Tuesday | February 09, 2016
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Zucchini leaves disappear

Hi Nick! First, I’ve noticed that a few zucchini leaves have been chewed away overnight. Seems like some voracious bug/rodent came in overnight and ate away at my leaves. Any ideas how to prevent this?

Second, my zucchini plants seem to be infested with ants. Some are black; others have a shade of red to them. They crawl all over my plants but don’t seem to eat anything. Any idea if I should be cautious or try to rid the plants of the ants. All of my zucchinis grow in pots.

Third, I’ve been really afraid of the dreaded pickleworm. My plants have not fruited yet, so do they pose any threat to my zucchinis during this stage? I feel like I won’t start putting a bird net up until the zucchinis start fruiting. They’re just over a month old. Thanks again for your advice! — J

1. Slugs are most likely the culprit chewing on the oldest leaves that are next to the ground. A night inspection will help clarify the situation. Baits and trap boards will help. More detailed information on slug and snail control can be found on my website at www.gardenguyhawaii.com.

2. I would not worry about the ants alone. As you’ve observed, they don’t seem to eat anything. Ants are, however, an indication of an insect infestation — aphids, scale, whitefly, etc. Inspect the plants carefully looking for these and other pests. In most cases, the pest can be treated with an oil and/or soap spray. The ants can be treated with baits. If there are positively no insect pests on the plants and the ants are just out searching for food, I would not be concerned. However, do keep in mind that ants interfere with biological control by keeping the good parasitic wasps and predators away.

3. The pickleworm will not be a threat to your crop until the female blooms begin to appear.

Aloha Nick, I have a Puakenikeni tree in North Kohala that was doing well and producing flowers until recently. The leaves are now turning yellow and dropping and the remaining flowers do not open. In the past I have applied chicken manure to fertilize. Would appreciate any advice you might have. Mahalo, CP

Unfortunately, descriptions like leaves turning yellow and dropping often indicate root rot. I would be particularly suspicious of this if the soil is of a clay nature, indicating poor drainage, and the tree is being overwatered. Since confirming root rot is a complicated process, at this point, I would prune the tree moderately and wait for sustained new growth to appear.

If the garden is irrigated, cut back on the frequency. You are possibly watering too often. Perhaps a lawn or annual flowers are planted next to the tree. As a general rule, these plants are not well matched to grow alongside trees, even though landscapers place them together frequently. Their water requirements are quite different, and therefore, irrigating for one would give too much or too little for the other. On the other hand, a well-drained soil will often negate the differences between tree and lawn water requirements and allow the two to be planted together. Once you have corrected any irrigation problems, the soil will begin to dry, and the tree may recover.

It is also possible that a one-time incident occurred such as a fertilizer or herbicide overdose; in this case the leaves would also show a tip and marginal burn.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegardenguy@earthlink.net.


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