Strawberry IPM Newsletter No. 3 – June 2014
Click on photos to enlarge.
STRAWBERRY GROWTH SLOW BUT STEADY AS HARVEST APPROACHES
Clippers, Tarnished Plant Bugs, and Spider Mites Active
Vegetable and Berry Growers Twilight Meeting
Wednesday, June 11, 2014 at 5:30 p.m.
Fairwinds Farm, Bowdoinham, Maine
Situation: The temperatures have remained fairly cool with more damp, cloudy days and, as a result, strawberry development has been relatively slow but steady as we head towards harvest time. A later start may be a good thing for pick-your-own fields, as it will better coincide with the end of the school year; but a few days of warm weather would really speed development. Most early varieties are now in the small green fruit stage, while later varieties are still in bloom. Early fields that started under row covers may be picking a few fruit next week.
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a twilight meeting at Fairwinds Farm in Bowdoinham on Wednesday, June 11 at 5:30 p.m. Pete and Cathy Karonis grow 10 acres of strawberries and approximately 40 acres of mixed vegetables in fields along the Kennebec River and have a farmstand and greenhouses in Topsham. They will host a tour of their strawberry, raspberry and vegetable plantings, and describe their growing and marketing practices. In addition, we’ll discuss the upcoming season and pest management issues facing vegetable and berry growers this year. One pesticide applicator recertification will be awarded for the meeting. Hold the date! We’ll meet at the strawberry fields in Bowdoinham.
From I-295, take Exit 37. Turn east towards Bowdoinham onto Route 125/138 South. Travel 1.4 miles to the stop sign, then turn left onto Route 24 North/River Road. Travel 0.7 mile and turn right onto Brown’s Point Rd. Go 2.6 miles (road veers to the right and becomes a dirt road) and the farm is on the left, across from 555 Brown’s Point Road. (Use this address for GPS reference. Signs will be posted.) Their contact information is: tel. 207.522.5064 or 207.522.0246, email email@example.com.
Strawberry bud weevil or “clipper” is still working in fields of late varieties that still have lots of unopened flower buds. Fields that have reached full bloom or beyond no longer need to be scouted for clipper. Damage in most fields remains fairly light, as early varieties went into bloom before clipper became very active. Three of the fields scouted this week were just over threshold for clipped buds, and clippers have been observed in other fields where the damage had not yet reached threshold.
Reminder to raspberry growers: Strawberry clipper will move onto raspberry buds after strawberry bloom. Check raspberry flower clusters for clipped buds and live clippers. Insecticide sprays to control raspberry fruit worm adults (which are also active at this time) should provide some control of clipper as well. Products registered for clipper on raspberries include Brigade®, Sevin XLR Plus® and Aza-Direct®.
Clipped Flower Buds from Strawberry Clipper, photo by David Handley
Third Instar Tarnished Plant Bug Nymph, photo by David Handley
Tarnished plant bug nymphs were over threshold in two fields scouted this week, but most fields still showed very little tarnished plant bug activity. However, it is important to keep scouting for nymphs throughout the bloom period because they can appear very quickly under warmer, drier conditions. Insecticide options for tarnished plant bug include malathion, Assail®, Brigade®, Bifenture®, Danitol®, and PyGanic®.
Strawberry Rootworm Beetle, photo by David Handley
Strawberry rootworm (not root weevil) adults and feeding injury were reported on strawberry plants last week The adult stage of this insect is a small (1/8”) dark brown beetle. The beetles feed on strawberry leaves during the spring and late summer, causing numerous small holes in the leaves. The adults in fields now will soon lay eggs. The larvae are small grubs that feed on the roots of strawberry plants, causing them to be stunted and weak. If these beetles and/or feeding injury is prevalent in a field, a treatment is recommended. Sevin 50WP® is registered for control of this pest, and sprays targeted at other insect pests at this time may also control rootworm. Strawberry rootworm should not be confused with root weevil, a larger insect that causes much more serious damage when present in a field.
Two-spotted spider mites were over the threshold (25% of leaves infested) in two locations this week, and smaller populations (under threshold) have been found in most fields. Mites can proliferate rapidly under hot, dry conditions, so it is important to scout for them often. Chemical control options for two-spotted spider mites include Acramite®, Savey®, Zeal®, Vendex®, Oberon®, Brigade®, Danitol®, Thionex® and JMS Stylet oil® (oils will cause plant injury if used in combination with captan or within 14 days of an application of sulfur).
Cyclamen mites: Two more fields we’ve scouted have shown symptoms of cyclamen mite injury this week. Infested plants show weak growth and yellow, crinkled leaves. The flower stems are small and short and the petals are deformed and sometimes look pink. Cyclamen mites are very hard to see, even with magnification. Portal®, Kelthane® or Thionex® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns where these mites reside.
Spittlebug, photo by David Handley
Spittlebugs: The frothy spittle masses on the leaf and flower stems from spittlebugs usually show up around bloom. Spittlebugs don’t pose a significant threat to the plants, but the spittle masses are a nuisance for pickers. Spittlebugs overwinter as eggs and the nymphs emerge in late May. Scouting for spittlebugs should start when the plants are at 10% bloom. Randomly inspect five, one square foot areas per field every week. Spread the leaves and inspect the crowns, leaf bases, leaf stems, and flower stems looking for the frothy spittle masses. Small, yellow-orange nymphs will be under the spittle. If the average number of spittle masses is more than two per foot, a treatment may be warranted. Spittlebugs tend to be a greater problem in weedy fields. Pesticides currently registered for spittlebug control include Provado®, Thionex®, Danitol® and Brigade®.
Diseases: The conditions have been wet enough in most fields to encourage Botrytis infections, which will lead to gray mold once the fruit start to ripen. Two to three sprays of fungicide during bloom are usually required to provide good protection against this disease.
Leather rot (Phytopthora cactorum) is still a concern for fields which have had long periods of standing water during this wet spring, especially if the fields were not mulched last fall. Fungicides applied for gray mold are generally not effective for leather rot. Foliar sprays of Aliette®, Agri-Phos® or Phostrol® applied during bloom or fruit development can help prevent leather rot.
Anthracnose fruit rot is a potential problem when fruit ripens in fields that are wet from irrigation or rain. This fungus disease is favored by warm, humid conditions and can spread rapidly during rains or when fields are irrigated with overhead sprinklers. In cool seasons, it may appear close to harvest or may not show up at all. Anthracnose fruit rot is identified by black sunken lesions with wet, orange (and sometimes gray) spore masses in them. The fungus can survive and multiply on leaves without visible symptoms, appearing suddenly as a fruit rot when the conditions are right. Fungicides such as Cabrio® and Abound® can provide good control of anthracnose.
Powdery Mildew, photo by David Handley
Powdery mildew symptoms of this fungus disease have just started showing up in fields this week. As the weather warms up expect it to become more prevalent. Mildew may first appear as purple or red streaks on the leaf and flower stems. Later, upward curling leaves and white, powdery growth on the undersides becomes evident. Keep an eye out for leaf cupping in your fields as the days start to get warmer. Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet oil® are registered to control powdery mildew.
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm Pest Management
P.O. Box 179 491 College Avenue
Monmouth, ME 04259 Orono, ME 04473
Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System.
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