transplanting on two different cultivars, Strawberry Festival and Camarosa.  At the higher rate of 0.1 applied after transplanting, phytoxicity symptoms developed.  Young leaves showed typical chlorosis and plants produced no fruit.  At the 0.01 rate (9.8 oz./100 gal) applied after transplanting, plants showed no damage on the foliage, and flowers and young green fruit looked normal until the fruit started to ripen.  Then green vegetative tissue developed from the seeds. At this concentration, approximately 40% of ‘Strawberry Festival’ and 50% of ‘Camarosa’ plants produced phylloid fruits. In the current season, a commercial field with glyphosate injury has shown an abundance of “brocco-berries”.  Thus, if “brocco-berries” or “tassel berries” are seen in a field, first check to see if glyphosate has been used.

Fig. 1. Phylloid strawberry, notice the abnormal development of the berry.

Natalia Peres¹ and Alicia Whidden^2
1GCREC-Bradenton, ²Hillsborough Cooperative Extension Service
Vegetarian 05-02