Pistachios are the single most-successful plant introduction to the United States in the 20th century. Part of this success is due to the alternative production practices that have made this crop more economical to grow. Controlled deficit irrigation (CDI) can produce 25% savings in irrigation water with no adverse effects. Reclaimed drainage water can be used for in-season irrigation up to 6 dS/m. Nitrogen applications can be adjusted for crop load and alternate bearing. Foliar sprays of boron, copper, and zinc can replace heavy ground applications to alleviated these micronutrient deficiencies. Some early season insect damage can be tolerated due to the tree's ability to compensate for the damage by filling a higher percentage of the remaining nuts, Maintaining a clean orchard floor can limit some insect pests. Mechanical pruning has been demonstrated to be cheaper and cause no loss in yield. Foliar fungal diseases can be partially controlled by limiting trajectory angle, frequency, and duration of irrigation or by using buried drip irrigation systems. Soil-borne fungal diseases and nematode damage are controlled by using resistant rootstocks.
W. Rademacher, G. Stammler, and P. Creemers
Many trials have demonstrated that apple and pear trees treated with the plant growth regulator prohexadione-Ca (BAS 125 W) are less susceptible to infestation by the bacterial disease fire blight. In further investigations we have studied the effect of this compound against fungal diseases, concentrating on scab (Venturia inaequalis) in apple. Working with apple seedlings and artificial inoculation under greenhouse and field-like conditions, scab infestation could be reduced by applications of prohexadione-Ca. Whereas this effect was rather marginal if inoculations were made shortly after treatment, highly significant effects were found in the time span of ≈1 to 4 weeks after application. Preliminary results from trials conducted under orchard conditions support these findings. We assume that, similar to the situation with fire blight, changes in phenylpropanoid metabolism are mainly responsible for the reduced scab incidence. It should not be ruled out, however, that anatomical and morphological changes caused by prohexadione-Ca may also contribute to this effect.
Arlette S. Cuomo, Steven E. Newman, Hassan H. Nassar, and Ronald J. Harkrader
There are many naturally occurring substances that have the potential to be adapted to modern pest control chemistry. Azadirachtin, an insect growth regulator, is one such naturally occurring compound that has been widely accepted in insect pest management. Quartenary benzophenanthridine alkaloids (QBAs) are known to be effective in the control of crop-damaging fungal diseases. QBAs can be isolated from plants in the Papaveraceae. Extracts of Macleaya cordata, a species rich in QBAs, were formulated for drench application to Cucumis sativa `White Wonder' seedlings. The seedlings were grown in a peat-lite medium using 10-cm plastic pots and inoculated with Rhizoctonia solani. Test formulations were prepared with and without QBAs and applied at 75, 150, and 300 ppm QBAs as a 100 ml/pot drench. The QBA formulations that provided effective control of Rhizoctonia solani lost 20% or fewer seedlings compared to the formulation without QBA, which lost more than 60% of the seedlings. Treated plants were evaluated confirming Rhizoctonia solani infection.
Steven E. Newman, Michael J. Roll, and Ronald J. Harkrader
Quaternary benzophenanthridine alkaloids (QBAs) isolated from plants in the family Papaveraceae are effective for the control of some fungal diseases. Extracts from Macleaya cordata, a species rich in QBAs, were formulated at 150 mg·L–1 QBA for spray application to greenhouse roses (Rosa sp.) infected with Sphaerotheca pannosa var. rosae (powdery mildew). The QBA formulation was applied at 10-day intervals. For comparison, copper sulfate pentahydrate, piperalin, and fenarimol also were applied to mildewinfected plants within the same greenhouse at their respective labeled rates. One day after treatment, visible symptoms of mildew infection were reduced 60% by QBA, whereas fenarimol, copper sulfate pentahydrate, and piperalin reduced the symptoms of infection 50%, 75%, and 85%, respectively. Subsequent studies demonstrated that a tank mix of QBA and piperalin provided enhanced control of powdery mildew on rose. Results from this study indicate that QBAs have the potential to be developed as a biorational fungicide for greenhouse use with both fungicidal and fungistatic activity.
Charles A. McClurg
Commercial producers of pumpkin (Cucurbita pepo) in the Mid-Atlantic region frequently experience losses from the fungal diseases powdery mildew (Erysiphe cichoracearum) and black rot (Didymella bryoniae). In addition to loss of fruit size in some cultivars, the diseases can result in poor-quality handles (fruit stems) and preand postharvest decay. Since the pumpkins are grown for fresh market ornamental use, their appearance, size, and quality are important in marketing strategies. Applications of recommended fungicides during the growing season, although costly, reduce losses in fruit size and quality from fungal pathogens. Subsequent storage studies have documented reduced losses and maintenance of handle quality of pumpkins treated with fungicides during the growing season. This suggests that those who want or need to store pumpkins prior to sale can evaluate costs and benefits of the program. Producers can also choose cultivars that are better suited to storage if fungicides will not be used.
