Vermont Vegetable and Berry News - May 15, 2005
Compiled by Vern Grubinger
University of Vermont Extension
(802) 257-7967 ext.13

(Steve Reiners, NYS Agricultural Experiment Station)

Phosphorus levels in many vegetable soils are in the high to very high range. Growers need to be aware that high phosphorus combined with low potassium levels can result in poor quality crops. A few years ago, a field of tomatoes experienced ripening problems - poor internal color with a mealy texture and off taste. Soil tests revealed that the soil had a phosphorus level in the excessive range while potassium levels were only moderate.
In another case, a field to be planted to cabbage tested low for potassium and optimum for phosphorus. Although a high potassium fertilizer was applied through most of the field, cabbage growing in areas that apparently did not receive this application developed black petiole or midrib. It is believed that this condition is caused by an imbalance of high P and low K. High phosphorus levels in soils that are borderline in zinc availability (high pH, cool, wet soils low in organic matter) may also cause zinc deficiencies, especially in zinc sensitive crops like sweet corn and snap beans.


I am seeing many standard soil test results coming through for high tunnels and greenhouses, and typically the results are ‘off the charts’ because this test is intended for open field situations. The ‘saturated media’ or potting soil test is more appropriate for greenhouse vegetable crops growing in highly fertile soils that have been heavily amended with compost or manure. This test measures major and minor nutrient levels, as well soluble salts (conductivity) and available nitrogen (nitrate and ammonium). The test costs $25 and requires a quart of soil. Send to UVM Ag Testing Lab, Hills Building, Carrigan Drive, Burlington VT 05405-0082. Include your contact information, greenhouse name and crop type. Ask that a copy be sent to me if you want recommendations.

(adapted from Meg McGrath, Long Island Horticultural Research Station)

Phytophthora blight can be potentially devasting in cucurbits, pepper, eggplant, and tomato. Last year in Vermont several farms had major crop losses where field drainage was less than optimal. Although this disease won't occur anytime soon, it is critical to be thinking about managing it now with early-season cultural practices. These include: Clean tractors and equipment between fields to avoid spreading the pathogen. Select fields where Phytophthora blight has never occurred when possible. An effective rotation period has not been identified yet, but use as long a rotation as possible when clean fields are not an option. Select well-drained fields for susceptible crops. Subsoil or chisel plow before planting to improve drainage. Select a pepper variety with resistance. When growing small-fruited pumpkins, select varieties producing hard, gourd-like rinds (such as Lil' Ironsides). Physically separate plantings of susceptible crops. Plantings should be located such that there is no opportunity for water to move from one to another. Construct raised firm beds without depressions for non-vining crops. A bed shaper should be used for bare ground culture, as well as with plastic mulch culture, to obtain beds that will last longer than a simple ridge. A dome-shaped bed will allow water to run off. Make sure water will be able to drain out of the field. If water has not drained well out of the field in previous years, then make a trench between beds or rows at their ends, make a ditch or waterway across the end of the field for water coming out of the field in the trenches. Do not plant in low areas, especially where standing water can occur after rain; plant a cover crop instead in these areas. Use a transplanter that does not leave a hole around the base of the plant. If necessary, drive slowly enough that workers can push the entire root ball into the soil and then bring soil around the base of the plant. Afterwards, have workers go through the field to inspect plants and fill in any holes that remain. Subsoil between rows after transplanting. Do not drive in fields when soil is wet to minimize compaction.

(adapted from NY Berry News.) See the New England Extension Small Fruit Pest Management Guide, including updates, for insecticide recommendations, on-line at:

Blueberries.  Cranberry Fruitworm and Cherry Fruitworm are the main blueberry arthropod pests in the spring and early summer. These moths overwinter as fully-grown larvae. They pupate in the spring and begin flying in late May and early June. Egg laying begins at around petal fall with eggs being placed at the base of newly set fruit. A sex pheromone is available to monitor the flight activity of adult cranberry fruitworm (Great Lakes IPM,, 989-268-5693). Applications of an insecticide may be required for sites with heavy pressure. Research in NJ indicates that in areas of moderate pressure, one application 5 to 7 days after petal fall provides as good control as two applications.

Other pests to keep an eye out for are plum curculio (makes a crescent shaped scar created from egg-laying on young fruit), leafrollers (larvae make shelters by silking together terminal leaves), and blueberry tip borer (larvae bore into stem causing shoot tips to die back). Later in the summer be alert for blueberry maggot flies, blueberry stem borer, and Japanese beetle.

Raspberries.  Be alert for feeding damage from the adult raspberry fruitworm (a beetle, light brown in color) on foliage and fruit buds. The larvae of this beetle pest feed inside flower buds and young fruit. Adult feeding damage on foliage creates a skeletonized appearance somewhat similar to the feeding damage caused by larvae of raspberry sawfly (pale green caterpillar-like body with many long hairs). Both the fruitworm and the sawfly appear during the prebloom period.

Tarnished plant bug (TPB) is a potential problem from bloom to harvest. Both the adults and their nymphs can cause deformed fruit, although the deformities are not as obvious in raspberries as in strawberries. An estimate of the economic threshold for TPB in raspberries is 10 to 20% of canes infested with adults or nymphs. Weedy fields aggravate TPB problems.

