White moths eating
Q A caller had white moths with green worms that have eaten broccoli, cauliflower and cabbage. They look like cabbage worms when she looked it up on the internet. She has removed all of the caterpillars and has covered everything with a screen, so they can’t get into the plants again. The only part of the leaves left are the veins. The food parts were not damaged, and the stem is still strong. Is there something or anything that she needs to do to have the food continue to grow? Fertilizer etc.? Will the food continue to grow without the leaves?
A Cabbage worms and cabbage loopers are very common pest problems of all of the typical vegetables that we grow in the cabbage family. Even though they are fairly small, there are usually quite a few on each plant and they can consume quite a bit of foliage while they are maturing. Certainly, the loss of leaf tissue will decrease the amount of edible “vegetable” that is produced because the caterpillar feeding reduces the ability of the plant to produce carbohydrates through photosynthesis. Using a screen or floating row-covers can be an means of excluding the moths from the plants so they cannot lay any additional eggs. But at this time of the year, I suspect that there are still other caterpillars on the plants that got missed as you were going through the plants to pick them off the plants. Next year try to get the floating row cover installed earlier in the season to provide better control of these pests.
Many people will dust or spray their plants with an insecticide to control them. Make sure that the vegetable you are treating is on the label and that it says it will control cabbage worms and cabbage loopers. Also, be sure to follow the pre-harvest interval. That is the number of days you have to wait after treating before you can safely harvest the produce. Some products, like the organic insecticide Bacillus thuringiensis (B.t.) Is much safer to use and can be very effective on smaller caterpillars.
Unknown weed to ID
Q Please tell me the name of this common South Dakota weed. (See photo.) I’m hoping the seed pods will help you identify it. Also, which herbicide that won’t harm grass could I use to kill it?
A This is a very common weed called common mallow (Malva neglecta). It is often found along the edges of lawns and gardens or in previously tilled areas. Even though this plant is only an annual, a single plant can grow over a foot tall and have a 2’ spread. The stems will often spread along the ground, growing nearly horizontal, but turning up at the ends. Each little seed pod will generally produce 10 seeds so it can multiply rather rapidly. The plant grows from a single taproot which is fairly easy to pull out when the plants are young, but become much more difficult to pull out as the plants mature. It can be treated with the typical broadleaf herbicides for lawn weed control and those will be quite effective when the plants are young, but less effective as the plants mature.
Holes in tomatoes with black bugs
Q I am a gardener in North Dakota. I have been gardening for 48 yrs. This year I too have one tomato plant that has holes eaten into the fruit. After exam, I found little (maybe 1/8-inch) black bugs. Never have I ever seen this, but they also were in over ripe raspberries. I don’t know what they are, but I removed all the tomatoes on that plant-red or green and destroyed them. Seems to have halted the progression for now. Love to read your articles in the Farm Forum. Keep up the good work for us gardeners.
A One of the most common garden insect questions I get asked is “what are those little black, spotted beetles that are in my sweet corn, tomatoes, raspberries and perhaps worst of all, in your beer!” These little nuisances are called picnic or sap beetles. They are attracted to ripe or damaged fruit and vegetables. I was harvesting some sweet corn that had some bird feeding damage at the tips of the ears one day. When I cut the tips off, a couple dozen of the little beetles came crawling out. Yuck! They found their way to the compost bucket in a hurry! The ears of corn that did not show any damage at the tips were just fine.
Once people find out what they are, they want to know how to get rid of them. That is a more difficult question to answer. These little guys are rather difficult to control. First, they are not that easily killed by insecticides. Secondly, just when you want to control them, that is the time that you are harvesting the produce too. Thirdly, if the beetles are feeding down inside an ear of corn or in an overripe tomato, it will be difficult to get the insecticide where it will kill the beetles. Sap beetles are also pretty good flyers and seem to have a good sense of smell to be able to find your beer, just a few minutes after you have opened it. Most garden insecticides have a pre-harvest interval, during which you are not supposed to harvest and eat the produce.
So, what can you do? The best thing to do is keep up with harvesting so that you don’t allow fruit to get over-ripe or remain on the plant after it has been damaged in some way. The sap beetles will be attracted to any waste fruit or vegetables too, so if you can keep waste materials away from your yard, that will help to reduce problems in the future. The adults will lay eggs near decomposing fruits and vegetables, so reducing waste piles will also help for next year. Some people take advantage of the beetle’s affinity to muskmelon (their favorite food) by using it as bait that they treat with an insecticide. As the beetles are attracted to the melons or rinds, they will be killed by the insecticide preventing them from laying eggs in the fall.
Q I have a gross hole in my tomato that’s oozing juice. (See photo.) This is my second tomato like this. Do you have any solutions or determinations?
A I think there are two different things going on here. First of all the malformation can just happen on its own some times. Some tomato varieties have more unusually shaped fruit than others. The large rotten looking spot could be late blight. There also appears to be some other damage to the fruit that made the hole in the rotten area. That could have been an entry point for a fungus or bacteria. This fungal disease often attacks the leaves, stems and fruit. Check out other parts of the plant for large, dark colored spots. If you could send some images of those I can take a look and see if those match up. Otherwise, continue removing any diseased fruit like this and get them out of the garden area.
Peach with a glob of clear gel
Q I am beginning to harvest my peaches this year when I came across this one that has a clear glob of gel coming out of it. (See photo.) What is that and do I need to treat it with anything?