M. Damayanti, G.J. Sharma, and S.C. Kundu
The application of gamma radiation for improving the storage of pineapple fruits [Ananas comosus (L.) Merr. cv. Queen] has been studied in an attempt to reduce decay caused by fungal pathogens such as Ceratocystis paradoxa (Dade)-Moreau and Penicillium purpurogenum Stoll. Gamma radiation at 50, 75, 100, 150, and 250 Gy improved shelf life. The maximum tolerable dose was ≈250 Gy. Fruits irradiated with up to 150 Gy and then stored at 25 to 28C maintained their texture better than did the controls. Radiation, particularly at doses >250 Gy, caused browning of the shin and softening of tissues. Browning increased with increasing radiation dose and storage duration. Excessively high doses promoted spoilage. Doses in the range of 50 to 250 Gy, in combination with storage at 11 to 13C, can be used to reduce postharvest losses in pineapple due to fungal diseases and senescence, thereby extending shelf life.
Steven E. Newman, Michael J. Roll, and Ronald J. Harkrader
Quaternary benzophenanthridine alkaloids (QBAs) isolated from plants in the family Papaveraceae are effective for the control of some fungal diseases. Extracts from Macleaya cordata, a species rich in QBAs, were formulated at 150 mg·L–1 QBA for spray application to greenhouse roses infected with Sphaerotheca pannosa var. rosae (powdery mildew). The QBA formulation was applied at 10-day intervals. For comparison, copper sulfate pentahydrate, piperalin, and fenarimol also were applied to mildew-infected plants within the same greenhouse at their respective labeled rates. One day after treatment, visible symptoms of mildew infection were reduced 60% by QBA, whereas fenarimol, copper sulfate pentahydrate, and piperalin reduced the symptoms of infection 50%, 75%, and 85%, respectively. Subsequent studies demonstrated that a tank mix of QBA and piperalin provided enhanced control of powdery mildew on rose. Results from this study indicate that QBAs have the potential to be developed as a biorational fungicide for greenhouse use with both fungicidal and fungistatic activity.
H. Melvin Couey
Heat treatments have been used to control fungal diseases and insect infestation of fruit for many years. However, with the development of effective fungicides and insecticides, especially fumigants, which could be applied cheaply and easily, interest in heat treatments waned. Stringent short- and long-term safety studies imposed by the U.S. Environmental Protection Agency has made retention of registration for many agricultural chemicals increasingly difficult. Some of the fumigants, such as ethylene dibromide, which were developed and used to control insects during the past 20 to 30 years, are no longer registered; others may lose registration in the future. These regulatory restrictions also increase the cost of developing new chemical fumigants and, therefore, interest in heat disinfestation has been revived (5).
F. Denardi, L. F. Hough, and A. P. Camilo
The principal area of apple (Malus domestica Borkh.) production in Brazil is in the south in the states of Santa Catarina, Rio Grande do Sul, and Paraná. In these states, apples are grown using modern technology, and trees are propagated on size-controlling rootstocks (1). Apple production areas are limited because present cultivars have inadequate climatic adaptation and a high level of susceptibility to fungal diseases, including apple scab [Venturia inaequalis (Cke.) Wint.], powdery mildew [Podosphaera leucotricha (Ell. & Ev.) Salm.], and bitter rot [Glomerella cingulata (Ston.) Spauld & Schrenk] (2). There is a need to develop early ripening cultivars that would make it possible to reduce the cost of chemical protection against diseases and also reduce the length of time that late-maturing apples must be stored until the beginning of the next summer's harvest.
Mary C. Halbrooks and John A. Mortensen
Early settlers from the northeastern and midwestern United States brought popular grape cultivars such as ‘Concord’ and ‘Niagara’ (Vitis labrusca L.) to Florida in the mid-1800s. In the 1890s, the opportunity to ship fresh fruit by rail to northern markets provided an incentive to establish commercial plantings of these cultivars. Declining productivity of these vines, caused by a disease known then as vine degeneration, and the high cost of shipping eventually forced growers out of business. Nearly 30 years later, cultivars with improved resistance to fungal diseases of fruit and foliage, developed by T.V. Munson (1909) of Texas, were introduced to Florida. Subsequently, several thousand hectares of grapes were established in central Florida for the home wine-making market of the prohibition era. Vine degeneration disease once again caused Florida’s grape industry to fail (Truskett, 1926).