Vermont Vegetable and Berry News May 24, 2006
Compiled by Vern Grubinger
University of Vermont Extension
(802) 257-7967 ext.13
vernon.grubinger@uvm.edu
http://www.uvm.edu/vtvegandberry

SEEDCORN MAGGOT
(Eric Sideman, Maine Organic Farmers and Gardeners)

Peas, beans, corn, potato sprouts and even cucurbits in the greenhouse are attacked by the larvae of this fly.  They are yellow-white maggots about a quarter of an inch long and sharply pointed at the head end. The symptom is usually that you see no germination,  and when you dig around you may find nothing left or may find the maggots burrowing into the seed.  Sometimes the seed germinates but only a weak or partially eaten plant is seen.  The injury is most likely to occur in cold wet seasons where the germination is slow, and also in soil high in organic matter.

The attack is early in the spring because the critter spends the winter as pupae in the soil or maybe free maggots in manure or unfinished compost. The adult is a grayish brown fly only about a third of an inch long.  It emerges in early spring and deposits eggs in rich soil, compost piles or near seeds and seedlings. Exposed peat or potting soil mix of transplants can also serve as attractive sites for females looking for a place to lay eggs. There are  a few generations each season.

The best method of dealing with this critter is to do everything you can to encourage quick germination and rapid growth.  In the cold, wet soils we have this spring the seeds are just sitting ducks.  Shallow planting helps when conditions are poor.  Best yet, wait for things to warm up and dry out.

BLUEBERRY FERTILIZATION
(adapted from Gary C. Pavlis, Rutgers Univ. Extensions)

Research conducted in the past two years in Michigan and New Jersey have radically changed my thinking regarding the fertilization of highbush blueberries. Research out of Michigan from Dr. Eric Hansen's lab, has shown that there must be leaf emergence and growth before you have uptake of fertilizer by the blueberry plant. The correct timing for the first N-P-K application is during bloom or shortly thereafter. The second application
should be made in late June in NJ. So, timing is the first change we have made.

After taking many leaf and soil samples this past year I have realized one very important thing. Fertilizer recommendations which are based on soil analysis are nearly worthless. Leaf and soil samples which had been taken from the same plant never agree, and the leaf analysis show what is actually getting into the plant. The only important thing that we learn from soil analysis is pH. Yes, soil pH is critical, and it must be known because leaf analysis results assumes that the pH is within the correct range. If it is not within that range, I would not rely on the leaf analysis recommendations. Every blueberry grower should have their blueberry soils tested for pH. If soil pH is not within the 4.5-4.8 range, this should be adjusted immediately. If the pH is higher, sulfur is added. If the pH is lower, lime is added. The amount of sulfur or lime depends on your pH and I would have the pH tested in the spring and fall until the proper range is attained. Thereafter, fall pH tests are best because adjustments can be made then and the pH will be correct by bud break in the spring.

This year's N-P-K application should be made according to the timing above, but realize that the amount, 600 lb/A of 10-10-10 on a mature planting is largely a guess until we take leaf samples in July. After that we can make recommendations based upon the leaf analysis. Note: this can only happen if the soil pH is correct or we must continue to guess on the recommendations. Lastly, these changes are needed because even though the samples we took last year were from growers who are some of the best blueberry growers in the world, 70% of the plants were deficient in nitrogen and 97% were deficient in one of the micronutrients. Nutrient deficiencies cause decreased yield, lower fruit quality, increased disease problems and plant mortality. We need to make these changes as soon as possible.

TRICHOGRAMMA WASP FOR CONTROL OF CORN BORER
(adapted from UMass Extension)

A recent UMass study funded by the New England Vegetable and Berry Growers Association Trichogramma worked well for control of European Corn Borer. Timing was critical, and some releases were too late to provide control in the target field. However, Trichogramma wasps were able to move by themselves to later plantings and provide control of this pest, saving sprays. Use of wasps reduced tractor time and soil compaction.

Trichogramma wasps are now commercially available from IPM Laboratories, Inc. Main St, Locke, NY, Phone (315) 487-2063. Place your order two or three weeks in advance! Cost is $15 per acre (plus shipping) for a release of 30,000 wasps per acre. UMass recommends at least two releases per block, one week apart. A higher rate of 50-60,000 wasps per acre may provide better control and more reduction in the need to spray. Plan to make the first release at whorl stage, after European corn borer flight has begun, and the second release just at tassel emergence. If you have questions about how to use Trichogramma, please call Pam Westgate at (413) 545-3696.

APPLYING COPPER AND OXIDATE
(Andy Wyenandt and Michelle Infante-Casella, Rutgers Univ. Extension)

Heavy rain, winds and hail can all cause injury to vegetable plantings. Some injury is quite noticeable, such as hail damage, however, other injury may go unnoticed. Cultural practices such as tying, staking, cultivation and pruning can also create entry ways for bacterial infections. Many growers may plan on applying copper fungicides or tank mixes. Although temperatures have been cool over the past few weeks. Be careful, when temperatures are high. High temperatures increase the possibility of phytotoxicity when using copper-based fungicides. In order to avoid this problem, growers should watch the daytime temperatures closely and avoid spraying if temperatures remain high. Management strategies to help avoid bacterial problems include not working in fields when the foliage is wet. If overhead irrigation is used try to irrigate in the
morning so foliage will dry quickly. Bacterial diseases thrive and spread when foliage remains wet for long periods of time.

Additionally, the product Oxidate is a promising tool in for control of bacterial diseases, especially in tomatoes. However, remember that Oxidate has no residual activity and should be used accordingly. Take caution when using this product on any crop and make sure to read the label. According to the product MSDS Oxidate contains hydrogen dioxide (synonym for hydrogen peroxide) and peroxyacetic acid. The MSDS also states that the pH is 1.33 and that combinations of Oxidate with bases and metals (to name a couple) should be avoided due to reactivity issues and product instability. Mixtures of Oxidate and copper hydroxide may possibly produce soluble copper which is known to be phytotoxic.

PLASTIC MULCH AND FERTILIZATION
(adapted from Steve Reiners, Cornell Extension)

If you need to broadcast fertilizer prior to planting, it is relatively easy to figure out how much to apply. If you are using plastic mulch, however, you may be applying more fertilizer than you need. In a typical mulched field, the width of the soil surface covered with mulch is usually three feet. The uncovered area is usually 2 to 3 feet depending on the row spacing. For our example, lets use two feet. Prior to laying plastic you need to add 50 pounds of N and 100 pounds of P and K.

Using a 10-20-20 fertilizer you could spread 500 pounds evenly across the acre. But you will be fertilizing the area that is between the rows, an area where crop roots will likely not be feeding but weeds will. If you have the equipment, it is much better to apply the fertilizer only to the area that will be covered with mulch. Since that will be only three feet of every five feet, that means that only 60% of an acre will be used by the crop. You can cut your fertilizer rate to 300 pounds per acre from 500 and still get the same effect. Once this is applied and the plastic is laid, you can use the same calculation to apply fertilizer through the drip system. If you need 20 pounds per acre of N, P, and K and are using a 20-20-20 soluble fertilizer, you will need only 60 pounds of fertilizer rather than 100 pounds. It all comes down to the fertilized-mulched acre. This is the percentage of an acre that is covered by plastic mulch where most of the crop roots will be found.  Applying fertilizer based on this will save you money and maintain your crop's quality.

Mention of pesticides is for information purposes only, no endorsement is intended nor is discrimination against products not mentioned. Always read and follow the label.

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