A Most of the stone fruits (Prunus sp.) can show a symptom called gummosis. Ordinarily it shows up on the side of the trunk or a stem, but it can show up on other parts of the plant too, like this fruit. In this case I don’t think there is anything to worry about. There may be an insect inside this fruit, or it may have been damaged in some other way, perhaps by a bird peck. This gel is kind of like hardened sap. If it shows up on the main stem of a plant, it is more often associated with a canker disease that can be serious.
Q A client said that after he mowed his daughter’s lawn, the mower blades were covered with a fine, rusty-colored dust as well as his shoes. He is wondering what is causing this. The lawn looks normal.
A You have described a common problem that often occurs about this time of year — rust. Rust is a fairly common problem, particularly under hot and humid conditions like we had last week. Certain types of lawn grass are also more susceptible to it.
Rust outbreaks are most common in late summer and early fall, although sometimes the disease is active in the early spring (especially on poorly nourished turf). Rust is a disease of slow growing turf, so factors that contribute to poor growth tend to favor rust development. Such factors include summer heat and drought stress, low nitrogen fertility, compaction, and shade. The rust itself is sometimes hard to see, look closely at any grass that seems to have a more yellowish color. Look for the orange pustules that will be on the leaf blades. See the attached image.
The good news is that usually it is more of a cosmetic problem than anything really that serious in most cases. So, I would not worry about it too much. A fall application of fertilizer will help the lawn to be more vigorous and less likely to get it in the future. Also, irrigate if possible during drought condition, raise mowing height to at least 2.5 to 3” to help the lawn grasses become more vigorous and able to withstand disease issues. Over-seeding shady areas with more shade tolerant grass species will also help. For more information see https://www.extension.purdue.edu/extmedia/bp/bp-110-w.pdf
Q I started seeing this plant in my flower bed earlier this summer. (See photo). I kind of liked the creamy-white flowers with the dark pink centers and yellow stamens so I did not pull it out. Now I have quite a few of them and sort of wish I had pulled them out. What is this plant and how do I control it in my flower bed?
A This is a plant called Venice mallow (Hibiscus trionum), also known as flower-of-an-hour because the flowers only remain open for a few hours. This is an annual that comes back from seed each year. It is common in cultivated areas and can become serious in some crop land. In a garden situation, mulching and regular pulling to prevent seed from forming will likely be the best options for managing this plant.
Little worms in my raspberries!
Q Help! I have been picking my raspberries this summer when I suddenly realized that many of them had little white worms crawling inside the fruit. Yuck! What are these worms and what should I do to get rid of them?
A This is another relatively new invasive pest called the spotted wing drosophila. The Spotted Wing Drosophila (Drosophila suzukii) or SWD, also called the spotted wing fruit fly, is a pest problem that originated in Asia and was only first identified here in the United States in California 2008. It was first seen in South Dakota in 2013. Since then it has shown up in many counties in South Dakota, but populations of the insect can be quite scattered. It has been found in many types of areas, but particularly where fruit is available for the fruit flies to feed on.
Management of SWD is difficult for several reasons. However, the first step in management should be monitoring to see if you have SWD in your yard or near your fruit crops. A simple monitoring trap can be made from a 32 oz plastic cup with lid. Place the traps in areas where the flies most like to spend their time — in the shade (usually the north side of the plant), in the fruit zone, using a stake or a wire attached to the sides of the trap, and fastened to a branch or trellis wire.
One of the most important practices for managing SWD in the home garden is sanitation. Pick fruit as soon as it is ripe and clean up and dispose of overripe or rotted fruit by sealing it in plastic bags and putting it in the trash. Don’t allow it to remain on the ground or on the bushes, to contribute to building the populations of SWD. It is not a good idea to put this damaged or overripe fruit in the compost pile either. Keep picked fruit stored in the refrigerator. Refrigeration will stop further development of larvae or eggs if they are present. Freezing fruit if it can’t be used within a day or so of picking will kill any larvae or eggs in the fruit. Small plantings may be protected with fine netting to exclude SWD using 1 mm (1/32 inch) mesh. Wait until pollination has taken place to apply the netting so that bees and other pollinators have access to the blossoms.
Several insecticides that are effective on SWD are labeled for use on fruits in home garden plantings. Before applying a pesticide, always read and follow all directions on the pesticide’s label. The crop (e.g. blueberry, strawberry, raspberry, cherry) must be listed on the label to legally use the product on it. Be sure to check the label and follow any restrictions on how long you must wait after you apply the insecticide until harvesting the fruit. Use protectant insecticide treatments starting when fruit first begins to color and continuing to harvest, according to the label instructions. They will protect fruit from infestation but will need to be applied before the eggs are laid in the fruit. Choose the most effective insecticides, when known, and check with local Extension staff to learn about the available options. Alternating the use of insecticides with different active ingredients will reduce the chance of insecticide resistance developing in SWD. Do not apply any insecticides during bloom or when bees are active. The most effective products for use against SWD in home fruit plantings contain the active ingredient spinosad or malathion. Pyrethrins, insecticidal soap, neem oil and horticultural oils have very low and short-lived activity against SWD.
For more information on how to monitor and manage SWD, see this article: http://igrow.org/gardens/gardening/spotted-wing-fruit-fly-damaging-fruit-crops/