Peach Bacterial Spot


Bacterial leaf spot of peach, also known as bacterial shot hole, is a common disease on older peach trees and nectarines. This peach tree leaf spot disease is caused by the bacterium Xanthomonas campestris pv. pruni. Bacterial spot on peach trees results in loss of fruit and the overall malaise of trees caused by recurrent defoliation. Also, these weakened trees are more susceptible to winter injury.


The most characteristic sign of peach tree leaf spot are angular purple to purple-brown spots on foliage, followed by the center of lesion falling out, giving the leaves a “shot hole” appearance. Leaves soon turn yellow and drop. Fruit has small water-soaked markings that enlarge and merge to eventually cover large areas. Cracking or pitting occurs along the lesions as the fruit grows, enabling brown rot fungus to infiltrate the fruit. Bacterial leaf spot also affects current season growth. Two types of cankers can be spotted on twigs. “Summer cankers” appear on green twigs after leaf spots can be seen. Cankers caused by the peach scab fungus look similar but are slightly raised while those caused by bacterial leaf spot are sunken and circular to elliptical. “Spring cankers” occur late in the year on young, tender twigs but only appear the following spring at buds or nodes right around the time the first leaves emerge.




Comments

Post a Comment

Popular posts from this blog

Squash Powdery Mildew

Image
  Powdery mildew, mainly caused by the fungus Podosphaera xanthii, infects all cucurbits, including muskmelons, squash, cucumbers, gourds, watermelons and pumpkins. In severe cases, powdery mildew can cause premature death of leaves, and reduce yield and fruit quality. Causes Powdery mildew infections favor humid conditions with temperatures around 68-81° F. In warm, dry conditions, new spores form and easily spread the disease. Symptoms of powdery mildew first appear mid to late summer in Minnesota.  The older leaves are more susceptible and powdery mildew will infect them first. Wind blows spores produced in leaf spots to infect other leaves. Under favorable conditions, powdery mildew can spread very rapidly, often covering all of the leaves. Although powdery mildew primarily infects leaves and vines, infections occasionally occur on cucumber or melon fruit. Powdery mildew does not directly infect squash fruit. Fewer and smaller fruit grow on infected plants. Reduced fruit quality oc
Read more

Tomato Target Spot

Image
Target spot on tomato fruit is difficult to recognize in the early stages, as the disease resembles several other fungal diseases of tomatoes. However, as diseased tomatoes ripen and turn from green to red, the fruit displays circular spots with concentric, target-like rings and a velvety black, fungal lesion in the center. The “targets” become pitted and larger as the tomato matures. Management Remove old plant debris at the end of the growing season; otherwise, the spores will travel from debris to newly planted tomatoes in the following growing season, thus beginning the disease anew. Dispose of the debris properly and don’t place it on your compost pile unless you’re sure your compost gets hot enough to kill the spores. Rotate crops and don’t plant tomatoes in areas where other disease-prone plants have been located in the past year – primarily eggplant, peppers, potatoes or, of course – tomatoes. Rutgers University Extension recommends a three-year rotation cycle to reduce soil-bo
Read more

Corn Northern Leaf Blight

Image
  Northern corn leaf blight (NCLB) is caused by the fungus Setosphaeria turcica. Symptoms usually appear first on the lower leaves. Leaf lesions are long (1 to 6 inches) and elliptical, gray-green at first but then turn pale gray or tan. Under moist conditions, dark gray spores are produced, usually on the lower leaf surface, which give lesions a "dirty" gray appearance. Entire leaves on severely blighted plants can die, so individual lesions are not visible. Lesions may occur on the outer husk of ears, but the kernels are not infected. On hybrids that contain an Ht gene for resistance to the fungus, lesions are smaller, chlorotic, and may develop into linear streaks. These lesions rarely produce spores. Lesions can eventually expand to a more oblong or “cigar” shape. They may also coalesce to form large areas of necrotic tissue. Dark spores may be observed in the lesions with the aid of a hand lens. Symptoms often begin on lower leaves; spores produced by primary lesions are
Read more