THE CANADIAN HORTICULTURIST 



181 



3. Leaves usually remaining green or 

 in severe cases becoming of a sickly 

 yellowish color. Spots on the under- 

 side of the leaf very small, rusty brown 

 or black. Sometimes showing on the 

 upper surface of the leaf as black spots 

 with yellow borders, seldom occurring 

 on the stems or pods. This is the true 

 Rust. 



BEAN ANTHRACNOSE 



"The anthracnose is the most com- 

 mon and destructive disease of beans. 

 It is very probably the disease that is 

 destroying your crop. Its most appar- 

 ent injury is on the pods, where it forms 

 large dark rusty brown or black spots. 

 It is on this account frequently known 

 as "pod spot." The disease may and 

 usually does occur, however, on all 

 parts of the plant except the roots. It 

 is caused by a fungus known to botan- 

 ists as CoUctotrichum lindcmuthianuw , 

 which lives as a parasite in the tissues 

 of the bean. 



"The disease makes its first appear- 

 ance on the bean seedlings, as they come 

 up. It may then be detected, on at 

 least some of the young plants, as brown 

 discolored sunken spots or cankers on 

 the seed-leaves or the stem. This early 

 appearance of the disease is due to the 

 fact that the fungus is usually carried 

 over winter in the seed and so is already 

 in the bean when it is planted. 



"From the spots on stem and seed- 

 leaves of the seedlings the spores find 

 their way to the large leaves and branches 

 ?f the rapidly growing plants. The 

 irge veins of the leaf are frequently 

 laten through and killed by the fungus, 

 ^nd holes or cracks with blackened 

 largins appear in the blade. While 

 this may not kill the leaf, it greatly 

 lessens its efficiency as a starch maker, 

 *and so indirectly but effectively reduces 

 the yield of seed. 



"It is from the attack of the disease 

 on the pods that the most direct and 

 apparent damage to the crop results. 

 During the time of blossoming and pre- 

 vious, the fungus has been spreading 

 and becoming established on the stems 

 and leaves, and it now attacks the young 

 and succulent pods. With their tender 

 growing tissue full of water and food 

 materials, these pods offer the best con- 

 ditions for the growth and development 

 of the parasite. Spores from the spots 

 on the leaves and stems fall on the pods 

 where, in the presence of moisture and 

 the high summer temperature, they 

 germinate, forming a little sprout or 

 germ tube, which penetrates the tender 

 skin of the pod and, branching in the 

 juicy tissues, gives rise to an anthrac- 

 nose canker. These first appear as little 

 brown or rusty spots, which enlarge and 

 darken until nearly or quite black. The 

 dead tissue dries and settles, leaving a 

 sunken place in the pod. The spores 

 may be scattered by the cultivator, the 

 pickers, by animals, or by the wind in 



damp or rainy weather. As the threads 

 or mycehum of the fungus penetrate 

 deeper into the pod they finally reach 

 the seed within. Unless the seed is 

 destroyed by the fungus, it ripens and 

 the enclosed mycelium becomes dormant. 

 The presence of the fungus in the seed 

 may usually be detected by the brown 

 or yellowish discoloration of the seed- 

 coat. When the seeds are badly affect- 

 ed, they become more or less shrivelled 

 as well as discolored. It is thus easy 

 to tell with considerable certainty 

 whether seed to be planted is affected 

 with anthracnose. When the seed is 

 planted in the spring the enclosed but 

 dormant fungus is planted with it. In 

 the soft and fleshy seed-leaves in which 

 it is imbedded the mycelium finds an 

 abundance of food and grows rapidly, 

 soon forming a spot or canker and produc- 

 ing spores which at once begin again to 

 spread the disease to neighboring healthy 

 plants. 



TREATMENT OF ANTHRACNOSE 



"Soaking the seed in formahn, cor- 

 rosive sublimate and other poisons, and 

 in hot water, have been tried by differ- 

 ent experimenters with varying results. 

 So far no one has been able to prevent 

 the disease entirely by such treatment. 

