Spraying disease control

Spraying for Control of South American Leaf Disease... 

Probably the greatest worker with Bordeaux spraying to control leaf disease was Mayne. He proved in India that timing was of the essence and that many sprayings under south India conditions were wasted. Through work on seasonal disease... 

Toxic effects have not stopped copper spraying, because toxicities have been far outweighed by good results from disease control. However, toxic effects need more serious study. They may be more noticeable in warm moist coffee regions than in the dried cooler parts. 

In India some of the early work was toward refinement of spraying to control leaf rust and the researchers started their studies with strong Bordeaux sprays. Munro and Sandararaman showed (46) that uncontrolled leaf disease reduced the coffee harvest very seriously, but that although 10-10-50 Bordeaux materially controlled the disease it depressed the fruit crop. With Bordeaux of formulas 5-5-50 or 2 -2 -50, the crop increase was one half to one third more than that produced under 10-10-50 Bordeaux or under no spray. 

Brazil is one of the few countries in the Americas that has applied insecticides for the control of visceral leishmaniasis (kala-azar). Since the areas of transmission often overlapped with those for Chagas disease, the insecticides used and areas sprayed were determined by the Chagas disease control programme. With the reduction in applications for Chagas disease control, the number of cases of kala-azar has... 

Successful chemical control of plant diseases requires proper timing. Plant disease control on some crops must begin before infection occurs. The protectant chemical must be applied when environmental conditions ate expected to be ideal for the development of plant pathogens. If the protectant is not applied in time, major crop damage may result or the application of the more expensive eradicant sprays may be needed. Label directions often call for routine protectant applications every 7 to 10 days during periods of prime infection risk. Almost all plant disease control chemicals are applied as cover sprays. The purpose is to reach and protect all potential sites of infection. 

Leaves curled and yellow plant stunted. Cause Aphids. Look for small, green, pink, gray, black, or white fluffy-coated, soft-bodied insects feeding on plants. Aphids can also transmit viral diseases. Control by knocking the pests off the plant with a blast of water, or use an insecticidal soap spray. Severe infestations can be controlled by spraying with neem or pyrethrin. 

Leaves with numerous small holes. Causes Rea beetles billbugs. Leaves may develop bleached-out spots or stripes. Rea beetles are tiny black insects that hop when disturbed. They can transmit disease and are likely to be more numerous after mild winters. Cover plants with row cover as soon as they come up to exclude beetles. Remove row cover when tassels form. Treat plants with a commercial neem or pyrethrin spray to control severe infestations. 

Leaves mottled yellow between veins leaf undersideS ave purple spots. Cause Downy mildew. A S the disease progresses, older leaves turn brown and die and younger leaves become infected. Treat plants with a dilute solution of copper spray to control see the caution on page 213 before spraying. Prevent problems by planting tolerant cultivars such as Fanci-pak , Liberty , Poinsett 76 , and Slicemaster . 

Leaves spotted, yellow, and drop early. Causes Septoria leaf spot anthracnose. Since both of these fungal diseases overwinter on old leaf litter, rake up the leaves or bury them under a thick mulch in autumn. Copper sprays also control both diseases. If defoliation occurs late in the season, it does plants little harm. 

Leaves puckered and reddish. Cause Peach leaf curl. Later in the season, infected leaves may yellow, shrivel, and drop. New growth is stunted and swollen and often dies. Fruit often drops prematurely and may have a reddish, irregular, rough surface. See page 165 for an illustration of this disease. You can t cure this fungal disease during the current season, but copper sprays or lime-sulfur sprays help control it. Resistant cultivars include Candor , Clayton , Com-Pact Red Haven , Correll , Dixieland , Elberta , Red Haven , and Stark EarliGlo . 

Leaves riddled with small holes. Cause Flea beetles. These small, shiny, black beetles hop when disturbed. They can transmit viral and bacterial diseases. Control severe infestations by spraying plants with pyrethrin. Prevent problems by protecting young plants with row cover. 

Zande, JC van de, R Meier and MT van IJzendoom, 1996. Spraying in-field vegetables deposit and biological efficacy, the effects of volume rates, dose, spray interval and air assistance on disease control. BCPC Conference — Pests and Diseases 1996, Brighton 18-21 November 1996, British Crop Protection Council, Famham, 343-348. 

Missouri. In 1971, a used oil transporter sprayed oil contaminated with TCDD on riding arenas and roads In Missouri for dust control. The death of about 60 horses and Illnesses In children led to an Investigation by the Centers for Disease Control (CDC). Health effects were attributed to TCDD In the oil In 1974 (4). However, governmental agencies responsible for action were under the mistaken Impression that TCDD had a half-life In the environment of one year and, therefore, carried out only minimal cleanup. In 1982, this problem resurfaced when Times Beach, a community near St. Louis, was evacuated after TCDD concentrations above 1,000 ppb were detected In soil samples. Decisions on this evacuation were carried out under an atmosphere of scientific uncertainty, public emotion, and political pressures within U.S. EPA. At present, there are 43 contaminated sites In Missouri, some of which are being excavated and restored. 

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