-2- 



late July, leaves on certain trees began to show yellowing and browning in 

 central spots as well as near the edges. These areas pro;.iptly died and be- 

 came brittle to the touch. C^uite soon, affected leaves began to fall off, 

 especially from the lower portions of growing shoots. 



At the pres' at time, the orchard is rather generally affected by this j, 

 malady which looks to us like a case of maj^nesium deficiency. This orchard soil 

 was foi^a-irly low in potassium, so potasii hus been applied liberally. The high 

 potassium condition f.t the present time evidently helps to bring out the mag- 

 nesium shortage, which actuall-r may be more serious than the original potash 

 shortage. This is further evidence that we have a deficiency of mf'.gnesium here 

 in Amh'^irst, as roportrjd in •" he May issue of Fruit Notes. 



There are similf ri jies bttvieen the foliage deficiency symptoms of 

 potassium and magnesium, rvriev^.r, the following differences should be noted. 

 In magnesium deficiency, t- ere Is usually nore or less yellow mottling of leaves ^ 

 although not alv/ays aviden- , and premature falling of l eaves is typical. These 

 t<:io features are not .'ound in .jotassium d~"ficiency. There are certain other 

 differences which need not be discussed at this time. 



If any grow^;r thi'iks .hat symptoms of magnesium shortage are showing 

 up in his orchard, l-;t us i.t the Colloge knoi. about it. This holds for symp- 

 toms of other def icioncios also. In short, look at your trees. They will tell 



you in their own w»y if th ir diet is O.K. , r. xu • i 



■' "' — -Lawrence Southwick 



RELATIQI^ OF YffiATIigR TO R BJ MITE INFESTATION 



In many orchards the number of over-wint^-ring eggs of the European 

 Red Mite in the epring of 1942 was very small, and the sevf^re infestation of 

 this pest which developed uarly this summer was f- itirelyu.predicted. 



Our only explanat on relates to the occurrence of ideal weather con- 

 ditions for egg laying at tae time when the few mites that hatched from the 

 winter eggs were ovipositing. It is well known t? at insects have a certain 

 definite peripd in their development for lajing most of their eggs and any un- 

 favorable condition during that period vrill cause them to lay fewer eggs. This 

 year favorable conditions at just the right time induced the mites to lay the 

 maximum number of eggs and to produce a soconu generation \vhich was larger and 

 more destructive than is usually produced by u larger first generation which 

 reaches the optimum period for egg laying during less favorable v;eather condi- 

 tions. 



In August in many orchards the red mite infestation was only normal, 

 or perhaps below normal, in coruparison v/itli the li.rge population which was 

 present earlier in the sumr ^r. 



This apparent reduction in the abiindance of the red mite in August can 

 be explained by the same reasoning; namely, that the conditions for oviposition 

 by the second or third generation were unfavorable and only a small number of 

 eggs were laid. At this time also the beneficial predators of the red mite 

 have increased and they are killing a large number of mites and mite eggs. 



J 



