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1 MSU Extension Publication Archive Archive copy of publication, do not use f current recommendations. Uptodate infmation about many topics can be obtained from your local Extension office. How to Recognize and Control Strawberry Fruit Rots Michigan State University Cooperative Extension Service F Folder Series Robert H. Fulton, Botany and Plant Pathology Issued May pages The PDF file was provided courtesy of the Michigan State University Library Scroll down to view the publication.

2 EXTENSION FOLDER F220 Strawberry Fruit Rots

3 Strawberry Fruit Rots By Robert H. Fulton Department o f Botany and Plant Pathology A disease survey of Michigan strawberry plantings disclosed that fruit rots caused by far the greatest loss to the growers. One reason f this is that all of these various rots have one trait in commonthey can infect a berry in any stage of its developlnent, from green to ripe. The grower should be concerned about rots but not alarrned, because occurrence of rots in any field will vary fronl year to year depending upon local weather conditions. Prolonged rains and moderate temperatures are requi red f extensive rot outbreaks. Identifying Fruit Rots Proper identification of the rots present in a planting is essential f carrying out an effective control progranl. The imptant strawberry fruit rot s common to Michigan show certain characteristics that will aid in this identification. Gray mold (Botrytis cinerea) This f ungous infection starts as a light brown spot which is watery at first but which never leaks. The pulp under this spot t urns dark brown. Soon the berry becomes dried out, nlumltiifies, and is covered with a gray dusty powder the spes of the f ungus. Ther e is NO distinct line between healthy and diseased strawbeity fruit tissues. Botrytis may also attack the strawberry blossoms, flower stalks, and leaves, turning thenl brown. Stemend rot hull rot (Dendrophoma obscurans) This f ungus attacks the sepal cap of the berry first, t urning it brovlll. The infection progresses down under t he cap into the stemend of t he fruit. The pulp of the berry t urns brown, soft, and watery. Fig. 2a. Left, healthy caps; right, cap infected with stem end hull rot. Fig. 1. Gray mold. 2 Fig. 2b. Berries sectioned to show : left, healthy berry; right, berry showing distinct line between diseased and healthy tissues. There IS a distinct line between good and diseased tissues. Dendrophoma nlay also attack leaves, causing an eggshaped pieshaped brown spot to fm. This is called leaf blight. Rhizoctonia brown rot (Rhizoctonia species) This is a soilbne rot ; infection starts where t he berry conles in contact wit h the soil. The rot is dry, spongy, and dark brown to black in 3

4 Fig. 3. Rhizoctonia brown rot. col. It generall y results in a onesided berry, the upper side developing nn1al1y while that in contact with the soil is rotting. Rhizoctonia rot develops slowly in the fruit so there IS a distinct li ne behveen healthy and diseased tissues. Leather rot (Phytophtha cactum) T his is another soilbne fruit rot which results in a. brown, watersoaked spot on green berries and in shades of brown to purple on n1aturing berries. These spots are softened but tough and leath ery. The vascular strands arteries of the berry are deeper brown than the pulp. A white mold growth may fm on the surface of the berry. Fig. 4. Leather rot. 4

5 TABLE lspray control program f strawberry fruit rots Time Amount* to use in: to Materials 1 gal. 100 gals. Remarks Apply water water Not effective through mulch, 1. Dn1ant to Limesulfur because infected over Delayed Dmant Liquid 7 2 'Ii gal. wintered plant parts ltiust I be thoughly wet by spray Powder 10 Not practical to eradicate infection. in lar<re IF plants are welladvanced quantities. befe n1ulch is removed, Use at strength given on eliminate this spray, as Organic label f controlling apple inj ury ltiay result. Con1 mercuries scab. mence sprays with #2. 2. When new leaves Use anyone Protective sprays at this are fully ex of the time aid in further reducing primary panded and following: infection. blossolti buds Ferbam ll/i are visible Zineb 1 '12 ZiraITI 2 Captan 2 I 3. PreBloom to BloOl11 4. When berries are V:~ grown 5. PreHarvest (3 Captan 2 days befe harvest) II/i lb. 11/2 lb. 2 lb. 2 lb. In wet seasons, gray mold may attack blossoms, leaves and developing fruit, which may result in extensive fruit infection pri to and during harvest. ~, 2 lb. Apply this spray if gray n10ld is quite evident and extensive rains are predicted. There is NO distinct line between healthy and diseased tissues. Leather rotinfected berries are BITTER to the taste, Control Measures Cultural program Control the soilbne rots, rhizoctonia and leather rot, by n1ulching the planting. This will prevent the ripening berries from con1ing in contact with the funguscontaminated soil. Spray program Control gray mold and stemend fruit rots economically by following the spray schedule in 5 * Abbreviation in table: stands fol' tablespoon Table 1. You can also control diseases that may attack the leaves and stems, namely leaf blight and leaf spot, by using this spray calendar. Time the sprays with the development of the strawberry plant and apply within a day two BE FORE predicted rains. REMEMBER, complete spray coverage of strawberry rows is essential f good control. Coope r a ti ve exte n s ion wk in a g ri c ulture a nd hom e economics. Michigan S ta te University a nd the U. S. Depa r t m ent of Agricult ut'e cooper a ting. P a ul A. Millet, Direct, Cooperati ve E xten s ion Ser vice. Mi chigan S ta te Uni ver s ity. E ast L a n s ing. Printed a nd dis tribut ed undel' Acts of CongTeSS, M ay S a nd June : i) : 56 10M 6