by George Looby, DVM
The Extension Service of the University of Connecticut covers almost every aspect of produce production in its ongoing effort to ensure producers in the state are made aware of that which is at the cutting edge of knowledge in their particular field. Not only does it strive to bring this knowledge to those who need it to be successful in their fields but it makes it convenient for them as well. The topic, Pests and Diseases of Small Fruits, was presented in three locations in the past month — Litchfield, Haddam and Brooklyn. The presenters were Mary Concklin, Associate Extension Educator, Fruit IPM and Joan Allen, Assistant Extension Educator, Plant Diagnostician.
Much of what is done in the area of disease and pest control falls in sustainable management practices. Among those which may be included in this program are monitoring, use of resistant varieties, cultural practices, sanitation, physical barriers, biological controls, biorational pesticides and conventional pesticides. All insects which prey on those which are harmful to crops may be called beneficial, thus supporting them becomes an important part of the overall pest control program in any operation. Providing plants which flower at various points in the growing season will provide food for a group of beneficials. Hoverflies like marigolds, tachinid flies are attracted to buckwheat, sunflowers attract assassin bugs and lacewings are fond of Queen Anne’s Lace. Many may find they are unknowingly supporting a group of beneficials.
Long before the role of beneficials was as well recognized and organized as it is today, lady beetles were recognized as “good” bugs. There are steps any grower can take to ensure he/she is doing all they can to provide a good environment for these and all other useful predators. First and perhaps most important, learn to recognize the bugs which are the useful ones. Oftentimes the differences between the good and the bad are very subtle making positive identification difficult. There are many resources available designed to make identification somewhat easier. Go to www.ipm.uconn.edu for help. Minimize the use of insecticides and when necessary use those which are selective as much as possible. Maintain some vegetative cover and provide some readily available nectar and pollen sources.
Wine making has become an increasingly important segment of northeastern agriculture over the past two decades and the end is not yet in sight. That industry together with the ongoing demand for table grapes puts grape culture and management high on the list of priorities for plant scientists. A bug which has attracted considerable attention in the past few years is the brown marmorated stink bug. Distinguishing this bug from its very close relatives is something of a challenge but it does have a few characteristics which set it apart. Control measures include the use of insecticides along the border of the vineyard with applications moving from the outside inward. An Asian wasp, Trissolcus japonicus, has been found to parasitize the eggs of the brown marmorated stink bug. Both insects are native to the same region of Asia.
Other grape pests and diseases include the grape berry moth, grape phylloxera, black rot, bunch rot, downy mildew and phomopsis cane and leaf spot. Many of the basic management practices mentioned earlier will do much to aid in the control of these conditions.
Of the many delights at the onset of the summer season, few match the taste of the first strawberries picked fresh from the patch. Along the route from the first greening of the leaves, strawberries can be beset with a host of problems before the first fruit is ready for harvest. High on the list is the aforementioned brown marmorated stink bug. Other bugs include spittlebugs, strawberry root weevil, strawberry bud weevil, tarnished plant bug, Cyclamen mite and slugs. Strawberry anthracnose is a fungal disease that produces a variety of lesions on the fruit that renders it unfit for sale. As is true with some other fungal diseases its development is favored by moisture and warmth. Control measures include practicing crop rotation, laying down straw mulch between the rows and minimizing activity in the field when conditions are wet. Other fungal diseases include gray mold and leather rot. There are at least four leaf spot diseases of strawberries. One of which, angular leaf spot, is caused by bacteria while the other three are each caused by a specific fungus. Here effective control will be determined by using the appropriate material for treatment, knowing a fungicide will have little effect in treating a bacterial disease. Powdery mildew is characterized by a white powdery growth on the underside of the leaf surface together with an upward leaf curl. It overwinters on living leaves and is favored by cool, damp weather. Red stele is a long-recognized disease of strawberries characterized by blue /green young leaves, red/orange older leaves, stunting, and red stele in the roots. It may be controlled by avoiding wet sites, planting resistant strains, use of systemic fungicides and fumigation. Black root rot is a disease of stressed plants in particular so efforts should be made to ensure growing conditions lessen the possibility. This disease expresses itself by showing poor vigor and blackened roots. Lessen stress factors by irrigating when needed, fertilization as determined by soil testing, mulch, avoiding soil compaction, good site selection and a three to six-year rotation program. Phytophthora crown rot is yet another fungal disease where the entire plant is seen to be wilting.
Brambles share many of the same conditions which affect other plants discussed during the presentation. One which is unique to raspberries is the raspberry cane borer and it may be one of the easier ones to diagnose. This bug has a two-year life cycle and the larvae create two concentric rings in the stem about ½ inch apart, six inches below the growing tip. The first year the larvae burrows down to the crown and in the second year feed on the crowns. There is no biological control and affected tips should be cut below the rings and destroyed. The Spotted wing Drosophila arrived in the northeast on the wind. It was first found on the west coast and then was carried by the wind to Florida where it was next found. From there to the northeastern states by the same carrier. When feeding it renders the surface of the fruit very unattractive, making it unsalable. One of the control measures advocated is the use of netting arranged so the entry consists of two doors with a small entryway between. It is suggested when entering, the outer door be closed before opening the second one and closing that one immediately when entering the netted area. Brambles are best grown on V trellises, this allows for better air circulation, better exposure to the sun and greater ease when picking. A word of caution when planting brambles or strawberries. Because of the persistence of verticillium wilt in the soil after tomatoes, potatoes and eggplant, it is recommended that there be a four to five year wait period before planting. Other diseases affecting brambles include late leaf rust, orange rust and spur blight.
Blueberries have several pests which can cause damage to this important crop including birds. Among the insect pests are the blueberry maggot, the cranberry fruitworm, the cherry fruitworm, the yellownecked caterpillar, the fall webworm, Putnam scale and the blueberry stem gall wasp. Mummy berry is a fungal infection which is best managed with good cultural practices plus fungicides. Phomopsis twig blight is characterized by stem dieback whose spread is favored by warm weather, rain and open wounds on the stems. Among the management suggestions is avoiding late season fertilization. The development of Fusicoccum canker twig blight is favored by cool, rainy weather where it causes cane dieback and cankers. Where there is a high incidence fungicides applied every two weeks from late dormancy to petal fall may be of value. Another fungal disease seen less frequently in the northeast is Botryosphaeria stem blight.
There are at least five viral and Phytoplasma diseases that may affect blueberries. These include blueberry shoestring disease, blueberry stunt, blueberry red ringspot, blueberry mosaic and blueberry scorch. Birds, deer and rodents all have a taste for blueberries and keeping them out of the patch requires more than a little resourcefulness and ingenuity. Netting, noises, repellents, traps, dogs, cats have all been tried with varying degrees of success.
Currants and gooseberries growers must contend with insects such as currant cane borer and currant aphids and diseases such as Anthracnose, powdery mildew and White Pine Blister Rust. It should be noted Ribes spp., which include gooseberries and currants, play a critical role in the spread of this important disease of white pines especially on the west coast. Without the presence of Ribes spp. the organism causing the disease cannot complete its life cycle. For many years, there was a Federal ban in effect regulating the growing of Ribes designed to halt the spread of this disease. This ban was lifted in the 1960’s. In some communities, there may still be bans in effect regulating their cultivation.
Once again, the Extension Service has provided an update which should assist growers as they prepare themselves for the upcoming season.
Pests and diseases of small fruit
by George Looby, DVM