Question: I found these in my garden. They are eating my tomatoes and eggplants. What is the best natural way to get rid of these critters?
Answer: These are tobacco hornworms (Manduca sexta). From the photo, you are already using the best natural method of getting rid of hornworms. Picking them off is as effective as any pesticide you might use. This is sometimes a challenge because they are the same color as the plant. Just look for damaged or missing leaves and they wonβt be too far away. You can just toss them aside or feed them your chickens if you have chickens. The trick is to examine your plants once a week so you catch them while they are still small and not eating as much. If you donβt get a thrill from the hunt and want to try something else, the organic insecticide Bacillus thuringiensis (Bt) is effective against the very small caterpillars. It is sometimes sold under the brand name Dipel. Simply apply it to the foliage as directed. This strain of Bt is toxic to caterpillars but nobody else. It may require repeat applications during the caterpillar-growing season because rain will wash it off the leaves and it degrades in the sun. Also, planting a variety of flowering plants around your vegetable garden will bring in some beneficial insects that may parasitize these caterpillars. The wasps that sting them feed on the pollen in your flowering plants and lay their eggs in the caterpillars.
Q: My wife and I have had a several-months-long debate regarding an ocotillo that we transplanted. She says its dead. I say itβs just fine. The plant has several stems coming from the middle of the base of the plant that remain green. There are many shoots as well that are white in color. We transplanted it about 20 months ago. I also thought I read on an Arizona horticulture site that it can take two to three years before we start to see the green leaves on the plant. Is the plant OK? Not that I know anything (Iβm a Midwesterner), but I have to believe as long as we see green, we will eventually see leaves growing back on the plant.
A: For most shrubs and trees, the shock of transplanting can set growth back a bit. The larger the plant, the longer it usually takes to recover and resume significant growth. Two to three years is a long time to wait but for woody plants that is sometimes how long it takes to see appreciable aboveground growth. If you were able to dig up a good portion of the roots when you transplanted, that would be a good start for the plant. Hopefully the spot you chose is similar desert soil with full sun exposure and you didnβt plant it too deep. Ocotillos do best in well-drained native soil. If all this is true, you are probably OK. Judging from your estimate of 20 months planting time, you transplanted in the cool part of the year and that is good as well. These plants can use a good, deep soak of water every two to three weeks when itβs not raining. The green parts should be encouraging and you might see some leaves following the monsoon rains.
Q: I live in the Green Valley area and my cherry tomato plants are 4 feet tall and somewhat scraggly. Some blooms and a few fruit. My question: Is it too early to prune back and how much to prune, half, a third, two-thirds? No hornworms yet, I just jinxed that...
A: The rule of thumb is donβt prune more than a third of your plant at a time. Tomatoes can be left alone and donβt require pruning but you may improve your yield by removing the suckers from indeterminate plants like yours. Suckers are the growth from the stem at an approximately 45-degree angle between the leaves and the fruiting part. They grow right out of the crotch between those two and the energy spent growing suckers takes away from energy used to produce the fruit. The other reasons to prune are to allow for air and light to reach the leaves or to keep the leaves off the ground. If your plants are scraggly, this might not be a concern until they put out more leaves. Also at 4 feet tall they might need some support. Hopefully you are already using a trellis or a stake.
Q. Can you help identify these guys on my grapes?
A: These are the western grape leaf skeletonizers (Harrisina brillians). They are moth caterpillars and they can do quite a bit of damage to grape plants if allowed. Fortunately, there are some natural enemies out there that sometimes keep them in check. Bacillus thuringiensis (Bt) is a good organic insecticide for these caterpillars but it works best when they are small. Simply apply to the leaves where they are feeding as directed on the label. Also be careful when handling these caterpillars because they possess stinging hairs on their bodies that can cause some irritation on your skin.
