October 24, 2016

Avalanche column

October 7, 2016

A gardener asked me why her tomatoes were not producing and appeared in a state of decline. She also sent me some photos. The full size tomatoes were doing worse than the cherry tomatoes.

Diagnosis is difficult with only pictures, so I requested more info including cultural practices and leaf samples.

Taking the leaves out of the plastic bag, I quickly knew what the problem was. I have these “visitors” in my garden.

The critter was embedded in the leaves. They burrow into the leaf or fold the leaf over and adhere the sides to make a tunnel.

To the untrained eye the plants just look like they are in a state of decline. One could think that the plants are tired and dyeing. This could not be further from the truth.

What is happening is a member of the lepidoptera (butterflies and moths) family of insects are laying their eggs on the growing tips of the tomato plant. After they hatch they burrow into the leaves as noted above. They stay on the leaves feeding and then migrate to the tomatoes. And it is at this point where they acquire their name, tomato pin worm. They burrow into the fruit on the sides or the top where the stem meets the fruit to pupate and repeat the cycle. The larvae that burrow into the side of the fruit leave a very small pin hole on the side of the fruit. For the most part this damage is cosmetic but it does decrease its sell-ability.

It is very strange but these guys have a tendency to destroy their food source. They feed on the growing points of the tomato plant which causes the plants decline and demise. The plants can not regenerate any new growth.

It is very likely that these critters are very prevalent in Alpine but go for the most part unnoticed except for the damage they do.

How do they go so unnoticed? These guys are tiny!!! You have to really be looking for them to see them. Tiny is maybe 1/4 to 1/2 the size of the printed letters on this page. Until you see one, a hand lens is very helpful.

Ahhh! But what to do? Preventing an infection is the easiest. The use of floating row covers works best. The cover needs to completly cover the plant and be anchored to the ground. It needs to remain on 24 /7 for the entire life of the plant. The cover is removed for harvest and any other bed work then replaced immediately. My infestations usually start somewhere around the end of July and towards the middle of August.

Infected plants can be sprayed with Bt. (Bacillus thurgensis, an organic spray for Lepidoptera) or Cold pressed neem oil. Spray weekly until active growth resumes and by all means Cover!!

Oh and this cover will prevent tomato horn worms too!!