Throughout the world, growers of horticultural crops employ a multitude of crop and pest management practices designed to reduce pests and minimize crop losses. Although weeds continue to afflict humans (65), host other pests (14), and cause appalling crop losses on a worldwide scale (66, 109, 110), certain weedy species may complement horticultural cropping systems. This paper reviews entomological, pathological, and crop-related literature where manipulation of a specific weed, a weed control practice, or a cropping system can suppress a crop pest. Perhaps horticulturists and colleagues will recognize an opportunity to improve our understanding and our ability to successfully manage one or more of the following examples, thereby improving production efficiencies within modern horticultural cropping systems.
Agricultural development requires functional infrastructures, a continued assimilation of old and new technologies, and increased involvement of people who are motivated to create behavioral changes among colleagues and farmers. As educators in graduate training programs, we provide basic horticultural and scientific training. However, we often neglect training in practical farming skills, leadership or administrative skills, communication strategies, and the study of human behavior related to the acceptance of new ideas, concepts, and techniques.
Purple nutsedge (Cyperus rotundus L.) is the most serious weed in cultivated crops throughout the tropics and subtropics. Intensive cultural practices such as those used in modern vegetable production tend to encourage the growth and distribution of purple nutsedge and other similar weeds, because they resist both traditional and modern methods of weed control. Tremendous amounts of human energy are required to reduce the growth of these weeds so that a satisfactory crop yield can be harvested. This paper describes some of the noxious characteristics of purple nutsedge and control measures that are currently being tested or used in Brazil and other Latin American countries.
Shrubs in the genus Dirca are rarely used in landscaping despite their shade tolerance and aesthetic qualities. A trial of 81 plants, 27 of each of three species, was established in 2007 in USDA hardiness zone 5a to evaluate survival and growth. After four winters, survival of Dirca mexicana (89%) was greater than survival of Dirca palustris from Florida (44%) and Dirca occidentalis (41%). Survival of Dirca palustris from Ontario, Canada, was intermediate (56%), but annual stem extension was only 60% that of Dirca mexicana and Dirca palustris from Florida. Surviving plants of Dirca mexicana and Dirca palustris from Ontario showed minimal winter injury, but tips of some stems of Dirca palustris from Florida and Dirca occidentalis were killed. Our data on survival, winter injury, plant health, and stem extension of the California-endemic Dirca occidentalis suggest it will be especially challenging to identify genotypes adapted for use in the Upper Midwest. In contrast, we conclude that another narrowly endemic species, Dirca mexicana, has potential as a new shrub for horticulture. Additionally, our results provide evidence for variation in cold-hardiness and annual stem extension of Dirca palustris. Although over half of plants from Florida had died after the first two winters, no additional mortality occurred over remaining years, and survivors were more vigorous than plants from Ontario. This suggests that exploitable variation in cold-hardiness and vigor exists among and within populations of this broadly distributed species.
The content and sterol composition of free sterols (FS), steryl esters (SE), acylated steryl glycosides (ASG), and steryl glycosides (SG) in pericarp tissue of bell pepper fruit from three cultivars (Capsicum annuum L. cv Gator Bell, Bell Tower, and Lady Bell) were determined at three stages of ripening (mature-green, turning, and red-ripe). In each cultivar, FS were predominant at all stages of ripening, with ≈5- to 20-fold lesser amounts of SE, ASG, and SG. The proportions of the sterol conjugates (SE, ASG, and SG) varied somewhat between cultivars, but there was a consistent increase in the ratio of SG to ASG with ripening. The sterol composition of steryl lipids was quite similar in the three cultivars, and only minor changes occurred with ripening. Sitosterol was always the major sterol, followed by campesterol. Sitosterol plus campesterol comprised 89% to 95% of the total sterols in FS, ASG, and SG, and 74% to 91% in SE. Cholesterol and stigmasterol were always present as minor (1% to 4%) constituents. In general, small increases in stigmasterol and several minor, unidentified sterols occurred with ripening, at the expense of sitosterol and campesterol. These changes were greatest in SE.
Nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylanaline] severely injured direct seeded tomatoes that were covered with soil or expanded vermiculite in the greenhouse and field. Powdered activated carbon increased the adsorptive capacity of a vermiculite anticrustant mixture and protected tomato and weed seedlings. A dequate seedling protection was obtained by spraying a 2-inch wide band of activated carbon over seedling furrows filled with vermiculite. Mechanical application of an activated carbon vermiculite mixture in 1-inch circular clumps protected tomato seedlings and protected fewer weeds than the 2-inch spray band. Granular carbons reduced soil crusting and protected seedlings from preemergence herbicides.
A uniform and convenient herbicide application technique was developed for home vegetable gardens. 4-(Methylsulfonyl)-2,6-dinitro-N,N-dipropylanaline (nitralin) was either sprayed on the soil surface, or applied to 1 m wide sheets of water soluble plastic. A light sprinkling of water released the nitralin from the water soluble plastic and permitted soil adsorption. Weed control was excellent when 3.4 kg/ha nitralin was applied to the soil with water soluble plastic. Germinating vegetable seeds were protected from nitralin injury with a mixture of activated carbon and vermiculite. The “no-cultivation concept” may have broad horticultural application, especially in home gardens where herbicides are difficult to use.
A time weighted land use index known as the crop intensity index (CII) was developed to assess and compare the actual area-time devoted to crop production with the total area-time available to a farmer or group of farmers during a specified time period, usually one year. The basic CII equation may be adopted to relate the actual area-time devoted to a single crop or group of crops such as vegetables compared to the total area-time available for all crops grown on that farmer’s land, or to assess the relative area-time of a single crop or group of crops compared to the actual area-time relationship of all crops grown on that farmer’s land.
As many as 50 different vegetable seed crops are grown annually in Oregon on an estimated 8000 total acres. Often less than 100 acres of parsley [Petroselinum crispum (Mill.) Num.] or celery [(Apium graveolens L. (Dulce group)] are grown, whereas several hundred acres of carrot (Daucus carota L.), radish (Raphanum sativus L.), and other crucifers are produced annually in Oregon. Many of these crops are planted in late summer and overwintered for vernalization. Both fall and spring planted crops are harvested in mid to late summer. Weeds must be controlled throughout the 4-11 months from planting to harvest to reduce interference and to prevent weed seeds from contaminating the harvested seed. Seed company representatives expressed concern that additional herbicide registrations were needed to control weeds in overwintering seed crops. Because these crops are considered to be minor by potential registrants, chemical manufacturers indicated little interest in adding seed crops to their labels, and university resources were inadequate to pursue registrations for the multitude of vegetable seed crops. A program patterned after 4-H efforts was designed to obtain herbicide registrations through the cooperative efforts of seed company volunteers and the extension service. The program provided training in field research techniques to enable seed company fieldman to conduct the field trials necessary to register herbicides for use on vegetable seed crops in Oregon.