Raspberry cane borer and related beetle species adults emerge in the spring, mate and start laying eggs. Larvae bore into canes during the season and for some species, the next season. They cause injury and death to canes and potentially entire crowns. The best time to kill adults is during the late pre-bloom period. As an alternative to insecticides, during the season remove wilted shoot tips below the girdled stem (two rows of punctures around an inch apart) where the egg of the raspberry cane borer has been placed. Also, during the dormant season remove and destroy canes with swellings.

Another pest that can cause serious injury to canes and the crown is the raspberry crown borer. The larvae of this moth feed at the base of the cane and into the crown over a two-year period. The first signs of a problem often appear during fruit maturation. The withering of and dying of canes, often with half matured fruit, can be a symptom of feeding damage at the base. Canes with these symptoms, and the associated crowns, should be removed during the growing season and destroyed. The adult moth does not appear until early August. It resembles a yellow jacket.

Two-spotted spider mite can become very numerous on foliage, causing white stippling on leaves. They seem to be most problematic in dry sites and/or in mild growing areas. Predatory mites can provide control, and they are often naturally present in raspberry fields where few broad-spectrum insecticides are used, but they can also be purchased from a supply house. It’s important to start control actions early before you see lots of severe injury to foliage (bronzing). Pests that might show up later in the season (bloom to harvest) include root weevil, Japanese beetle, picnic beetle, and potato leafhopper.

Strawberries.  During the pre-bloom period the strawberry bud weevil (clipper) is the main arthropod pest to watch out for. In recent years, we have learned that many strawberry cultivars, such as Jewel and Seneca, can tolerate a fair amount of bud loss from this pest, although at sufficient densities, it can still be a problem. As a rough rule of thumb, treat for clipper when you observe more than one clipped primary or secondary flower bud or more than 2 tertiary buds per truss, on more than one truss per foot of row. Once flowers are open they are no longer at risk from clipper. Clipper often is a more severe problem along borders of plantings, near woods.

Also during the pre-bloom period, and extending through harvest, and sometimes after renovation, the two-spotted spider mite can be a problem. Look for whitish or yellowish stippling on leaves. Current threshold is 5 mites per leaf or about 25% of leaflets have at least 1 mite. This is likely a conservative threshold for a healthy planting. For insecticide control, coverage is very important, especially on the underside of leaves.

Tarnished plant bug (TPB) is the key insect pest of strawberries during bloom to near harvest. Both adult bugs and the nymphs cause injury (deformed fruit) but nymphs are probably of the greatest concern for June-bearing cultivars. The economic threshold is one nymph per two flower clusters (you sample by tapping cluster over a white plate and counting nymphs that fall off). It is worth sampling for this pest on a regular basis since it varies in population size from place to place and from one year to the next. Spraying a pesticide when nymph counts are below threshold costs money and may kill beneficial arthropods unnecessarily. Good weed management can help reduce problems with TPB.

Cyclamen mite is a potentially serious pest that seemed to show up in more fields than usual three years ago but was not very prevalent recently. The mites get active in the spring with populations peaking after bloom. The mites like to feed on young leaf tissue (just as the leaves are unfolding). The mites themselves are difficult to see without a good hand lens. Cyclamen-damaged leaves tend to be stunted and crinkled.

Strawberry sap beetle is a small, brownish beetle that seems to be increasing as a pest. Both the adult beetles and the larvae feed on ripe and overripe fruit. SSB probably does not move into strawberry fields in significant numbers until fruit begins to ripen.

Spittlebug starts appearing on leaves, stems, and flowering racemes about bloom time and extending into harvest. They overwinter as eggs in the soil and hatch out as temperatures rise in the spring. The nymphs crawl up the plant and begin feeding on the xylem tissue (the water conducting vessels of the plant). There are not a lot of nutrients in xylem and therefore nymphs need to process a lot of sap, extracting the few nutrients out for their use and excreting the remaining water. This water is frothed into white spittle, which helps protect the nymphs from desiccation and natural enemies. You can often find several nymphs within a spittle mass. Feeding by spittlebugs, if extensive, can stunt plants and reduce berry size. Perhaps more importantly, the spittle masses are a nuisance to pickers. Threshold for spittlebug masses is 1 mass per foot row. Weedy fields tend to have more problems with spittlebugs.

The larvae of several root weevil species feed on roots and crowns and when abundant can cause serious damage to plantings. Beds with heavy infestations show distinct patches or spots that appear stunted and have reduced yields. Drought stress aggravates the injury from larval feeding. Chemical control is targeted at the adults that emerge in mid to late June. Look for characteristic adult feeding damage on leaves (notching from the edge) to help determine timing. The adults feed for a few days before starting to lay eggs. Some growers have also had success controlling root weevil larvae using parasitic nematodes. These can be applied either in late April and early May and/or in the fall. Use sufficient water to get good penetration. Rotation out of strawberries is the best remedy for root weevils. They are wingless and do not move a great distance. However, new plantings should be placed 50 meters or more from an infested planting.