July 22, 1994
Perennial grasses, such as quackgrass and nimblewill, are some of the most difficult to control weeds in the lawn. Control is difficult because there is no herbicide that will selectively destroy these weeds. Also, pulling or digging these perennial grasses is often unsuccessful. The best way to control quackgrass, nimblewill, and other undesirable, perennial grasses in the lawn is to spot treat the weed-infested areas with glyphosate (Roundup, Kleenup, etc.).
Bacterial spot has been observed on pepper during the past several weeks. This disease, caused by the bacterium Xanthomonas campestris pv. vesicatoria, is favored by warm and humid conditions. The disease organism can be spread by rain or during overhead irrigation.
A rarely observed disease of field-grown tomatoes, called "leaf mold", was found last week in a commercial field in west central Iowa. Leaf mold, caused by the fungus Cladosporium fulvum, causes white to yellowish spots with diffuse margins on upper surfaces of the older, lower leaves. The spots are so diffuse, in fact, that the yellowing often looks more like a nondescript mottling. The most distinctive symptom is on the underside of leaves, where patches of olive-green, fuzzy mold are found. Infected leaves curl up, wither, and may eventually drop from the plant.
The proper time to harvest some vegetable crops is fairly easy to determine. Tomatoes turn red when ripe. Onions are harvested when the tops fall over and begin to dry. While some vegetables exhibit clear signs, the proper time to harvest other crops may require a little more knowledge and experience. Guidelines for harvesting and storing various vine crops are presented below.
Garden harvest is in full swing (quite a difference from just one year ago). For the best quality, harvesting should be done at the correct stage of plant development. Herbs, like other garden produce, have their peak time for flavor. Full-size leaves contain the maximum amount of volatile oils providing the greatest flavor and fragrance.