Field Crickets 

 Leaf -miners Beet or Spinach Leaf -miner 



rugs. Sugar beets are also sometimes attacked. The leaf stems are 

 often eaten and deep pits are eaten in the crowns of the beets. Figure 7, 

 Plate IV, Page 17 represents an immature female field cricket. 



5. LEAF-MINERS 



Thus far in our discussion of leaf feeding insects only those which 

 feed exposed on the surface of the leaves have been considered. There is 

 another group of leaf feeders, however, which live protected within gal- 

 leries, or "mines," as they are popularly called, which result from the 

 eating away of the pulp of the leaves while the outer portion or epidermis 

 is left untouched. Some of these mines are serpentine in form, while 

 others are irregular in shape, becoming unsightly and discolored as the 

 season advances. 



Several species of leaf-miners are known to attack sugar and garden 

 beets and mangels. However, only the following species appears to do 

 any considerable damage to the sugar beet crop. 



(a) BEET OR SPINACH LEAF-MINER 



(Figs. 1, 2, 3, 4 and 5, Plate III, Page 15) 



NATURE OF INJURY 



The beet leaf-miners burrow into leaves and feed upon the pulp. 

 At first the mines appear as tortuous whitish or brownish lines on the 

 blade of the leaf. As the miners increase in size the mines become la.^ge, 

 irregular areas, as shown in Figure 1, Plate III, Page 15. 



While still inhabited the mines may have a watery appearance, 

 and in case the greater part of a small leaf is mined out the leaf droops 

 and appears to be decaying. If such leaves are held between the ob- 

 server and a strong light the miner can be seen within, usually near the 

 side of the mine. 



If the weather is very warm, dry beet leaves may wilt and lie on the 

 hot soil during very warm days". Sometimes portions of these leaves are 

 killed by the heat. These dead areas often appear very similar to the 

 deserted mines of leaf-miners. They can be distinguished from them 

 very easily, however, by the fact that the pulp still remains, there being 

 no cavity between the upper and lower surfaces of the leaves. 



Ordinarily the damage to sugar beets is so slight that no account 

 need be made of it. Occasionally, however, the miners are so numerous 

 that they materially injure a crop. The destruction of the inner portion 

 of the leaves has the same effect as though the entire leaf were destroyed. 



METHODS OF CONTROL 



It is doubly fortunate that the injury is usually so slight that reme- 

 dial measures are not required, as there is no known remedy practical 

 for field use. Several poisons have been tried, but all have proved un- 

 satisfactory. 



Picking Infested Leaves 



In the case of small gardens the infested leaves can be picked off 

 and destroyed. This will prevent the rapid multiplication of the miners. 



110 



