Weather conditions have been dry, and we have been seeing issues like drought stress, heat blast, and upright dieback manifest (see disease section for more on UDB).
Some growers have been reporting uneven growth on bogs, and some overly lush areas. This could be due to winterkill issues. Areas with flowers/fruit use the fertilizer to support the fruit while areas with injury have invested the nutrients in vegetative growth.
Things to think about regarding pesticides.
Keep an eye on PHIs. As we enter August, be mindful of each pesticide’s pre-harvest interval (PHI). Depending on when you harvest, you might be approaching the end of your application windows for the use of some products – especially for herbicides like Stinger (50-day PHI), Poast (60-day PHI), and QuinStar (60-day PHI). Intensity One has a 30-day PHI. If using Ridomil for a late summer phytophthora application, know it has a 45-day PHI. Also keep in mind that handlers may impose a longer PHI than the product label. For example, the insecticide carbaryl (Sevin, etc.) has a 7-day PHI on the label but most handlers have a 75-day PHI!
Prepare pesticide reports. Start thinking about getting your pesticide report into your handler. Many are due the last week of August, only 3 weeks away.
Insects
While we are approaching the time to manage scale – mid August, very few reports of infestations have surfaced. Most dead areas are from lack of water (drought stress) and dead uprights peppered through the bog are attributed to Upright Dieback. Active scale now would show dying vine and you should be able to see the tiny scale on the stems, leaves, and berries if that is the problem. Very few sites warrant a spray this year!
Flea Beetle has been sited but again, it is rare, and you would need to have a super population (20-50) to warrant a Diazinon spray.
Weeds
If you have the time and manpower to wipe weeds, this could be a good time to start. While conventional wisdom is to wait until plants are moving resources down into the roots to apply glyphosate for maximum efficacy, it can be highly effective on many species throughout the season. For very aggressive species like phragmites and Japanese knotweed, do NOT wait to tackle them. Wipe as soon as you notice them.
Growers are still applying grass herbicides like Intensity One, but keep in mind that it is much less effective when grasses flower/make seeds and we are approaching that time for poverty grass.
Diseases
Upright dieback. We are hearing reports of upright dieback appearing. Once infected, plants show symptoms (dead uprights and leaf drop). Factors exacerbating the disease are prolonged periods of drought and/or heat stress. Try to avoid stress with properly timed irrigation.
While symptoms are showing now, the infection likely occurs during or shortly after bud break. Fungicide now will not control the disease. Spring fungicide applications at bud break and/or early bud expansion give excellent control of the disease. If you suspect upright dieback, you can get samples diagnosed by the plant pathology lab to rule out other causes for similar symptoms (contact Leela for information on what to collect and how to bring samples to her lab).
Remember that our fruit rot fungicides work as protectants, not as curatives. That means if you apply a fungicide AFTER you see the rot, it will do no good. In general, applying fungicides this late for rot management is of little use.
Cranberry Plant Tissue and Soil Testing
Soil and tissue tests can be used to diagnose deficiencies of mineral elements, monitor soil pH, and aid in the making decisions for fertilizer. These tests are also required for Nutrient Management record keeping. A soil test alone is virtually useless in determining a fertilizer recommendation for cranberry. We recommend testing soil every 3-5 years to monitor any change in soil pH. We recommend tissue sampling every 2-4 years. Regular tissue testing meets the mandate for testing in the Massachusetts Nutrient Management Regulations since this is the UMass recommended testing for cranberry.
Because soil test results for phosphorus are difficult to interpret for cranberry soils, tissue tests are more useful for setting target fertilizer ranges than soil tests. Because levels within the cranberry plant can fluctuate throughout the growing season, research has identified the time between August 15 and September 15 as the period when nutrient levels are most stable - and therefore the best time to collect tissue samples.
Collect one composite sample for each management area. A management unit may vary in size but will generally be a single variety that is treated uniformly. For routine analysis, usually one sample per bog is adequate. If your acreage is more than 10 acres or is of varied productivity or differing varieties, taking more than one sample may provide more specific information.
The best time to sample cranberry bogs is when the soil is not waterlogged. Wet soils give falsely high P values. Soil samples may be collected with tissue samples in the late summer if no sanding is planned. Otherwise, sample soil in the spring.
Tissue samples: Samples for cranberry tissue analysis should include upright tips only (do not strip off the leaves) and should NEVER contain roots, soil, runners, fruit, or trailing woody stems. Do not collect samples when plants are wet. Collect no more than the top 2 inches of new growth (mix flowering and vegetative uprights). As you walk a transect across the bog, collect enough material to make about 1 – 1.5 cups (at least 50 upright tips). Always request nitrogen determination. This increases the test cost, but nitrogen levels in the tissue test are an important indicator of plant status and the success of fertilizer programs.
Soil samples: Samples for analysis of soil nutrients should NOT contain stems, leaves, or the surface duff layer (trash). These are all organic contaminants and will bias the organic matter (OM) determination for the sample. The inclusion of some roots is generally unavoidable. Use a soil probe with a 1–2-inch diameter to collect cores of 4–6-inch depth. Minimum requirements: 4 cores for up to 1 acre; and 1 core for each additional 2 acres up to a total of 10 cores/management unit. After the trash layer on the surface of each is discarded, these cores are combined to make a sample. Collect enough soil to fill a 1 qt plastic bag about ¾ full. At home, open the bags and dry the soil at room temperature for a day or two. Clearly mark each sample bag. OM determination (usually an additional charge) is often useful.
Methods of analysis vary by lab – so it is best to pick a lab and stick with it over the years. For phosphorous, the UMass Soils Lab uses the Morgan test. However, the Bray test for soil P is the most commonly used in other labs for samples from the eastern United States. Standard P ranges for both methods are provided in the Chart Book.