February 15, 2001
compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 ext. 13, or

by David T. Handley, James F. Dill, Univ. of Maine Cooperative Extension

Strawberry production in northern New England is limited by a relatively short growing season, severe winter conditions, and the root rot disease red stele (Phytophthora fragaria).  Nearly all the fruit is sold fresh, either as  "pick-your-own" or at nearby farm markets, making high fresh fruit quality essential. There are presently no strawberry breeding programs in the northern New England region.  Thus introductions from breeding programs in other regions must be tested in order to evaluate their adaptability and performance under New England growing conditions and cultural practices.

Materials and Methods:
The trial was established at Highmoor Farm, part of the Maine Agricultural and Forestry Experiment Station, in Monmouth, Maine.  Fourteen strawberry varieties were planted from dormant crowns on May 17-18, 1999 (Table 1).  The silt loam soil was amended with 10-10-10 fertilizer at a rate of 500 lb. per acre prior to planting.   The plots were established as narrow matted rows. Crowns were initially planted one foot apart within rows, with four feet between rows.  Flowers were removed during the planting year, and runner plants were allowed to root to fill out the rows to a width of two feet.  Each plot was 20 feet long. Each variety/treatment was replicated four times in a randomized complete block design.  The plots were sidedressed with 10-10-10 fertilizer at a rate of 200 lb. per acre on 3 August, and straw mulch was applied over the planting for winter protection on 2 December.  The mulch was raked off of the plants on 23 March 2000.  Calcium nitrate was applied over the plants at a rate of 80 lb. per acre on 5 May.  The planting was sprayed twice with a combination of recommended fungicides and insecticides during the bloom period to control fruit rots, tarnished plant bug and strawberry bud weevil.  Harvest began on 27 June 2000 and continued twice weekly through 14 July.  Fruit was harvested from each plot, graded, counted and weighed.  Data was subjected to Analysis of Variance and mean separation using the test for Least Significant Difference.

Two of the varieties planted, Allstar and Annapolis, were eliminated from the trial due to very poor establishment, probably the result of storage problems with the crowns prior to planting.  The planting year of the trial was characterized by drought, resulting in many plots being poorly filled at the end of the season. This very likely lowered yield performance.  The cultivars Mesabe, Brunswick and Mira produced the highest yields of marketable fruit in this trial (Table 2).  Cavendish, Sable, Jewel, Cabot and Mohawk produced acceptable yields. Evangeline, Northeaster, Honeoye, and Winona produced relatively low yields.  Cabot produced the largest fruit in the trial, followed by Cavendish, Brunswick, Mohawk and Jewel. Based on the first year of harvest in this trial, Mesabe, Brunswick and Mira appear to be promising new cultivars for the northern New England climate, producing very good yields and having good fruit quality characteristics (Figure 2).  Cavendish and Jewel continue to perform well in this region, where they have become commercial standards.  Sable appears to be a promising new early ripening variety for the region, and Cabot offers growers a very large, late ripening berry which may find a specialty market.   Northeaster and Honeoye performed poorly in this trial, unlike previous trials in this region.  This is likely due to drought stress during the establishment year.

Table 1. Origins and characteristics of 12 strawberry varieties planted in 1999 at Monmouth, Maine.

Variety              Origin               Season           Disease Resistance
Mesabe             Minnesota         Mid-late         Red Stele, 5 races; Leafspot
Brunswick         Nova Scotia      Midseason     Red stele, 3 races; Leafspot
Mira                  Nova Scotia      Midseason     Red stele, 3 races; Leafspot
Cavendish         Nova Scotia       Midseason     Red stele, 3 races; Leafspot
Sable                Nova Scotia       Early              Red stele, 3 races
Jewel                New York          Midseason     None
Cabot               Nova Scotia        Late              Red stele, 3 races
Mohawk           USDA-ARS       Early             Red Stele, 5 races; Verticillium,
Evangeline         Nova Scotia       Early             Red stele, 3 races
Northeaster       USDA-ARS      Early              Red stele, 3 races; Leafspot
Honeoye           New York          Early-mid      None
Winona             Minnesota           Late              Red stele, 5 races

Table 2.  Yield characteristics of 12 strawberry varieties harvested in Monmouth, Maine 2000.

