VEGETABLE CROPS. 687 



Fusarium Diseases. 



Several Fusarium diseases causing wilting are known. One form causes 

 a staining of the tissues of the Btem to a pink <>r red colour. A form 

 occurring in French beans — apparently the American Dry Root Rot — is also 

 known. 



Control. — These diseases arc must common where continuous cropping is 

 practised. Rotation is just as important with legumes as with other crops, 

 i- -oil-borne diseases tend to accumulate when land is continuously cropped 

 i" the same family of plants. Obtain clean, well-filled seed. Select the best 

 plants in the plot when saving seed. Destroy all diseased plants and rubbish 

 from the crop by fire. 



Insect Pests of Beans and Peas.* 



French Bean Fly. 



This little black fly (Agromyza pliaseoli), about one-twelfth of an inch 

 m length, does a good deal of damage to French bean crops in some dis- 

 tricts. The fly lays its eggs upon the stem near the ground, and the result- 

 ant maggots tunnel along under the skin, leaving the stem rusty-red and 

 c-racked, so that the plant eventually dies. 



Growers report that spring crops are seldom, if ever, damaged by this 

 moth to any appreciable extent, but as the weather becomes warmer the 

 flies gradually breed up and develop in such numbers as to be very destruc- 

 tive in the fall of the year. 



In good growing weather some advantage can be gained over the pest by 

 hilling up the soil round the plants, so that the stems are covered; the 

 bean plant then puts out a fresh supply of fibrous roots above the damaged 

 tissue. The hilling up of the bean rows also protects the stems if it is done 

 before the flies first appear. No spray or wash that has been used seems to 

 have any effect upon the flies; and as the maggots do not feed upon the 

 surface of the plant but under shelter of the tissue, no poisonous spray upon 

 the foliage would injure them. 



As with many other pests, this is a case for clean cultivation. The 

 maggots pupate in the bean stems, from which, if the plants are allowed to 

 remain in the field, the flies emerge in due course. It would be advisable to 

 pull and burn all infested bean plants as soon as the last picking has 

 been gathered; otherwise, if the plants remain dead and dry, many pupa? 

 may drop out of the cavities in the stems, and, falling on the earth, remain 

 in the ground long after the dry stalks have been removed. Several growers 

 have reported that, although they had cleaned up and burnt all the old beans 

 the previous season, they found the following year, when they planted beans 

 in the same land, that they had not got rid of the flies. Probably some 

 pupa? had dropped from the damaged bean plants before they were removed. 



Bean Aphis. 



The small bean aphides develop through the summer months on various 

 plants, including the many varieties of beans. At this time they are all 

 females, some winged, but many wingless, and they give rise to their 

 young without the aid of males, the young aphis being born vivipax-ously, 

 that is, extruded alive. The aphis are born in rapid succession, and the 

 numbers increase with amazing rapidity. The effect of these thousands of 

 tiny insects, each sucking up sap by means of its little beak, is to cause 



* Goinpiled Ly Officer.-? of the Entomological Branch. 



