Massachusetts IPM Berry Blast

ID/Disease Cycle: Symptoms of gray mold include light brown areas on fruit; a powdery gray growth produced on rotted fruit and leaf tissue; and whole rotted berries that retain their general shape but become tough and dry.

The fungus overwinters in living plant tissue and proliferates in the spring as leaves die. Favored by cool, wet weather, the fungus infects new blossom tissue and remains latent until fruit starts to ripen.  Then visible symptoms occur. Secondary infections may occur when spores that cling to ripening fruit germinate in moist packaging conditions after the fruit is harvested, causing uncontrollable storage rots.

Damage: The main damage to the crop is from reduced quantity and quality of yield.  In years when wet weather prevails during bloom and ripening periods, significant crop losses can occur.

Management:
Monitoring: Consult scouting records from previous years to determine if carry-over inoculum is likely to be present.  Scout fields weekly in the current year starting in the pre-bloom period for symptoms.  Monitor weather conditions especially during bloom to determine if infection periods are imminent or have occurred.

Control strategies:
Cultural/Biological:
• Maintain narrow rows and good spacing between rows in order to promote good air circulation and drying conditions.
• Avoid applying excess Nitrogen prior to harvest; this promotes vegetative growth which limits air circulation and creates a dense vegetative canopy.
 • Maintain good soil coverage with mulch that reduces splashing from rain or irrigation.
• Use drip irrigation instead of overhead irrigation whenever possible; this reduces wetting and therefore reduces infection periods.
See other recommendations in the summary table below.

Chemical:

• Apply recommended fungicides starting at bloom, especially if field history or present weather conditions indicate high risk of disease infection.

• Repeat applications during bloom and early fruitset only if weather conditions are conducive to disease development.

• Continue applications as fruit ripens only if disease is found present in the field and weather conditions are conducive to disease development.

• Rotate fungicide materials from different FRAC groups to avoid promoting the development of resistant strains of this disease.

Root Weevil Management (Otiorhynchus spp. and Polydrusus spp.) - adapted from D. Handley, UMaine Coop. Ex.
Fields that were infested with root weevils last summer should be inspected for grubs this spring. Infested plants appear week and stunted, usually in somewhat circular patches in a field. Digging under the plants will reveal small (1/4”-1/2”) crescent-shaped legless grubs. Typically, the grubs begin to pupate when the plants are in bloom. A soil drench of Platinum® (thiamethoxam) insecticide during the spring and/or fall when the grubs are active in the soil can provide control. However, Platinum® has a 50 day pre-harvest interval, so it is too late for applications in most fruiting fields this year. Platinum® may also be used as a pre-plant or planting treatment for root weevils. It is not too late to put on an application of nematodes to control the grubs (optimal timing is about mid-May). Two species of nematodes appear to offer the best control of root weevil grubs. Heterorhabditis bacteriophora (Hb) appears to be the best candidate for control of root weevils when the soil temperature is above 60 degrees, and is available from Green Methods, www.greenmethods.com/site-info; the Integrated Biocontrol Network, www.biconet.com; and Koppert Biological Systems, www.koppertonline.com.

Nematodes are living organisms and they can be killed if they are misapplied. Order nematodes ahead of time and be ready to apply them through a sprayer or irrigation soon after they arrive. Refrigerate them if you cannot apply right away. Do not apply nematodes using a sprayer with a piston pump. Use clean equipment, removing all screens finer than 50-mesh. Apply nematodes in early morning or evening in a high volume of water to already moist soil, pre-irrigating if needed. Apply another ¼ inch of irrigation after application to wash them onto and into the soil. Researchers and suppliers recommended 250 (if banded in the row) to 500 million per acre, at a cost of $100-$200 per acre depending on volume and source. Nematodes tend to work best in heavily infested fields. Strawberry plants can recover their vigor remarkably well if crown feeding has not occurred and diseases haven’t taken over the roots.

Once the adults become active in July, bifenthrin (Brigade®) will provide some control if used at the highest labeled rates. The best timing for this spray is at night during the peak feeding activity of adults, before they start laying eggs, or about the time harvest ends. (Source: UMaine Strawberry IPM News No. 1 2016)