Variety             Kg/Plot             Lbs./Acre        Grams/Berry       Peak Harvest             Comments
Mesabe             13.7                  16,406                 11.2                      7/5                 Sweet, juicy, soft
Brunswick         13.2                  15,845                 12.4                      7/5                 Firm, dark, good flavor
Mira                  13.1                  15,676                   9.4                      7/5                 Sweet, soft
Cavendish         11.2                  13,471                 14.0                      7/5                 Odd color pattern, sweet
Sable                 10.3                  12,327                 10.4                      6/27               Soft, sweet
Jewel                   9.3                  11,195                 12.1                      7/5                 Attractive, sweet
Cabot                  8.5                  10,008                 20.7                      7/5                 Very large, rough, sweet
Mohawk              8.1                    9,681                 12.3                      6/27               Small, sweet, dark
Evangeline           6.5                     7,846                 10.0                      6/27               Small, tart
Northeaster         5.4                     6,441                 11.5                      6/27               Strong, odd flavor
Honeoye             5.2                     6,305                 11.4                      6/27               Poor flavor
Winona               4.9                     5,837                 10.5                      7/5                 Rough, soft, mild

LSD 0.051   3.8    3.0

1 Data within a column must differ by this much to be considered statistically different according to the test for Least Significant Difference (95% confidence level).
2 Numbers extrapolated from small plot data.  Yields can vary greatly from site to site. These numbers may not reflect actual yields obtained in grower fields.

This regional conference will be held at the Holiday Inn and Conference Center, Manchester, N.H., on Feb. 26,27 and 28, 2001. Whether you're a seasoned farm direct marketer, are dreaming about being one or are somewhere in between, you'll leave this conference with your head full of ideas. There will be 24 different sessions divided into the following tracks: roadside stands and pick-your-own; farmers' markets; specialty foods and processing; beginning farmers; and AG-tourism. For registration information, call Charlie Tacet, (413) 529-9232.

A new 15-page fact sheet by Leanne Pundt, UConn Extension and Tina Smith, UMass Extension is now available. It contains information on managing plant height, diseases, insects and mites, as well as tables listing labeled insecticides, fungicides, and biological controls. Includes 10 color pictures. Contact me for a free copy.

(adapted from factsheet above, and tri-state greenhouse IPM workshop 2000)
Fungus gnat larvae feed on decaying organic matter and often injure seedlings by feeding on young roots and stems of plants. This feeding provides an entry for diseases. The larvae are translucent white and legless with a shiny black head. They are 1/4 inch long when mature. Fungus gnat adults are 1/8 inch long, mosquito-like, with long antennae and clear wings that have Y-shaped veins. They are weak fliers and can often be seen resting on or walking over growing media and foliage. Each female can lay up to 300 whitish eggs, in clusters of 20, on the soil surface or in crevices in the potting media. Eggs hatch in about 6 days and then larvae feed for 12 to 14 days before changing into pupae for 5 to 6 days. Adults live for up to 10 days. In most greenhouses the lifecyle will take about a month; at 75 degrees the time from egg laying to adult is about 3 weeks.

Monitor for adults by frequently inspecting yellow sticky cards placed horizontally at the soil line next to the base of plants. Early detection of adults is key to effective biocontrol by timely application of B.t. soil drench (such as Gnatrol) to control the larvae soon after hatch. Remember that B.t. works only on larval stage. It should be applied 4 to 10 days after planting for best effect. The colder the soil the longer the delay. For greenhouse vegetable transplants set in the ground, apply B.t. drench about a week after watering in plants. Raw, peeled potato chunks, one inch in diameter and a half inch thick placed on the soil surface can be used to monitor for larvae, which will congregate underneath. To be effective, B.t. should be applied before large numbers of larvae are present.

Fungus gnats often seek out fresh moist potting soil to lay eggs, attracted to the fermentation process going on. When setting out new plants, the first generation of larvae can be expected 3-4 weeks after planting, although often it is not very noticeable. The second generation 3-4 weeks after that is very noticeable.

B.t. controls fungus gnat larvae but NOT shorefly larvae. Shorefly larvae do not injure plants by direct feeding but they can spread disease. Like fungus gnats, shorefly adults are also about one eight inch long, but they have a more robust body, short antennae and dark wings with light spots. On vegetable bedding plants, shorefly adults can be controlled with repeat applications of neem-based insecticide containing azadarachtin, Azatin XL.

Preventive strategies help minimize fungus gnat and shorefly populations. Thoroughly inspect incoming plant material for infestations. Remove discarded plant material and growing media from the greenhouse and eliminate weeds growing beneath benches. Keep areas below benches free of spilled potting mix, weeds and other debris in which fungus gnats might breed. Eliminate standing pools of water on solid benches, on walks, and under benches by proper grading and drainage and by watering plants in a way that limits runoff. Eliminate algae as best you can. There are commercially available products for treating walks and other surfaces that tend to have algae. Research has shown that fungus gnat problems are most serious in potting mixes amended with composts lacking in maturity (not completely composted). Microbial activity is excessively high in such mixes, and fungus gnats thrive.

April 10: Greenhouse IPM 'on-farm workshop', Killdeer Farm, Norwich.
May 22: Strawberry IPM 'on-farm workshop', Norris Berry Farm, Monkton.

(Mention of pesticide brand names is for information purposes only, no endorsement or discrimination is intended. Always follow the label.)