-6- 



Warm weather stimulates the growth of the disease -producing organisms that invade and 

 infect weakened plants. The particular fungi associated with root and crown rots vary 

 greatly, depending upon the area and season. 



Phytophthora root rot {Phytophthora aryptogea) is favored by cool , wet conditions . In- 

 fected alfalfa plants wilt and die, with little or no stunting. Infected crown and 

 taproot tissue becomes soft and watersoaked and turns yellow to tan in color. Phyto- 

 phthora root rot is usually worst in the low, wet areas of fields. 



Possible control measures include: 



1. Grow only well-adapted, high-yielding varieties recommended for your area. 



2. Avoid overgrazing, rank growth, and very high rates of nitrogen fertilizer. 



3. Plow under thin, unproductive stands. Where possible, rotate every four to six 

 years with nonlegume crops, preferably grasses or cereals. 



4. Plant only in well-drained soil and avoid low areas that are subject to flooding. 



See Report on Plant Diseases No. 302 } Root and Crown Troubles of Alfalfa. Copies are 

 available by writing to Department of Plant Pathology, 218 Mumford Hall, Urbana 61801. 



EQUIPMENT 



NEW EQUIPMENT 



New equipment has become available recently for applying pesticides . 



Span spray is one of the most recent developments . The span sprayer is a ground appli- 

 cator that uses a hydraulic motor to drive a fan. From the hub of the fan, the pesti- 

 cide solution is released into the air stream created by the fan. Several fans can be 

 mounted to provide a swath up to 80 feet wide. 



Research information is not yet available on the effectiveness of pesticide applications 

 using the span sprayer, compared to using conventional sprayers. Studies are needed to 

 discover particle distribution and drift when the span sprayer is operated under vari- 

 ous conditions. Therefore, specific recommendations regarding its use cannot be made. 

 However, the following comments based on field observation may be helpful. 



The advantages of the span sprayer are faster pesticide application and the low volume 

 of water required- -in some cases less than a gallon per acre. The disadvantages of 

 using this type of sprayer are the possible difficulty in obtaining uniform coverage 

 and reasonable control of spray drift. 



The span sprayer, like mist blowers, breaks up the concentrated spray into minute drop- 

 lets. These tiny droplets are light and can become airborne- -resulting in excessive 

 drift, especially when they are required to travel a great distance before reaching the 

 intended target. Even a slight cross wind would have a major effect on the distribu- 

 tion pattern. The problems of drift control and uniformity of distribution are some- 

 what similar to those encounted with aerial applications. 



There are other potential problems relating to the span sprayer. Many herbicide labels 

 specify that they are to be applied with larger volumes of water using ground equipment 

 than the amount that would normally be used with a span sprayer. For example, the AAtre 



