Causes of Poor Spring Plant Growth in Plasticulture Strawberries

Three aspects to think about are:

• what the plants look like in the spring compared to what they looked like the previous fall,
• what the winter weather conditions, your overwintering practices, and any other practices were, and 
• which varieties you are growing, as different varieties are prone to different problems.

If your plants were growing great last fall, but look questionable in the spring, you can focus on a few likely possibilities.  Winter injury is always a concern, and if the plants weren't covered with row cover or straw when cold temperatures arrived, the crowns could have gotten damaged.  Winter injury in the crown will appear as a more consistent or diffused color in the crown in mild cases, and "corkiness" or complete death of the crown in severe cases.  In contrast when a disease is the problem, there is usually a pretty stark change in color from healthy cream to brown or reddish-brown within the crown tissue.  It the planting is one that was carried over, winter injury is especially likely, as the crowns grow taller and are more exposed to cold air temperatures.

If the plants were covered with straw, keep in mind that windy conditions may have uncovered some of the plants at inopportune times.  Sometimes we see more winter injury on knolls where the rows are exposed to more wind.

And finally, mite populations can increase rapidly when row covers are used for protection, and their feeding can decrease plant vigor.  The milder temperatures under row covers can keep two-spotted spider mites active and populations increasing for a good portion of the winter. Flip over some leaves, and look for mites on the undersides.  In spring, two-spotted spider mites will be an orange color.   If dormant plants were used as the planting stock, and plants and new leaf growth looks "compressed" in the spring, it may be worth getting the plants checked for cyclamen mites.  Cyclamen mites are too small to see even with a good hand lens, so a microscope will be needed.  Extension personnel in some county offices have access to microscopes, or the sample may need to be sent elsewhere.

If your plants did not grow well last fall, and don't look great this spring either, it's likely that the same problem is still around and will need to be identified. In the past, strawberry plug plants have been diagnosed with several diseases including Neopestalotiopsis, most commonly in 'Ruby June' and 'Chandler'; anthracnose crown rot in 'Chandler'; Phytophthora crown rot in 'Flavorfest' and 'Malwina'; and angular leaf spot in 'Malwina'. With Neopestalotiopsis plants generally grow poorly in the fall after planting and varying percentages die during the fall or over the winter. The plants that do make it through the winter generally do not decline further in the spring. With Phytophthora crown rot and angular leaf spot (a bacterial disease -see photo below), plants here and there have wilted and collapsed, but this hasn't been obvious until a couple of months after planting.

Leaf dessication can be differentiated from leaf diseases as leaves will often be consistently dry, brown, and crispy around the edges of most leaves if dessication was the problem, and this will show up across a large area of the planting. Dessication is possible even in well-watered plantings because once the soil freezes, the roots can't take up water to replace what the leaves have lost.

When diagnosing problems, it is helpful to cut through several plant crowns from top to bottom. You can often tell more by cutting the crowns in this way rather than cutting the crown crosswise.