 The fungus mycelium is imbedded in 

 the bean itself. Any poison that will 

 penetrate sufficiently to kill the fungus 

 will usually kill the seed. There are also 

 other objections : that soaked seeds can- 

 not be conveniently handled in the 

 planter and if allowed to dry, many will 

 'shp' their coats; the reduction in 

 'stand' and consequent necessity of 

 planting a larger quantity of seed is also 

 another objection. On the whole, seed 

 treatment cannot yet be recommended. 

 "Selection of clean seed is of first im- 

 portance in growing a clean crop. All 

 beans to be planted should be most 

 carefully "hand picked" and all beans 

 showing discolorations, wrinkles or blis- 

 ters should be discarded. It has been 

 found that in some cases where 95% of 

 the beans were marketable, only one per 

 cent, was fit jar seed. As soon as the 

 bean plants are well through the ground, 

 they should be carefully examined and 

 all diseased seedlings pulled up, carried 

 jrom the field in a sack, and burned. This 

 is the second step in the contest with 

 the anthracnose and it is important, 

 since even the most expert will overlook 

 some of the diseased seeds in sorting. 



SPRAYING WITH BORDEAUX 



"As soon as the plants are well up, 

 and the first pair of true leaves begins 

 to unfold, spray thoroughly with Bor- 

 deaux mixture. Probably the best form- 

 ula to use is five pounds copper sulphate, 

 and four pounds of stone lime to 50 gal- 

 lons of water. A stronger solution has 

 been found to dwarf the plants, while 

 the weaker solution is eru'ally as effective 

 in preventing the anthracnose. This 

 should be so thoroughly applied that every 



plant above ground will be completely 

 covered. In about 10 days or two weeks 

 the plants should have a second spray- 

 ing, using the same strength of mixture. 

 This application should be as thorough 

 as the first to cover and protect the new 

 growth of leaves and branches. Unless 

 excessive rains wash the mixture off, it 

 will not be necessary to spray again 

 until the pods are forming, shortly after 

 blossoming. A third appHcation of the 

 same strength and thoroughness should 

 now be made. The nozzles should be 

 so arranged that the pods as well as 

 stems and leaves will be thoroughly coated. 

 "In most cases three sprayings will 

 be sufficient. If the seed was badly 

 diseased and if the plants show an 

 abundance of the anthracnose, more 

 sprayings will probably be necessary to 

 insure a clean crop. The effect of heavy 

 rains in washing off the mixture may be 

 overcome by adding to the Bordeaux 

 mixture the following: two pounds 

 resin, one pound sal soda, one gallon of 

 water. Boil together until of a clear 

 brown color. Add one-half this amount 

 to each barrel of the Bordeaux. An 

 extra spraying between the second and 

 third, and another after the third when 

 the pods are nearly full grown, will be 

 sufficient in the worst cases. 



"The removal and destruction of dis- 

 eased pods and stalks is also a matter not 

 to be overlooked. While the disease is 

 most commonly carried over in the seed, 

 it has also been demonstrated that dis- 

 eased pods and stems thrown on the 

 fields in which beans are to be planted 

 will result in a marked increase of the 

 disease the next season. For this rea- 

 son all diseased pods and stalks should 

 be burned, or, if they go into the manure 

 pile, the manure should not be put on 

 fields in which beans are to be planted. 

 "Cultivating or working in tfie beans 

 when wet should be avoided as much as 

 possible. 



SUSCEPTinilJTY OF VARIETIES 

 "Certain varieties are more susceptible 

 than others to this disease. This is not- 

 ably true of the common 'Wax' varieties. 

 Numerous 'Rust Proof varieties have 

 been placed on the market, but while 

 some of them are more or less resistant, 

 probably all will spot under conditions 

 most favorable to the fungus. Depend- 

 ence, therefore, should not be placed on 

 the resistance ability of any variety. 

 All should be thoroughly sprayed if im- 

 munity to the disease is to be expected. 

 No record has been discovered of an- 

 thracnose on Lima beans. 



If the vegetable grower wishes to 

 obtain the maximum profit from grow- 

 ing vegetables under glass he must pay 

 strict attention to details from the time 

 the seed is sown until the crop is 

 marketed, and then immediately put 

 another crop in its place. — H. E. Reid, 

 Toronto. 



